---------------------------------------------------------- Kitfox-List Digest Archive --- Total Messages Posted Wed 05/10/06: 29 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:37 AM - Re: Thrust - Over Rated (Michael Gibbs) 2. 03:54 AM - Re: Re: Elevator hinge tab question?? (Lynn Matteson) 3. 04:40 AM - Re: 912S/ oil cooler efficiency (Fox5flyer) 4. 06:14 AM - Kitfox for sale (Gill Levesque) 5. 06:32 AM - Re: Re: Thrust - Over Rated (Randy Daughenbaugh) 6. 08:11 AM - Re: 912S/ oil cooler efficiency (Fred Shiple) 7. 10:19 AM - Re: Grounding of fuel tanks (Donald STEVENSON) 8. 10:47 AM - Re: Bing 54 Choke cable adjustment?? (Jim Burke) 9. 01:18 PM - Re: Tundra tyres. (Michel Verheughe) 10. 04:24 PM - Re: Kitfox for sale (John Anderson) 11. 04:24 PM - Re: Re: Thrust - Over Rated (John Anderson) 12. 04:59 PM - Hydraulic brakes (Malcolmbru@AOL.COM) 13. 05:24 PM - Re: Kitfox for sale (Gill Levesque) 14. 05:24 PM - Re: Hydraulic brakes (RAY Gignac) 15. 05:26 PM - Re: Hydraulic brakes (Rexster) 16. 05:30 PM - Re: Tundra tyres. (RAY Gignac) 17. 05:41 PM - Re: Re: Thrust - Over Rated (wingsdown) 18. 07:18 PM - Re: Re: Thrust - Over Rated (John Anderson) 19. 07:25 PM - Re: Re: Thrust - Over Rated (John Anderson) 20. 07:44 PM - Re: Re: Thrust - Over Rated (wingsdown) 21. 08:06 PM - Re: Hydraulic brakes (Mike Ford) 22. 08:25 PM - Re: Bing 54 Choke adjustment (Guy Buchanan) 23. 08:43 PM - Re: Hydraulic brakes (kurt schrader) 24. 08:46 PM - Re: Re: Thrust - Over Rated (kurt schrader) 25. 09:07 PM - Re: Hydraulic brakes (Lowell Fitt) 26. 10:14 PM - Re: Re: Thrust - Over Rated (kurt schrader) 27. 10:24 PM - Re: Re: Thrust - Over Rated (kurt schrader) 28. 11:06 PM - Re: Re: Thrust - Over Rated (kurt schrader) 29. 11:16 PM - Re: Thrust...Overrated? (kurt schrader) ________________________________ Message 1 _____________________________________ Time: 12:37:37 AM PST US From: Michael Gibbs Subject: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: Michael Gibbs Kurt sez: > My flame suite on for another long one... > : > : > When I flew the C-130, the pitch could be as high as... > : > : > So I am saying this. The prop that produces the most... > : > : > So that is why I wanted a meter that simply measures... > : > : > Is this too much at once? Hope it can be understood... > : > : > One day I will simplify this... Reminds me of something Mark Twain once wrote: "I apologize for such a long letter, I didn't have time to write a short one." :-) Mike G. N728KF ________________________________ Message 2 _____________________________________ Time: 03:54:02 AM PST US Subject: Re: Kitfox-List: Re: Elevator hinge tab question?? From: Lynn Matteson --> Kitfox-List message posted by: Lynn Matteson I'm curious as to how you got the chuck of the flex shaft to clear the elevator tube on the elevator tabs that are in the middle of the elevator? I couldn't find anything that would clear this area, hence my making the 8-foot-long reamer. Lynn On Tuesday, May 9, 2006, at 11:30 PM, darinh wrote: > --> Kitfox-List message posted by: "darinh" > > Thanks to all who responded. I have solved the problem using a nifty > little gadget I picked up at the local Lowe's. It is a flexibly drill > shaft. I simply installed a 13/64 bit and drilled out the elevator > tabs to allow for 1/32" oversized hole. The elevator went together > excellent and works great! Thanks again, > > Darin > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=33749#33749 > > ________________________________ Message 3 _____________________________________ Time: 04:40:27 AM PST US From: "Fox5flyer" Subject: Re: Kitfox-List: 912S/ oil cooler efficiency --> Kitfox-List message posted by: "Fox5flyer" I can't help with the oil temps Fred, but congrats on getting the floats in the air. How's the teething process going? Deke ----- Original Message ----- From: "Fred Shiple" Sent: Tuesday, May 09, 2006 9:52 PM Subject: Kitfox-List: 912S/ oil cooler efficiency > --> Kitfox-List message posted by: Fred Shiple > > I've a question regarding oil cooler efficiency on a Kitfox with a 912S: > My Series 6/ 912S was built with the Skystar optional oil cooler. During the past two summers at temps over 95F I'd have to lower the nose after talk off/climb after about 1 to 1 1/2 minutes as oil temp reached 260F (red line 266F). At 100F (a rare occurance in NW Ohio) had to throttle back from 75% to 65% for the same reason. > Now that I'm flying on floats, I've begun to see the same thing at 75-80 degrees. I'm flying 12-15 mph slower (at the same rpm/manifold pressures) as anticipated with the extra drag. The water and cylinder head temps have remained well in the green with or without the floats. I saw temps consistant with prior years operations in the month prior to install of the floats two weeks ago. > Any advice is appreciated as I'm now concerned about warmer weather operation. > Fred > > ________________________________ Message 4 _____________________________________ Time: 06:14:26 AM PST US From: Gill Levesque Subject: Kitfox-List: Kitfox for sale --> Kitfox-List message posted by: Gill Levesque Hi All, Due to unforseen circumstances I sadly announce that my beloved Kitfox is for sale! . 100hrs. TTAE, 582 grey head with 3:1 redrive ,no spinner. factory refinished GSC three blade prop(sept/05) Factory custom seat cover,baggage sack and cover,door and windshield post panels, carpet kick panels, nice panel with AS,ALT,VSI,Quad EGT/CHT,slip indicator,2 Tachs,water temp, ELT remote, Garmin 12 GPS, Panel mounted Delcom radio, wing strut cuffs, wing tip strobes,Tinted Lexan all around ! Always hangered! A good looking and great flying ( cruise 95 mph ind. solo!!) plane! Plane is in Southern Ontario Canada $27,500.00 CAN Email me off list for pics and any questions Gil Levesque C-IGVL --------------------------------- All new Yahoo! Mail - --------------------------------- Get a sneak peak at messages with a handy reading pane. ________________________________ Message 5 _____________________________________ Time: 06:32:17 AM PST US From: "Randy Daughenbaugh" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "Randy Daughenbaugh" Thanks Kurt! As usual, another great post. Maybe you can shed some light on my following comment. You want to get the rpm's up on takeoff so you can use the power, but you want to have more pitch for more thrust at speed. You can approach this with an in-flight adjustable prop, or you can get close by having a prop that "slips" during take off, letting the engine rev up, but still has enough pitch to make some thrust at speed. I think this is a difference between the skinny blades of the warp drive and wide, high lift blades of the Powerfin. My CFI friend (16,000 hours) was impressed, but not favorably, on how my Powerfin prop was "connected" to the air. Engine rpm was not determined as much by throttle position as by airspeed. In my plane, he was trying to teach me to set rpm to certain number at different points in the approach. This works on his plane with the Warp drive. But with the powerfin, you can pull the power off but unless you slow the plane, the rpm doesn't change. The powerfin does make a great brake. So is "prop slip" part of the formula in getting a prop to best fit torque, and power? Randy . -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of kurt schrader Sent: Tuesday, May 09, 2006 6:35 PM Subject: Re: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader My flame suite on for another long one..... --------------------------------- > Randy sez: > > >In short, if you want more thrust, all you have to > >do is sacrifice top speed. Therefore, thrust is > >irrelevant. > ------------------------- > Mike G. > N728KF > If you want more thrust AND more top speed, you get > an in-flight adjustable prop. You wouldn't drive > your car in one gear all the time, why operate your > airplane that way? ---------------------------- Good point Mike, There is a misunderstanding on the list of thrust, HP and torque. The whole purpose of the prop is to convert power into thrust. Thrust is the most relevant measure. It moves the plane. But we are not talking about static thrust. You need the best thrust at the speed you are flying for best performance. Max static thrust is best at zero speed only. Max takeoff thrust is best somewhere around 1/2 your takeoff speed. Max climb thrust is best at climb speed. Max cruise thrust is best at.... ahhh you get it. A fixed pitch prop will give you its max thrust at only one speed. You are compromising only in that you pick the speed you want to have it perform best at. At all other speeds, faster or slower, it will give less then max thrust. A variable or constant speed prop will still have one best speed, but the curve will be flatter. It will perform almost as well at all speeds as a fixed pitch prop for its one speed. Say a cruise fixed pitch gives efficiencies of: 50% in takeoff 75% in climb 85% in cruise A climb prop might give: 65% in takeoff 85% in climb 80% in cruise The variable prop might give: 75% in takeoff 82% in climb 83% in cruise I have a friend who has a Champ product, his 3rd in 2 years. His 150 HP constant speed Champ would perform equal to his 180 HP fixed pitch Champ, except around one speed. That speed depended upon which fixed pitch prop he installed. He might get better climb, but equal cruise, or better cruise, but equal climb from the extra 30 HP. In his case, he used the prop that meant they cruised equally, but the fixed pitch climbed better with the 30 more HP. If it had a constant speed prop, it would have used the 30 extra HP for better performance all across the speed range. His fixed pitch got off the ground better, but burned more for the same cruise speed. Another way to say it is that the variable prop was almost worth the 30 extra HP. This is my problem with static thrust measurements. It only gives you the measurement for the best prop at no speed. How useful is that? I think that is what Randy was saying. Static thrust is only good when static. It is already losing performance in the takeoff roll, but not so badly as when at cruise speed. A cruise prop would be poor but increasing performance in the takeoff roll, and continue to get better all the way up to cruise. The climb prop is of course in between, getting better, then getting worse as speed increases. As to HP and torque, if you are swinging a 2x4 around with your engine, it will take HP and torque to do, but produce no thrust. If you have a feathered prop, it will take lots of HP and torque to swing and still produce no thrust. The efficiency of the prop to produce thrust is what makes the hp and torque meaningful. As a prop increases pitch, it moves more toward a feathered prop in that the angle of lift of the prop is more against torque and less forward producing thrust. Lift of the prop is always about 90 degrees to the blade. A pitch of say 20 degrees means that some of the prop's lift is pulling air in a circle