Europa-List Digest Archive

Fri 03/20/09


Total Messages Posted: 11



Today's Message Index:
----------------------
 
     1. 01:40 AM - =?ISO-8859-1?Q?Re=3A_Europa-List=3A_Woodcomp_Propellers? (Carl Pattinson)
     2. 02:59 AM - Electric VP Prop Reliablity (Mark Burton)
     3. 04:00 AM - Re: Woodcomp Propellers (stephan@scassel.se)
     4. 04:49 AM - Re: Constant Speed Prop and failure modes. (nwcmc@tiscali.co.uk)
     5. 06:05 AM - Re: Electric VP Prop Reliablity (Mark Burton)
     6. 09:39 AM - Re: Constant Speed Props, etc. (ALAN YERLY)
     7. 11:58 AM - Re: Constant Speed Props, etc. (Karl Heindl)
     8. 02:07 PM - Re: Constant Speed Props, etc. (Paul McAllister)
     9. 06:18 PM - Re: Constant Speed Props, etc. (Fred Klein)
    10. 10:30 PM - Re: Constant Speed Props, etc. (ALAN YERLY)
    11. 10:56 PM - Re: Constant Speed Props, etc. (ALAN YERLY)
 
 
 


Message 1


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    Time: 01:40:22 AM PST US
    From: "Carl Pattinson" <carl@flyers.freeserve.co.uk>
    Subject: =?ISO-8859-1?Q?Re=3A_Europa-List=3A_Woodcomp_Propellers?
    X-mailer: iAVMailScanner 1.5.6.4 My Woodcomp propeller (the one I need to modify) is William Mills old one (it was not fitted to his aircraft at the time of his accident). It is about three years old and was probably one of the first to be fitted in the UK. For the avoidance of doubt these propellers are definitely fitted with an end stop mechanism. If you look at the photo there is a machined groove to the right of the bronze coloured cog. There is an M6 bolt through the front of the hub which locates in the groove limiting the blade travel. The problem is that this prop has the facility for reverse thrust so the end stop is of no use if the motor takes the blade beyond fine pitch. Thats why I need to get it modified. I assume that your propeller Jos will have been the same. To say that there is no mechanical stop is untrue. The majority of Woodcomp propellers have a shorter groove which limits the travel between coarse and fine (or fine and feathered if it is the feathering variety). Anyone with a "normal" Woodcomp prop has nothing to worry about in this respect. If a motor burns out you have to question whether it was protected properly with the correct rating fuse. If the motor is subjected to extreme demands it will draw more current and blow the fuse before the windings failed. Were such a failure occurr with the normal mechanical stop arrangement the propeller would still be in the normal range, continue to produce thrust and the aircraft should be flyable. Knowing what I know now I would still buy the Woodcomp propeller again but I would not fit a propeller (of any make) that didnt have mechanical end stops. Variable pitch propellers carry additional risks (compared to fixed). So does flying!!! All you can do is try and minimise them. The moral is dont fly with a prop that can go into reverse - it isnt worth the doubtful advantages. Carl Pattinson G-LABS _______________________________________ No viruses found in this outgoing message Scanned by iolo AntiVirus 1.5.6.4 http://www.iolo.com


    Message 2


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    Time: 02:59:51 AM PST US
    Subject: Electric VP Prop Reliablity
    From: "Mark Burton" <markb@ordern.com>
    Folks, What follows is a general comment and is not related to any specific failure of an electric VP prop system. Jos is right to question the quality of the electrics (motor/switches/diodes/wiring, etc.) on the Woodcomp SR3000. However, in my opinion, the SR3000 is not substantially different in quality compared to the other low-cost electric VP props. In fact, I would rate another low-cost prop as having a far worse reliability record than the SR3000 (motor burnouts, intermittent operation, etc.) I also have experience of yet another manufacturer's products that have exhibited electrical failures. So although Woodcomp could almost certainly do better, they are not alone in this regard. This potential for failure of the propeller system must be acknowledged by the pilot and they should be mentally prepared for that eventuality. So, whatever brand of VP prop you have (cheap or expensive), be prepared for it to stop functioning at any time. To reduce the chance of that happening, inspect the prop/hub/wiring regularly. Ensure that the brushes are in good condition (slip rings clean) and that the pitch change mechanism operates freely (but not with excessive backlash) throughout the normal pitch range. Most importantly, check that the range of pitch movement is such that the aircraft can still fly with the pitch stuck at any position in that range. With regard to hard pitch stops that come into effect if a switch fails, it would be sensible to actually test that the fine pitch hard stop is in a position that will help save your hide. I suggest that having determined the correct position of the electrical switch, measure the static RPM with the pitch on the limit and then (carefully) override the switch and move the pitch to the hard limit (use a low voltage perhaps to move the pitch slowly to the stop?) You then run the engine again and compare the static RPM with the static RPM you achieved with the pitch on the electrical limit. You can decide on what is an acceptable rise in RPM. Probably, not much given that the electrical limit was likely to be set close to the finest position acceptable for safe operation. Finally, make sure that the pilot (you) fully understands how the pitch is controlled (controller modes, manual operation, etc.) and what the appropriate controller settings are for the various flight scenarios. As part of the pre-flight self-briefing before every flight, acknowledge the fact that the pitch may freeze just as you acknowledge the fact that the donkey may quit at any time. Regards, Mark Read this topic online here: http://forums.matronics.com/viewtopic.php?p=235337#235337


