---------------------------------------------------------- Zenith-List Digest Archive --- Total Messages Posted Sat 10/30/04: 20 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:40 AM - Re: Priming Aluminum (wizard-24@juno.com) 2. 02:38 AM - Reply to Matt re Priming Al for Zenith Aircraft (Howard Carter) 3. 04:09 AM - Re: Beautiful 701 (skyshops) 4. 05:17 AM - Re: Beautiful 701 (ron wehba) 5. 06:15 AM - XL nose-wheel fork (Rico Voss) 6. 09:50 AM - Re: Priming Aluminum (JERICKSON03E@aol.com) 7. 10:05 AM - VG's on horizontal stabilizer (Dabusmith@aol.com) 8. 10:48 AM - Re: VG's on horizontal stabilizer (Land Shorter) 9. 12:12 PM - Roll trim (roy vickski) 10. 02:19 PM - 801 Fuel tank set up (Keystone Engineering LLC) 11. 03:52 PM - Re: VG's on horizontal stabilizer (Benford2@aol.com) 12. 04:44 PM - Replacement Canopy Recomendation (Bill Howerton) 13. 07:05 PM - Re: Replacement Canopy Recomendation (Michel Therrien) 14. 07:54 PM - Gross Weight (Jeff Paden) 15. 08:36 PM - Re: Replacement Canopy Recomendation (Trevor Page) 16. 08:39 PM - Re: HD wing assembly guide (Trevor Page) 17. 08:43 PM - 601 and fuel return line, redux (Trevor Page) 18. 09:04 PM - Re: 601 and fuel return line, redux (Jerry Latimer) 19. 10:04 PM - Re: Gross Weight (Larry McFarland) 20. 11:19 PM - Re: Gross Weight (Jeff Paden) ________________________________ Message 1 _____________________________________ Time: 12:40:27 AM PST US Subject: Re: Zenith-List: Priming Aluminum From: wizard-24@juno.com --> Zenith-List message posted by: wizard-24@juno.com > What is the preferred method for priming Aluminum. What methods > are the best? My advice on this would be to check the archives: http://www.matronics.com/archives Do a search on primer, and you'll get more information than you'll know what to do with. This topic pops up every 6 months or so, so the archives are loaded. do not archive Now includes pop-up blocker! Only $14.95/ month - visit http://www.juno.com/surf to sign up today! ________________________________ Message 2 _____________________________________ Time: 02:38:39 AM PST US From: Howard Carter Subject: Zenith-List: Reply to Matt re Priming Al for Zenith Aircraft 0.00 FORGED_RCVD_HELO Received: contains a forged HELO --> Zenith-List message posted by: Howard Carter Matt, there are several methods that are acceptable: 1. Spray yellow zinc chromate on both sides of parts. Paint the outer surfaces with your finish paint scheme. This is the way Boeing does it for all their planes; 2. Use a corrosion proofing primer like Sanchem No-Ox-ZD-500. This stuff meets the MIL spec salt spray requirements, and is cheaper and also readily available; 3. Spray the stuff recommended by ZAC called Cortec. This stuff does not meet the MIL spec requirements; 4. Use an oil spray after the plane is built. The oil, called Corrosion X, will creep everywhere and eventually start coming out of the seams on the skins, making a mess requiring frequent washing. 5. Don't prime the interior surfaces. Cessna uses 2024 Alclad and never bothered to put in corrosion protection. My 172D had no priming inside. (Piper used ZnCr .) Dont forget to scuff the surfaces with Scotchbrite pads and then wash the parts with toluene or similar solvents before painting with anything. Some perspective to consider: how many years and flying hours do you expect of you plane? Your preference! Howard Carter ________________________________ Message 3 _____________________________________ Time: 04:09:11 AM PST US From: "skyshops" Subject: RE: Zenith-List: Beautiful 701 --> Zenith-List message posted by: "skyshops" Thanks for the compliment, this is one of our happy customers. Danny Skyshops.org -----Original Message----- From: owner-zenith-list-server@matronics.com [mailto:owner-zenith-list-server@matronics.com] On Behalf Of Rick Subject: Zenith-List: Beautiful 701 --> Zenith-List message posted by: Rick Saw a beautiful 701 on the flight line today at the Light Sport Expo in Sebring! N987PD. Beautiful plane...I believe it will go home to KY soon.... Rick Orlando, FL http://www.geocities.com/n701rr/index.html == == == == ________________________________ Message 4 _____________________________________ Time: 05:17:02 AM PST US From: "ron wehba" Subject: Re: Zenith-List: Beautiful 701 --> Zenith-List message posted by: "ron wehba" where is the picture at? ----- Original Message ----- From: "skyshops" Subject: RE: Zenith-List: Beautiful 701 > --> Zenith-List message posted by: "skyshops" > > Thanks for the compliment, this