Brodhead Pietenpol Association

Original Posted By: Oscar Zuniga
Jim=3BWelcome to the list and glad to hear that you arebuilding/restoring a Pietenpol for posterity in themuseum. Fire away with questions. As to the cabanebrace struts=2C I photographed and measured the strutson my airplane=2C NX41CC=2C and have drawn up detailsof the measurements and connections and will postthose on Monday. Be aware that the length of theactual struts will vary greatly between airplanesbecause many people lengthen the cabanes toprovide a bit more headroom and to make it easierto get in and out of the cockpits. Also=2C when usingengines lighter than the original Ford (such as theCont. A65 in my case)=2C it is often necessary to pivotthe wing aft on the cabanes in order to get the CGto work. On my airplane=2C the cabanes are tilted aft4" so the dimensions I've given on the details arenot to be taken as absolute.You'll also notice that the lower ends of my cabanebraces are "bologna slice" style cut on the lowerend so that the ends are parallel to the top of thelongeron=2C but they sure don't need to be... theycan be cut square. And there are many othervariations on the way the tabs are shaped=2C attachmentmethods=2C etc.-mine is just one way but it works.Oscar ZunigaAir Camper NX41CCSan Antonio=2C TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________

Original Posted By: "jimbir"
Attached are a photo of the cabane brace struts on my airplanealong with a sketch of how they are made. Your own wing andcabane geometry may differ=2C so my dimensions are for generalguidance only.Oscar ZunigaAir Camper NX41CCSan Antonio=2C TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net/9j/4AAQSkZJR ... ___Subject: Pietenpol-List: Re: cabane brace struts

Original Posted By: "Gene & Tammy"
OscarThanks for the great drawing. One question, is there only one tab welded to theupper end of the cabane strut or are there two, one on each side?Thanks Jim B.Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: Oscar Zuniga
Oscar you do GOOD work!Gene ----- Original Message -----

Original Posted By: CozyGirrrl(at)aol.com
Jim=3B sorry that I didn't make the detail clear on the upperattachment. Yes=2C there are tabs on each side of eachcabane=2C such that the rod end bearing is captured betweenthe two tabs and bolted through.Oscar ZunigaAir Camper NX41CCSan Antonio=2C TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________

Original Posted By: brian.e.jardine@l-3com.com
For those of you who are building or have a Piet with a wing tank, I would like to relate to you a little advice from William Wynne the Corvair guy. He was a front seat passenger in his Piet when the pilot somehow got into a spin at 80 ft. AGL.The plane crashed. The design is very strong and the plane easily repairable except for one flaw.That adjustable link at the top of the diagonal cabane.Upon impact, it buckled, the wing shifted forward severing the fuel line and covering William with gas. Otherwise he was OK.The pilot was dazed. While William was trying to assist getting the pilot free, the plane caught fire, dripping fuel on the hot Corvair, burning the plane to a crisp and causing major burns and multiple operations to William Wynne over the next couple yrs.Suggestion: Use the adjustment for trimming the CG. Once satisfied, replace the diagonal cabane with a sturdy fixed cabane.Roman Bukolt, NX20795On Mar 2, 2009, at 7:33 AM, Oscar Zuniga wrote:> Attached are a photo of the cabane brace struts on my airplane> along with a sketch of how they are made. Your own wing and> cabane geometry may differ, so my dimensions are for general> guidance only.>> Oscar Zuniga> Air Camper NX41CC> San Antonio, TX> mailto: taildrags(at)hotmail.com> website at http://www.flysquirrel.net>>> ________________________________________________________________________________

Original Posted By: "Bill Church"

Original Posted By: "walt"
Roman: you mean like this? (see pic)When 41CC went over on its back=2C my cabane braces bothneeded to be replaced and one of the rod ends broke. I haveno idea how the airplane would have fared if it had been fittedwith the 1/8" brace cables in the original X-fashion across thestarboard side passenger's side cabanes.Many Piets have no adjustment in the brace struts. For anexcellent example=2C look at the great pix that Walt posted just afew days ago of his airplane. I think it has fixed struts.Oscar ZunigaAir Camper NX41CCSan Antonio=2C TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net/9j/4Re0RXhpZ ... __________

Original Posted By: owner-pietenpol-list-server(at)matronics.com
I think that rather than trying to make the structure crash proof, it wouldbe far more effective to not get into a spin at 80' AGL. I've heard thisfrom WW several times, blaming the fire on the centersection fuel tank.I've seen similar results from an impact in a J-3 where the fuel tank endedup in the front seat passenger's lap, but the result in that case was not sofortunate in that both occupants burned to death. The simple fact is, ifyou knew exactly how the plane will impact, you can design the structure toresist that impact loading. Designing it to withstand any type of impactwould result in an M-1 Abrams, not an airplane.Build it light, build it simple and fly it safely.Jack PhillipsNX899JP _____

