Brodhead Pietenpol Association

Original Posted By: vistin(at)juno.com
In a message dated 8/31/99 11:51:18 PM Central Daylight Time, ronr(at)onlinemac.com writes:>Ron, I think Douglas Fir is a fine choice for for rib capstrip material. However, I have to say...I kind of cringe when I hear anyone adopt the notion that a little additional weight here or there will be ok since you'll have a little more power. I am a strong believer in the philosophy that weight should one of the foremost considerations in every component that goes into an airplane. You may be talking just a few ounces here and a few there..and before you blink you've got 16 ounces..then..more and more. I look at it as though there will come a day when I want to get out of a certain airport and I will appreciate the few pounds that I saved in the construction of the plane. One of those days when its hot, perhaps I over ate for lunch, and my passenger just bought some airplane part he couldn't do without to carry home. It is on those days that you suddenly rethink your confidence in your extra horsepower as the pine trees are looming taller and taller as you approach them in ground effect. Sorry...don't mean to preach to the choir. As for Douglas Fir for capstrip material, I have some data to pass on and I have an opinion to pass along for what it is worth. First, the data....you should expect a Douglas Fir rib to weigh in the neighborhood of 11 or 12 ounces. I have a Douglas Fir rib that I built as a "first-off" part when I made my rib jig. It is strictly dimensioned to the plans in the 1932 flying and Glider Manual. Recently I compared it with one of Chuck Gantzer's Red Cedar ribs and found mine to be almost 4.5 ounces heavier. His cedar ribs all averaged around 7.8 ounces or so. So the bottom line is...the difference in a wing with Douglas Fir ribs and an identical one with cedar ribs comes out to about 8.5 pounds. Now for my opinion. Red Cedar or Spruce is the way to go with Ribs. I have chosen to go with Cedar after reading what others have posted about it and after seeing Chuck G's wing. I have always felt that the 1/4 X 1/2 cross section for rib capstrips and bracing is a little on the over-engineered side. Thats not based on anything more than a feeling I get when I look at the Pietenpol wing as compared to various other wings of bigger and faster type certified airplanes (like wacos etc..) which have much smaller rib material cross-section. The Cedar isn't quite as strong as Spruce, but is just about the same weight. The sacrifice in strength to me is justified as I feel the ribs are over-designed to start with. And the much lower cost of the cedar really makes it the best choice in my opinion. I recently bought eight 2" X 4" X 12' boards for just under $50. This is enough material to make 2 shipsets of ribs. I hand selected these from a local Lumber supply place thats having a going out of business sale. Many of the boards I rejected were knotty...but with some diligent searching I was able locate some beautiful boards cut in the right direction with nice straight vertical grain. For some further data on the strength of the Western Red Cedar ribs...refer below to a previous email post by Mike Cushway from a few weeks back. Anyway..thats all I have for now. Keep it light!!!! Terry "always has an opinion" BowdenSubj: Re: RIB TESTING RESULTSDate: 8/21/99 5:07:52 PM Central Daylight Time________________________________________________________________________________

Original Posted By: oil can
Ron,I'll second the vote to keep it as light as possible, for the same reasons as Terry mentioned...the wing is over designed, and lighter wood will certainly pay dividends. I don't measure weight in ounces...I measure it in grams !! A couple of other weight saving things I've done are rounding the sharp corners of every stick in the wing (saved about 10 grams), and I scaluped all the gussets (saved over 3 ounces here), and as for all the hardware, I used lengths that showed 2 threads and no more. Also, I weighed each completed rib, and located the densest ones closest to the center of the wing, and progressivly lighter toward the tips. It's important (when possible) to locate mass as close as possible to the centerline, to aid in handling characteristics. Think about it...a baton twirler throws her baton up in the air at a givin rpm, and as a result of Newton's law, it's spinning at almost the same rpm when she catches it. This occurs because the mass is at the tips. Well, that's my two cents worth.Chuck Gantzer________________________________________________________________________________

