Brodhead Pietenpol Association

Original Posted By: "Bill Church"
Subject: Pietenpol-List: Jack Textor new C-85 engineEXCELLENT news Jack--- thrilled for you !!!!!!!If you need a test pilot just call:)Mike C.________________________________________________________________________________Subject: Pietenpol-List: Re: Purchased an Engine

Original Posted By: Jim Ash
Exciting, isn't it, Jack?I have almost the exact same engine sitting in my garage. I got mine about fourmonths ago. Mine is a C-75-12, with a tapered shaft. From what I've been ableto gather, the C-75 is physically the same engine as the C-85, the only differenceis the operating RPM (2275 for the C-75 vs 2575 for the C-85). The A-75,however, IS a different animal than the C-75.Anyway, I'd have to say you made a good choice. But then, I'm a little biased.Bill C.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 11 Mar 2010 18:06:23 -0500 (GMT-05:00)

Original Posted By:> shad bell
ShadThere are other . The jets in the carb are larger also.Dale> [Original Message]

Original Posted By: Dan Yocum
Finite element analysis isn't necessary. Hand analysis would be considerably easier and as accurate.As it turns out, the two ways to build that spar are equivalent.With the first approach, there doesn't seem to be a technical reason to make the dado 3/4" deep. All that's needed is to locate the web and provide enough glue area to ensure a firm bond. Since most glues likely to be used will be stronger than the wood in in-plane shear, a person could even glue the caps to the web without the dado, if they hold the position while clamping. But a nominal small dado would be better. Smaller dados would let the builder make the web shallower, too, and therefore probably cheaper.David Paule>> Has anybody done the finite element analysis on the strength provided by > this method, Mike's second, in his picture? I was pondering this just > last night...________________________________________________________________________________Date: Fri, 12 Mar 2010 20:33:44 -0600

Original Posted By: "Dick N"
If the net cross-sections are the same and if the wood's grain is running the same direction, then they are equivalent. I don't know what the original routed section is so I can't comment about that.David Paule>> As it turns out, the two ways to build that spar are equivalent.>> Would these both be equivalent, or nearly so, to the 1"-wide-routed-out > method prescribed by BHP? I get that the glue joint would be stronger > than the wood, but would the overall strength of the resulting I-beam be > equivalent to a solid piece of wood that's scalloped out?>> Thanks,> Dan>________________________________________________________________________________

Original Posted By: "taildrags"
OscarThats how I did mine.Dick N.----- Original Message -----

Original Posted By: "Mike Whaley"
The "Spirit of St. Louis" spars are done like Mike's second sketch. 1/2" web,3/4" corner pieces, total 2" thick at top and bottom of spar. Good enough forLindbergh and 450 gallons of gasoline.-Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: "Rick Holland"
When I worked for Steen Aero, the company airplane (Hale Wallace's lastSkybolt, N3HW) had routed spars. While it's never had problems, Hale andothers agreed (after the fact) that it was a fundamental mistake to do this.In the end you only save a very small amount of weight (I think it was under2 lbs, even for a biplane), and it can (potentially) significantly reducethe rigidity of the spars. You also risk messing up while doing the routingprocess and converting the piece to very expensive scrap wood!! Obviouslyit's worked on many aircraft over the decades, but really, why risk it forsuch a miniscule advantage and high potential cost?I'd say that if you really want the beefiness of 1" spars but the lighterweight of 3/4" spars, you'd be better off making your spars 7/8" thick,without routing them. Or not worrying about it and going with the 1"...seems to me that the spar is one of those things where a little extrastrength really isn't a bad thing at all, and the weight difference would bebetter made up on other things. On my project, I believe I'll probably endup with laminated spars, as this reduces the chances of a hidden defectburied in the wood, you can use shorter wood pieces, they weight the same,they fail progressively rather than completely at once (hopefully that willnever be an issue!) and they are more warp-resistant. Strength is at leastas strong as a solid spar, and with the tests from the Skybolt laminatedspars, it was found they were usually about 25% stronger than the solidversions.Mike WhaleyMerlinFAC(at)cfl.rr.com----- Original Message -----

Original Posted By:> "Rick Holland"
What was the orientation of the web plywood grain?The Piet spar is 4 3/4" wide. What you are going to removeis 3 1/2" of that 1/4" deep on both sides. The length of therouted areas will be close to 12' on each side of thefuselage. There are two spars, one front, one rear, so eightof these routed areas. This comes to 1008 cubic inches.There are 1728 cubic inches in a cubic foot. One cubic ftof spruce weighs 31 lb. This all means that there will beeighteen pounds of wood removed. Each of us then hasto ask, " Is this important to me?"The only way to be experimentaly sure is to weight theboard BEFORE routing and again after, not trying tocollect what dust and chips you can find on the floor.Your router sprays stuff all over the shop grasshopper. :-)Clif"If we love flying so much why are we in a hurry to get there?"> When I worked for Steen Aero, the company airplane (Hale Wallace's last> Skybolt, N3HW) had routed spars. While it's never had problems, Hale and> others agreed (after the fact) that it was a fundamental mistake to do > this.> In the end you only save a very small amount of weight (I think it was > under> 2 lbs, even for a biplane), and it can (potentially) significantly reduce> the rigidity of the spars. You also risk messing up while doing the > routing> process and converting the piece to very expensive scrap wood!! Obviously> it's worked on many aircraft over the decades, but really, why risk it for> such a miniscule advantage and high potential cost?>> I'd say that if you really want the beefiness of 1" spars but the lighter> weight of 3/4" spars, you'd be better off making your spars 7/8" thick,> without routing them. Or not worrying about it and going with the 1"...> seems to me that the spar is one of those things where a little extra> strength really isn't a bad thing at all, and the weight difference would > be> better made up on other things. On my project, I believe I'll probably end> up with laminated spars, as this reduces the chances of a hidden defect> buried in the wood, you can use shorter wood pieces, they weight the same,> they fail progressively rather than completely at once (hopefully that > will> never be an issue!) and they are more warp-resistant. Strength is at least> as strong as a solid spar, and with the tests from the Skybolt laminated> spars, it was found they were usually about 25% stronger than the solid> versions.>> Mike Whaley> MerlinFAC(at)cfl.rr.com>>> ----- Original Message -----

Original Posted By: "bryan green"
This is how I did it. An engineering friend thought the strength would befine. He also thought the wider cap on top would help because caps usuallybreak in compression first. I'm not an engineer! More pictures on my siteJackwww.textors.com DSMMyron, Group----here is how I did my spar and how I would do it againproposed in the attached sketch. I did a cost analysis of both methods and it was pretty much a wash as Irecall with the proposed methodbeing way less work by not having to route out U-channels in those upper andlower 'caps'.Mike C.________________________________________________________________________________

Original Posted By: "Jack"
Hi Jack, what did you do at each rib location?Bryan GreenElgin SC----- Original Message -----

Original Posted By: "Jack"
Bryan,Not sure what your mean...I glued the ribs at the caps and didn't fillbehind uprights.JackHi Jack, what did you do at each rib location?Bryan GreenElgin SC----- Original Message -----

Original Posted By: gliderx5(at)comcast.net

Original Posted By: "David Paule"
> Subject: Re: Pietenpol-List: Re: Purchased an Engine>>> I think the only physical difference between the a-65 nad a-75 was theaddition of a oil passage drilled in the rods (at the bearing caps) forbetter lubrication, I also believe that a 65 can be modified to a 75. Ilooked a buying a luscomb a few years back, and was studying up on it.>> Shad>>> >>________________________________________________________________________________