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Somebody on this list recently said of their Pietenpol, "I built itairworthy - not crashworthy."Gary BootheCool, Ca.PietenpolWW Corvair ConversionTail done, Fuselage ready for gear(12 ribs down.) _____

Original Posted By: CozyGirrrl(at)aol.com
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Original Posted By:> owner-pietenpol-list-server(at)matronics.com [mailto:owner-pietenpol-list-server(at)matronics.com
I was referring to the diagonal strut, not the vertical ones.I don't think you'll convince William Wynne that they are safe.The mounting brackets are strong enough. The DIAGONAL strut made of the same material as the vertical cabanes are strong enoughThe bolts connecting both ends are strong enough. But the adjustable Rod- end Bearing threaded end in its mated fitting apparently, isn't strong enough.Flexible fuel tubing would be great, or a fuel tank in the fuselage. Still once you know the length of the diagonal cabane support, there' no further need for adjustment, so why not be safe and use a strut of proper length with just bolt holes drilled the proper distance apart?Roman Bukolt NX20795On Mar 2, 2009, at 4:00 PM, Bill Church wrote:> Roman,>> You suggest installing a "sturdy fixed cabane".> What would be the definition of "sturdy", in this instance?> Should it be strong enough to resist impact with the earth at a > speed of 50 mph? 60 mph? 80mph? At what angle?> I guess the point I'm trying to make is that the parasol wing, > sitting on cabanes, isn't going to be "sturdy" no matter what you do.> In a crash, something is going to break - hopefully not the pilot or > passenger.> You could make the struts out of 1" diameter solid titanium, and > then the loads would just be transferred to the little sheet metal > brackets and the little bolts that everything is held together with.>> I would think it would be more important to have flexible fuel > lines, than to make the forward struts extra strong and fixed. If > the fuel had not leaked onto the hot engine, there would not have > been the disaster that occurred.>> On the other hand, the plans don't spell out what size of tube to > use for these struts, and I've seen many different sizes used. Some > of those I've seen look to be WAY too small to have sufficient > strength if loaded in compression. These struts are not decorative - > they should not be trifled with. I just don't think that making them > adjustable makes them unsafe.>> Bill C.>

Original Posted By: "Bill Church"
Jack,Thanks for the info.I am not using PolyFiber, but I can see how to do the same thing with my StewartSystems products. Essentially you glue the fabric to the lower ribs then ironit a bit, do the lacing and the final shrink on the bottom at least is afterits laced, makes sense. I was thinking a little shrink then pull it up, but thatwould make the tension unpredictable, what you described sounds like it wouldwork better.Was concerned about tensioning only top or bottom too much, but you can't justriblace the bottom so I suppose the top would need to be pretty taunt (littlemore than the bottom maybe but not final shrink) to get it all to come out right.Didn't recall anyone discussing it and wanted to have a plan before I started covering.Jim D.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: RE: Pietenpol-List: cabane brace strutsDate: Tue, 3 Mar 2009 14:10:52 -0500

Original Posted By: owner-pietenpol-list-server(at)matronics.com
The most important feature of this particular setup is thatthe top mount is significantly below the wing moutingbolt. There is NO proper triangulation. Therefore anyuntoward stress is, as is shown in the picture, going tobend the cabane resulting in the breakage you see.If those diagonals were bolted at or VERY near thewing mount bolt with the centerline lined up with thatbolt any damage would have been significantly less.Any such strut can be a lot smaller than appearsadequate if the line of tension and compression isdirectly down it's centerline. Clif That's all the information we are given regarding the diagonal braces. The rest is up to the builder to figure out. We have no details regarding the brackets at the top of the cabanes, or how they are attached, or what they are attached to. Since there is no official design for this component, it is impossible to say that it is or isn't sufficient. Bill C.------------------------------------------------------------------------------

Original Posted By: "Phillips, Jack"
Subject: Re: Pietenpol-List: cabane brace strutsPieters, I have a little experience with cabane braces. I made my first flight on Sep. 20 08. off my strip on my farm which is 50 foot wide and half mile long. I spent 8 years building this modified GN-l with probably toomany extras. I weigh 230 so need extra weight up front. My flight weight was 1050. I climbed at about 400 feet per minute and 60 mph per the airspeed. It flew tail low with the stick in my gut. I flew the pattern, got over some trees and was right where I wanted to be; landed and cannot remember thetouch down but it must have been pretty good or I would remember it. I drifted into the tall thin (6 ft) government acres which I had done in taxi testmaking 180 turns with not a problem. Just as I came out, at a very slow speedover we went. I have a fuel tank behind the engine so no problem there. I had a hard time getting my weight off the shoulder straps to slide out. I think with stronger braces it would have just gone up on the nose. I have a joint in the top of my cabanes for moving the wing. The worst part is I had a Beech Roby veriable pitch prop that I bought for $850 and two newblades will cost me $2000. My cg was at 28 percent and I had 160 lbs on the tail wheel while I was in it. Experts tell me, down thrust on the enginewould help on the tail low flight. So far I am waiting for new insperation to start the rebuild. Ken Conrad in cool Iowa PS I would send pictures but I don't know how.**************A Good Credit Score is 700 or Above. See yours in just 2 easy steps! %3D62%26bcd%3DfebemailfooterNO62)________________________________________________________________________________Subject: RE: Pietenpol-List: cabane brace strutsDate: Wed, 4 Mar 2009 08:13:44 -0500