and not just pushing it back. That takes HP. When I flew the C-130, the pitch could be as high as 55 degrees in cruise. More than 1/2 the HP went to spinning the air and less than 1/2 went to thrust. Our props don't get that bad due to our less pitch. But a heavily pitched prop may take the same HP/torque as a finer pitched prop at higher RPM. The faster turning, lower pitched prop will produce more thrust, to a point. That point is determined by the most efficient rpm for the prop compared to mach number, and the most efficient rpm for the engine. Those 2 may not match. A less efficient prop may take more HP or torque to give the same performance, not more. A more efficient prop will give more thrust with the same HP/torque. HP and torque don't tell the whole story. They don't give thrust, except as the prop allows. So I am saying this. The prop that produces the most thrust will be the one that has its best speed closest to your engine's favorite RPM, but does it at the speed you are flying. Also it has to be the most aerodynamically efficient. Max static thrust equals first gear only. Takeoff props equal second gear. Climb props equal third gear. Cruise props are overdrive. Variable props are automatic trannys. That is Mike's point. The actual performance of the plane will be determined by just how much thrust it can produce today on this fuel, at this temp, at this density altitude, with this prop, at this speed, with these sparkplugs, at this rpm and manifold setting..... You can measure all that, or you can just measure thrust. So thrust is really the key, but it has to be measured now, at your speed and with all variables. Static thrust is good for fans, not planes. Thrust is what happens after all the variables are in place. HP and torque are only what you are putting into a prop, not what is coming out, which changes with prop efficiency, speed, air density..... So that is why I wanted a meter that simply measures the thrust output on board at all speeds, altitudes, settings, etc. It will tell you what performance you are getting now, whatever now is. And instead of HP, you can simply measure fuel flow if the engine is tuned right. That is, if the fuel air ratio is the same, fuel in equals power out. That you can compare to whatever you want to change and see if it made things better or worse. 10% more thrust with the same fuel flow is 10% better no matter how you got it. 10% more HP or 10% more torque might just mean a 10% worse prop is giving equal thrust for more gas. Bottom line: Thrust = performance. Fuel flow = energy and $ in to produce the thrust. The best prop will be the one that gives you the most thrust per fuel flow at the speed you want it. A fixed pitch will peak at a given speed with a strong curve. A variable prop will have a broader curve. You have to pick the prop that peaks at the speed and rpm that best matches your engine and most important performance goal. This is critical for fixed pitch, but less critical for variable. Then you can compare one prop against another to see which gives the most thrust at the same fuel flow. Is this too much at once? Hope it can be understood. You want thrust. Thrust moves the plane. We just aren't use to measuring it directly. Fuel flow is what we pay to get it and max fuel flow is how much power is available under present conditions. One day I will simplify this..... Kurt S. S-5 flying and 1/2 done. __________________________________________________ ________________________________ Message 6 _____________________________________ Time: 08:11:07 AM PST US From: Fred Shiple Subject: Re: Kitfox-List: 912S/ oil cooler efficiency --> Kitfox-List message posted by: Fred Shiple Hi, Deke, The plane/floats are flying well. The pilots doing better ;). A Kitfox on floats is as much fun as I've ever had flying. I'll get some pictures on the site once I get the trim painted- too busy flying now. Fred I can't help with the oil temps Fred, but congrats on getting the floats in the air. How's the teething process going? Deke ________________________________ Message 7 _____________________________________ Time: 10:19:24 AM PST US From: Donald STEVENSON Subject: Re: Kitfox-List: Grounding of fuel tanks --> Kitfox-List message posted by: Donald STEVENSON Hi Lynn, I finally tried to install the ground braid to the filler neck only to discover the tanks I have are fitted with aluminium filler necks, so much for soldering to them, I'll have to find some other way to connect the ground, Thanks for you help, Don Lynn Matteson wrote: --> Kitfox-List message posted by: Lynn Matteson That might have been me, Don. I used the Aircraft Spruce 1/4" tin plated copper braid p/n 863, p.419. I attached it to the spar with a ring terminal under a washer, then the spar attaching nut. I soldered the braid to the filler neck, being careful to put it low enough to clear the filler cap. I used a 200-watt soldering iron to do the job. Lynn On Friday, April 28, 2006, at 04:39 PM, Donald STEVENSON wrote: > --> Kitfox-List message posted by: Donald STEVENSON > > > Some weeks ago I saw discussions on grounding of the filler neck on > the fiberglass fuel tanks (M4) to the rear spar with copper braid. My > question is what size brade is required and how is it connected to the > spar? I beleave it was soldered to the tank neck. Thanks in advance, > Don > > Don Stevenson, Caledon, Ontario, Canada > M4/1200-912s Speedster > > ________________________________ Message 8 _____________________________________ Time: 10:47:40 AM PST US From: "Jim Burke" Subject: Re: Kitfox-List: Bing 54 Choke cable adjustment?? --> Kitfox-List message posted by: "Jim Burke" I sure could use some help,Can someone tell me the proper way to adjust the cables on the Bing 54 Carb.for the > new chokes? I don't want them to stand open or maybe not open at all when > the choke is pulled. > The springs in the new chokes are about twice as strong as the ones > in the old chokes. Is this a upgrade in the chokes so they seal better? or > should I use the old springs? I had to make a tool to compress the new > springs so I could install the ends on the choke cable. > > Thanks for your input, > > Jim N94 ________________________________ Message 9 _____________________________________ Time: 01:18:16 PM PST US From: Michel Verheughe Subject: Re: Kitfox-List: Tundra tyres. --> Kitfox-List message posted by: Michel Verheughe Thank you for your help, guys. Skyflyte, how long have you had those bumps in your tyres? Have you tried to inflate them hard, as Kurt suggests it? Rex, thanks for the "googling" I read all of the links. I will eventually remove the tyres and find out what is the problem. But right now, I have difficulties to understand how a fold in the inner tube can produce what I see. But I am still a very young pilot and I have much to learn. Of course, I'll let everyone informed of my findings, once the tyre are removed and inspected. Cheers, Michel do not archive ________________________________ Message 10 ____________________________________ Time: 04:24:26 PM PST US From: "John Anderson" Subject: RE: Kitfox-List: Kitfox for sale --> Kitfox-List message posted by: "John Anderson" What model is it Gil? From: Gill Levesque Subject: Kitfox-List: Kitfox for sale --> Kitfox-List message posted by: Gill Levesque Hi All, Due to unforseen circumstances I sadly announce that my beloved Kitfox is for sale! . 100hrs. TTAE, 582 grey head with 3:1 redrive ,no spinner. factory refinished GSC three blade prop(sept/05) Factory custom seat cover,baggage sack and cover,door and windshield post panels, carpet kick panels, nice panel with AS,ALT,VSI,Quad EGT/CHT,slip indicator,2 Tachs,water temp, ELT remote, Garmin 12 GPS, Panel mounted Delcom radio, wing strut cuffs, wing tip strobes,Tinted Lexan all around ! Always hangered! A good looking and great flying ( cruise 95 mph ind. solo!!) plane! Plane is in Southern Ontario Canada $27,500.00 CAN Email me off list for pics and any questions Gil Levesque C-IGVL --------------------------------- All new Yahoo! Mail - --------------------------------- Get a sneak peak at messages with a handy reading pane. _________________________________________________________________ Need more speed? Get Xtra Broadband @ http://jetstream.xtra.co.nz/chm/0,,202853-1000,00.html ________________________________ Message 11 ____________________________________ Time: 04:24:26 PM PST US From: "John Anderson" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" Or you can turbo charge. This sort of does what a VPP does to a degree in that the RPM doesn't have to alter too much to increase power for t/off. You can set the prop at a courser angle and increase boost for t/off. John A. From: "Randy Daughenbaugh" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "Randy Daughenbaugh" Thanks Kurt! As usual, another great post. Maybe you can shed some light on my following comment. You want to get the rpm's up on takeoff so you can use the power, but you want to have more pitch for more thrust at speed. You can approach this with an in-flight adjustable prop, or you can get close by having a prop that "slips" during take off, letting the engine rev up, but still has enough pitch to make some thrust at speed. I think this is a difference between the skinny blades of the warp drive and wide, high lift blades of the Powerfin. My CFI friend (16,000 hours) was impressed, but not favorably, on how my Powerfin prop was "connected" to the air. Engine rpm was not determined as much by throttle position as by airspeed. In my plane, he was trying to teach me to set rpm to certain number at different points in the approach. This works on his plane with the Warp drive. But with the powerfin, you can pull the power off but unless you slow the plane, the rpm doesn't change. The powerfin does make a great brake. So is "prop slip" part of the formula in getting a prop to best fit torque, and power? Randy .. -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of kurt schrader Sent: Tuesday, May 09, 2006 6:35 PM Subject: Re: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader My flame suite on for another long one..... --------------------------------- >Randy sez: > > >In short, if you want more thrust, all you have to > >do is sacrifice top speed. Therefore, thrust is > >irrelevant. >------------------------- >Mike G. >N728KF >If you want more thrust AND more top speed, you get >an in-flight adjustable prop. You wouldn't drive >your car in one gear all the time, why operate your >airplane that way? ---------------------------- Good point Mike, There is a misunderstanding on the list of thrust, HP and torque. The whole purpose of the prop is to convert power into thrust. Thrust is the most relevant measure. It moves the plane. But we are not talking about static thrust. You need the best thrust at the speed you are flying for best performance. Max static thrust is best at zero speed only. Max takeoff thrust is best