    Message 3


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    Time: 04:00:43 AM PST US
    Subject: Re: Woodcomp Propellers
    From: stephan@scassel.se
    Hi I have read the thread with great interest and I think I need to add some facts. Some already stated by Jos and Frans. I have used WoodComp SR2000 for three years with 100% success so far. Also vent to WoodComp for a two days course in order to conduct service and get a better understanding. It was very interesting indeed. The quality of the different propeller parts is very good. I was allowed to put one SR2000 and one SR3000 together. Supervised of course :-) Here goes my list of remarks 1. WoodComp makes good propellers. Propellers installed on many ultralights/experimentals with success 2. SR2000 end stop is better then SR3000. More ruggedized. The micro switch used on SR3000 is not the very best. I was a bit surprised when I first saw them 3. SR2000 has push-rods instead of gear in order to change pitch. That means that the SR2000 can not move to superfine. 4. When you throttle back in order to enter the landing pattern for example, the RPM will drop as soon as the end stop has been reached as explained by Jos 5. Normally you do not throttle back as much as Jos did in cruise but that was due the fact the controllers settings was wrong. 6. The end-stop should not normally be reached turning from climb- to cruise-regime as Frans explained My conclusion: End stop that works is mandatory. SR3000s micro switch is not the very best, Jos reaction was human. He throttle back due the MAP reading. Frans is correct the end stop was not the start of the event chain. The incorrect setting seems to start the situation. With a working end stop this sad accident would probably not happend If the propeller goes wild or wrong setting: TURN OVER TO MANUAL. Use manual now and then in order get used. Drill this as much you simulate engine failure: Turn electric pump on switch to reserve tank One other thing worth mentioning here: Set the HYSTERESIS regime to 100 (WoodComp recommendation) That means that the regulator does not trigger the servo for minor changes in prop-speed (rpm) If the prop speed (rpm) drops let say 70 rpm, the servo will stay passive. This saves the servo and the mechanics evidently Best regards Stephan Cassel LN-STE Mono 140 hours


    Message 4


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    Time: 04:49:55 AM PST US
    From: "nwcmc@tiscali.co.uk" <nwcmc@tiscali.co.uk>
    Subject: Constant Speed Prop and failure modes.
    It should also be remembered that a prop stuck in a coarse setting can be an issue as well. To this end it is worth checking that the aircraft can climb away safely from a go-around at short finals at low speed in this condition. I flew C-130s for 9 years and without doubt the propellers with their control systems were studied more closely than any other technical aspect of the aircraft. On this aircraft there are 6 different safety features that are designed to limit the rpm of the engine. This was particularly important for an engine/prop combination that was designed to run at constant speed. On the RAF C-130s the engines produced about 5000shp each and the propeller angle could reach 55 degrees in the cruise and keeping the rpm within the 98-102%rpm limit needed some high quality engineering. The incident below whilst not relevant to the Europa might make interesting reading. An Orion aircraft (which uses the same engine/prop combination as the C-130) had a very testing incident which makes one aware that, even after many years of trouble free operation, it is possible to get into a situation where a prop can bite. In this case the crew was flying in a naval military exercise many miles offshore. This entailed a long transit at high level, a significant amount of time of slow flight at low level, followed by another high level transit back to their base. The problem came when a fault in one of the propeller control systems caused an outboard prop to pitch lock during the low level phase of the flight. This is one of the safety features to prevent the prop going too fine. However because of the power/altitude/speed combination the prop was stuck in low pitch. This isnt normally a problem as the engine speed can be contained by continuing to fly at a low TAS. It still takes the total attention of one crew member using the throttle to keep the rpm within limits. However in this case, to be able to reach the nearest airfield, the aircraft needed to climb as it had insufficient range at low altitude. The crew was faced with the choice of a premeditated ditching or to intentionally increase the TAS by climbing and accept the risk catastrophic failure as the prop was forced into an overspeed situation. They decided to choose the latter. The highest rpm that the safety features can normally cope with is 108%. As they climbed the prop rpm increased until finally the engine and propeller broke away from their mountings. Afterwards this was calculated to have happened at about 170%rpm. Fortunately the engine/prop combination fell away without damaging the aircraft. The crew managed to continue their flight to a safe landing. When William Mills first flew into my strip with the first Woodcomp prop with beta range capability I had a chat with him about the dangers of props that can operate in the beta range. I thought it a risky feature which was totally unnecessary on the Europa. As Jos found, even in forward fine pitch the situation can very quickly become uncontrollable should something go wrong. I would suggest that owners of Europas with VP props may like to check that the settings for the mechanical stops for both low and high pitch on their propellers enable safe low speed flight. Nigel Charles Get up to 50% off Norton Security - http://www.tiscali.co.uk/securepc _________________________________________________________