Original Posted By: Oscar Zuniga
If you look at this pix:http://flycorvair.com/pietosh3.jpgthe third jpg down on this page:http://flycorvair.com/wynne.htmlThe profile on the top of the left hand brace appears to be a rod end bearing. Beyond that making it unbreakable would be impractical. Hit it hard enough and something is bound to give, be it the cabanes or the fuselage longerons they attach to. I believe WW's salient point was to not make the fuel lines out rigid tubing as this was what ruptured when the wing shifted on impact. in WW's own words: "I think it would be a lot better to have all braided lines in this case. Loosely secured, so they can't be pulled out as easily"Michael in Maine ----- Original Message -----

Original Posted By: Oscar Zuniga
If you look at this pix:http://flycorvair.com/pietosh3.jpgthe third jpg down on this page:http://flycorvair.com/wynne.htmlThe profile on the top of the left hand brace appears to be a rod end bearing. Beyond that making it unbreakable would be impractical. Hit it hard enough and something is bound to give, be it the cabanes or the fuselage longerons they attach to. I believe WW's salient point was to not make the fuel lines out rigid tubing as this was what ruptured when the wing shifted on impact. in WW's own words: "I think it would be a lot better to have all braided lines in this case. Loosely secured, so they can't be pulled out as easily"Michael in Maine ----- Original Message -----

Original Posted By: Michael Perez
Those look very good, a direct line from the top boltthrough the brace bolt to the bottom bolt.If you draw out a line drawing of the triangle what it showsis that if you ran head first into something thus causingthe wing to try to go forward, the brace strut, being longerthan the cabane, will attempt to " pole vault" the cabaneup and out. So the major forces appear to be one pullingthe lower cabane fitting out of the top longeron and theother in pushing the bottom of the brace down and forward at the same time. There's other stuff going onwith the motor mount as well.You know, Volvo was the first to angle the connectionbetween the engine/tranny and the drive shaft to make the engine drop and go under the passenger compartmentin a head on collision. This idea could be incorporatedinto the motor mounts used on our various engines.For example, in the Corvair mount, the forward, long, bottombrace tube could be bent down in the middle with abreakaway brace from there to the top of the rear bracestrong enough for everyday operation but with a specificload limit designed in. Exceed the limit, the brace ripsapart, the fortube bends down, the engine folds downand back. A shearpin ala outboard motor prop would do it.It's all about energy management. The amount of energyconsumed in this process slows the overall impact onthe human occupants considerably.First you make it airworthy then see what can be done tocreatively make it crashworthy without making it anyheavier. Personaly I don't plan on doing a header into anythingbut around here every cloud hides a very large rock.Clouds come from somewhere, they've even beenknown to spontaneously appear out of nothing. A friendof mine made his own cloud in a loaded Beaver while flying out of a valley ( between large rocky things) on Vancouver Island. Scared the Beejeezus out of him!Clif Clif, do you mean like these pictures show? Cabane Struts 2 shows the diagonal strut attachment to the top of the forward cabane strut on my airplane. Note that the diagonal strut is basically inline with the attachment to the cabane and the cabane attachment to the wing fitting Cabane Strut - Front 1 shows how I made the fitting for the cabane strut. Note that this fitting carries the attachment of the diagonal strut straight to the wing attach fitting, so there is no tendency for a compression load on the diagonal strut to cause the cabane strut to buckle. Cabane Strut - Front 2 shows how this fitting is welded into the top of the cabane strut, capturing the bushing that attaches to the wing attach fitting. Jack Phillips NX899JP Raleigh, NC ________________________________________________________________________________Date: Thu, 5 Mar 2009 04:59:26 -0800 (PST)

Original Posted By: "Patrick Panzera"
Did anyone else spot the Russian Pietenpol under related videos in that linkthat Pat provided?A Russian Pietenpol flying with a Suzuki engine no less.that has to be a first:http://www.youtube.com/user/VLADIMIRBUGOGAI sent him a note to forward some pix to Chris Tracy so that he may beincluded in his listingMichael in Maine----- Original Message -----

Original Posted By: Doug Bowman