Brodhead Pietenpol Association

Original Posted By: "Catdesigns"
I'm wondering if anyone knows if Mr. Buckolt is still selling the full sizeprofiles of the 612 and 613.5 airfoil? I have his snail-mail address. I alsoemailed him through his website, but haven't heard back- thus the question.Wouldn't want to call and disturb the man.Read this topic online here:http://forums.matronics.com/viewtopic.p ... 9=0A=0A=0A ________________________________________________________________________________Subject: Pietenpol-List: Re: Plane sitting: need list advice on elevator controlhorns

Original Posted By: "Gary Boothe"
Jeff,It's possible that thimble on the lower horn collapsed some , but it really doesn'tseem that likely. The geometry might have changed some with the bend. Iguess the repair would depend on what you can do there and what equipment youhave. Really the best thing to do would be to cut a small opening in the fabric,probably just the bottom of the elevator, remove the horn and replace withan exact copy. It's probably very possible to weld a "scab" onto each sideof the horn. It could probably be done to the point of being just as structurallysound or even better than it was, and probably not noticeable. It wouldbe really nice though to be able to open that fabric up, not just to remove thehorn but to also inspect the wood to make sure there are no cracks. It reallyis something that could be accomplished in one looong day or an evening andthe next day, if you have torches and the fabric and dope available. To do afabric patch right there would not be bad and really could be done in the spanof one day. What a bummer though! I really feel for you! But on the bright side, you'd besurprised how good you get at making repairs after stuff like this.Good Luck!Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Jeff,This is not advice.just my opinion: If I were in your shoes, I would make astiffener out of 12 or 14 ga 4130. It would be shaped like the horn, fromtop to bottom. I would be able to prime it and paint it, then slip it thruthe fabric and bolt it, top and bottom, with about 3 bolts on each side. Allthis would be done if I felt assured that the wood was OK.The real bummer may be with your instructor. It must be hard enough to findsomeone to go up in your plane, now he's feeling extra guilty. Good luck & keep us posted with what YOU decide to do.Gary BootheCool, Ca.PietenpolWW Corvair ConversionTail done, working on fuselage (endless metal parts!)(12 ribs down.) _____

Original Posted By: Steve Eldredge
Ryan;You could ask Riblett but If I remember correctly, Doc Mosher's narrativeand analysis ondetermining CG range for the Piet pretty much covered most conventionalairfoils at least as a starting point. Here's Doc's commentary, fromOct. of 2002:======================Recently there have been some questions concerning establishing practicalCG limits on homebuilt Pietenpols. Perhaps by going back to the Piet era(1930s) we can gain an insight about how the CG limits were established inthose days ("That's how Bernie did it.")Years ago, the CAA published a manual that all the A&E mechanics (Aircraft& Engine mechanics in those days) used as a standard for airworthy repairsand alterations. It was called the "Department of Commerce, Civil Aeronautics Administration Manual 18." The title was "Maintenance,Repair, and Alteration of Certificated Aircraft, Aircraft Engines, Propellers, andInstruments." Manual 18 had a bunch of changes over the years, sodon't use a Manual 18 printed later than 1941 or it may not have these 1930s tipsabout weight and balance limits.Back in the early 1930s, the Type Certificate Data Sheets that were issuedby the CAA for each model of certificated airplane were quite brief - 10or 12 lines of print. Today, those same TCDSs for those antique airplanesstill appear in that brief, sweet, naive condition. Compare that with today's TCDS of the popular Aeronca Champion - 32 pages!So if the C.G. limits are not set by the FAA in a TCDS (and of course, onyour homebuilt experimental Pietenpol there is no TCDS), how can you knowwhere the limits should be? If you can find an old pre-WWII Manual 18 (myreference is "As amended June 1, 1941), you will find a couple of interesting rules of thumb about Center of Gravity locations.For instance, on page II-5, under "E. APPROVED CENTER OF GRAVITYLIMITS"1. Current Models - stated on the pertinent aircraft specification in percent of the MAC or in inches aft of a given datum. This information maybe obtained from the local Civil Aeronautics Inspector.2. Older Models - In the case of those models for which approved limits are not given on the specification or listing, it will usually be acceptable to assume the limits to be at 18% and 30% of the MAC for low andmid wing monoplanes and 22% and 34% of the MAC for high wing monoplanes andbiplanes.Inasmuch as several models are known to have satisfactory flight characteristics with the C.G. beyond such arbitrary positions, these shouldnot be considered hard and fast limits. In such cases, approval will depend largely upon the recommendations of the examining inspector. The major consideration governing approval of such cases will be the relativechange in the empty weight C.G. due to the alterations, rather than the absolute C.G. extremes.If the approved forward limit thus determined is exceeded, it may be considered satisfactory provided that it is demonstrated to the local CivilAeronautics Inspector that the aircraft can be landed in the three-point position when landed in the extreme forward condition.Page II-6 of old CAA Manual 18 goes on to say:G. DETERMINATION OF LOADED CENTER OF GRAVITY EXTREMES (The most forward and most rearward C.G. positions obtainable as equipped and with the mostcritical distribution of useful load.) The loaded extremes may be determined either, (1) by weighing the two loaded conditions or, (2) by computation. Both procedures have a common objective; namely, to demonstrate that, under the most adverse loading conditions (forward and aft), the C.G. positions will not exceed the approved limits (Part E) which have been determined by flight test as the most extreme positions atwhich the model will satisfactorily comply with the Civil Air Regulations.A note on page II-17 states:When the necessary information is not included in the pertinent specifications (as for older models), it will be necessary to obtain suchdata by computation and actual measurement.OK, when you start your establishment of loaded C.G. limits on your Pietenpol, lets use these old CAA limits (22% of the MAC for forward limitand 34% of the MAC for the rearward limit on your high wing monoplane). Aforward C.G. may make it so you cannot land the airplane in a three-pointposition (put another way, the engine is just too heavy for the too-smallelevators at slow speed to overcome). A rearward C.G. starts to get intoproblems with stability and spin recovery. Vaughan Askue in his book Flight Testing Homebuilt Aircraft says "C.G. provides the most direct method the pilot has for controlling pitch stability. Moving the C.G. forward increases the effectiveness of the horizontal tail and improves both static and dynamic stability. The primary objective of a stability test program is to prove that the airplane has acceptable stability characteristics at a limiting C.G. This C.G. then becomes the aft C.G. limit called out in the airplane's limitations. If moving the C.G. limitforward gives acceptable stability without hurting the utility of the airplane, then this is the simplest fix for a stability problem.What does all this mean in your Piet? If you establish the fore and aft loaded C.G. limits at something like 22% and 34% of the Mean Aerodynamic Chord and try to stay away from the rear limit as much as possible (that'sthe one where instability starts to take over), you will probably be OK.Historically, most Piets come out of the jig being tail heavy because theydon't have that heavy Ford A engine on the front end of the teeter-totter. If you increase the arm of the engine weight of a 220# Corvair engine, for example, (move it 4 or 5 inches forward of where the Ford used to be) your Piet will probably not be chronically tail heavy. Then, if you want, you can tweak it by moving the wing fore or aft- usually aft - to really set the loaded CG between your goal numbers of 22/34%That's how Bernie did it. It still works. A pound is a pound the world around.Oscar ZunigaSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net=0A=0A=0A ________________________________________________________________________________

