Brodhead Pietenpol Association

Original Posted By: owner-pietenpol-list-server(at)matronics.com
That's a great testimony, Max!In the last few days, 3 alternatives have been mentioned: Pine, Fir andPoplar. Is everyone who is using a Spruce alternative using Fir for thespars?Gary Boothe Cool, CA _____

Original Posted By: Clif Dawson

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Clif,What about spars of laminated strips of Hemlock?Or do you have other plans...Bill _____

Original Posted By: owner-pietenpol-list-server(at)matronics.com
I had not heard that laminating spars was OK. Fine by me if it is, but is iteasier to find four good pieces of wood, or worry about all those gluejoints? If the joints are not a problem, do all the pieces have to be fulllength? Just thinking 'out loud'...Speaking of Mike Cuy; did you purchase his video? It sounds like it would behelpful.Gary _____

Original Posted By: "Glenn Thomas"

Original Posted By: owner-pietenpol-list-server(at)matronics.com
If done properly, the glue joint is stronger than the wood, especially withmodern glues. So a laminated spar is actually stronger than a solid spar.AC 43-13 1B permits the replacement of a solid spar with a laminated spar.(If you don't have a copy, you need to get one - and read it).The wood used for solid spars is usually the best quality wood available, asit is basically carrying the whole load. Most of the other members in theairplane are gusseted and reinforced, whereas the spar "is what it is". Itis much easier to get hold of fourteen-foot lengths of 3/4" x 3/4" (or 3/4"x 1/2", or whatever) wood with the proper characteristics (growth rings,grain runout, etc) than it is to find fourteen-foot lengths of 3/4" x 5"clear wood that meets the specs. If joints in the lamination strips cannotbe avoided, they must be scarfed joints, staggered as far apart as possible,and located as far outboard as possible (where the stresses are lower).Laminated spars is not a new idea. I have read that BH Pietenpol usedlaminated spars in his later creations.Laminated spars are definitely more labor intensive, but if you are payingyourself the same wage that I'm paying myself to build my plane, the laborcost is negligible. There should be a definite savings in material cost,though.Personally, I wouldn't hesitate to use a laminated spar. But I'm planning touse a built-up spar like they do in the UK. It is reportedly stronger,lighter and cheaper than a solid Spruce spar.Bill C. _____

Original Posted By: Ryan Mueller

Original Posted By: del magsam

Original Posted By: "jimboyer(at)hughes.net"

Original Posted By: Owen Davies

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Owen,http://www.cpc-world.com.Peter.Wonthaggi Australia-----Original Message-----

Original Posted By: Ryan Mueller

Original Posted By: Clif Dawson

Original Posted By: Clif Dawson

Original Posted By: owner-pietenpol-list-server(at)matronics.com [mailto:owner-pietenpol-list-server(at)matronics.com] On Behalf Of Ryan Mueller
To:Subject: RE: Pietenpol-List: Spruce AlternativesRyan and Owen, Good reference info, thanks! Jack www.textors.com ----------------

Original Posted By: Pietsrneat(at)aol.com
To:pietenpol-list(at)matronics.comSubject: Re: Pietenpol-List: Plywood Spar WebsPietsrneat(at)aol.com wrote:> I am planning on using a plywood web as well. What size are you > using? I bought 1/8, 45 degree but am wondering now whether it is > hefty enough. I am currently working on the metal and the gear, so > I've got plenty of time to get input and figure it out.My understanding is that the PFA-approved plans call for 1/8. Not sure if it's 45-degree, it that would make sense, of course. This is with the web on the front side and some parts of the back, especially the center section and perhaps 18 inches centered on the strut attach fittings. Using an I-beam structure, I don't know what you would need.FWIW, Paul Best's article from the April 1961 edition of Sport Aviation shows a solid spruce spar 6 x 1-5/8 inches as having a bending strength of 60,000 lb. A version with a 1/8 birch plywood web and spruce caps made up from 1 x 3/4 spruce (2-1/8 total spar thickness) is quoted at the same strength. So is a version with a 3/32-inch mahogany plywood web and caps made from 1 x 1-1/4 mahogany (2-3/32 total spar thickness.) His illustration shows 45-degree grain, and the text mentions cutting and splicing from 90-degree marine plywood.The interesting difference is the weight. Best shows the plank spar as weighing 1.827 lb per foot. The 1/8 ply with spruce comes in at 1.340 lb/ft, the mahogany/ply version at only 1.200 lb/ft. For a Piet, the mahogany/ply spar saves over 17.5 lb.A correction appended to the article modifies all of the above slightly, but the basic concepts remain correct.Here is the part I love: Best quotes the price of spruce at $1.05 per foot, with the spruce/birch ply coming in at $0.97 per foot and the mahogany/mahogany ply at just $0.65! We may need to adjust those figures slightly.Incidentally, the article quotes ANC 18 as recommending lamination of spar caps to eliminate the risk that hidden defects will compromise the spar.There is a reference to NACA Report 344, "The Design of Plywood Webs for Airplane Wing Beams," which sounds well worth having. I believe it should be available online, though I can't recall where. If anyone has the URL, I'd love to know.Ah. Just found it at a UK mirror site: http://naca.central.cranfield.ac.uk/report.php?NID=908. There are a number of other really interesting reports linked from http://naca.central.cranfield.ac.uk/cit ... 1-cit.html. I am downloading some of them now!Owen________________________________________________________________________________