is one of our happy customers. > > Danny > Skyshops.org > > -----Original Message----- > From: owner-zenith-list-server@matronics.com > [mailto:owner-zenith-list-server@matronics.com] On Behalf Of Rick > To: 701 List > Subject: Zenith-List: Beautiful 701 > > --> Zenith-List message posted by: Rick > > Saw a beautiful 701 on the flight line today at the Light Sport Expo in > Sebring! N987PD. > > Beautiful plane...I believe it will go home to KY soon.... > > > Rick > Orlando, FL > http://www.geocities.com/n701rr/index.html > > > == > == > == > == > > ________________________________ Message 5 _____________________________________ Time: 06:15:43 AM PST US From: Rico Voss Subject: Zenith-List: XL nose-wheel fork --> Zenith-List message posted by: Rico Voss I sent a note to ZAC Tech Support regarding the XL nose wheel fork being a little undersized (considering that the HD and HDS both had doublers). Response was that the "XL requirements are being reviewed". [Hopefully] More to follow... [If anybody hears anything, please let us know.] Rico, XL/3300--still fusing, KC Slugworks do not archive __________________________________ ________________________________ Message 6 _____________________________________ Time: 09:50:10 AM PST US From: JERICKSON03E@aol.com Subject: Re: Zenith-List: Priming Aluminum --> Zenith-List message posted by: JERICKSON03E@aol.com In a message dated 10/30/2004 2:41:23 AM Central Daylight Time, wizard-24@juno.com writes: --> Zenith-List message posted by: wizard-24@juno.com > What is the preferred method for priming Aluminum. What methods > are the best? My advice on this would be to check the archives: http://www.matronics.com/archives Do a search on primer, and you'll get more information than you'll know what to do with. This topic pops up every 6 months or so, so the archives are loaded. One of the best sources of info for us home builders is an FAA manual. AC 43.13-1B/2A. Acceptable Methods, Techniques, and Practices. Aircraft Inspection, Repair @ Alterations. It covers corrosion control,,, your question. Can be ordered through AC catalogues & EAA. Inexpensive and full of info. It is the way to understand AC maintenance, and has guidance for most things AC. Practical info, nonpressurized aircraft. If you start out using it as a guide, it will aid you in becoming an FAA Repairman,,, for your home built aircraft. It also can help us understand Inspection. The MOST frequently accomplished AC maintenance action. It covers things like what to inspect & how to inspect. I hope that others, EAA members, A&P mechanics and IA's will add to this, and encourage the Repairmen, and future Repairmen among us. Jerry ________________________________ Message 7 _____________________________________ Time: 10:05:21 AM PST US From: Dabusmith@aol.com Subject: Zenith-List: VG's on horizontal stabilizer --> Zenith-List message posted by: Dabusmith@aol.com Has anyone ever put VG's on the underside of the horizontal stabilizer of the 701 or 801? Anyone know what effects they might have? Dave Smith N701XL 300+hrs and loving this plane! Graham WA ________________________________ Message 8 _____________________________________ Time: 10:48:39 AM PST US From: Land Shorter Subject: Re: Zenith-List: VG's on horizontal stabilizer --> Zenith-List message posted by: Land Shorter Dave, I've been wanting someone to try them since all my predictions say it should work fabulous on the 701/801 tail. With my 100% money back guarantee you should give mine a try using double-stick tape and let us all know what you find. Or fly over here to North Idaho and I'll put them on for you and then we can both hop in our planes and go have some fun at some of the local short strips :) Joa www.landshorter.com Dabusmith@aol.com wrote: --> Zenith-List message posted by: Dabusmith@aol.com Has anyone ever put VG's on the underside of the horizontal stabilizer of the 701 or 801? Anyone know what effects they might have? Dave Smith N701XL 300+hrs and loving this plane! Graham WA --------------------------------- ________________________________ Message 9 _____________________________________ Time: 12:12:53 PM PST US From: roy vickski Subject: Zenith-List: Roll trim --> Zenith-List message posted by: roy vickski Regards to the group, 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) vs a constant trim tab position (which provides trim force proportional to speed). His is a 200 mph+ aircraft with a controllable flight envelope of over 100mph. My question is