Original Posted By: helspersew(at)aol.com
Raymond asked:>When I brought it up a while back somebody posted that>the plans have a mistake in them for calculating weight>and balance. Can someone tell me what it is?I don't know what others may have found in the plans, buthere are my comments on them. I'm looking at the GregaGN-1 weight and balance page dated 9-17-65, data for N4705G.In that information, I find a math error when calculatingthe forward and rearward CG extremes, in that the weightsadd up to 949 lbs. but are shown as 959 lbs., which wouldnot be a big deal except that there is a very puzzlingand unconventional way of stating the CG. Convention isthat all moments are taken relative to the datum, which isthe leading edge of the wing, but Grega says that the emptyCG is relative to the main wheel weighing point, and thencontinues by saying that the empty CG relative to the datumis the empty CG relative to the main wheel weighing pointplus the moment arm of the main wheels. Not sure I followthat.The main problem that I see with the calculation is that theempty CG is not correct. I get an empty CG of 19.05" usingconventional calculation methods. This is quite tail-heavy,considering that my airplane's empty CG is 11.36" aft ofdatum.Using the empty CG that I get using the weights and momentarms that Grega listed for his airplane, running through thecalcs for forward and rearward CG extremes on his calculationpage, I get 23.83" aft of datum for the forward loading caseand 23.34" aft of datum for the aft loading case (no, I don'thave those backwards... the CG actually improves in his aftloading case). Both of those numbers are well outside ofGrega's specified CG range of 18.1 to 20.7" aft of datum, andwell outside of recognized ranges of 25 to 33% of wing chordor 15" to 20" aft of leading edge. Quite tail heavy.I compared a few numbers between my airplane and Grega's to see where the differences might be, even though my airplanehas the wing cabanes shifted aft about 4" from vertical. Thecenter of my main axles are 7" aft of wing LE while Grega'sare 7.5"; oil is 24" forward while Grega's is 23"; fuel is 6"while Grega's is 1.5" forward; pilot position is identical at23" aft; passenger is 21" aft in my airplane and 24" aft inGrega's; but the big difference is that the center of mytailwheel axle is 155.5" aft of wing LE while Grega's is morethan a foot farther aft, at 169". With an empty loading onmy tailwheel of only 20 lbs. compared to Grega's 52 lbs., thedifference is quite telling.So... I'm not sure how Grega computes his aircraft's CG usinga moment arm for the empty airplane of the "aerodynamic centerof airfoil" instead of the aircraft's empty CG aft of datum,but that's how he comes up with an empty CG of 19.5", a forwardloaded CG of 18.9" and a rearward loaded CG of 20.1". Perhapsthose of you who fly GN-1s can shed some light on your actualbalance numbers?Oscar ZunigaAir Camper NX41CC... empty weight 624 lbs., no oilSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net ________________________________________________________________________________Subject: Pietenpol-List: More taxiing, tail lift-off, NX929DH reportDate: Sun, 20 Jun 2010 18:41:23 -0400
Pietenpol-List: More taxiing, tail lift-off, NX929DH report
RE: Pietenpol-List: Skipp, Pictures of Ohio Piet Gathering
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Shad,I got a few of you and Skip (Sorry I didn't get any of Ed's piet). Wish Icould have stayed longer, I hate it when work gets in the way of a goodtime. I compressed these for e-mail. I have a few others as well so if youwant the full size version or all of the ones I took, just let me know and Iwill send them to your e-mail address. Thanks for hosting,Jason Holmes-----Original Message-----
Shad,I got a few of you and Skip (Sorry I didn't get any of Ed's piet). Wish Icould have stayed longer, I hate it when work gets in the way of a goodtime. I compressed these for e-mail. I have a few others as well so if youwant the full size version or all of the ones I took, just let me know and Iwill send them to your e-mail address. Thanks for hosting,Jason Holmes-----Original Message-----
Pietenpol-List: Re: More taxiing, tail lift-off, NX929DH report
Original Posted By: "taildrags"
That's fantastic news Dan!I hope Jim gives you the all clear and that the weather cooperates, tomorrow. Today would have been perfect with these 3 mph winds.Be careful!Dan-- yocum(at)gmail.comOn Jun 20, 2010, at 5:41 PM, helspersew(at)aol.com wrote:> Hello all,>> Today I went back and re-safetied all the stuff on the carb that I > had off yesterday. Got my cowling pieces all back into place. Had to > mark my front throttle- open, closed. Glued on the obligatory > leather patches to the LE of the horizontal stab where the cables > rub. I have been looking forward to that part for ten years. You > really know you have built a Pietenpol Aircamper when you get to > that part. You guys that have deviated from plans to avoid > this....you are missing something...those have to be there otherwise > its really not a Piet. :O)>> After I was satisfied with all that, I took her out for more > taxiing. Boy she really starts easy if you follow the procedure. 1/2 > shot of prime, pull through mags off 5 blades, mags hot and it pops > right off. Taxied for about 45 min, and when I got a little guts, > gave her a little gun on the grass and raised the tail. I really had > to hold myself back, she really wanted to FLY!!!.>> So tomorrow is the inspection. I will give a full report before the > end of the day.>> Thanks for listening,>> Dan Helsper> Poplar Grove, IL.>>________________________________________________________________________________Subject: Pietenpol-List: Re: More taxiing, tail lift-off, NX929DH report
That's fantastic news Dan!I hope Jim gives you the all clear and that the weather cooperates, tomorrow. Today would have been perfect with these 3 mph winds.Be careful!Dan-- yocum(at)gmail.comOn Jun 20, 2010, at 5:41 PM, helspersew(at)aol.com wrote:> Hello all,>> Today I went back and re-safetied all the stuff on the carb that I > had off yesterday. Got my cowling pieces all back into place. Had to > mark my front throttle- open, closed. Glued on the obligatory > leather patches to the LE of the horizontal stab where the cables > rub. I have been looking forward to that part for ten years. You > really know you have built a Pietenpol Aircamper when you get to > that part. You guys that have deviated from plans to avoid > this....you are missing something...those have to be there otherwise > its really not a Piet. :O)>> After I was satisfied with all that, I took her out for more > taxiing. Boy she really starts easy if you follow the procedure. 1/2 > shot of prime, pull through mags off 5 blades, mags hot and it pops > right off. Taxied for about 45 min, and when I got a little guts, > gave her a little gun on the grass and raised the tail. I really had > to hold myself back, she really wanted to FLY!!!.>> So tomorrow is the inspection. I will give a full report before the > end of the day.>> Thanks for listening,>> Dan Helsper> Poplar Grove, IL.>>________________________________________________________________________________Subject: Pietenpol-List: Re: More taxiing, tail lift-off, NX929DH report