somewhere around 1/2 your takeoff speed. Max climb thrust is best at climb speed. Max cruise thrust is best at.... ahhh you get it. A fixed pitch prop will give you its max thrust at only one speed. You are compromising only in that you pick the speed you want to have it perform best at. At all other speeds, faster or slower, it will give less then max thrust. A variable or constant speed prop will still have one best speed, but the curve will be flatter. It will perform almost as well at all speeds as a fixed pitch prop for its one speed. Say a cruise fixed pitch gives efficiencies of: 50% in takeoff 75% in climb 85% in cruise A climb prop might give: 65% in takeoff 85% in climb 80% in cruise The variable prop might give: 75% in takeoff 82% in climb 83% in cruise I have a friend who has a Champ product, his 3rd in 2 years. His 150 HP constant speed Champ would perform equal to his 180 HP fixed pitch Champ, except around one speed. That speed depended upon which fixed pitch prop he installed. He might get better climb, but equal cruise, or better cruise, but equal climb from the extra 30 HP. In his case, he used the prop that meant they cruised equally, but the fixed pitch climbed better with the 30 more HP. If it had a constant speed prop, it would have used the 30 extra HP for better performance all across the speed range. His fixed pitch got off the ground better, but burned more for the same cruise speed. Another way to say it is that the variable prop was almost worth the 30 extra HP. This is my problem with static thrust measurements. It only gives you the measurement for the best prop at no speed. How useful is that? I think that is what Randy was saying. Static thrust is only good when static. It is already losing performance in the takeoff roll, but not so badly as when at cruise speed. A cruise prop would be poor but increasing performance in the takeoff roll, and continue to get better all the way up to cruise. The climb prop is of course in between, getting better, then getting worse as speed increases. As to HP and torque, if you are swinging a 2x4 around with your engine, it will take HP and torque to do, but produce no thrust. If you have a feathered prop, it will take lots of HP and torque to swing and still produce no thrust. The efficiency of the prop to produce thrust is what makes the hp and torque meaningful. As a prop increases pitch, it moves more toward a feathered prop in that the angle of lift of the prop is more against torque and less forward producing thrust. Lift of the prop is always about 90 degrees to the blade. A pitch of say 20 degrees means that some of the prop's lift is pulling air in a circle and not just pushing it back. That takes HP. When I flew the C-130, the pitch could be as high as 55 degrees in cruise. More than 1/2 the HP went to spinning the air and less than 1/2 went to thrust. Our props don't get that bad due to our less pitch. But a heavily pitched prop may take the same HP/torque as a finer pitched prop at higher RPM. The faster turning, lower pitched prop will produce more thrust, to a point. That point is determined by the most efficient rpm for the prop compared to mach number, and the most efficient rpm for the engine. Those 2 may not match. A less efficient prop may take more HP or torque to give the same performance, not more. A more efficient prop will give more thrust with the same HP/torque. HP and torque don't tell the whole story. They don't give thrust, except as the prop allows. So I am saying this. The prop that produces the most thrust will be the one that has its best speed closest to your engine's favorite RPM, but does it at the speed you are flying. Also it has to be the most aerodynamically efficient. Max static thrust equals first gear only. Takeoff props equal second gear. Climb props equal third gear. Cruise props are overdrive. Variable props are automatic trannys. That is Mike's point. The actual performance of the plane will be determined by just how much thrust it can produce today on this fuel, at this temp, at this density altitude, with this prop, at this speed, with these sparkplugs, at this rpm and manifold setting..... You can measure all that, or you can just measure thrust. So thrust is really the key, but it has to be measured now, at your speed and with all variables. Static thrust is good for fans, not planes. Thrust is what happens after all the variables are in place. HP and torque are only what you are putting into a prop, not what is coming out, which changes with prop efficiency, speed, air density..... So that is why I wanted a meter that simply measures the thrust output on board at all speeds, altitudes, settings, etc. It will tell you what performance you are getting now, whatever now is. And instead of HP, you can simply measure fuel flow if the engine is tuned right. That is, if the fuel air ratio is the same, fuel in equals power out. That you can compare to whatever you want to change and see if it made things better or worse. 10% more thrust with the same fuel flow is 10% better no matter how you got it. 10% more HP or 10% more torque might just mean a 10% worse prop is giving equal thrust for more gas. Bottom line: Thrust = performance. Fuel flow = energy and $ in to produce the thrust. The best prop will be the one that gives you the most thrust per fuel flow at the speed you want it. A fixed pitch will peak at a given speed with a strong curve. A variable prop will have a broader curve. You have to pick the prop that peaks at the speed and rpm that best matches your engine and most important performance goal. This is critical for fixed pitch, but less critical for variable. Then you can compare one prop against another to see which gives the most thrust at the same fuel flow. Is this too much at once? Hope it can be understood. You want thrust. Thrust moves the plane. We just aren't use to measuring it directly. Fuel flow is what we pay to get it and max fuel flow is how much power is available under present conditions. One day I will simplify this..... Kurt S. S-5 flying and 1/2 done. __________________________________________________ _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ ________________________________ Message 12 ____________________________________ Time: 04:59:32 PM PST US From: Malcolmbru@AOL.COM Subject: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: Malcolmbru@aol.com I have a KF2 finished in 1999 and can find nothing in my records on the brakes. They are hydraulic and look like matko but they have no writing at all on them. They are all aluminum and the peddles look just like the ones in the builders manual as do the axis one caliper is sticking , the rotor gets real hot and the other is leaking rite through the wall. like a poris spot in the aluminum What to do? ________________________________ Message 13 ____________________________________ Time: 05:24:24 PM PST US From: Gill Levesque Subject: RE: Kitfox-List: Kitfox for sale --> Kitfox-List message posted by: Gill Levesque Sorry John ,I forgot that It's a model 4 1050 Gil John Anderson wrote: --> Kitfox-List message posted by: "John Anderson" What model is it Gil? From: Gill Levesque Subject: Kitfox-List: Kitfox for sale --> Kitfox-List message posted by: Gill Levesque Hi All, Due to unforseen circumstances I sadly announce that my beloved Kitfox is for sale! . 100hrs. TTAE, 582 grey head with 3:1 redrive ,no spinner. factory refinished GSC three blade prop(sept/05) Factory custom seat cover,baggage sack and cover,door and windshield post panels, carpet kick panels, nice panel with AS,ALT,VSI,Quad EGT/CHT,slip indicator,2 Tachs,water temp, ELT remote, Garmin 12 GPS, Panel mounted Delcom radio, wing strut cuffs, wing tip strobes,Tinted Lexan all around ! Always hangered! A good looking and great flying ( cruise 95 mph ind. solo!!) plane! Plane is in Southern Ontario Canada $27,500.00 CAN Email me off list for pics and any questions Gil Levesque C-IGVL --------------------------------- All new Yahoo! Mail - --------------------------------- Get a sneak peak at messages with a handy reading pane. _________________________________________________________________ Need more speed? Get Xtra Broadband @ http://jetstream.xtra.co.nz/chm/0,,202853-1000,00.html --------------------------------- Make free worldwide PC-to-PC calls. Try the new Yahoo! Canada Messenger with Voice ________________________________ Message 14 ____________________________________ Time: 05:24:25 PM PST US From: "RAY Gignac" Subject: Re: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: "RAY Gignac" Couple of things to look at: One of the spacers on the calipers could = be binding and needs to be cleaned. As for the leak, O ring in the = caliper could be bad allowing the leak and both problems are an easy = fix. Matco sells the new O rings and new spacers if you are unable to = clean them! Ray ----- Original Message ----- From: Malcolmbru@aol.com To: kitfox-list@matronics.com Sent: Wednesday, May 10, 2006 7:57 PM Subject: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: = Malcolmbru@aol.com I have a KF2 finished in 1999 and can find nothing in my records on = the brakes. They are hydraulic and look like matko but they have no = writing at all on them. They are all aluminum and the peddles look just like the = ones in the builders manual as do the axis one caliper is sticking , the = rotor gets real hot and the other is leaking rite through the wall. like a = poris spot in the aluminum What to do? = = http://www.matronics.com/Navigator?Kitfox-List = = = = http://www.matronics.com/contribution = = ________________________________ Message 15 ____________________________________ Time: 05:26:31 PM PST US From: "Rexster" Subject: Re: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: "Rexster" Those probably are Matco brakes. I changed from Matco to Cleveland and w= as very impressed with the difference. With the Matco brakes, some peopl= e were breaking rudder pedals trying to hold the plane during run-ups. W= ith the Clevelands, rudder pedal forces were greatly reduced. That's my = experience. Rex Phelps/ Michigan -- Malcolmbru@aol.com wrote: --> Kitfox-List message posted by: Malcolmbru@aol.com I have a KF2 finished in 1999 and can find nothing in my records on the= = brakes. They are hydraulic and look like matko but they have no writ= ing at all = on them. They are all aluminum and the peddles look just like the on= es in = the builders manual as do the axis one caliper is sticking , the roto= r = gets real hot and the other is leaking rite through the wall. like a po= ris spot = in the aluminum What to do? = = = = = = = =

Those probably are Matco brakes. I changed from Matco to Clevel= and and was very impressed with the difference. With the Matco brakes, s= ome people were breaking rudder pedals trying to hold the plane during r= un-ups. With the Clevelands, rudder pedal forces were greatly reduced. T= hat's my experience.