Original Posted By: Jeff Boatright
Plane sitting: need list advice on elevator control hornsJeffThe stretch in the cable might be an indication of additional trouble. There could be damage to something else in the system and not just isolated to the horn. Other damage could occur before the horn gave way and relieved the stress. I know you did not want to hear this, but my $ .02 worth.Barry( still groggy from a late night at the Big Piet Factory) ----- Original Message -----

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Jeff,You reported that you tried to bend the horn back to position, but that itended up looking a little like an hour glass. That alone would probablyaccount for a dimensional change from where the original hole was.Furthermore, once the horn was bent, you really have no way of knowingexactly where the original position was. It is conceivable that thefabricator may not have had the horn straight to begin with. It may havebeen favoring the opposite direction.I'm glad you have decided to give it a thorough inspection.just don't wastetime chasing ghosts.Gary BootheCool, Ca.PietenpolWW Corvair ConversionTail done, working on fuselage (endless metal parts!)(12 ribs down.) _____

Original Posted By: Ryan Michals

Original Posted By: BYD(at)att.net
Jeff, I would look for wood splitting near all the attachment bolts in the tail and controlsetup. The front of the elevator would be the most likely spot. Also,check to make sure the brace wire fittings are ok. I think Gary might be correct on the cable could go slack just from trying to bendit back. You really dont know where the hole was before it bent and how closeto that position you have it now. As for fixing, the quickest horn to make would be a flat plate horn. I think theGN-1 uses flat plate horns. I can check my GN-1 plans when I get home andgive you more detail if you want. Without seeing the damaged horn I would behesitant to weld on a patch to repair the horn. Seems like this is an importantpart of the plane that contributes to a gentle return to earth.--------Chris TracySacramento, CAWestCoastPiet.comRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: Ryan Michals
Chris wrote->Without seeing the damaged horn I would be hesitant to weld on a patch>to repair the horn. Seems like this is an important part of the plane>that contributes to a gentle return to earth.That was my feeling about my rudder horn so I was good and ready tomake a new one. However, my master machinist/welder/shop supervisorlooked it over and told me that I wouldn't need to heat the part beforestraightening it out and working it back into its "airfoil" shapesince it had not deformed that severely. As I say, we were good andready to make a new part but it was not deemed necessary once we workedit back out to original shape and dressed it. Hopefully, Jeff's canbe worked back out too.I think the slack cable situation will end up being Case #3 of the scenarios he laid out... either crushed or broken wood. And yet, that'sthe nice thing about wood: there are many ways to repair it.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Date: Tue, 30 Dec 2008 15:53:14 -0800 (PST)