---------------------------------------------------------- Zenith-List Digest Archive --- Total Messages Posted Sun 10/31/04: 19 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:05 AM - Re: Gross Weight (cgalley) 2. 06:10 AM - (Andy Smith) 3. 06:46 AM - Re: Gross Weight (Larry) 4. 07:03 AM - Re: Gross Weight (familie chesterman) 5. 08:02 AM - Re: Fw: Zeniyh-List: Re: CH601 XL nose wheel fork (Jack Russell) 6. 08:04 AM - Re: Gross weight (Brandon Tucker) 7. 08:55 AM - Jeff Paden: Big-a$$ engine installation (James Brigman) 8. 10:21 AM - Re: Zenith-List Digest: 20 Msgs - 10/30/04 (Grant Corriveau) 9. 10:39 AM - Re: Re: Zenith-List Digest: 20 Msgs - 10/30/04 (Cdngoose) 10. 10:46 AM - Re: Zenith-List Digest: 20 Msgs - 10/30/04 (Grant Corriveau) 11. 11:50 AM - RE; Gross Weight (roy vickski) 12. 02:21 PM - Re: Jeff Paden: Big-a$$ engine installation (cgalley) 13. 03:33 PM - Re: Jeff Paden: Big-a$$ engine installation (Larry McFarland) 14. 04:57 PM - Re: RE; Gross Weight (Jeff Paden) 15. 05:01 PM - Re: Re: Zenith-List Digest: 20 Msgs - 10/30/04 (Jeff Paden) 16. 05:07 PM - Re: Re: Gross weight (Jeff Paden) 17. 05:13 PM - Re: Gross Weight (Jeff Paden) 18. 06:46 PM - Canopy build order (Bill Steer) 19. 11:38 PM - Re: Jeff Paden: Big-a$$ engine installation (cgalley) ________________________________ Message 1 _____________________________________ Time: 03:05:56 AM PST US From: "cgalley" Subject: Re: Zenith-List: Gross Weight --> Zenith-List message posted by: "cgalley" Hate to burst your bubble. The stall speed is probably much higher even though you airspeed says 45 mph. Most airspeeds are very inaccurate at low speed due to positional errors of the pitot. Using my Bellanca 14-13-2 the listed speed is 48 MPH but I see an indicated airspeed of 38 MPH before the break. You might want to get out the GPS and see what it says by trying several directions to cancel out the wind. This is what the Test period is all about. Flutter is not the only problem at higher speeds. There are some strength considerations. The FAA establishes the red-line by demonstrating flight to a number and then making the red-line at 90% of this demonstrated figure. The faster you go, the stronger the airframe has to be to withstand air loads and turbulence. That is why the safe maneuvering speed is much less than the red line. The VNE for your plane you say is 167. That is designed into the airframe by the designer. You probably don't have an margin of error for gust loading above that point unless you have redesigned the airframe. Just one bout of clear air turbulence could ruin your day. Or you could do the damage yourself by full rapid control inputs. I hate to say this but your plane is every designer's worse nightmare. When you make the modifications then all the careful calculations of the designer are gone. I hope that you understand that due to liability considerations, the factory probably will not give advice. Remember it is no longer a Zenith design, it is yours and yours alone due to the deviations from the design parameters. Right now there is a move underfoot to ground a certified airplane via an AD. Why? Because these airplanes have been re-engined not even with greater weight but just added horsepower. I hope you can get some structural analysis done. All airplanes fly better when they are lighter. Cy Galley EAA Safety Programs Editor Always looking for ideas and articles for EAA Sport Pilot ----- Original Message ----- From: "Jeff Paden" Subject: Re: Zenith-List: Gross Weight > --> Zenith-List message posted by: "Jeff Paden" > > > I have had many members of the list point out the fact that I have installed > a 260 hp engine. However this is not the problem as is easy to see when you > do the calculations. The engine I installed is only 110 lbs heavier than > the 180 hp engine that the aircraft was tested with. This also keeps me > within the max installed power plant weight as I had checked this before > installing the engine. > My aircraft is 1560 lbs empty and the proto was 1147 lbs empty. This means > that some how I have added over 400 lbs and the engine only accounts for 110 > lbs of that. If I had the other 300 lbs to play with then I would not have > a problem at all. > > As for swapping out the engine for a smaller one, that just simply is not an > option. Everything was built around this engine and if needed then I will > simply have a very nice two place aircraft or only carry 20 gal of fuel with > four. > So far I have found that almost every aspect of the figures on the web site > are WAY off and I am just looking for answers as to why. > > For example, the Vne is published at 167 mph however I have done flutter > testing up to 190 mph with no sign of any problems as of yet and that is > still only at 75% power. I will post to the list once I figure out what the > real Vne is. By the way, I do NOT recommend to anyone on the list that you > perform flutter testing unless you really know what you are doing. I have a > friend who is a test pilot and he is the one that is helping me with this > test. Do the test wrong and you will destroy the aircraft and probably not > survive the test. > > With that said, I have also found that my stall speed is 45 mph with full > flaps so the fact that the aircraft is heavy has not increased that number > as we expected it to do. Also my take off roll is only about 500 feet but > that is probably because of the extra power. > > Once I have all the numbers confirmed then I will post them all to the list. > > I guess my next job is to try to find a way to make the aircraf lighter but > I really can't think of anything that is going to make that happen. > > Thank you all for your help and don't worry, after putting one aircraft in > the trees I don't have any plans of flying this one in any condition that > would be unsafe. We just need to figure out what is "SAFE" for this > aircraft and the published numbers simply do not seem to have anything to do > with my aircraft. > > Jeff Paden > CH-640 Test flight stage. > > > Jeff, > The gross weight is defined by structure and hardware that's heavly > calculated to provide > a safe platform for weight, maneuvering