Rex Phelps/ Michigan



-- Malcolmbru@aol.com wrote:
--> Kitfox-= List message posted by: Malcolmbru@aol.com

I&= nbsp;have a KF2 finished in 1999 and = can find nothing in my  records on&nb= sp;the 
brakes.   They are hydraulic&nb= sp;and look like  matko  but they&nbs= p;have no writing at all 
on them. = ;  They are all aluminum  and th= e peddles  look just like the ones&nb= sp;in 
the  builders manual as do =  the axis  one caliper is sticking&nb= sp;, the rotor 
gets real hot  and=  the other is leaking rite through th= e wall. like a poris spot 
in &nbs= p;the aluminum  What to do? 





 = ;
 
 



________________________________ Message 16 ____________________________________ Time: 05:30:29 PM PST US From: "RAY Gignac" Subject: Re: Kitfox-List: Tundra tyres. --> Kitfox-List message posted by: "RAY Gignac" I wanted to add my thoughts on the tire issue! I searched high and low = for similar tires like the old slick tires sold by Denney years ago, I = have used turf glide on the old style ATV wheel and on my Matco 6" split = wheel! I decided to go to Air Tacs on my split wheels, and I am glad I = did so much better. Here is my set up: Matco 6" split wheel with 600x6 = air trac tires. Still using the original Matco brakes. Ray Model IV 1200, 912ULS ----- Original Message ----- From: Michel Verheughe To: kitfox-list@matronics.com Sent: Wednesday, May 10, 2006 4:10 PM Subject: Re: Kitfox-List: Tundra tyres. --> Kitfox-List message posted by: Michel Verheughe = > Thank you for your help, guys. Skyflyte, how long have you had those bumps in your tyres? Have you tried to inflate them hard, as Kurt suggests it? Rex, thanks for the "googling" I read all of the links. I will eventually remove the tyres and find out what is the problem. But right now, I have difficulties to understand how a fold in the inner tube can produce what I see. But I am still a very young pilot and I have much to learn. Of course, I'll let everyone informed of my findings, once the tyre = are removed and inspected. Cheers, Michel do not archive = = http://www.matronics.com/Navigator?Kitfox-List = = = = http://www.matronics.com/contribution = = ________________________________ Message 17 ____________________________________ Time: 05:41:23 PM PST US From: "wingsdown" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "wingsdown" Excellent point John. Rick -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of John Anderson Sent: Wednesday, May 10, 2006 4:21 PM Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" --> Or you can turbo charge. This sort of does what a VPP does to a degree in that the RPM doesn't have to alter too much to increase power for t/off. You can set the prop at a courser angle and increase boost for t/off. John A. From: "Randy Daughenbaugh" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "Randy Daughenbaugh" Thanks Kurt! As usual, another great post. Maybe you can shed some light on my following comment. You want to get the rpm's up on takeoff so you can use the power, but you want to have more pitch for more thrust at speed. You can approach this with an in-flight adjustable prop, or you can get close by having a prop that "slips" during take off, letting the engine rev up, but still has enough pitch to make some thrust at speed. I think this is a difference between the skinny blades of the warp drive and wide, high lift blades of the Powerfin. My CFI friend (16,000 hours) was impressed, but not favorably, on how my Powerfin prop was "connected" to the air. Engine rpm was not determined as much by throttle position as by airspeed. In my plane, he was trying to teach me to set rpm to certain number at different points in the approach. This works on his plane with the Warp drive. But with the powerfin, you can pull the power off but unless you slow the plane, the rpm doesn't change. The powerfin does make a great brake. So is "prop slip" part of the formula in getting a prop to best fit torque, and power? Randy .. -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of kurt schrader Sent: Tuesday, May 09, 2006 6:35 PM Subject: Re: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader My flame suite on for another long one..... --------------------------------- >Randy sez: > > >In short, if you want more thrust, all you have to > >do is sacrifice top speed. Therefore, thrust is > >irrelevant. >------------------------- >Mike G. >N728KF >If you want more thrust AND more top speed, you get >an in-flight adjustable prop. You wouldn't drive >your car in one gear all the time, why operate your >airplane that way? ---------------------------- Good point Mike, There is a misunderstanding on the list of thrust, HP and torque. The whole purpose of the prop is to convert power into thrust. Thrust is the most relevant measure. It moves the plane. But we are not talking about static thrust. You need the best thrust at the speed you are flying for best performance. Max static thrust is best at zero speed only. Max takeoff thrust is best somewhere around 1/2 your takeoff speed. Max climb thrust is best at climb speed. Max cruise thrust is best at.... ahhh you get it. A fixed pitch prop will give you its max thrust at only one speed. You are compromising only in that you pick the speed you want to have it perform best at. At all other speeds, faster or slower, it will give less then max thrust. A variable or constant speed prop will still have one best speed, but the curve will be flatter. It will perform almost as well at all speeds as a fixed pitch prop for its one speed. Say a cruise fixed pitch gives efficiencies of: 50% in takeoff 75% in climb 85% in cruise A climb prop might give: 65% in takeoff 85% in climb 80% in cruise The variable prop might give: 75% in takeoff 82% in climb 83% in cruise I have a friend who has a Champ product, his 3rd in 2 years. His 150 HP constant speed Champ would perform equal to his 180 HP fixed pitch Champ, except around one speed. That speed depended upon which fixed pitch prop he installed. He might get better climb, but equal cruise, or better cruise, but equal climb from the extra 30 HP. In his case, he used the prop that meant they cruised equally, but the fixed pitch climbed better with the 30 more HP. If it had a constant speed prop, it would have used the 30 extra HP for better performance all across the speed range. His fixed pitch got off the ground better, but burned more for the same cruise speed. Another way to say it is that the variable prop was almost worth the 30 extra HP. This is my problem with static thrust measurements. It only gives you the measurement for the best prop at no speed. How useful is that? I think that is what Randy was saying. Static thrust is only good when static. It is already losing performance in the takeoff roll, but not so badly as when at cruise speed. A cruise prop would be poor but increasing performance in the takeoff roll, and continue to get better all the way up to cruise. The climb prop is of course in between, getting better, then getting worse as speed increases. As to HP and torque, if you are swinging a 2x4 around with your engine, it will take HP and torque to do, but produce no thrust. If you have a feathered prop, it will take lots of HP and torque to swing and still produce no thrust. The efficiency of the prop to produce thrust is what makes the hp and torque meaningful. As a prop increases pitch, it moves more toward a feathered prop in that the angle of lift of the prop is more against torque and less forward producing thrust. Lift of the prop is always about 90 degrees to the blade. A pitch of say 20 degrees means that some of the prop's lift is pulling air in a circle and not just pushing it back. That takes HP. When I flew the C-130, the pitch could be as high as 55 degrees in cruise. More than 1/2 the HP went to spinning the air and less than 1/2 went to thrust. Our props don't get that bad due to our less pitch. But a heavily pitched prop may take the same HP/torque as a finer pitched prop at higher RPM. The faster turning, lower pitched prop will produce more thrust, to a point. That point is determined by the most efficient rpm for the prop compared to mach number, and the most efficient rpm for the engine. Those 2 may not match. A less efficient prop may take more HP or torque to give the same performance, not more. A more efficient prop will give more thrust with the same HP/torque. HP and torque don't tell the whole story. They don't give thrust, except as the prop allows. So I am saying this. The prop that produces the most thrust will be the one that has its best speed closest to your engine's favorite RPM, but does it at the speed you are flying. Also it has to be the most aerodynamically efficient. Max static thrust equals first gear only. Takeoff props equal second gear. Climb props equal third gear. Cruise props are overdrive. Variable props are automatic trannys. That is Mike's point. The actual performance of the plane will be determined by just how much thrust it can produce today on this fuel, at this temp, at this density altitude, with this prop, at this speed, with these sparkplugs, at this rpm and manifold setting..... You can measure all that, or you can just measure thrust. So thrust is really the key, but it has to be measured now, at your speed and with all variables. Static thrust is good for fans, not planes. Thrust is what happens after all the variables are in place. HP and torque are only what you are putting into a prop, not what is coming out, which changes with prop efficiency, speed, air density..... So that is why I wanted a meter that simply measures the thrust output on board at all speeds, altitudes, settings, etc. It will tell you what performance you are getting now, whatever now is. And instead of HP, you can simply measure fuel flow if the engine is tuned right. That is, if the fuel air ratio is the same, fuel in equals power out. That you can compare to whatever you want to change and see if it made things better or worse. 