Original Posted By: "Conrad, Bart D"
Subject: Pietenpol-List: Re: Don't say that!!!>>>Did you consider lightening the last 25% of the spar on either>side? The outboard ends carry about 75% less load this far out.>I'm working up a box spar out of plywood sides and spruce or>poplar center. According to "Stress Without Tears", the spars>can be lightened a great deal as you proceed from root to tip. A>built up spar will allow progressively lighter construction>towards the ends. A routed spar could also have more and more>wood removed as you progress from root to tip. When I finish>laying it out, I'm going to go over it with a civil engineer who>works in my office to verify my calculations. I'll be glad to>put it on line at that time for further comments.>>Mike Bell>Columbia, SC>>>Rcaprd(at)aol.com on 09/02/99 12:29:30 AM>>Please respond to Pietenpol Discussion >>To: Pietenpol Discussion >cc:>Subject: Re: Don't say that!!!>>>Ron,>I'll second the vote to keep it as light as possible, for the>same reasons as>Terry mentioned...the wing is over designed, and lighter wood>will certainly>pay dividends. I don't measure weight in ounces...I measure it>in grams !!>A couple of other weight saving things I've done are rounding the>sharp>corners of every stick in the wing (saved about 10 grams), and I>scaluped all>the gussets (saved over 3 ounces here), and as for all the>hardware, I used>lengths that showed 2 threads and no more. Also, I weighed each>completed>rib, and located the densest ones closest to the center of the>wing, and>progressivly lighter toward the tips. It's important (when>possible) to>locate mass as close as possible to the centerline, to aid in>handling>characteristics. Think about it...a baton twirler throws her>baton up in the>air at a givin rpm, and as a result of Newton's law, it's>spinning at almost>the same rpm when she catches it. This occurs because the mass>is at the>tips. Well, that's my two cents worth.>Chuck Gantzer>>________________________________________________________________________________

Original Posted By: Mike Bell
Did you consider lightening the last 25% of the spar on eitherside? The outboard ends carry about 75% less load this far out.I'm working up a box spar out of plywood sides and spruce orpoplar center. According to "Stress Without Tears", the sparscan be lightened a great deal as you proceed from root to tip. Abuilt up spar will allow progressively lighter constructiontowards the ends. A routed spar could also have more and morewood removed as you progress from root to tip. When I finishlaying it out, I'm going to go over it with a civil engineer whoworks in my office to verify my calculations. I'll be glad toput it on line at that time for further comments.Mike BellColumbia, SCRcaprd(at)aol.com on 09/02/99 12:29:30 AMPlease respond to Pietenpol Discussion cc:Subject: Pietenpol-List: Re: Don't say that!!!Ron,I'll second the vote to keep it as light as possible, for thesame reasons asTerry mentioned...the wing is over designed, and lighter woodwill certainlypay dividends. I don't measure weight in ounces...I measure itin grams !!A couple of other weight saving things I've done are rounding thesharpcorners of every stick in the wing (saved about 10 grams), and Iscaluped allthe gussets (saved over 3 ounces here), and as for all thehardware, I usedlengths that showed 2 threads and no more. Also, I weighed eachcompletedrib, and located the densest ones closest to the center of thewing, andprogressivly lighter toward the tips. It's important (whenpossible) tolocate mass as close as possible to the centerline, to aid inhandlingcharacteristics. Think about it...a baton twirler throws herbaton up in theair at a givin rpm, and as a result of Newton's law, it'sspinning at almostthe same rpm when she catches it. This occurs because the massis at thetips. Well, that's my two cents worth.Chuck Gantzer________________________________________________________________________________

Original Posted By: Michael D Cuy
I'm interested in the entry door!! I'd like to see whatothers have done here.Mike BellColumbia, SC"Davis, Marc" on 09/01/99 08:09:32 PMPlease respond to Pietenpol Discussion cc:Subject:I have some questions I hope you guy can shed some light on.Does anyone know of a direct drive Subaru EA81 Peat? What kindofperformance?Over and above the 1933 plans what are the other Peat addendumavailable andwhat are the sources? I've head of the following:Builders ManualBuilding video1932 Flying and glider manualLong fuselage3 piece wingSteel fuselageCorvair engineEntry DoorHinged wing section for easy entryAny others you guy know about?Do you know sources for the above?Which of these have worked well or not so well?Thank you,Marc Davis________________________________________________________________________________

Original Posted By: Mike Bell
I would like to see the math for the progress load. Post it on the web whenyour done, alongwith a drawing.Greg Yotz-----Original Message-----

Original Posted By: oil can
In a message dated 9/2/99 9:23:16 AM Central Daylight Time, mbell(at)sctcorp.com writes:>Mike, lightening the spars at the tips has been a thought of mine, but violating the spars gives me the heebie jeebies !! I've never heard it done before, but I would be very interested in any info ya find on it.Chuck Gantzer________________________________________________________________________________