Brodhead Pietenpol Association

Original Posted By: AMsafetyC(at)aol.com
Hello EverybodyIt's been a long time since I've contributed anything to the list. I've been readingthe postings quietly, but recently the question of tapering the top of thespars to match the profile of the wing section has bothered me. I'm concernedthat tapering the spars my lead to a concentration of compression forces atthe tip of the taper and result to failure of the spar. Has anyone done an analysisof the tapered spars?Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: "Cuy, Michael D. (GRC-RXD0)[ASRC]"
Subject: Re: Pietenpol-List: Introducing MyselfWelcome Bob,I can find no better way to spend time than building my Piet, some times its about the destination and some times its about the journey and when you build a Piet it becomes both no matter what side you start on.John RecineLititz PA**************Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-plea ... 0000002598)________________________________________________________________________________Subject: RE: Pietenpol-List: Introducing MyselfDate: Tue, 19 Feb 2008 11:25:36 -0600

Original Posted By: "Rick Holland"

Original Posted By: "Rick Holland"
Welcome Bob!I believe you're right on the 495 corridor. I'm in Storrs, CT and in your areafrequently with a son in college in Easton and my company headquartered in Hopkinton.I've been at it for about 2 years now and have little to show for myenthusiasm except a set of completed ribs. It will be nice to have a local contact.We should get together some time.Take care,Glenn--------Glenn ThomasN?????http://www.flyingwood.comRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 19 Feb 2008 11:09:22 -0700

Original Posted By: "Rick Holland"

Original Posted By: "Rick Holland"

Original Posted By: HelsperSew(at)aol.com
I don't think I stated my concern clearly enough. I am concerned with the sparfailing in bending. The fabric transfers the upward force of the air from thebottom side of the wing to the ribs which in turn transfer forces to the spare.Since the ribs are evenly spaced at about 1ft. on center one can assume thatthe bending force on the spar is evenly distributed along the length of the spar(beam). Beams concentrate tension and compression forces at I believe thetop and bottom 1/3rds to their sections. If there is a taper to the top of thebeam the beam in theory gets deeper and the compression forces get concentratedcloser the the infinitesimally small tip of the taper on the beam. The steeperthe taper the closer the forces are concentrated into the tip. So I supposemy question really was has anyone looked at how great a taper can be given tothe beam before the reduced area of the taper will lead to failure of the beam(spar) in compression? I think what would happen in the event of failure isthat a buckling of the wood fibers wood be observed down to where the spar reachesfull section width then stop. But, the buckling may not stop.Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By:
Subject: Re: Pietenpol-List: Re: Tapered Spar ScareMy eyes are glazing over. Honestly I think you are being too smart by half. In other words, don't worry about this. It would not happen in a million years, unless of course you are planning to do outside loops or lumshevaks (sp).My airplane will only be doing 30 to 40 degree banks at the most. For any airplane spar to fail is quite rare. Dan HelsperPoplar Grove, IL.**************Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-plea ... 0000002598)________________________________________________________________________________Date: Tue, 19 Feb 2008 14:06:29 -0800

Original Posted By: "Jack T. Textor"
Hello,Just building my wing rib jigs, and have no experience with T-88. For the joints,any feedback on cutting holes at the joints versus using plastic to keep T-88off the jig? I've heard don't use wax paper because it contaminates the otherside(?)Thanks,SteveRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: RE: Spam> Pietenpol-List: Re: Tapered Spar ScareDate: Tue, 19 Feb 2008 16:09:56 -0600

Original Posted By: "Phillips, Jack"

Original Posted By: "Rick Holland"

Original Posted By: gliderx5(at)comcast.net
Steve,It's strictly up to you. Whatever you prefer.Epoxy has a tendancy to run (usually when you're not looking). I have seenphotos of some builder's work that looks as though the glue was applied witha big paintbrush (glue all over the place). Mix up a batch of epoxy, andbuild a few test joints to see how the stuff works, and how neat you can be.Even if you cut the holes at the joints, you'll probably still wantsomething to catch the drips that fall through the holes (like a sheet ofplastic film, maybe?). Personally, I went with small pieces of plastic film, only at the jointlocations. See some photos here: http://www.mykitplane.com/Planes/buildL ... r%20Camper Bill C.________________________________________________________________________________

Original Posted By: shad bell
If I was building again I'd keep the spars square just because that's what theplans call for and it keeps things much simpler that way. But just as an asidethe '39 Aeronca wings I'm working on now have highly beveled spars front andrear. Beveled to match the shape of the rib. I'm really sure there is no concern.The issues would be in adjusting the wing strut attach fittings as theywrap over the top of the spar and possibly attaching the top compression struts,since they attach to the top of the spar with a flat gusset. There may beother things too. As we "Piet Purists" always say, "One change always leadsto many more, stick to the plans". Sorry, had to get that one in there. Justa little fun in stirring the pot. Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 19 Feb 2008 15:32:42 -0800 (PST)

Original Posted By: Glenn Thomas
Glenn,THANK YOU ! This is outstanding and definitely gives me a clear picture of where to go from here. Rick's advise was very helpful and your pictures and descriptions are great.Thanks for the welcome too. While I am just beginning my Piet, I am hopeful that some day I might be able to know enough to offer the kind of incredible advise like yours. Right now my expertise is in asking questions !Thanks again for the help.Jim ----- Original Message -----