and power loading. On the simple > side, you can put an > engine that weighs much more than the 180 to 220 HP engine, but you pay a > price in safety and > performance that should become obvious. Anytime you have more tail weight > than the > baggage you're able to carry, you've gotten outside of the fine art of a > design specification > that's initially intended to keep you and yours safe for a long period of > time. The engine > limits assure that the elevator will offer adequate resistance to pitching > moments from turbulence > and stalls so long as the plane is balanced within the envelope. The limits > also assure that the > engine mounts and attachments will not crack prematurely from fatigue of the > engine torque and > prop pulse. Both of these design elements are huge for the designer. These > are tested and > designed with safety factors that assure a reasonable lifespan. When one > exceeds the specification > the first compromise is in wear and working fatigue life. Little else will > be noticable, but > time becomes a bigger player as a few bad landings and weather work against > the airframe. > > I've tried to put my finger on the exactitude of your problem and it is > this. > It is much safer to consider the practical solution of trading engines to > get within specification > and resolve every problem you've had to deal with. > Larry McFarland - 601HDS > > ________________________________ Message 2 _____________________________________ Time: 06:10:01 AM PST US From: Andy Smith 0.00 FROM_HAS_MIXED_NUMS From": contains.numbers.mixed.in.with.letters.1.16.MISSING_SUBJECT.Missing.Subject:header@matronics.com --> Zenith-List message posted by: Andy Smith help ===== Sami Wegner __________________________________ ________________________________ Message 3 _____________________________________ Time: 06:46:33 AM PST US From: "Larry" Subject: Re: Zenith-List: Gross Weight --> Zenith-List message posted by: "Larry" Jeff, even though I don't see eye to eye with Zenith on some items like tires, they always respond to me. Sometimes I don't like the response but I always get a response. Perhaps you should double check the address and request a reply, if that doesn't work pick up the phone. I'm sure there is some mix up, you haven't called them dirty names have you? kidding! Larry N1345L Do not archive. ----- Original Message ----- From: "Jeff Paden" Subject: Zenith-List: Gross Weight > --> Zenith-List message posted by: "Jeff Paden" > > I know I have asked this before but I am going to try one more time to see > if anyone can point me in the correct direction. > > I need to know what limits the gross weight of an aircraft. How does the > engineer calculate gross weight of an aircraft? > > I ask this because at this moment I have a VERY powerful CH-640 that I can > only take one passenger in which does not seem logical at all. > > I know the aircraft will fly WAY over the published gross weight but I am > trying to figure out what goes in to the calculations so that I can come up > with a logical gross weight for my aircraft. The 2200 lbs that is published > simply is not logical for an aircraft that has an empty weight of 1560 lbs. > > Before anyone says it, YES, I have asked ZAC for assistance but as of yet I > have not had any response from them. As a matter of fact I have not had any > response from them about any of my questions since I have completed the > aircraft which is very upsetting for me but I guess I will just have to > figure things out on my own. That is why I hope that someone on this list > may be able to point me in the right direction. > > Thank you for any assistance you can offer. > > Jeff Paden > > ________________________________ Message 4 _____________________________________ Time: 07:03:03 AM PST US From: familie chesterman Subject: Re: Zenith-List: Gross Weight --> Zenith-List message posted by: familie chesterman This is likely a dumb question, but are you sure about the accuracy of your scales when you did the weight and balance? 300lbs is a lot. Was your tool box sitting in the fuselage? dave c > > > > Jeff Paden > > > > > ________________________________ Message 5 _____________________________________ Time: 08:02:55 AM PST US From: Jack Russell Subject: Re: Zenith-List: Fw: Zeniyh-List: RE: CH601 XL nose wheel fork --> Zenith-List message posted by: Jack Russell Buryl: I think the measurment between the forks should read 135mm not 35mm. Would you check this please? I measured my XL fork and it is 140mm so I don't think that the Hd doubler will work. Thanks Jack In Clovis CA --> Zenith-List message posted by: "burylhill" Jack: My 601 HD fork doubler measures 100mm deep X 150mm Down the side. 35mm between the U. Drawings show 410mm Developed Length. I think the whole metal length before the bend ( R15mm ) is 410mm X 100mm. Jack Russell -Clovis CA 601 XL Jabiru 3300 Progress update at: http://www.geocities.com/clojan@sbcglobal.net/zodiacbarn.html ________________________________ Message 6 _____________________________________ Time: 08:04:01 AM PST US From: Brandon Tucker Subject: Zenith-List: RE: Gross weight --> Zenith-List message posted by: Brandon Tucker Jeff, Maybe I am off base here, but I am much more concerned about the extra 300lbs in the airframe than the extra 110 lbs in the engine. Better than half the list is using an engine that is considerably heavier power plants than the engines that Chris had in mind. There is a ton of documentation on compensating for extra engine weights, from the Subaru in the 601, to Ben's Ford in the 801. Jeff has stated that the engine is within the max designed weight. We can't say that for the 701 guys looking into Corvair, and Subaru engine installations. My question is what in the !