Pietenpol-List: Re: Continental engines in Pietenpols

[matronics]

Original Posted By: Barry Davis
Henry,My Pietenpol was built from plans obtained from Mr Pietenpol in1959 and are for the "Improved" version drawn by Mr. Hoopman.They are true blueprints with the blue background, having whitelines and lettering. A relic of the past, because most plans todayhave blue or black lines, etc. on a white (or nearly so) background.Therefore my plans must be for the so-called "short" fuselage.In the May 1956 EXPERIMENTER (the EAA publication that laterbecame SPORT AVIATION) there was a good article on the Pieten-pol airplanes that included a number of letters from owners & build-ers of Piets. Among these was a letter from Bernard Pietenpol him-self in which he recommended moving the firewall forward by six inches if alighter Continental (or similar) engine was going to be us-ed. The main reason for this is to get the center of gravity where itbelongs. Side benefits are more leg room in the front cockpit and morespace for a forward fuel tank, if used.Bernard cautioned against extending the forward fuselage bay anymore than 6 inches, because he had tried this and found the aircraftdid not handle well in a steep slip.I followed his advice and used the engine mount from an Aeronca11AC Chief (the 7AC Champion mount is the same). This is an 8inch mount, with the front mount pads 8 inches from the firewall. So,in effect, the Continental engine mounting points are 8 + 6 = 14 in.from the orginal firewall for the Ford engine. In 1963, a friend builta Pietenpol with a 14 inch long (plus) mount using the original fire-wall location and built recesses into the firewall to accomodate thefront occupant's feet! I opted for the lengthened fuselage, and madeit two inches wider (26 inches outside dimension) at the cockpits.This modification has been a success, allowing more clothing to be worn forcold weather flying.For your information, my a/c Wt. and Balance document gives thesedimensions:Datum is wing LE. Main wheel axle (weighing point) is 6.5 inchesaft of datum with the wing moved aft a bit for balance. The tail wheelweighing point (axle) is 149 inches aft of datum. [Note that I movedthe main wheels forward from the position shown on the plans be-cause I wasusing brakes (don't remember how much; it was a long time ago).]With a C85-8 engine, wooden propeller, and full oil tank (4 litres, orabout 4 US quarts) the empty weigh is 638 lbs., the weight on thetail scale is 18 lbs. with the top longeron level.In the absence of definite center of gravity limits, I decided that theABSOLUTE LOADED AFT LIMIT must not exceed 20 inches aft ofdatum (33% of chord) and that the aircraft should be flown carefullyas this limit is approached. By adjusting the wing position aft (a neatPietenpol feature) until the center section struts are nearly parallel tothe fuselage truss members directly below them, I was able to obtain theseCG figures:Most Forward Loading 14.3 inches aft of datumMaximum approved gross weight is 1150 lbs.This a/c was flown for about 115 hours with an A 65, and had thewing positioned as described above. Then a C85-12 (without start-er & generator) was installed and the wing was moved forward a bitto take into account the heavier engine. Subsequently, a C85-8, afew pounds heavier than the A65, was installed and the wing wasonce more moved to about the original position. A couple of yearsago, I installed a different C85-12 and simply left the wing where itwas.The slight nose-heaviness experienced now is, in my opinion,far less dangerous than a tail-heavy condition and I have no intentionof changing anything again. One thing to watch is the weight of yourtail wheel assembly. Mine is very light with the tubing A-frame yoke,compression spring (John Deere part), and a 4 inch castor wheel(ball bearing type). The castor wheel is inexpensive and should bereplaced when the bearings get loose; I replace mine after about60 - 75 hours in dusty conditions. This lightweight unit alone will im-provethe CG picture a lot.I must include the disclaimer that this information is provide as aguide only. Just because it works for me doesn't necessarily meanit will work for you because each homebuilt aircraft is unique (for ex-ample, parts are not interchangeable). Hope this information is whatyou need. Good luck.Graham________________________________________________________________________________

[matronics]

Original Posted By: michael list
to Graham Hansen Thanks so much for the information. I appreciate it, its just what I need.Henry Williams________________________________________________________________________________