during decel flight (landing) on our relatively slow aircraft, do the planes with aileron tabs set for cruise exhibit roll tendencies and if so is it much to worry about. Roy Szarafinski 701 plans __________________________________ ________________________________ Message 10 ____________________________________ Time: 02:19:06 PM PST US From: Keystone Engineering LLC Subject: Zenith-List: 801 Fuel tank set up --> Zenith-List message posted by: Keystone Engineering LLC Paul and Mel I have my 801 set up with the two interior tanks always on except for an emergency / maintenance shut off and the two outboard tanks are valved in the wing root. The two tanks fuel lines hook together in the wing root. I have been happy and have not had any problems. I have a had time or two that one tank seemed to drain faster from one tank than the others. What invariably had happened was I was flying out of square because of a lateral imbalance and I was not firm enough with the controls to keep it square on a long flight. On one flight I got concerned and intentionally cross controlled the plane to even out the fuel. It evened out in 1/2 an hour or so. I do not have the aluminum boxes under the seats, just one gaskolator under the pilots seat. I do not have a return line from the carburetor. My fuel lines flow continually upward toward the wing or the carburetor. Other than problems with fuel going from one inside tank to the other when I park on a slope, I'm happy with the way it is set up. I learned early on not to parking 45 degrees down the beach like I always had done. I now park straight down the beach. This is tough to do on a steep beach when you are by yourself. When I had a flat on a sand bar and was lifting on one lift strut to get the tire off the ground, I did spill fuel out of the lower tank after a while but the wing I was holding up got lighter as the fuel switched tanks. Bill Wilcox N801BW Prop spinner installed with no speed gain but the engine seems smoother. 140 hrs Lycoming O-360 Valdez, AK Time: 03:17:43 AM PST US From: "Mel Hinde" Subject: Re: Zenith-List: Re: Fuel Senders --> Zenith-List message posted by: "Mel Hinde" Paul, Would not advise connecting two tanks together. My 801 was built with the two inboards connected and the two outboards connected together as per the ZAC instructions. I was continually getting air bubbles in one line or the other and it would empty one tank and then suck air. Whichever tank wasn't empty would then be unusable. At first I put a positive pressure vent into the caps and it helped, but didn't completely solve the problem. The little tank (mixer) that ZAC supplied in the kit to mount under the seats, one for inboard and one for outboard tanks, has an air space in the top (trap??) and it continues to feed air back into the lines when the engine is shut down. Obviously, these gather at any high spot or in front of the elbows and create an air lock. Even on the ground for days the tanks do not equalize. Had to put individual line valves in all four lines. When I switch to a tank that has air in the line, gas flows fine but the air bubbles come back after I switch that tank off. I had installed four gas gauges, fortunately so can monitor the levels. To complicate things, the mechanical pump has a return line to tank one of one third of the fuel drawn, so have to continually switch to tank one to keep it from overflowing and then back to one of the others. Nightmare. HINDE, Mel CH801, Walter LOM 337B, c/s prop ________________________________ Message 11 ____________________________________ Time: 03:52:05 PM PST US From: Benford2@aol.com Subject: Re: Zenith-List: VG's on horizontal stabilizer --> Zenith-List message posted by: Benford2@aol.com In a message dated 10/30/2004 11:49:26 AM Mountain Daylight Time, landshorter2@yahoo.com writes: > > I've been wanting someone to try them since all my predictions say it should > work fabulous on the 701/801 tail. With my 100% money back guarantee you > should give mine a try using double-stick tape and let us all know what you > find. > > I am close to norhtern Idaho but the prop blast of the Ford might dislodge them into next week. Ben Haas N801BH jackson Hole Wy ________________________________ Message 12 ____________________________________ Time: 04:44:09 PM PST US From: "Bill Howerton" Subject: Zenith-List: Replacement Canopy Recomendation --> Zenith-List message posted by: "Bill Howerton" After weeks and weeks of working on my canopy, I was finally ready