#@* happened with the airframe weight? I know that you double and triple checked your numbers when weighing your aircraft, but something is way (weigh) off! :) That is the first place I would be looking into. You built from kit right? I don't think it is even possible to add 300 lbs of weight unless you skinned it with .050 stainless! Maybe I missed a post that explained this, but I don't think so. Let's not lecture on engine weights and weight in the tail when many of the Subaru guys have been putting batteries behind the passenger compartment to compensate for engine weight. Respectfully, Brandon Tucker 601 HDS wings, tail complete do not archive __________________________________ ________________________________ Message 7 _____________________________________ Time: 08:55:42 AM PST US From: "James Brigman" Subject: Zenith-List: Jeff Paden: Big-a$$ engine installation --> Zenith-List message posted by: "James Brigman" > From: "Jeff Paden" > Subject: Zenith-List: Gross Weight ... > I need to know what limits the gross weight of an aircraft. How does the > engineer calculate gross weight of an aircraft? > I ask this because at this moment I have a VERY powerful CH-640 that I can > only take one passenger in which does not seem logical at all. ... > what goes in to the > calculations so that I can come up with a logical gross > weight for my aircraft. The 2200 lbs that is published > simply is not logical for an aircraft that has an empty > weight of 1560 lbs. ... > installed a 260 hp engine. However this is not the problem > The engine I installed is only 110 lbs heavier than the > 180 hp engine the aircraft was tested with. > This also keeps me within the max installed power > plant weight as I had checked this before installing the engine. > My aircraft is 1560 lbs empty and the proto was 1147 lbs empty. > This means that some how I have added over 400 lbs and > the engine only accounts for 110 lbs of that. If I had > the other 300 lbs to play with then I would not have > a problem at all. Jeff; First: congratulations are in order for your completing a CH-640 and installing such a nice engine. I see from your website where you went with an O-540 instead of the usual O-360. Thanks for the fresh update to your builder page on the ZAC website - your plane looks beautiful. I have complete lust for your aircraft...I'm hoping that a 640 will be "my next airplane". :-) Now: I'm not gonna tell you HOW on anything. From your website, you seem to know what kind of plane you want to end up with. You are right that basic weight does not determine useful load capacity. In fact, for many certified GA planes, there are STC's for engine upgrades that actually increase gross weight a bit, not decrease it. However, there's more to it than just gross weight: Structural load design, empennage sizes CG and weight distribution are as important as gross weight. I don't have the answers, but here's where I would look if I were in your shoes. 1) Be clear about one thing: you went 20hp over the powerplant design for this aircraft, per http://www.zenair.com/specifications.html. I'm sure all us builders routinely tax the patience of our fathers at ZAC. I know I have ;-) Reading between the lines at http://www.zenair.com/engine.html, it almost looks like Chris purposefully excluded the O-540 as an engine choice. 2) There's got to be both a Weight & Balance table as well as a POH for the CH-640. These are the base documents which will precisely answer your questions about how to calculate gross weight. The CH-640 has a certified GA brother, so there ought to be a W&B template and a POH template for it. Although they are not available online from ZAC (for good reason) the versions for the 601 are available at http://www.zenithair.com/zodiac/6-up-bldr.html 3) Aircraft engine weights are published as optimistically as possible. This means "DRY" (no engine oil, coolants or fuel) and WITHOUT starter, alternator, carb/intake or even magnetos. This could account for as much as 100lbs of the extra weight you're seeing. Here's a great webpage for engine reference: http://www.wanttaja.com/avlinks/engines.htm Ron has an interesting link on "structural efficiency" which shows how widely the gross weight of aircraft can vary with their various engines and airframes. 4) How much heavier is your panel than the "stock" ZAC panel for the 640? I remember when I sat in the ZAC CH-640 at Sun 'n Fun, it had the typical 6-pack, a couple radios, a transponder and a small assortment of engine instruments (I think six or eight small gauges?). Chris likes to keep his panels simple, it really helps with the CG. 5) Did you go with the stock fuel tanks to feed that bit O-540, or did you beef those up a bit too? For reference between yours and several GA planes, see http://www.zenair.com/performance-comparison.htm. You could have picked up 80lbs of weight there easily. 6) Where's your battery placement? Is it on the firewall or back behind in the rear of the plane? Don't you have to use a bigger battery to start that 540? If so, how much weight did that add? 7) You've clearly been flying the aircraft to generate test data. How's it handle in the flare? What happens in the stall? What about landing speed? I know from past history that some guys who built 601's with bigger engines in the UK had to beef-up their HS attach points and install larger HS's to get PFA certification. (that might still be in the archives here) ________________________________ Message 8 _____________________________________ Time: 10:21:18 AM PST US Subject: Zenith-List: Re: Zenith-List Digest: 20 Msgs - 10/30/04 From: Grant Corriveau --> Zenith-List message posted by: Grant Corriveau > Concerning roll trim I found an interesting article in > contact magazine #77, the author who is a lancair235 > driver states that any lateral imbalance should be > countered with a constant force (spring) If you are interested in a simple and easy to install spring/bungee chord aileron trim system, there are at least 2 ideas that have been proposed by listers -- I can't find them on my computer right now... should be in the matronics archives, or the www.ch601.org website. do not archive Grant ________________________________ Message 9 _____________________________________ Time: 10:39:04 AM PST US From: "Cdngoose" <601xl@sympatico.ca> Subject: RE: Zenith-List: Re: Zenith-List Digest: 20 Msgs - 10/30/04 --> Zenith-List message posted by: "Cdngoose" <601xl@sympatico.ca> Here is one Idea that Grant referred to http://www.ch601.org/resources/trim/bungee_trim.htm Mark Townsend Alma, Ontario Zodiac 601XL