    Message 5


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    Time: 06:05:14 AM PST US
    Subject: Re: Electric VP Prop Reliablity
    From: "Mark Burton" <markb@ordern.com>
    In my previous message, I talked about checking that the fine pitch hard stop was in a sensible position. I forgot to mention that if you want to do that check, be very careful not to damage the switches in the hub because with some hub designs (not all) if you overrun the limit switches, something will break (most likely the switch). So, before you attempt such a test, look at the switches and how they are activated and convince yourself that when the pitch moves to the hard limit, nothing will be damaged. You may feel that this test is not required as the manufacturer will have set the hard stop to a suitable position. Personally, I no longer believe prop manufacturers when they say they have set the limit switches to the correct position. I am similarly sceptical about the position of hard limits. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=235350#235350


    Message 6


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    Time: 09:39:45 AM PST US
    From: "ALAN YERLY" <budyerly@msn.com>
    Subject: Re: Constant Speed Props, etc.
    We haven't firmed that up yet Fred. I believe the Sensenich blades are really designed for the new 432 and much final testing needs to be done. Other blades are being tested which appear to be retrofitable (is that a word?). Frankly I doubt there will be a significant change over the WD blades, but that is what testing is for. As you are aware, wider chord blades require a somewhat larger base . I'll keep you guys posted on the testing as I get it as we don't want to release a product until it is thoroughly tested or make promises we can't keep. As you well know I am not a politician. Bud Custom Flight Creations www.customflightcreations.com<http://www.customflightcreations.com/> ----- Original Message ----- From: Fred Klein<mailto:fklein@orcasonline.com> To: europa-list@matronics.com<mailto:europa-list@matronics.com> Sent: Friday, March 20, 2009 1:56 AM Subject: Re: Europa-List: Constant Speed Props, etc. On Mar 19, 2009, at 9:11 PM, ALAN YERLY wrote: Martin will be sending the new blades to me for test also. I will run a test of the fixed warp drive, standard Airmaster AP332 with Warp drive blades and the new Kiev blades. Bud...Do you know whether or not the new blades are compatible w/ the AP332 hub? Fred http://www.matronics.com/Navigator?Europa-List<http://www.matronics.com/N avigator?Europa-List> http://www.matronics.com/contribution<http://www.matronics.com/contributi on>


    Message 7


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    Time: 11:58:51 AM PST US
    From: Karl Heindl <kheindl@msn.com>
    Subject: Constant Speed Props, etc.
    What is a 432 ? From: budyerly@msn.com Subject: Re: Europa-List: Constant Speed Props=2C etc. We haven't firmed that up yet Fred. I believe the Sensenich blades are really designed for the new 432 and much final testing needs to be done. Other blades are being tested which appea r to be retrofitable (is that a word?). Frankly I doubt there will be a si gnificant change over the WD blades=2C but that is what testing is for. As you are aware=2C wider chord blades require a somewhat larger base . I'll keep you guys posted on the testing as I get it as we don't want to releas e a product until it is thoroughly tested or make promises we can't keep. As you well know I am not a politician. Bud Custom Flight Creations www.customflightcreations.com ----- Original Message ----- From: Fred Klein Sent: Friday=2C March 20=2C 2009 1:56 AM Subject: Re: Europa-List: Constant Speed Props=2C etc. On Mar 19=2C 2009=2C at 9:11 PM=2C ALAN YERLY wrote: Martin will be sending the new blades to me for test also. I will run a te st of the fixed warp drive=2C standard Airmaster AP332 with Warp drive blad es and the new Kiev blades. Bud...Do you know whether or not the new blades are compatible w/ the AP332 hub? Fred href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhr ef="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c