10% more thrust with the same fuel flow is 10% better no matter how you got it. 10% more HP or 10% more torque might just mean a 10% worse prop is giving equal thrust for more gas. Bottom line: Thrust = performance. Fuel flow = energy and $ in to produce the thrust. The best prop will be the one that gives you the most thrust per fuel flow at the speed you want it. A fixed pitch will peak at a given speed with a strong curve. A variable prop will have a broader curve. You have to pick the prop that peaks at the speed and rpm that best matches your engine and most important performance goal. This is critical for fixed pitch, but less critical for variable. Then you can compare one prop against another to see which gives the most thrust at the same fuel flow. Is this too much at once? Hope it can be understood. You want thrust. Thrust moves the plane. We just aren't use to measuring it directly. Fuel flow is what we pay to get it and max fuel flow is how much power is available under present conditions. One day I will simplify this..... Kurt S. S-5 flying and 1/2 done. __________________________________________________ _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ ________________________________ Message 18 ____________________________________ Time: 07:18:01 PM PST US From: "John Anderson" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" Yes Rick, I'm sure that's why I'm getting such a good result performance wise. John From: "wingsdown" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "wingsdown" Excellent point John. Rick -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of John Anderson Sent: Wednesday, May 10, 2006 4:21 PM Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" --> Or you can turbo charge. This sort of does what a VPP does to a degree in that the RPM doesn't have to alter too much to increase power for t/off. You can set the prop at a courser angle and increase boost for t/off. John A. From: "Randy Daughenbaugh" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "Randy Daughenbaugh" Thanks Kurt! As usual, another great post. Maybe you can shed some light on my following comment. You want to get the rpm's up on takeoff so you can use the power, but you want to have more pitch for more thrust at speed. You can approach this with an in-flight adjustable prop, or you can get close by having a prop that "slips" during take off, letting the engine rev up, but still has enough pitch to make some thrust at speed. I think this is a difference between the skinny blades of the warp drive and wide, high lift blades of the Powerfin. My CFI friend (16,000 hours) was impressed, but not favorably, on how my Powerfin prop was "connected" to the air. Engine rpm was not determined as much by throttle position as by airspeed. In my plane, he was trying to teach me to set rpm to certain number at different points in the approach. This works on his plane with the Warp drive. But with the powerfin, you can pull the power off but unless you slow the plane, the rpm doesn't change. The powerfin does make a great brake. So is "prop slip" part of the formula in getting a prop to best fit torque, and power? Randy .. -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of kurt schrader Sent: Tuesday, May 09, 2006 6:35 PM Subject: Re: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader My flame suite on for another long one..... --------------------------------- >Randy sez: > > >In short, if you want more thrust, all you have to > >do is sacrifice top speed. Therefore, thrust is > >irrelevant. >------------------------- >Mike G. >N728KF >If you want more thrust AND more top speed, you get >an in-flight adjustable prop. You wouldn't drive >your car in one gear all the time, why operate your >airplane that way? ---------------------------- Good point Mike, There is a misunderstanding on the list of thrust, HP and torque. The whole purpose of the prop is to convert power into thrust. Thrust is the most relevant measure. It moves the plane. But we are not talking about static thrust. You need the best thrust at the speed you are flying for best performance. Max static thrust is best at zero speed only. Max takeoff thrust is best somewhere around 1/2 your takeoff speed. Max climb thrust is best at climb speed. Max cruise thrust is best at.... ahhh you get it. A fixed pitch prop will give you its max thrust at only one speed. You are compromising only in that you pick the speed you want to have it perform best at. At all other speeds, faster or slower, it will give less then max thrust. A variable or constant speed prop will still have one best speed, but the curve will be flatter. It will perform almost as well at all speeds as a fixed pitch prop for its one speed. Say a cruise fixed pitch gives efficiencies of: 50% in takeoff 75% in climb 85% in cruise A climb prop might give: 65% in takeoff 85% in climb 80% in cruise The variable prop might give: 75% in takeoff 82% in climb 83% in cruise I have a friend who has a Champ product, his 3rd in 2 years. His 150 HP constant speed Champ would perform equal to his 180 HP fixed pitch Champ, except around one speed. That speed depended upon which fixed pitch prop he installed. He might get better climb, but equal cruise, or better cruise, but equal climb from the extra 30 HP. In his case, he used the prop that meant they cruised equally, but the fixed pitch climbed better with the 30 more HP. If it had a constant speed prop, it would have used the 30 extra HP for better performance all across the speed range. His fixed pitch got off the ground better, but burned more for the same cruise speed. Another way to say it is that the variable prop was almost worth the 30 extra HP. This is my problem with static thrust measurements. It only gives you the measurement for the best prop at no speed. How useful is that? I think that is what Randy was saying. Static thrust is only good when static. It is already losing performance in the takeoff roll, but not so badly as when at cruise speed. A cruise prop would be poor but increasing performance in the takeoff roll, and continue to get better all the way up to cruise. The climb prop is of course in between, getting better, then getting worse as speed increases. As to HP and torque, if you are swinging a 2x4 around with your engine, it will take HP and torque to do, but produce no thrust. If you have a feathered prop, it will take lots of HP and torque to swing and still produce no thrust. The efficiency of the prop to produce thrust is what makes the hp and torque meaningful. As a prop increases pitch, it moves more toward a feathered prop in that the angle of lift of the prop is more against torque and less forward producing thrust. Lift of the prop is always about 90 degrees to the blade. A pitch of say 20 degrees means that some of the prop's lift is pulling air in a circle and not just pushing it back. That takes HP. When I flew the C-130, the pitch could be as high as 55 degrees in cruise. More than 1/2 the HP went to spinning the air and less than 1/2 went to thrust. Our props don't get that bad due to our less pitch. But a heavily pitched prop may take the same HP/torque as a finer pitched prop at higher RPM. The faster turning, lower pitched prop will produce more thrust, to a point. That point is determined by the most efficient rpm for the prop compared to mach number, and the most efficient rpm for the engine. Those 2 may not match. A less efficient prop may take more HP or torque to give the same performance, not more. A more efficient prop will give more thrust with the same HP/torque. HP and torque don't tell the whole story. They don't give thrust, except as the prop allows. So I am saying this. The prop that produces the most thrust will be the one that has its best speed closest to your engine's favorite RPM, but does it at the speed you are flying. Also it has to be the most aerodynamically efficient. Max static thrust equals first gear only. Takeoff props equal second gear. Climb props equal third gear. Cruise props are overdrive. Variable props are automatic trannys. That is Mike's point. The actual performance of the plane will be determined by just how much thrust it can produce today on this fuel, at this temp, at this density altitude, with this prop, at this speed, with these sparkplugs, at this rpm and manifold setting..... You can measure all that, or you can just measure thrust. So thrust is really the key, but it has to be measured now, at your speed and with all variables. Static thrust is good for fans, not planes. Thrust is what happens after all the variables are in place. HP and torque are only what you are putting into a prop, not what is coming out, which changes with prop efficiency, speed, air density..... So that is why I wanted a meter that simply measures the thrust output on board at all speeds, altitudes, settings, etc. It will tell you what performance you are getting now, whatever now is. And instead of HP, you can simply measure fuel flow if the engine is tuned right. That is, if the fuel air ratio is the same, fuel in equals power out. That you can compare to whatever you want to change and see if it made things better or worse. 10% more thrust with the same fuel flow is 10% better no matter how you got it. 10% more HP or 10% more torque might just mean a 10% worse prop is giving equal thrust for more gas. Bottom line: Thrust = performance. Fuel flow = energy and $ in to produce the thrust. The best prop will be the one that gives you the most thrust per fuel flow at the speed you want it. A fixed pitch will peak at a given speed with a strong curve. A variable prop will have a broader curve. You have to pick the prop that peaks at the speed and rpm that best matches your engine and most important performance goal. This is critical for fixed pitch, but less critical for variable. Then you can compare one prop against another to see which gives the most thrust at the same fuel flow. Is this too much at once? Hope it can be understood. You want thrust. Thrust moves the plane. We just aren't use to measuring it directly. Fuel flow is what we pay to get it and max fuel flow is how much power is available under present conditions. One day I will simplify this..... Kurt S. S-5 flying and 1/2 done. __________________________________________________ _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ _________________________________________________________________ Discover fun and games at @ http://xtramsn.co.nz/kids ________________________________ Message 19 ____________________________________ Time: 07:25:07 PM PST US From: "John Anderson" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" And re stippage mentioned below, I have the skinny blades on my w/drive and when the throttle is closed the RPM dropps off quite quickly and not a lot of braking effect. But thrust wise it seems very good. John A. From: "wingsdown" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "wingsdown" Excellent point John. Rick -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of John Anderson Sent: Wednesday, May 10, 2006 4:21 PM Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" --> Or you can turbo charge. This sort of does what a VPP does to a degree in that the RPM doesn't have to alter too much to increase power for t/off. You can set the prop at a courser angle and increase boost for t/off. John A. From: "Randy Daughenbaugh" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "Randy Daughenbaugh" Thanks Kurt! As usual, another great post. Maybe you can shed some light on my following comment. You want to get the rpm's up on takeoff so you can use the power, but you want to have more pitch for more thrust at speed. You can approach this with an in-flight adjustable prop, or you can get close by having a prop that "slips" during take off, letting the engine rev up, but still has enough pitch to make some thrust at speed. I think this is a difference between the skinny blades of the warp drive and wide, high lift blades of the Powerfin. My CFI friend (16,000 hours) was impressed, but not favorably, on how my Powerfin prop was "connected" to the air. Engine rpm was not determined as much by throttle position as by airspeed. In my plane, he was trying to teach me to set rpm to certain number at different points in the approach. This works on his plane with the Warp drive. But with the powerfin, you can pull the power off but unless you slow the plane, the rpm doesn't change. The powerfin does make a great brake. So is "prop slip" part of the formula in getting a prop to best fit torque, and power? Randy .. -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of kurt schrader Sent: Tuesday, May 09, 2006 6:35 PM Subject: Re: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader My flame suite on for another long one..... --------------------------------- >Randy sez: > > >In short, if you want more thrust, all you have to > >do is sacrifice top speed. Therefore, thrust is > >irrelevant. >------------------------- >Mike G. >N728KF >If you want more thrust AND more top speed, you get >an in-flight adjustable prop. You wouldn't drive >your car in one gear all the time, why operate your >airplane that way? ---------------------------- Good point Mike, There is a misunderstanding on the list of thrust, HP and torque. The whole purpose of the prop is to convert power into thrust. Thrust is the most relevant measure. It moves the plane. But we are not talking about static thrust. You need the best thrust at the speed you are flying for best performance. Max static thrust is best at zero speed only. Max takeoff thrust is best somewhere around 1/2 your takeoff speed. Max climb thrust is best at climb speed. Max cruise thrust is best at.... ahhh you get it. A fixed pitch prop will give you its max thrust at only one speed. You are compromising only in that you pick the speed you want to have it perform best at. At all other speeds, faster or slower, it will give less then max thrust. A variable or constant speed prop will still have one best speed, but the curve will be flatter. It will perform almost as well at all speeds as a fixed pitch prop for its one speed. Say a cruise fixed pitch gives efficiencies of: 50% in takeoff 75% in climb 85% in cruise A climb prop might give: 65% in takeoff 85% in climb 80% in cruise The variable prop might give: 75% in takeoff 82% in climb 83% in cruise I have a friend who has a Champ product, his 3rd in 2 years. His 150 HP constant speed Champ would perform equal to his 180 HP fixed pitch Champ, except around one speed. That speed depended upon which fixed pitch prop he installed. He might get better climb, but equal cruise, or better cruise, but equal climb from the extra 30 HP. In his case, he used the prop that meant they cruised equally, but the fixed pitch climbed better with the 30 more HP. If it had a constant speed prop, it would have used the 30 extra HP for better performance all across the speed range. His fixed pitch got off the ground better, but burned more for the same cruise speed. Another way to say it is that the variable prop was almost worth the 30 extra HP. This is my problem with static thrust measurements. It only gives you the measurement for the best prop at no speed. How useful is that? I think that is what Randy was saying. Static thrust is only good when static. It is already losing performance in the takeoff roll, but not so badly as when at cruise speed. A cruise prop would be poor but increasing performance in the takeoff roll, and continue to get better all the way up to cruise. The climb prop is of course in between, getting better, then getting worse as speed increases. As to HP and torque, if you are swinging a 2x4 around with your engine, it will take HP and torque to do, but produce no thrust. If you have a feathered prop, it will take lots of HP and torque to swing and still produce no thrust. The efficiency of the prop to produce thrust is what makes the hp and torque meaningful. As a prop increases pitch, it moves more toward a feathered prop in that the angle of lift of the prop is more against torque and less forward producing thrust. Lift of the prop is always about 90 degrees to the blade. A pitch of say 20 degrees means that some of the prop's lift is pulling air in a circle and not just pushing it back. That takes HP. When I flew the C-130, the pitch could be as high as 55 degrees in cruise. More than 1/2 the HP went to spinning the air and less than 1/2 went to thrust. Our props don't get that bad due to our less pitch. But a heavily pitched prop may take the same HP/torque as a finer pitched prop at higher RPM. The faster turning, lower pitched prop will produce more thrust, to a point. That point is determined by the most efficient rpm for the prop compared to mach number, and the most efficient rpm for the engine. Those 2 may not match. A less efficient prop may take more HP or torque to give the same performance, not more. A more efficient prop will give more thrust with the same HP/torque. HP and torque don't tell the whole story. They don't give thrust, except as the prop allows. So I am saying this. The prop that produces the most thrust will be the one that has its best speed closest to your engine's favorite RPM, but does it at the speed you are flying. Also it has to be the most aerodynamically efficient. Max static thrust equals first gear only. Takeoff props equal second gear. Climb props equal third gear. Cruise props are overdrive. Variable props are automatic trannys. That is Mike's point. The actual performance of the plane will be determined by just how much thrust it can produce today on this fuel, at this temp, at this density altitude, with this prop, at this speed, with these sparkplugs, at this rpm and manifold setting..... You can measure all that, or you can just measure thrust. So thrust is really the key, but it has to be measured now, at your speed and with all variables. Static thrust is good for fans, not planes. Thrust is what happens after all the variables are in place. HP and torque are only what you are putting into a prop, not what is coming out, which changes with prop efficiency, speed, air density..... So that is why I wanted a meter that simply measures the thrust output on board at all speeds, altitudes, settings, etc. It will tell you what performance you are getting now, whatever now is. And instead of HP, you can simply measure fuel flow if the engine is tuned right. That is, if the fuel air ratio is the same, fuel in equals power out. That you can compare to whatever you want to change and see if it made things better or worse. 10% more thrust with the same fuel flow is 10% better no matter how you got it. 10% more HP or 10% more torque might just mean a 10% worse prop is giving equal thrust for more gas. Bottom line: Thrust = performance. Fuel flow = energy and $ in to produce the thrust. The best prop will be the one that gives you the most thrust per fuel flow at the speed you want it. A fixed pitch will peak at a given speed with a strong curve. A variable prop will have a broader curve. You have to pick the prop that peaks at the speed and rpm that best matches your engine and most important performance goal. This is critical for fixed pitch, but less critical for variable. Then you can compare one prop against another to see which gives the most thrust at the same fuel flow. Is this too much at once? Hope it can be understood. You want thrust. Thrust moves the plane. We just aren't use to measuring it directly. Fuel flow is what we pay to get it and max fuel flow is how much power is available under present conditions. One day I will simplify this..... Kurt S. S-5 flying and 1/2 done. __________________________________________________ _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ _________________________________________________________________ Need more speed? Get Xtra Broadband @ http://jetstream.xtra.co.nz/chm/0,,202853-1000,00.html ________________________________ Message 20 ____________________________________ Time: 07:44:23 PM PST US From: "wingsdown" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "wingsdown" If anyone else has the CAP 140, get some altitude pull power reverse pitch , apply power. If you have never been forced to lean forward in flight it's a trip...watch you air speed, it bleeds off quick. Also great for that unexpected down wind short field landing. Don't know how I know that. You can do some pretty fast base to finals and put her on the numbers, takes some nerve though, the pitch doesn't return that fast should you need forward power. I use to love to back up from the fuel pumps, the looks you get are just amazing. Rick -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of John Anderson Sent: Wednesday, May 10, 2006 7:15 PM Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" --> Yes Rick, I'm sure that's why I'm getting such a good result performance wise. John From: "wingsdown" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "wingsdown" Excellent point John. Rick -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of John Anderson Sent: Wednesday, May 10, 2006 4:21 PM Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "John Anderson" --> Or you can turbo charge. This sort of does what a VPP does to a degree in that the RPM doesn't have to alter too much to increase power for t/off. You can set the prop at a courser angle and increase boost for t/off. John A. From: "Randy Daughenbaugh" Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: "Randy Daughenbaugh" Thanks Kurt! As usual, another great post. Maybe you can shed some light on my following comment. You want to get the rpm's up on takeoff so you can use the power, but you want to have more pitch for more thrust at speed. You can approach this with an in-flight adjustable prop, or you can get close by having a prop that "slips" during take off, letting the engine rev up, but still has enough pitch to make some thrust at speed. I think this is a difference between the skinny blades of the warp drive and wide, high lift blades of the Powerfin. My CFI friend (16,000 hours) was impressed, but not favorably, on how my Powerfin prop was "connected" to the air. Engine rpm was not determined as much by throttle position as by airspeed. In my plane, he was trying to teach me to set rpm to certain number at different points in the approach. This works on his plane with the Warp drive. But with the powerfin, you can pull the power off but unless you slow the plane, the rpm doesn't change. The powerfin does make a great brake. So is "prop slip" part of the formula in getting a prop to best fit torque, and power? Randy .. -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of kurt schrader Sent: Tuesday, May 09, 2006 6:35 PM Subject: Re: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader My flame suite on for another long one..... --------------------------------- >Randy sez: > > >In short, if you want more thrust, all you have to > >do is sacrifice top speed. Therefore, thrust is > >irrelevant. >------------------------- >Mike G. >N728KF >If you want more thrust AND more top speed, you get >an in-flight adjustable prop. You wouldn't drive >your car in one gear all the time, why operate your >airplane that way? ---------------------------- Good point Mike, There is a misunderstanding on the list of thrust, HP and torque. The whole purpose of the prop is to convert power into thrust. Thrust is the most relevant measure. It moves the plane. But we are not talking about static thrust. You need the best thrust at the speed you are flying for best performance. Max static thrust is best at zero speed only. Max takeoff thrust is best somewhere around 1/2 your takeoff speed. Max climb thrust is best at climb speed. Max cruise thrust is best at.... ahhh you get it. A fixed pitch prop will give you its max thrust at only one speed. You are compromising only in that you pick the speed you want to have it perform best at. At all other speeds, faster