EJ 2.2L Osprey 2 serial # 751 www.ch601.org www.Osprey2.com -----Original Message----- If you are interested in a simple and easy to install spring/bungee chord aileron trim system, there are at least 2 ideas that have been proposed by listers -- I can't find them on my computer right now... should be in the matronics archives, or the www.ch601.org website. Grant ________________________________ Message 10 ____________________________________ Time: 10:46:53 AM PST US Subject: Zenith-List: Re: Zenith-List Digest: 20 Msgs - 10/30/04 From: Grant Corriveau --> Zenith-List message posted by: Grant Corriveau > For example, the Vne is published at 167 mph however I have done flutter > testing up to 190 mph ... you will destroy the aircraft and probably not > survive the test. Jeff, If ZAC published a vne of 167 mph, it doesn't mean that they encountered flutter at 168 mph. It's probably because that's as fast as they dared / cared to take the airframe. I'm glad you mentioned that you have a test pilot friend working this for you - are you parachute equipped too? He should be able to help answer these questions ... you will find textbooks written about this stuff. It's complicated... Beyond the aerodynamic issues there are all the issues that others have mentioned regarding wear and tear on the landing gear, wing spar, engine mounts, and all the stress points over time. FWIW this is true of all size aircraft. The airliner I used to fly was eventually certified to a higher MTOW, but we weren't able to make use of it until the landing gear had been reinforced -- and along with that all the paperwork and performance numbers had to be recomputed. But this was only allowed AFTER the aircraft had been in service a significant number of hours, and the airframe had proven itself under constant monitoring, etcc... You're facing the same task on a smaller scale. Your plane will become a test plane and maybe your future passengers need to be forewarned? Again, the best source for any allowance to the Max TOW is the designer. Also you seem to have a HUGE increase in empty weight compared to the prototype - over 30%? Are you sure this is so? That's an awful lot of weight. Besides the engine, where did it all come from? Did you make other modifications/imrovements? Have you ever added it all up? I'd be very uncomfortable not knowing why my aircraft is so much heavier... Good luck -- be careful! -- Grant Corriveau C-GHTF / HDS / CAM100 ________________________________ Message 11 ____________________________________ Time: 11:50:30 AM PST US From: roy vickski Subject: Zenith-List: RE; Gross Weight --> Zenith-List message posted by: roy vickski Hello Jeff and regards to the group, > I need to know what limits the gross weight of an aircraft. How does the > engineer calculate gross weight of an aircraft? Sand bags. Lots of them. I guess engineers can make all the calculations on a supercomputor and come up with a very close theoretical approximation of performance but I think the real test is real weight. Gross weight is related to g force and load factor. The (ultimate?)load limit factor for an airframe is based on the maximum ammount of g force (weight)it can withstand before damage occurs. So a 2200# gross weight airframe rated for 6 g's ultimate load shouldn't be damaged up to a weight of 13,200 pounds. But subject a 2500# gross weight to 6 g's and get 15,000 pounds Angle of attack and g force have a near linear relationship. In level flight double triple,or quadruple the angle of attack and the g force (weight) doubles,triples, or quadruples. If at 150mph un-accelerated flight with an angle of attack of 3 degrees, a gust or stick deflection increases the angle of attack to 18 degrees the airframe would be subjected to 6 g's(18/3=6). Angle of attack and airspeed also have a relationship. The same airframe at 180mph could have an angle of attack of 2 degrees and would experience 6 g's at 12 degrees aoa, well below critical aoa, and 7 g's at 14 degrees aoa. If the load limit factor of the airframe was 6 g's damage could result. On page 3 of my 701 plans there is a warning about the decrease in load factor if opereating overweight, there is also a formula. The 701 sp has an ultimate load factor of 6 g's pos. "g" overgross = 6 x design gross weight/actual gross weight, then divide this by 1.5(saftey factor)to get the load limit factor. I believe the load limit factor of the airframe defines which catagory the aircraft qualifies for under the design standards of FAR23. I invite any and all corrections and clarifications as I am also learning. What is interesting about the CH640 is it is based on the CH2000 certified which has a saftey factor of 2. Which may or maynot mean anything to the 640. >For example, the Vne is published at 167 mph however I have done flutter testing up to 190 mph with no sign of any problems ... Vne is 90% of the speed that flutter occurs, 190x.9=171 171mph-167mph = 4mph. This seems close enough to be inside the margin of error of the gauge, pitot, static system. Has the question of gauge accuracy and calibration to TAS been adressed? As Larry mentioned, and I respect his knowledge and opinion, many things need to be considered for "safe" operation. And I think what Jeff wants to know is how far he can crowd or exceed the published Vne, Vc (Vno) and weight limitations "safely". William Wynne has a sobering and realistic grasp on the concept of risk versus saftey on page 7 of his corvair conversion manual, personally I can say that his common sense philosophy has adjusted my attitude toward my hobby in a positive direction. Also what I know about maneuvering speed, load limits, and angle of attack, I learned from Rod Machado's Private Pilot Handbook which explains these relationships very well. There are companies that provide engineering and testing services for experimental aircraft, they advertise in the EAA publications under the heading of "services". IMHO a qualified second and even third opinion of the design with its subsequent modifications would go far to understand the limitations of this aircraft and minimize un-necessary risks. Respectfully Roy Szarafinski 701 plans __________________________________ ________________________________ Message 12 ____________________________________ Time: 02:21:50 PM PST US From: "cgalley" Subject: Re: Zenith-List: Jeff Paden: Big-a$$ engine installation --> Zenith-List message posted by: "cgalley" Strange you mention 601 motor mounts. I have pictures of FAILED 601 motor mount attachment fittings. Fittings that failed with a Subaru engine. I don't know if part of the additional weight is due to the addition of a constant speed prop. It hangs about 60 to 80 pounds in itself as far forward as one can get. It has a large moment arm working on the motor mount and the attach points. I don't know the weight of the approved engine but for sake of discussion let's say the factory engine was 300 pounds and the motor mount was designed to handle 6 gs. It means that it is designed to withstand an 1800 pound load. Adding 100 pounds is a 33% increase in weight. Divide the original design load by 400 pounds and the g loads that the structure can handle is now only 4.5 gs To put it another way the structure with the lighter load will break at 6 gs but now it only takes 4.5 gs. Now there is a safety factor but you can see that increasing the weight over the designed loads decreases even the safety factor by 25%. Another good reason to build as designed and as light as possible. All the little extras do add up. Cy Galley EAA Safety Programs Editor Always looking for ideas and articles for EAA Sport Pilot ----- Original Message ----- From: "James Brigman" Subject: Zenith-List: Jeff Paden: Big-a$$ engine installation > --> Zenith-List message posted by: "James Brigman" > > > From: "Jeff Paden" > > Subject: Zenith-List: Gross Weight > ... > > I need to know what limits the gross weight of an aircraft. How does > the > > engineer calculate gross weight of an aircraft? > > I ask this because at this moment I have a VERY powerful CH-640 that I > can > > only take one passenger in which does not seem logical at all. > ... > > what goes in to the > > calculations so that I can come up with a logical gross > > weight for my aircraft. The 2200 lbs that is published > > simply is not logical for an aircraft that has an empty > > weight of 1560 lbs. > ... > > installed a 260 hp engine. However this is not the problem > > The engine I installed is only 110 lbs heavier than the > > 180 hp engine the aircraft was tested with. > > This also keeps me within the max installed power > > plant weight as I had checked this before installing the engine. > > My aircraft is 1560 lbs empty and the proto was 1147 lbs empty. > > This means that some how I have added over 400 lbs and > > the engine only accounts for 110 lbs of that. If I had > > the other 300 lbs to play with then I would not have > > a problem at all. > > Jeff; > First: congratulations are in order for your completing a CH-640 and > installing such a nice engine. I see from your website where you went > with an O-540 instead of the usual O-360. Thanks for the fresh update to > your builder page on the ZAC website - your plane looks beautiful. I > have complete lust for your aircraft...I'm hoping that a 640 will be "my > next airplane". :-) > > Now: I'm not gonna tell you HOW on anything. From your website, you seem > to know what kind of plane you want to end up with. You are right that > basic weight does not determine useful load capacity. In fact, for many > certified GA planes, there are STC's for engine upgrades that actually > increase gross weight a bit, not decrease it. However, there's more to > it than just gross weight: Structural load design, empennage sizes CG > and weight distribution are as important as gross weight. I don't have > the answers, but here's where I would look if I were in your shoes. > > 1) Be clear about one thing: you went 20hp over the powerplant design > for this aircraft, per http://www.zenair.com/specifications.html. I'm > sure all us builders routinely tax the patience of our fathers at ZAC. I > know I have ;-) Reading between the lines at > http://www.zenair.com/engine.html, it almost looks like Chris > purposefully excluded the O-540 as an engine choice. > > 2) There's got to be both a Weight & Balance table as well as a POH for > the CH-640. These are the base documents which will precisely answer > your questions about how to calculate gross weight. The CH-640 has a > certified GA brother, so there ought to be a W&B template and a POH > template for it. Although they are not available online from ZAC (for > good reason) the versions for the 601 are available at > http://www.zenithair.com/zodiac/6-up-bldr.html > > 3) Aircraft engine weights are published as optimistically as possible. > This means "DRY" (no engine oil, coolants or fuel) and WITHOUT starter, > alternator, carb/intake or even magnetos. This could account for as much > as 100lbs of the extra weight you're seeing. Here's a great webpage for > engine reference: http://www.wanttaja.com/avlinks/engines.htm Ron has an > interesting link on "structural efficiency" which shows how widely the > gross weight of aircraft can vary with their various engines and > airframes. > > 4) How much heavier is your panel than the "stock" ZAC panel for the > 640? I remember when I sat in the ZAC CH-640 at Sun 'n Fun, it had the > typical 6-pack, a couple radios, a transponder and a small assortment of > engine instruments (I think six or eight small gauges?). Chris likes to > keep his panels simple, it really helps with the CG. > > 5) Did you go with the stock fuel tanks to feed that bit O-540, or did > you beef those up a bit too? For reference between yours and several GA > planes, see http://www.zenair.com/performance-comparison.htm. You could > have picked up 80lbs of weight there easily. > > 6) Where's your battery placement? Is it on the firewall or back behind > in the rear of the plane? Don't you have to use a bigger battery to > start that 540? If so, how much weight did that add? > > 7) You've clearly been flying the aircraft to generate test data. How's > it handle in the flare? What happens in the stall? What about landing > speed? I know from past history that some guys who built 601's with > bigger engines in the UK had to beef-up their HS attach points and > install larger HS's to get PFA certification. (that might still be in > the archives here) > > ________________________________ Message 13 ____________________________________ Time: 03:33:24 PM PST US From: "Larry McFarland" Subject: Re: Zenith-List: Jeff Paden: Big-a$$ engine installation --> Zenith-List message posted by: "Larry McFarland" Cy, A correction is perhaps in order here. The engine wasn't a Subaru, but a Rotax 912. I had to send drawings of the 912 mount to permit one to be made to replace the one that had cracks in addition to the broken attachment fittings. This was a 10-yr old plane that had seen some rough runways and was exposed to the damp ocean air in the UK. The mount was 3/4"-.035 wall 4130 tube. I recommended .049 as replacement for durability and an easier welding job. Larry Do not archive Subject: Re: Zenith-List: Jeff Paden: Big-a$$ engine installation > --> Zenith-List message posted by: "cgalley" > > Strange you mention 601 motor mounts. I have pictures of FAILED 601 motor > mount attachment fittings. Fittings that failed with a Subaru engine. ________________________________ Message 14 ____________________________________ Time: 04:57:21 PM PST US Received-SPF: none (MAIL-SERVER.madbbs.com: domain of jeffpaden@madbbs.com does not designate any permitted senders) From: "Jeff Paden" Subject: Re: Zenith-List: RE; Gross Weight --> Zenith-List message posted by: "Jeff Paden" Thank you VERY much. This was exactly the type of response I was looking for. Now I have a few different directions I can go to learn more about what goes in to the calculations. And you are correct, I am trying to figure out what the aircraft will do safely and what ever that ends up being is what I will stick to. The last thing I want to do is to push an aircraft beyond safe operating limits. Thank you again Jeff Paden Hello Jeff and regards to the group, > I need to know what limits the gross weight of an aircraft. How does the > engineer calculate gross weight of an aircraft? Sand bags. Lots of them. I guess engineers can make all the calculations on a supercomputor and come up with a very close theoretical approximation of performance but I think the real test is real weight. Gross weight is related to g force and load factor. The (ultimate?)load limit factor for an airframe is based on the maximum ammount of g force (weight)it can withstand before damage occurs. So a 2200# gross weight airframe rated for 6 g's ultimate load shouldn't be damaged up to a weight of 13,200 pounds. But subject a 2500# gross weight to 6 g's and get 15,000 pounds Angle of attack and g force have a near linear relationship. In level flight double triple,or quadruple the angle of attack and the g force (weight) doubles,triples, or quadruples. If at 150mph un-accelerated flight with an angle of attack of 3 degrees, a gust or stick deflection increases the angle of attack to 18 degrees the airframe would be subjected to 6 g's(18/36). Angle of attack and airspeed also have a relationship. The same airframe at 180mph could have an angle of attack of 2 degrees and would experience 6 g's at 12 degrees aoa, well below critical aoa, and 7 g's at 14 degrees aoa. If the load limit factor of the airframe was 6 g's damage could result. On page 3 of my 701 plans there is a warning about the decrease in load factor if opereating overweight, there is also a formula. The 701 sp has an ultimate load factor of 6 g's pos. "g" overgross 6 x design gross weight/actual gross weight, then divide this by 1.5(saftey factor)to get the load limit factor. I believe the load limit factor of the airframe defines which catagory the aircraft qualifies for under the design standards of FAR23. I invite any and all corrections and clarifications as I am also learning. What is interesting about the CH640 is it is based on the CH2000 certified which has a saftey factor of 2. Which may or maynot mean anything to the 640. >For example, the Vne is published at 167 mph however I have done flutter testing up to 190 mph with no sign of any problems ... Vne is 90% of the speed that flutter occurs, 190x.9171 171mph-167mph 4mph. This seems close enough to be inside the margin of error of the gauge, pitot, static system. Has the question of gauge accuracy and calibration to TAS been adressed? As Larry mentioned, and I respect his knowledge and opinion, many things need to be considered for "safe" operation. And I think what Jeff wants to know is how far he can crowd or exceed the published Vne, Vc (Vno) and weight limitations "safely". William Wynne has a sobering and realistic grasp on the concept of risk versus saftey on page 7 of his corvair conversion manual, personally I can say that his common sense philosophy has adjusted my attitude toward my hobby in a positive direction. Also what I know about maneuvering speed, load limits, and angle of attack, I learned from Rod Machado's Private Pilot Handbook which explains these relationships very well. There are companies that provide engineering and testing services for experimental aircraft, they advertise in the EAA publications under the heading of "services". IMHO a qualified second and even third opinion of the design with its subsequent modifications would go far to understand the limitations of this aircraft and minimize un-necessary risks. Respectfully Roy Szarafinski 701 plans __________________________________ ________________________________ Message 15 ____________________________________ Time: 05:01:05 PM PST US Received-SPF: none (MAIL-SERVER.madbbs.com: domain of jeffpaden@madbbs.com does not designate any permitted senders) From: "Jeff Paden" Subject: Re: Zenith-List: Re: Zenith-List Digest: 20 Msgs - 10/30/04 --> Zenith-List message posted by: "Jeff Paden" I agree, I was shocked when we did the weight and balance to find that the aircraft was so darn heavy. While building I was very careful to try to keep everything as light as possible because I knew that my engine was going to add 110 lbs. However we have used two different sets of scales and the fact is that the aircraft is very heavy. I sure wish that I could