today for final assembly -- or so I thought. As I was in the process of fitting the bubble to the frame, I noticed that the holes no longer lined up. As I worked to adjust the frame.... SNAP!!! The bubble got a one-foot crack which seemed to grow all the way across the top in a matter of seconds. AAARRRGGGHHHH!!! Needless to say, I'm now looking for a new canopy bubble. I've heard some of you talk about Todd's Canopies in the past. Can you tell me whether his canopies are any good, would you recommend them? I went to his website, and he specifaclly mentions that he has canopies for the CH 601, which I believe is the same one as the XL, but i want to make sure before I order one. Also are there any other canopy makers that you guys would recommend? ________________________________ Message 13 ____________________________________ Time: 07:05:14 PM PST US From: Michel Therrien Subject: Re: Zenith-List: Replacement Canopy Recomendation --> Zenith-List message posted by: Michel Therrien Todd is the one to use. He does good work, good service, good price and crating charge is included. do not archive --- Bill Howerton wrote: > --> Zenith-List message posted by: "Bill Howerton" > > > After weeks and weeks of working on my canopy, I was > finally ready today for > final assembly -- or so I thought. As I was in the > process of fitting the > bubble to the frame, I noticed that the holes no > longer lined up. As I > worked to adjust the frame.... SNAP!!! The bubble > got a one-foot crack > which seemed to grow all the way across the top in a > matter of seconds. > AAARRRGGGHHHH!!! Needless to say, I'm now looking > for a new canopy bubble. > > I've heard some of you talk about Todd's Canopies in > the past. Can you tell > me whether his canopies are any good, would you > recommend them? I went to > his website, and he specifaclly mentions that he has > canopies for the CH > 601, which I believe is the same one as the XL, but > i want to make sure > before I order one. Also are there any other canopy > makers that you guys > would recommend? > ===== ---------------------------- Michel Therrien CH601-HD, C-GZGQ http://mthobby.pcperfect.com/ch601 http://www.zenithair.com/bldrlist/profiles/mthobby http://pages.infinit.net/mthobby __________________________________ http://mobile.yahoo.com/maildemo ________________________________ Message 14 ____________________________________ Time: 07:54:03 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: 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 15 ____________________________________ Time: 08:36:09 PM PST US From: Trevor Page Subject: Re: Zenith-List: Replacement Canopy Recomendation --> Zenith-List message posted by: Trevor Page Yup, call Todd. He's the man you want to talk to. Got mine in perfect condition and shipping was fast from Florida. Trevor Page 601 HD On Oct 30, 2004, at 7:43 PM, Bill Howerton wrote: > --> Zenith-List message posted by: "Bill Howerton" > > After weeks and weeks of working on my canopy, I was finally ready > today for > final assembly -- or so I thought. As I was in the process of fitting > the > bubble to the frame, I noticed that the holes no longer lined up. As I > worked to adjust the frame.... SNAP!!! The bubble got a one-foot crack > which seemed to grow all the way across the top in a matter of seconds. > AAARRRGGGHHHH!!! Needless to say, I'm now looking for a new canopy > bubble. > > I've heard some of you talk about Todd's Canopies in the past. Can > you tell > me whether his canopies are any good, would you recommend them? I > went to > his website, and he specifaclly mentions that he has canopies for the > CH > 601, which I believe is the same one as the XL, but i want to make sure > before I order one. Also are there any other canopy makers that you > guys > would recommend? > > > _- > ======================================================================= > _- > ======================================================================= > _- > ======================================================================= > _- > ======================================================================= > > > > ________________________________ Message 16 ____________________________________ Time: 08:39:26 PM PST US From: Trevor Page Subject: Re: Zenith-List: HD wing assembly guide --> Zenith-List message posted by: Trevor Page Thanks for the pointer Randy. My kit was purchased as a project and one wing is complete and the other just needs the nose skin. However a month