or slower, it will give less then max thrust. A variable or constant speed prop will still have one best speed, but the curve will be flatter. It will perform almost as well at all speeds as a fixed pitch prop for its one speed. Say a cruise fixed pitch gives efficiencies of: 50% in takeoff 75% in climb 85% in cruise A climb prop might give: 65% in takeoff 85% in climb 80% in cruise The variable prop might give: 75% in takeoff 82% in climb 83% in cruise I have a friend who has a Champ product, his 3rd in 2 years. His 150 HP constant speed Champ would perform equal to his 180 HP fixed pitch Champ, except around one speed. That speed depended upon which fixed pitch prop he installed. He might get better climb, but equal cruise, or better cruise, but equal climb from the extra 30 HP. In his case, he used the prop that meant they cruised equally, but the fixed pitch climbed better with the 30 more HP. If it had a constant speed prop, it would have used the 30 extra HP for better performance all across the speed range. His fixed pitch got off the ground better, but burned more for the same cruise speed. Another way to say it is that the variable prop was almost worth the 30 extra HP. This is my problem with static thrust measurements. It only gives you the measurement for the best prop at no speed. How useful is that? I think that is what Randy was saying. Static thrust is only good when static. It is already losing performance in the takeoff roll, but not so badly as when at cruise speed. A cruise prop would be poor but increasing performance in the takeoff roll, and continue to get better all the way up to cruise. The climb prop is of course in between, getting better, then getting worse as speed increases. As to HP and torque, if you are swinging a 2x4 around with your engine, it will take HP and torque to do, but produce no thrust. If you have a feathered prop, it will take lots of HP and torque to swing and still produce no thrust. The efficiency of the prop to produce thrust is what makes the hp and torque meaningful. As a prop increases pitch, it moves more toward a feathered prop in that the angle of lift of the prop is more against torque and less forward producing thrust. Lift of the prop is always about 90 degrees to the blade. A pitch of say 20 degrees means that some of the prop's lift is pulling air in a circle and not just pushing it back. That takes HP. When I flew the C-130, the pitch could be as high as 55 degrees in cruise. More than 1/2 the HP went to spinning the air and less than 1/2 went to thrust. Our props don't get that bad due to our less pitch. But a heavily pitched prop may take the same HP/torque as a finer pitched prop at higher RPM. The faster turning, lower pitched prop will produce more thrust, to a point. That point is determined by the most efficient rpm for the prop compared to mach number, and the most efficient rpm for the engine. Those 2 may not match. A less efficient prop may take more HP or torque to give the same performance, not more. A more efficient prop will give more thrust with the same HP/torque. HP and torque don't tell the whole story. They don't give thrust, except as the prop allows. So I am saying this. The prop that produces the most thrust will be the one that has its best speed closest to your engine's favorite RPM, but does it at the speed you are flying. Also it has to be the most aerodynamically efficient. Max static thrust equals first gear only. Takeoff props equal second gear. Climb props equal third gear. Cruise props are overdrive. Variable props are automatic trannys. That is Mike's point. The actual performance of the plane will be determined by just how much thrust it can produce today on this fuel, at this temp, at this density altitude, with this prop, at this speed, with these sparkplugs, at this rpm and manifold setting..... You can measure all that, or you can just measure thrust. So thrust is really the key, but it has to be measured now, at your speed and with all variables. Static thrust is good for fans, not planes. Thrust is what happens after all the variables are in place. HP and torque are only what you are putting into a prop, not what is coming out, which changes with prop efficiency, speed, air density..... So that is why I wanted a meter that simply measures the thrust output on board at all speeds, altitudes, settings, etc. It will tell you what performance you are getting now, whatever now is. And instead of HP, you can simply measure fuel flow if the engine is tuned right. That is, if the fuel air ratio is the same, fuel in equals power out. That you can compare to whatever you want to change and see if it made things better or worse. 10% more thrust with the same fuel flow is 10% better no matter how you got it. 10% more HP or 10% more torque might just mean a 10% worse prop is giving equal thrust for more gas. Bottom line: Thrust = performance. Fuel flow = energy and $ in to produce the thrust. The best prop will be the one that gives you the most thrust per fuel flow at the speed you want it. A fixed pitch will peak at a given speed with a strong curve. A variable prop will have a broader curve. You have to pick the prop that peaks at the speed and rpm that best matches your engine and most important performance goal. This is critical for fixed pitch, but less critical for variable. Then you can compare one prop against another to see which gives the most thrust at the same fuel flow. Is this too much at once? Hope it can be understood. You want thrust. Thrust moves the plane. We just aren't use to measuring it directly. Fuel flow is what we pay to get it and max fuel flow is how much power is available under present conditions. One day I will simplify this..... Kurt S. S-5 flying and 1/2 done. __________________________________________________ _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ _________________________________________________________________ Discover fun and games at @ http://xtramsn.co.nz/kids ________________________________ Message 21 ____________________________________ Time: 08:06:44 PM PST US From: Mike Ford Subject: Re: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: Mike Ford How many other people out there have Cleveland brakes? Do you like them? I have just recently broken the left control arm off of my model 4's rudder pedal. About two weeks before that, I was attempting to fix a small weep at the caliper (weeping at the fitting). After I got the pedals bled, I'd test them out. I've always had a hard time breaking the tail wheel free when spinning to the right. I would also have a hard time getting the plane to go straight after a successful spin to the left (which is why I looked into the brake fluid weep in the first place) When testing the brakes, I'd use them in a heavy manner trying to get them to hold enough to spin the plane, but I ended up fatiguing the rudder pedal assembly instead. I've tried to the weep about 7 times, even took it to an A&P, but all the fussing has ended up making the leak worse. I would now be happy with the leak I had before trouble shooting. I'm currently having my pedals fixed and reinforced. Are Cleveland brakes a world of difference? I've also read up on the brake it procedure for the Matco brakes. I have not tried it yet. I was told that they look to be worn in correctly. Mike Ford M4 speedster 912 Rexster wrote: --> Kitfox-List message posted by: "Rexster" Those probably are Matco brakes. I changed from Matco to Cleveland and w= as very impressed with the difference. With the Matco brakes, some peopl= e were breaking rudder pedals trying to hold the plane during run-ups. W= ith the Clevelands, rudder pedal forces were greatly reduced. That's my = experience. Rex Phelps/ Michigan -- Malcolmbru@aol.com wrote: --> Kitfox-List message posted by: Malcolmbru@aol.com I have a KF2 finished in 1999 and can find nothing in my records on the= = brakes. They are hydraulic and look like matko but they have no writ= ing at all = on them. They are all aluminum and the peddles look just like the on= es in = the builders manual as do the axis one caliper is sticking , the roto= r = gets real hot and the other is leaking rite through the wall. like a po= ris spot = in the aluminum What to do? = --------------------------------- Yahoo! Mail goes everywhere you do. Get it on your phone. ________________________________ Message 22 ____________________________________ Time: 08:25:40 PM PST US From: Guy Buchanan Subject: Re: Kitfox-List: Bing 54 Choke adjustment --> Kitfox-List message posted by: Guy Buchanan At 07:12 AM 5/7/2006, you wrote: > Now would someone tell me the proper way to adjust the cables on the >new chokes? I adjusted mine so there was some play in the cable housing at the carb. In other words: I pulled the black boot at the carb end of the choke cable well up the cable. I installed the entire choke system. I then backed out the adjuster until there was about .03" vertical play in the cable housing at the carb. I then tightened the adjusting nut and checked the play again. I then pulled the boot down over the adjusting nut and tie wrapped the top and bottom of the boot so the cable housing couldn't pull up. Guy Buchanan K-IV 1200 / 582 / 99.9% done, thanks mostly to Bob Ducar. ________________________________ Message 23 ____________________________________ Time: 08:43:43 PM PST US From: kurt schrader Subject: Re: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: kurt schrader Hi Mike, If you read any airplane for sale papers, they always proudly say they have Clevelands when they do. It is a selling point because they work and the Matco's are paper weights in comparison. Nothing is cheap, but replacing the brakes might keep you from bending the plane in the future. Mine work and hold the plane on runup with maybe 35% of the force I could put on them. That is with a 140 HP engine, but run up at about 40% power. I have run it up harder, but I'd worry about nosing over with 100% power before the brakes would slide. It doesn't seem to need any more brake force, even at higher power. kurt S. S-5/NSI turbo --- Mike Ford wrote: .............. > Are Cleveland brakes a world of difference? > > Mike Ford > M4 speedster 912 __________________________________________________ ________________________________ Message 24 ____________________________________ Time: 08:46:54 PM PST US From: kurt schrader Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader Not me Rick ;-) I know Lance did this with another, bigger plane and had it down at something like 165 degrees and full reverse! It works, but frankly, I am a chicken. :-( Maybe in a few more years and 100's more Fox hours.... kurt S. --- wingsdown wrote: > If anyone else has the CAP 140, get some altitude > pull power reverse > pitch , apply power. If you have never been forced > to lean forward in > flight it's a trip...watch you air speed, it bleeds > off quick. Also > great for that unexpected down wind short field > landing. Don't know how > I know that. You can do some pretty fast base to > finals and put her on > the numbers, takes some nerve though, the pitch > doesn't return that fast > should you need forward power. I use to love to > back up from the fuel > pumps, the looks you get are just amazing. > > Rick __________________________________________________ ________________________________ Message 25 ____________________________________ Time: 09:07:55 PM PST US From: "Lowell Fitt" Subject: Re: Kitfox-List: Hydraulic brakes --> Kitfox-List message posted by: "Lowell Fitt" Mike, this is from the old days, but one oldtimer I respected quite a bit when he was on the list cautioned about too much braking on a tail dragger. I have the matcos and yes it takes a bit of pressure to hold the airplane during run-up, but I can easily lift the tail wheel with heavy breaking on landing. The rudder pedal failures were an issue and the reinforcement was ADd several years ago. As to the assymetry in braking, obviously that needs addressing. Lowell ----- Original Message ----- From: "Mike Ford" Sent: Wednesday, May 10, 2006 8:04 PM Subject: Re: Kitfox-List: Hydraulic brakes > --> Kitfox-List message posted by: Mike Ford > > How many other people out there have Cleveland brakes? Do you like them? > I have just recently broken the left control arm off of my model 4's > rudder pedal. > > About two weeks before that, I was attempting to fix a small weep at the > caliper (weeping at the fitting). After I got the pedals bled, I'd test > them out. I've always had a hard time breaking the tail wheel free when > spinning to the right. I would also have a hard time getting the plane to > go straight after a successful spin to the left (which is why I looked > into the brake fluid weep in the first place) > > When testing the brakes, I'd use them in a heavy manner trying to get them > to hold enough to spin the plane, but I ended up fatiguing the rudder > pedal assembly instead. > > I've tried to the weep about 7 times, even took it to an A&P, but all the > fussing has ended up making the leak worse. I would now be happy with the > leak I had before trouble shooting. > > I'm currently having my pedals fixed and reinforced. > > Are Cleveland brakes a world of difference? > > I've also read up on the brake it procedure for the Matco brakes. I have > not tried it yet. I was told that they look to be worn in correctly. > > > Mike Ford > M4 speedster 912 > > > Rexster wrote: --> Kitfox-List message posted by: > "Rexster" > > Those probably are Matco brakes. I changed from Matco to Cleveland and w= > as very impressed with the difference. With the Matco brakes, some peopl= > e were breaking rudder pedals trying to hold the plane during run-ups. W= > ith the Clevelands, rudder pedal forces were greatly reduced. That's my = > experience. > Rex Phelps/ Michigan > > > -- Malcolmbru@aol.com wrote: > --> Kitfox-List message posted by: Malcolmbru@aol.com > > I have a KF2 finished in 1999 and can find nothing in my records on the= > = > > brakes. They are hydraulic and look like matko but they have no writ= > ing at all = > > on them. They are all aluminum and the peddles look just like the on= > es in = > > the builders manual as do the axis one caliper is sticking , the roto= > r = > > gets real hot and the other is leaking rite through the wall. like a po= > ris spot = > > in the aluminum What to do? = > > > --------------------------------- > Yahoo! Mail goes everywhere you do. Get it on your phone. > > > ________________________________ Message 26 ____________________________________ Time: 10:14:44 PM PST US From: kurt schrader Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader You guys are too fast for me to get back to you... Simple becomes complex, or is it just me lately? You are right. I don't have time to shorten this! Yes, there is a lot more to prop selection. The number of blades and cord of the blade add up to what is called solidity. I don't remember all of the prop facts without researching it again, but here are a few things: The prop is thought of as a screw and the plane of rotation the prop disk. So if the screw were to fill just one full revolution with one blade, it would be 100% solid. That is, no space you could poke 90 degrees thru the disk without hitting blade. A wide cord blade fills more of the disk than a narrow cord. Two blades more than one, three more than two, etc. More solidity generally = less slip. Slip is greater at low speeds. The "perfect" prop would theoritically have one (1) infinately long and infinately thin blade with a counter weight. Very little solidity, but what an aspect ratio! Spin this as slow as possible to just barely create thrust and that is as close to 100% efficient as you can get. No tip losses or friction to measure, etc. Forget ground clearance and gearing down friction losses though! ;-) There have been very few one blade props! Tried? Yes, but very few. None infinate.... There have been a few 3 blade props that outperformed the 2 blade props they replaced, but I would fault the 2 bladed for not being as efficient as it could have been. Other considerations are ground clearance requires more solidity to absorbe the HP without more length. Wider blades and more blades absorbe more HP when length is restricted. If you add HP, you probably will need more solidity by adding another blade, or at least wider blades. Engine vibration may favor 3 blades. Even numbers are better structurally, but odd are better for vibration absorbtion. Quiet operation comes from more blades going slower. Efficiency comes from running the tips around mach .80 or so, depending on the airfoil and tip design. A slanted tip like a swept back wing, seems to help. The faster the tips can go without creating a lot of drag, the closer the rest of the blade comes to its best speed. The more leading edges you have, the more air to divide and the more shockwave drag. Thus fewer blades win here. Longer blades blow more air around and outside of the plane. The plane fills less of the slipstream, so it slows less of it down. Extending the prop even a few inches away from the cowl reduces drag measurably. See how LoPresti opens up the airflow behind the prop and around the cowl on all his mods. Direct drive higher rpm engines require shorter blades to avoid tips reaching mach one, which cause a lot of drag and noise. But shorter blades are less efficient. Noise = waste. There is a direct relationship here. Check your kids stereo. Watts for decibels. Bell Helicopter actually figured how much HP it took to do Wap Wap... Then they changed the tips. Noise does not = thrust or lift. Twist, airfoil shape, taper, tip shape, flex, material (wood, metal, composit, combinations) Props aren't as simple as they look and only good testing will provide a good design or comparison between designs. It is still quite a bit of art since there are so many factors to compromise on. So where does this actually get us? When I lived in KY, I had a hill to climb up to the runway almost right out of the hangar. One day I was on that hill and trying to get it going because I was about to stop. I added pitch, then power and rolled backwards down the hill. More power = less thrust? I had stalled the prop! I was just slinging air. More RPM and less pitch and it clawed right up the hill as it should. In this case slip was a real bad deal. I was surprised at how much power I had put in it (stalled) and it felt like nothing. It seemed like at full power I could have pushed the plane backwards by hand. WOW! I learned from that. RPM, then pitch. Note: That is with narrow cord Warp blades. Those little racers that are trying to get as much as possible out of the same size little engine use props that are way over-pitched for takeoff. I was told they were stalled at the beginning of the roll, but now I don't know. Isn't someone here a racer who can tell us? Maybe they are still light enough to get going stalled then the prop grabs when it unstalls on the roll. So Randy, a little bit backwards. You should get less slip with less pitch and more RPM on the same prop, stalled or not but certainly a lot of slip stalled. You are slipping more at higher pitch and low rpm. But you're correct with the solitity of the blades, I think. Wider cord or more blades will work better slow, and narrow blades will grip better at speed, or at least waste less. There is a lot of slip at low speed and solidity will help here. Going fast though, the high aspect ratio thin blades win. Whew.... Kurt S. __________________________________________________ ________________________________ Message 27 ____________________________________ Time: 10:24:05 PM PST US From: kurt schrader Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader I am still trying to find the best pitch for my CAP prop for landing. Too little and go-around is just a noisy landing. Too much and the rpm decreases with speed until the engine is near dead on rollout. A touch of throttle to keep RPM up and I float forever. The difference in pitch is still hard to find for me. I need to find a measure to make it simple. This is where the fixed pitch prop is easier, unless I had a constant speed prop. ;-) I don't have the pitch meter, but wish I had something for consistancy. Any experienced CAP drivers have a solution? Kurt S. S-5/NSI turbo + CAP --- John Anderson wrote: > And re slippage mentioned below, I have the skinny > blades on my w/drive and > when the throttle is closed the RPM dropps off quite > quickly and not a lot > of braking effect. But thrust wise it seems very > good. John A. __________________________________________________ ________________________________ Message 28 ____________________________________ Time: 11:06:23 PM PST US From: kurt schrader Subject: RE: Kitfox-List: Re: Thrust - Over Rated --> Kitfox-List message posted by: kurt schrader Sounds like it is right in there John. My goal is 100 knots cruise at less than 6 gph. Not as slippery as the IV's and earlier, but comfortable to sit in. Right now I am more comfortable at 85 knots (97 mph for those who use it) and 5 gph. I need more drag reduction devices, but I decided to test each as I add them to see what really does what. So my plane started out a drag bucket and is improving with each add on, so far. My top speed used to be 95 knots and you could feel it fight! Another problem is that my engine goes lean, even at full rich, around the 4000 rpm area. No problem higher or lower, but I don't like the EGT's from 3600 to 4300. I cruise at 3200 rpm and it is quiet. :-) Kurt S. --- John Anderson wrote: > Early days on fuel flow but seems to be around 15 > litres per hour and I > don't have a flow meter. 4500 on t/o, more there if > I want with prop setting > but that's what I use, climb 1200fpm. 97kts at 4300. > Just me in it tho at this early stage. John __________________________________________________ ________________________________ Message 29 ____________________________________ Time: 11:16:49 PM PST US From: kurt schrader Subject: Re: Kitfox-List: Thrust...Overrated? --> Kitfox-List message posted by: kurt schrader Hi Clem, I would really like to see more prop testing on our planes too. There are a lot of considerations with the different engines and Fox models, but we have so many opportunities. What engine is he running the wood prop on the Rans? Maybe someone with the same engine here would benefit. Generally speaking, the 2 blade should be the best compromise. Someone who really knows what they are doing with prop aerodynamics would probably make the best blades out of composit, due to the ability to form it better. Kurt S. __________________________________________________