get ZAC to answer some email and then maybe I could rest a little better. However for some reason they are ignoreing my email and I have no idea of why. Maybe they are not getting the email because of some spam filter or something. I plan on calling them on Monday to see what is going on. Thank you all for your help Jeff Paden Also you seem to have a HUGE increase in empty weight compared to the prototype - over 30%? Are you sure this is so? That's an awful lot of weight. Besides the engine, where did it all come from? Did you make other modifications/imrovements? Have you ever added it all up? I'd be very uncomfortable not knowing why my aircraft is so much heavier... Good luck -- be careful! -- Grant Corriveau C-GHTF / HDS / CAM100 ________________________________ Message 16 ____________________________________ Time: 05:07:03 PM PST US Received-SPF: none (MAIL-SERVER.madbbs.com: domain of jeffpaden@madbbs.com does not designate any permitted senders) From: "Jeff Paden" Subject: Re: Zenith-List: RE: Gross weight --> Zenith-List message posted by: "Jeff Paden" I agree with you on this one and that is what I want to know also. Where the heck did all the weight come from! That is why I said that I would like to see the prototype on scales because I just can not believe that my aircraft is that much heavier than it is supposed to be. I for one was SHOCKED. Jeff Paden Maybe I am off base here, but I am much more concerned about the extra 300lbs in the airframe than the extra 110 lbs in the engine. Better than half the list is using an engine that is considerably heavier power plants than the engines that Chris had in mind. There is a ton of documentation on compensating for extra engine weights, from the Subaru in the 601, to Ben's Ford in the 801. Jeff has stated that the engine is within the max designed weight. We can't say that for the 701 guys looking into Corvair, and Subaru engine installations. My question is what in the !#@* happened with the airframe weight? I know that you double and triple checked your numbers when weighing your aircraft, but something is way (weigh) off! :) That is the first place I would be looking into. You built from kit right? I don't think it is even possible to add 300 lbs of weight unless you skinned it with .050 stainless! Maybe I missed a post that explained this, but I don't think so. Let's not lecture on engine weights and weight in the tail when many of the Subaru guys have been putting batteries behind the passenger compartment to compensate for engine weight. Respectfully, Brandon Tucker 601 HDS wings, tail complete do not archive ________________________________ Message 17 ____________________________________ Time: 05:13:30 PM PST US Received-SPF: none (MAIL-SERVER.madbbs.com: domain of jeffpaden@madbbs.com does not designate any permitted senders) From: "Jeff Paden" Subject: Re: Zenith-List: Gross Weight --> Zenith-List message posted by: "Jeff Paden" Actually I did not deviate from the design. The engine I installed is prop limited to 240 hp which is the max allowed hp and the installed engine weight is a few pounds below the published max. Also Chris approved the installation of this engine before I even purchased it. I made sure to check everything before putting the past two years into building her and ZAC has always been very good at answering any questions I had while building. We have actually helped each other out quite a bit over the past two years. I am the one that fixed the CD they send to all builders since the one they sent to me did not work at all and my business at that time was web page design and the CD is nothing more than a web page on CD. We have a good working relationship and I am sure that if I can ever get ahold of them that they will be able to clear up most of my questions Thank you for your input though Jeff Paden --> Zenith-List message posted by: "cgalley" Hate to burst your bubble. The stall speed is probably much higher even though you airspeed says 45 mph. Most airspeeds are very inaccurate at low speed due to positional errors of the pitot. Using my Bellanca 14-13-2 the listed speed is 48 MPH but I see an indicated airspeed of 38 MPH before the break. You might want to get out the GPS and see what it says by trying several directions to cancel out the wind. This is what the Test period is all about. Flutter is not the only problem at higher speeds. There are some strength considerations. The FAA establishes the red-line by demonstrating flight to a number and then making the red-line at 90% of this demonstrated figure. The faster you go, the stronger the airframe has to be to withstand air loads and turbulence. That is why the safe maneuvering speed is much less than the red line. The VNE for your plane you say is 167. That is designed into the airframe by the designer. You probably don't have an margin of error for gust loading above that point unless you have redesigned the airframe. Just one bout of clear air turbulence could ruin your day. Or you could do the damage yourself by full rapid control inputs. I hate to say this but your plane is every designer's worse nightmare. When you make the modifications then all the careful calculations of the designer are gone. I hope that you understand that due to liability considerations, the factory probably will not give advice. Remember it is no longer a Zenith design, it is yours and yours alone due to the deviations from the design parameters Right now there is a move underfoot to ground a certified airplane via an AD. Why? Because these airplanes have been re-engined not even with greater weight but just added horsepower. I hope you can get some structural analysis done. All airplanes fly better when they are lighter. Cy Galley EAA Safety Programs Editor Always looking for ideas and articles for EAA Sport Pilot ----- Original Message ----- From: "Jeff Paden" Subject: Re: Zenith-List: Gross Weight > --> Zenith-List message posted by: "Jeff Paden" > > > I have had many members of the list point out the fact that I have installed > a 260 hp engine. However this is not the problem as is easy to see when you > do the calculations. The engine I installed is