Original Posted By: "Jack T. Textor"
[/quote]In a unifromly-loaded plain (3/4" thick, no routing) spar under a positivevertical load, the stresses can be visualized as a straight-line progressionfrom maximum compression at the top-most fiber to a maximum tension at thebottom-most fiber, passing through zero stress at the neutral point, close tothe middle. > > > That's why I mentioned that compression and tension is basically concentratedin the top and bottom thirds of the beam with the center 1/3 being of littleuse other that resisting shear and spacing the top and bottom 1/3s of the spar.That's why it's okay to rout the spar. As the point of the taper gets higherand higher the stresses at the top of the the spar, in this case where the taperoccurs, are resisted by a smaller and smaller section. > > > Honestly I think you are being too smart by half. In other words, don't worry aboutthis. It would not happen in a million years, unless of course you are planningto do outside loops or lumshevaks (sp). My airplane will only be doing30 to 40 degree banks at the most. For any airplane spar to fail is quite rare.> > > > That's what I was hoping. That it is nothing. But, it's your butt being helda few thousand feet in the air by a couple of pieces of wood only a few inchesdeep. I know if the bevel is only slight this thread is for nothing but whereis that cut off for an allowable taper?> > > > Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: RE: Spam> Pietenpol-List: Re: Tapered Spar ScareDate: Tue, 19 Feb 2008 17:51:41 -0600

Original Posted By: Owen Davies
Brown Gravy wrote:> Hello Everybody> > It's been a long time since I've contributed anything to the list. I've beenreading the postings quietly, but recently the question of tapering the top ofthe spars to match the profile of the wing section has bothered me. I'm concernedthat tapering the spars my lead to a concentration of compression forcesat the tip of the taper and result to failure of the spar. Has anyone done ananalysis of the tapered spars?I know a structural engineer who can shed some light on this, for curiosity, andI will run it by him and post back later.Mike--------Piet-builder-who-hopes-to-be-flying-next-summerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 19 Feb 2008 20:05:52 -0500

Original Posted By: "gcardinal"
Sorry folks. didn't mean to scare anyone. I guess I should have titled the postingdifferently. "Tapered Spar Scare" was a bit strong. I was just curious ifsomeone had looked into the matter. I too was considering built-up spars witha tapered top, but then got to thinking about all those things I learned in my"statics" class many years ago and my experiences with making bows and how bowswith deep narrow bellies are more likely to fail in compression.> I know a structural engineer who can shed some light on this, for curiosity,and I will run it by him and post back later.> > MikeThanks. That'll settle the matter for me.Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: "Brown Gravy"
Fear not, Mr. Gravy.Beveling the top of the spar is a perfectly good way to get an additional 1/8" of spar depth. It is a good thing.Greg C.NX18235 has 130+ hours on a beveled spar.......----- Original Message -----

Original Posted By: "KMHeide, BA, CPO, FAAOP"

Original Posted By:> John Hofmann
Subject: Re: Pietenpol-List: Re: Tapered Spar ScareTruly words to live by, I am going to post this in my office for reference in dealing with the business world, I may even add a few:Words of reassurance and appearence: We don't want to disconcert the masses now do we son , Consoling a co worker following the meeting : you're a good looser and I like good looser's. I bet you've had a lot of practice.Exercising creativity and improvising solutions: The lake Axle, the Lake Humility: No I cant say that I'm the best pilot in the world Scooter, I would have to say Earnst Kessler the German flying Ace is the best, I'm the second best pilot in the worldExploring options: Will it do an outside loop?JohnIn a message dated 2/20/2008 11:00:35 P.M. Eastern Standard Time, jhofmann(at)reesgroupinc.com writes:--> Pietenpol-List message posted by: John Hofmann John R,Now you've got the spirit! All of life's problems can be solved through "The Great Waldo Pepper."Greet Strangers: "Hello Good People!"Protect Wimminfolk: "He's a Four-Flusher Mary Beth."Learn about culture: "Duke, into the opera singer costume"Become a new entrepreneur: "You take this to the gas station every time I need it and at the end of the day I'll give you a free ride."Lessons in advertising: "I knew she wasn't worth top billing."Learn about sharing: "Nebraska is mine!"Return from a business trip: "Look who's home."Advanced aircraft design: "It's gonna be a monoplane."ALL of life's questions and problems solved.-john-John HofmannVice-President, Information TechnologyThe Rees Group, Inc.2810 Crossroads Drive, Ste 3800Madison, WI 53718Phone: 608.443.2468 ext 150Fax: 608.443.2474Email: jhofmann(at)reesgroupinc.comOn Feb 20, 2008, at 9:00 PM, AmsafetyC(at)aol.com wrote:> --> Pietenpol-List message posted by: AmsafetyC(at)aol.com>> Ezra. Its not a biplane!>> John> Sent from my Verizon Wireless BlackBerry>> -----Original Message-----

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Build to the prints and you'll not fit in it? Jim-----Original Message-----

Original Posted By: "Glenn Thomas"
Dear Walt,AMEN to that!Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 21 Feb 2008 20:47:33 -0500

Original Posted By: Owen Davies

Original Posted By: "Don Emch"
Dear Glenn,AMEN to that!Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Control question

Original Posted By: "gcardinal"
I'm planning to fly this weekend, I'll check.Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: AMsafetyC(at)aol.com
> To:pietenpol-list(at)matronics.com> Subject: Pietenpol-List: Re: Tapered Spar Scare>>> --> Pietenpol-List message posted by: John Hofmann >>> A one inch spar failing in compression from a bevel?> Brown Gravy?> "The IT Girl of the Sky?">> It must be time to level this discussion with a quote:>> "I Haven't had an unlimited budget you know. It's not going to look> look like something out of a museum, all clean and dusted. I'm a> designer and I don't give a d@nm about clean. That's what's so unique> about this plane, the design. Concentrate on that. The Design. Well,> there it is, the Stiles Skystreak.">> -Ezra Stiles->> You may now return to serious Pietenpol discussion.>> -john (the idiot)->> Do Not Archive>>**************Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-plea ... 0000002598)________________________________________________________________________________