ago I picked up a new set of LE wing tanks so the skin will have to partially come off the completed wing. Plumbing for strobes/pitot etc.. is already installed an waiting! Trev On Oct 29, 2004, at 9:49 PM, Randy Stout wrote: > --> Zenith-List message posted by: Randy Stout > > Trevor > > There is no guide for the HD. The guide for the HDS seemed a bit > difficult to follow as all the dimentions were different. Just read > through the HDS guide to get the basic idea, then go for it. Make sure > you use lots of clecos and don't rivet anything until you are sure > everything is correct. The wings were fairly easy until I got to the > outboard edges. The cut around the edge is pretty much freehand. You > just make it fit the end rib. > > You also might want to consider any wiring, or plumbing before you > close it up for good. It's hard to add afterwards. > > Randy Stout > n282rs "at" earthlink.net > www.geocities.com/r5t0ut21 > > -----Original Message----- > From: Trevor Page > To: zenith-list@matronics.com > Subject: Zenith-List: HD wing assembly guide > > --> Zenith-List message posted by: Trevor Page > > Listers, its time for me to install the nose skin on the one wing I > have left to complete and I don't have the assembly guide for the HD > wing. I have HDS guide from the ZAC website but I'm not sure if they > are assembled in the same manner. > > Can anyone confirm they are the same? If not can one provide me with > the HD wing assembly guide in PDF? > > Thanks! > > Trevor Page > 601HD 97% complete > > > _- > ======================================================================= > _- > ======================================================================= > _- > ======================================================================= > _- > ======================================================================= > > > > ________________________________ Message 17 ____________________________________ Time: 08:43:02 PM PST US From: Trevor Page Subject: Zenith-List: 601 and fuel return line, redux 0.00 FORGED_RCVD_HELO Received: contains a forged HELO --> Zenith-List message posted by: Trevor Page Since my last question seems to have slipped through the cracks I'll have to ask it again. I'm in the process of installing a 912UL in my 601 and it has a fuel return line on the carb distribution manifold. Is it required for me to run this back into the header tank or can I cap it off? ZAC hasn't answered me and the instructions make no mention of it. Thanks! Trevor Page 601 HD ________________________________ Message 18 ____________________________________ Time: 09:04:33 PM PST US From: "Jerry Latimer" Subject: RE: Zenith-List: 601 and fuel return line, redux --> Zenith-List message posted by: "Jerry Latimer" The fuel return line is called out to prevent vapor lock and to prevent over flowing the carbs float bowls. Whether they are needed is kind of up to the builder. The Rotax install manual does call them out. Jerry Latimer 601 HDS rotax 912 -----Original Message----- From: owner-zenith-list-server@matronics.com [mailto:owner-zenith-list-server@matronics.com] On Behalf Of Trevor Page Subject: Zenith-List: 601 and fuel return line, redux --> Zenith-List message posted by: Trevor Page Since my last question seems to have slipped through the cracks I'll have to ask it again. I'm in the process of installing a 912UL in my 601 and it has a fuel return line on the carb distribution manifold. Is it required for me to run this back into the header tank or can I cap it off? ZAC hasn't answered me and the instructions make no mention of it. Thanks! Trevor Page 601 HD ________________________________ Message 19 ____________________________________ Time: 10:04:09 PM PST US From: "Larry McFarland" Subject: Re: Zenith-List: Gross Weight --> Zenith-List message posted by: "Larry McFarland" 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. More importantly I'd do it for the very people who trust you and will fly with you as well as regaining useful transport, not just fast limited transport. You could even possibly bring a tent and camp out at Oshkosh next year if you had a smaller engine. It's your decision to make and I have to respect that, even if I find it difficult. If you must fly, fly safe. Larry McFarland - 601HDS ----- 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 20 ____________________________________ Time: 11:19:51 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" 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