only 110 lbs heavier than > the 180 hp engine that the aircraft was tested with. This also keeps me > within the max installed power plant weight as I had checked this before > installing the engine. > My aircraft is 1560 lbs empty and the proto was 1147 lbs empty. This means > that some how I have added over 400 lbs and the engine only accounts for 110 > lbs of that. If I had the other 300 lbs to play with then I would not have > a problem at all. > > As for swapping out the engine for a smaller one, that just simply is not an > option. Everything was built around this engine and if needed then I will > simply have a very nice two place aircraft or only carry 20 gal of fuel with > four. > So far I have found that almost every aspect of the figures on the web site > are WAY off and I am just looking for answers as to why. > > For example, the Vne is published at 167 mph however I have done flutter > testing up to 190 mph with no sign of any problems as of yet and that is > still only at 75% power. I will post to the list once I figure out what the > real Vne is. By the way, I do NOT recommend to anyone on the list that you > perform flutter testing unless you really know what you are doing. I have a > friend who is a test pilot and he is the one that is helping me with this > test. Do the test wrong and you will destroy the aircraft and probably not > survive the test. > > With that said, I have also found that my stall speed is 45 mph with full > flaps so the fact that the aircraft is heavy has not increased that number > as we expected it to do. Also my take off roll is only about 500 feet but > that is probably because of the extra power. > > Once I have all the numbers confirmed then I will post them all to the list. > > I guess my next job is to try to find a way to make the aircraf lighter but > I really can't think of anything that is going to make that happen. > > Thank you all for your help and don't worry, after putting one aircraft in > the trees I don't have any plans of flying this one in any condition that > would be unsafe. We just need to figure out what is "SAFE" for this > aircraft and the published numbers simply do not seem to have anything to do > with my aircraft. > > Jeff Paden > CH-640 Test flight stage. > > > Jeff, > The gross weight is defined by structure and hardware that's heavly > calculated to provide > a safe platform for weight, maneuvering and power loading. On the simple > side, you can put an > engine that weighs much more than the 180 to 220 HP engine, but you pay a > price in safety and > performance that should become obvious. Anytime you have more tail weight > than the > baggage you're able to carry, you've gotten outside of the fine art of a > design specification > that's initially intended to keep you and yours safe for a long period of > time. The engine > limits assure that the elevator will offer adequate resistance to pitching > moments from turbulence > and stalls so long as the plane is balanced within the envelope. The limits > also assure that the > engine mounts and attachments will not crack prematurely from fatigue of the > engine torque and > prop pulse. Both of these design elements are huge for the designer. These > are tested and > designed with safety factors that assure a reasonable lifespan. When one > exceeds the specification > the first compromise is in wear and working fatigue life. Little else will > be noticable, but > time becomes a bigger player as a few bad landings and weather work against > the airframe. > > I've tried to put my finger on the exactitude of your problem and it is > this. > It is much safer to consider the practical solution of trading engines to > get within specification > and resolve every problem you've had to deal with. > Larry McFarland - 601HDS > > ________________________________ Message 18 ____________________________________ Time: 06:46:32 PM PST US From: "Bill Steer" Subject: Zenith-List: Canopy build order --> Zenith-List message posted by: "Bill Steer" I've just started working on the canopy for my 601 HD and am wondering about the build order (I'm using the side-tilt). The manual says to construct the frame so it fits nicely on the fuselage and then to "fine tune" it to fit the canopy. Does that mean the frames, parts 6E4-1 and 6E4-2, are cut to about the dimensions shown in the plans, so it fits the fuselage, and then the canopy itself is trimmed to fit that frame? That doesn't seem to allow for raising and lowering the height of the canopy with dimension "h" shown on the plans. And the frames and the other frame parts can obviously only be drilled once, so can't be changed for fine tuning. Last, does "fine tune" refer to changing the shape of the frames so they exactly fit the canopy? Thanks very much for any help. Bill ________________________________ Message 19 ____________________________________ Time: 11:38:02 PM PST US From: "cgalley" Subject: Re: Zenith-List: Jeff Paden: Big-a$$ engine installation --> Zenith-List message posted by: "cgalley" Ah CRS strikes again. Point is that the Attachment points can fail with even a lighter engine. Better check carefully with a heavier engine. I think a Rotax is even lighter than a Subaru. ----- Original Message ----- From: "Larry McFarland" Subject: Re: Zenith-List: Jeff Paden: Big-a$$ engine installation > --> Zenith-List message posted by: "Larry McFarland" > > Cy, > A correction is perhaps in order here. > The engine wasn't a Subaru, but a Rotax 912. I had to send drawings > of the 912 mount to permit one to be made to replace the one that had cracks > in addition to the broken attachment fittings. This was a 10-yr old plane > that > had seen some rough runways and was exposed to the damp ocean air > in the UK. The mount was 3/4"-.035 wall 4130 tube. I recommended .049 > as replacement for durability and an easier welding job. > > Larry > Do not archive > > Subject: Re: Zenith-List: Jeff Paden: Big-a$$ engine installation > > > > --> Zenith-List message posted by: "cgalley" > > > > Strange you mention 601 motor mounts. I have pictures of FAILED 601 motor > > mount attachment fittings. Fittings that failed with a Subaru engine. > >