    Message 8


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    Time: 02:07:30 PM PST US
    Subject: Re: Constant Speed Props, etc.
    From: Paul McAllister <paul.the.aviator@gmail.com>
    Hi Bud, I am not an aerodynamicst, not even an amature one but I was wondering why you didn't think the Kiev blades will be much of an improvement over the Warp Drive blades. The reason I ask is that I do know that I get an increase in TAS up to about 10,000' with my AP332 Warpdrive / 914T combination, but after the speed doesnt increase much. I hear from the Whirlwind folks that this is not the case for them, higher faster. Given that something isn't happening as expected I am concluding that there is some design parameter(s) that are not appropriate for a an aircraft that flies at Europa speeds / altitudes. Any insight that you could share with me would be appreciated. Thanks, Paul On Fri, Mar 20, 2009 at 11:32 AM, ALAN YERLY <budyerly@msn.com> wrote: > Frankly I doubt there will be a significant change over the WD blades, > but that is what testing is for. As you are aware, wider chord > blades require a somewhat larger base . > As you well know I am not a politician. > > Bud > >


    Message 9


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    Time: 06:18:44 PM PST US
    From: Fred Klein <fklein@orcasonline.com>
    Subject: Re: Constant Speed Props, etc.
    On Mar 20, 2009, at 2:00 PM, Paul McAllister wrote: > I am not an aerodynamicst, not even an amature one but I was > wondering why you didn't think the Kiev blades will be much of an > improvement over the Warp Drive blades. Bud, I too was surprised at your apparent skepticism as to whether those Kiev blades may offer improvement over the current WD blades in the Airmaster hub. I had several long emails w/ Martin on the subject...perhaps 2 years ago...and my recollection is that he was quite candid about the WD blades being less than optimal given the flight envelope and length limitations of the blades for the Europa. My understanding is that the WD blade stock is much longer, and when cut down to length required, they lose much of their twist...to such an extent I've read that the inner portions of the blades create negative thrust under certain conditions. I've speculated that the relative lack of twist may be a factor in engine cooling...just speculation, I have, of course, no direct experience. Assuming that the "432" references a new hub, I hope it's available with other than a Rotax flange. Fred