Original Posted By: "Jack T. Textor"
Subject: Pietenpol-List: Plywood Spar WebsOwen, I am planning on using a plywood web as well. What size are you using? I bought 1/8, 45 degree but am wondering now whether it is hefty enough. I am currently working on the metal and the gear, so I've got plenty of time to getinput and figure it out.RonIn a message dated 2/22/2008 7:18:36 P.M. Eastern Standard Time, owen5819(at)comcast.net writes:Of course, my current plan is to save weight by using a one-piece wing, and a plywood-web spar would save a little bit more. It also avoids having to plane down 5/4 or 2x stock because 1x is not even an honest 3/4 these days.**************Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-plea ... 0000002598)________________________________________________________________________________Subject: RE: Pietenpol-List: Spruce AlternativesDate: Sat, 23 Feb 2008 08:20:56 -0600

Original Posted By: Owen Davies

Original Posted By: Ryan Mueller

Original Posted By: Owen Davies

Original Posted By: Owen Davies

Original Posted By: Owen Davies

Original Posted By: "Jack T. Textor"
In reading comments by Mr. Pietenpol about the longer version fuselage, Inotice that he recommends 4" longer struts and slanted back 3". Would anyoneon the list care to comment about those recommendations?Gary BootheCool, CA________________________________________________________________________________Subject: RE: Pietenpol-List: Spruce AlternativesDate: Sat, 23 Feb 2008 11:08:26 -0600

Original Posted By:> Jack T. Textor
Jack and all,I got to see Larry Harrison's Poplar Piet. I noticed the longerons werespruce and asked him about it. He said he did not use poplar for longeronsor spars.I would not use poplar for any part of the airplane that is very long orneeds to flex. The fibers in poplar are allot shorter than they are in anytype of spruce. To test this take a piece of each and rip it on the bandsaw. The sawdust from poplar is just that, dust, the sawdust from spruce islong and stringy. Poplar is great to work with and would be great for theV-blocks in the fuse side where you want a hard place to drill a hole oranyplace that needs to be strong mainly in compression. It is also greatfor drawer sides, but that has nothing to do with airplanes. Skip> [Original Message]

Original Posted By: "Jack T. Textor"
JackThere a few tables that show all the useable woods and their strength,weight andfeatures. By comparison yellow poplar was listed with almost identical numbersas the spruce. With that info and local availability the poplar met my needsJohnPiet in poplarSent from my Verizon Wireless BlackBerry-----Original Message-----

Original Posted By: Owen Davies
I am seriously considering 1 8th Aluminium web with poplar top and bottom flangesI believe the last time I checked the metal was rated at almost 10 times the woodJohnSent from my Verizon Wireless BlackBerry-----Original Message-----

Original Posted By: "Gary Boothe"
Subject: Re: Pietenpol-List: Plywood Spar WebsI was going to use it on an I-beam spar. I read the article below and thought it would be substantial enough. However, once I looked at the 1/8" upclose, it just didn't seem like it would fly.Ron_http://westcoastpiet.com/images/Construction/I%20Beam%20Analysis.pdf_ (http://westcoastpiet.com/images/Constru ... alysis.pdf) In a message dated 2/23/2008 11:16:54 A.M. Eastern Standard Time, owen5819(at)comcast.net writes:Using an I-beam structure, I don't know what you would need.**************Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-plea ... 0000002598)________________________________________________________________________________

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Rick,This is on page 2 of the =93Converting the Corvair Engine=94 guide, under=93MODIFICATIONS.=94 BHP discusses extending the fuse and a few other things.The exact quote is, =93The center struts were made 4=94 longer and slanted back3.=94 In this section, he also states that the =93=85.wing spars were made of seven =BE=94x =BE=94 strips and 1/8=94 plywood plates on the sides, where all the fittings andribs are located=85=94Gary _____

Original Posted By: Owen Davies

Original Posted By: "jimboyer(at)hughes.net"

Original Posted By: "jimboyer(at)hughes.net"

Original Posted By: Ryan Mueller

Original Posted By: "jimboyer(at)hughes.net"

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Ryan,That was my take, too. He is definitely talking about weight and balanceissues concerning the stretched version. He went on to discuss moving thelanding gear forward about 4=94, but I don=92t think very many have.Thanks, Gary _____

Original Posted By: Gary Boothe
Gary,Bill Rewey says to move the axle forward 3" if you have brakes, thats what I did.Skip----- Original Message -----