    Message 10


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    Time: 10:30:31 PM PST US
    From: "ALAN YERLY" <budyerly@msn.com>
    Subject: Re: Constant Speed Props, etc.
    Paul, I am only a junior aerodynamicist. Propeller blade design is still a zen art. Too many theta, beta sigma deltas to patiently wade through and design a prop. The math is not beyond me, ( I have a computer program for doing the gymnastics and iterations, (but my kid the aero engineer has to get me in to it...go figure). I can say that most designs take into account the assumptions of where the max efficiency of their design will be optimized. When designing a prop blade, it is hard to get a prop that does all things well. We buy a CS prop to accelerate fast, give max climb and optimum efficiency at the exact torque/power curve for the specified aircraft at a specified cruise speed and altitude, but propeller blade designers don't know your plane, engine or the altitudes you intend to use, so they assume for a specific engine and speed/altitude, and don't tell anyone. For you Paul, the next two paragraphs are a bit basic, but somebody less experienced may glean some knowledge or correct me. Example: For max static thrust and quick acceleration of say a float plane/airboat, you design the prop so the entire prop blade is pulling very close to the stall angle based on the rotational speed for takeoff power/torque and forward speed. This gets the plane on the step quickly and off the water. But, once you pass about 80 Kts the blade angle of attack falls off due to forward speed, cowl stagnation point / flow interruption and the reduction of power to max continuous for the climb. To design a perfectly optimized fixed pitch propeller, the following is optimized by trial and error: For takeoff, the blade bites as described above. During the transition to climb, the tip unloads slightly and the root takes up the difference. At cruise the tip unloads further leaving the root to take up the slack. Balancing this twist means the propeller designer and aircraft/power plant designer must cooperate to achieve this goal. So the fixed pitch designer at WD makes his blade so that there is extra pitch at the hub decreasing to the tip so as speed increases the root pulls the load the tip can't, but only to a point. Typically 7500-9500 feet and 120 Kts is about max you'll ever get unless you've got a clean airplane like a Europa and you get 130 Kts... Take the Airmaster with the Warp Drive (WD) blades. On a slow aircraft like a Rans S-7 or a Kitfox. Let's say their optimum cruise will be 110 Kts at 7500 feet for that plane. A fixed 68 inch WD prop can be twisted to give max static thrust, and high climb, but then the pitch is too low for optimum cruise, and the plane only makes 105 Kts because the tip is unloaded and prop efficiency drops. So we put the WD blades on a CS prop hub. Now the static thrust and high climb are there but once at cruise we adjust the pitch to coarse to allow the prop to bite more and be at the optimum pitch for 110-115 Kts or a little higher. Now let's go to our 914 and 15,000 foot cruise. The WD blade is a good strong blade, but the assumed efficient cruise altitude of the blade may not have been optimized for 15,000 feet and 175 KTAS pulled by an engine making 70 HP and 70 ft lbs of torque at altitude. As altitude goes up, we know the rules about how density affects the TAS. The blade (wing) of the prop is now at a higher Reynolds number which results in a lower lift curve slope. In the rarified air up there, the dynamic pressure is less so less lift (or pull) is provided, and the velocity (True) is higher, so the vector made by the rotational angle of the disk and the Velocity vector forces the blade to a higher angle of attack to bite (course prop pitch). The higher altitude decreases the thrust (or lift of the blade) and you find yourself with the blade generating max lift, and or in fact stalling at some point and not operating efficiently. I believe it is a high probability the torque of the 914 engine is higher than the prop requires for max efficiency at altitude. Hence the CS mechanism adjusts the prop to a more coarse setting to absorb the torque demanded by the throttle, but that puts the blade at an angle which lowers the overall efficiency of the blade. Therefore you experience the effect of no appreciable increase in speed the higher you go. The WD blade is most probably being over driven by the 914 at altitude. I presume you experimented with many manual pitch settings, manifold pressures and RPM settings looking for max performance. I am well behind you as my schedule does not allow a lot of time to climb to altitude and test, but I am hoping for a break this spring. My gut feeling will be that I will need to throttle back to gain efficiency and be satisfied with 40 mpg instead of 30 and get to my destination a little slower. >From my Airplane Aerodynamics reference by Dommasch, Sherry and Connolly, "Because of the factors discussed above, we find that the over all shape of a propeller is determined by the maximum speed at which it must operate efficiently. A low-speed planform should be slender with well rounded tips, whereas a high speed planform should have a large chord, with the maximum amount of blade area concentrated in the minimum diameter. Because the major portion of the thrust is derived from the outer portion of the blades, a high speed propeller is generally characterized by paddle shaped tips that place the area where it can best be utilized. What's the fix? To translate the above academic explanation, the best example is to look at WWII prop designs of the VDM propeller used on the ME 109. Early versions had the thin profile blade we see on our WD narrow chord blades. But as engine performance and the demand for higher altitudes increased, the designers went to a wider prop of more surface area to absorb the torque, and to create more thrust out of the blade normally lost due to the effects of higher altitude. They were limited by the diameter of the prop due to ground clearance, and production forced them to stick to three blades so they fattened the blades, increased the pitch of the root and went to war (see pictures of the Ta 152 for an even higher altitude and speed prop). Takeoff performance wasn't that much better because the larger blade area demanded more torque/power than available and the pitch was reduced lowering efficiency at takeoff, but mid altitude climb and acceleration, as well as cruise was improved. By the way the VDM was a variable pitch prop, with a visual indicator of prop pitch in the cockpit, not a constant speed prop. Talk about pilot work load. In the US we did the same for the P-47 by changing the Hamilton Standard prop from a thin blade to a thicker blade as WD did and made the prop Constant Speed to reduce pilot work load. God I love history... Right now Airmaster is looking at a number of blades that fit our hub and future hubs. Problem is, the blade designs are many, and twist features are not that much different than the WD. My comment on the Kiev blade is that it doesn't appear to have much more twist, but it does seem to have more area. It is in use on lower altitude/low performance ultralight and trike aircraft. It is light, but, is its hollow design tough enough for the 914 at high Q, and for our Europa, all the Kiev prop blades are longer (67") than we can normally use. Sensenich (fixed) and Whirlwind (oil pump driven hydraulic) have wider chord blades than the WD and may hold an advantage in some areas, but give a thumping sound as the pressure wave hits the aircraft. Airmaster does use their own Europa to test prop blade performance. In my opinion, if some blade was significantly better for the three blade AP332, it would be on there already. Since we have new meat in the prop market, there are more choices in the blades, and the Rotax / WD is very popular so the new blades favor that LSA speed/altitude market now and use a similar hub attachment and blade design. I'm afraid there is not a lot of call for high altitude low power high speed props like we need for cruise at 15,000 feet. Also the market has to be satisfied, many lower performance aircraft enjoy the Airmaster and aren't in need of a major change, while other markets need a longer two blade prop for static thrust. Wider blades restrict feathering or cowl clearance in some aircraft. These are the things being evaluated at this time. It takes time, money and testing. Good Night, Bud ----- Original Message ----- From: Paul McAllister<mailto:paul.the.aviator@gmail.com> To: europa-list@matronics.com<mailto:europa-list@matronics.com> Sent: Friday, March 20, 2009 5:00 PM Subject: Re: Europa-List: Constant Speed Props, etc. Hi Bud, I am not an aerodynamicst, not even an amature one but I was wondering why you didn't think the Kiev blades will be much of an improvement over the Warp Drive blades. The reason I ask is that I do know that I get an increase in TAS up to about 10,000' with my AP332 Warpdrive / 914T combination, but after the speed doesnt increase much. I hear from the Whirlwind folks that this is not the case for them, higher = faster. Given that something isn't happening as expected I am concluding that there is some design parameter(s) that are not appropriate for a an aircraft that flies at Europa speeds / altitudes. Any insight that you could share with me would be appreciated. Thanks, Paul On Fri, Mar 20, 2009 at 11:32 AM, ALAN YERLY <budyerly@msn.com<mailto:budyerly@msn.com>> wrote: Frankly I doubt there will be a significant change over the WD blades, but that is what testing is for. As you are aware, wider chord blades require a somewhat larger base . As you well know I am not a politician. Bud http://www.matronics.com/Navigator?Europa-List<http://www.matronics.com/N avigator?Europa-List> http://www.matronics.com/contribution<http://www.matronics.com/contributi on>


    Message 11


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    Time: 10:56:31 PM PST US
    From: "ALAN YERLY" <budyerly@msn.com>
    Subject: Re: Constant Speed Props, etc.
    Fred, See my other post to Paul. I agree about the Warp Drive Blades. Even in the longer blade lengths it is not the best blade for altitude. I find them very good in the 7500 to 9500 foot range for our aircraft using 100 Hp engines. It is not a perfect world. The Kiev blades appear too long also. Ergo, my fear is the blade will be less efficient when trimmed for our plane unless those pesky Russians remake the blades for us as you normally can't whack a hollow blade prop to length. Maybe VDM will make a smaller version of the Me109 blade for our use. Anybody know them? I never thought of myself as skeptical, just cautiously optimistic...(Sarcastic humor through years of training though.) Bottom line testing will tell. I'm excited about the near future, but patient. Bud ----- Original Message ----- From: Fred Klein<mailto:fklein@orcasonline.com> To: europa-list@matronics.com<mailto:europa-list@matronics.com> Sent: Friday, March 20, 2009 9:12 PM Subject: Re: Europa-List: Constant Speed Props, etc. <fklein@orcasonline.com<mailto:fklein@orcasonline.com>> On Mar 20, 2009, at 2:00 PM, Paul McAllister wrote: > I am not an aerodynamicst, not even an amature one but I was > wondering why you didn't think the Kiev blades will be much of an > improvement over the Warp Drive blades. Bud, I too was surprised at your apparent skepticism as to whether those Kiev blades may offer improvement over the current WD blades in the Airmaster hub. I had several long emails w/ Martin on the subject...perhaps 2 years ago...and my recollection is that he was quite candid about the WD blades being less than optimal given the flight envelope and length limitations of the blades for the Europa. My understanding is that the WD blade stock is much longer, and when cut down to length required, they lose much of their twist...to such an extent I've read that the inner portions of the blades create negative thrust under certain conditions. I've speculated that the relative lack of twist may be a factor in engine cooling...just speculation, I have, of course, no direct experience. Assuming that the "432" references a new hub, I hope it's available with other than a Rotax flange. Fred http://www.matronics.com/Navigator?Europa-List<http://www.matronics.com/N avigator?Europa-List> http://www.matronics.com/contribution<http://www.matronics.com/contributi on>




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