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Skip,Thanks! That was Mr. Pietenpol's advice, too. Did you leave the attachpoints the same and just change the geometry?Gary Boothe Cool, CA _____

Original Posted By: "Rick Holland"

Original Posted By: Ryan Mueller

Original Posted By: "Don Emch"
I met and talked with Larry Harrison too. He's a great guy with a tremendous amountof common sense and know-how. And like Skip said he didn't use poplar forspars or longerons. Please be careful and know what you are putting into yourairplane. When you are bouncing around in nasty butt-puckering turbulence,you and your passenger will be thankful!Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Center Struts

Original Posted By: "Skip Gadd"
I believe later on Mr. Pietenpol felt that 4" was too much of an extension on thecabanes because it gave somewhat of a pendulum effect with power changes. He said 2" was probably a better amount to lengthen them. That's what I did andmany others have done. Decent head room getting in and out and behaves normallywith power changes.Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: Gary Boothe
Gary,Yes, Just change the geometry, like Rick said. You pretty much have to leave theattach points the same as they should coincide with the uprights in the fuseside.SkipHales Landing West Virginia----- Original Message -----

Original Posted By: "allthumbs"
No I just dragged it around. Next year I'll make a ski for it because the airstripsget rough when they are all frozen up and the wheel doesn't glide over themthe way a ski does.Don EmchRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Spruce Alternatives

Original Posted By: owner-pietenpol-list-server(at)matronics.com
Sorry,I didn't phrase that correctly. Thanks for catching my error, Clif.What I meant was simply that the glue joints (if done correctly) will be asstrong or stronger than the wood. Of course, a chain is only as strong asits weakest link, so the laminated spar will never be stronger than the woodused to build it with.Bill C. _____

Original Posted By: Grover Summers

Original Posted By: Bill Church
BillI may be wrong about this, but I would disagree on that point as stated. If a spar is built up of 3/4x3/34 laminations to a height of 4 1/4" with staggered joints and grain which is alternated, the total beam will be much stronger than the wood it is made of.Dick N. ----- Original Message -----

Original Posted By: "allthumbs"
What I have done before is to IMAGE a .jpg into an AutoCAD drawing and either traceover the image to create the line drawing off the image (after SCALEing it,of course, and using DRAWORDER to place the image behind the working layerso you can see the lines you're drawing), or just using the image itself to drawup whatever you want to fit over it. There are 3-views of the small-blockContinentals in Tony Bingelis' books, for example, as well as (I believe) Evans'"Light Plane Designer" or whatever his book is called. You can scan thoseto create your .jpgs.Most 3-views give dimensions between mounting points or other clear dimensionsto use to SCALE the image to correct size.When I was fabricating the new stainless firewall for 41CC, I used this techniquewith a head-on digital picture of the front of the fuselage. It worked perfectly,but the builder (me) was too smart for my own good. I forgot to notchthe corners of the lower piece of the firewall like Corky had, in order to makeit removeable. It fit like a charm with slots to slip nicely over the enginemount points, but it's now trapped in place by the engine mount bolts. Sigh.You would think we would be making new mistakes, but it's always the sameold ones ;o) Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Subject: Pietenpol-List: Re: Spruce Alternatives

Original Posted By: Oscar Zuniga
I worry about using epoxy on laminated wing spares, marine epoxy can creep at higher temperatures, of course the wing will be painted alight color to reflect the sun's rays. or the laminations could be tightly clamped and some other glue used such as Gorilla glue, not nearas messy either. anyone have experience with epoxy that has a higher temperature rating than marine epoxy such as Raka?I think a very Strong spare would be two separate units ofbirch plywood one with 90 degree grain, one normal, then cap striped with Douglasfirwith an abundance of nails, this would be strongest and yet lightenough of any spar. The birch plywood would be scarfed splicedat an angle having a splice two inches long in 1/8 ply this would be thestrongest in my opinion, note I haven't built a plane just planing on it.Oh yes there would be insert pieces of wood at scarf points.--------RussellRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: "allthumbs"
I really hate to beat this subject too far, but we have to be very careful about re-engineering a spar too much. In using plywood, unintended stresses can be created that can cause failure. The loading has to flow over the entire beam. The solid and laminated spars along with some box beam spars have been proven.Resorsinol is the only glue approved for certified aircraft. T-88 has been widely used for a long time. Gorilla glue has been discussed on the list a few times although I'm not aware of anyone who has actually used it.Dick N.----- Original Message -----

Original Posted By: "Rob Stapleton, Jr."
There is a test matrix which was published in an issue of experimenter magazinea few years back on on a glue that is the same as Gorilla glue,The results showed comparable with other high performance glues.The spares that I am going to build are nothing new no new or re-engineering herethey were building them that way in WW-1, birchply box spares that is. Roger man also uses this on his stuff.--------RussellRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________

Original Posted By: Tim