Jack Kretmar Posted June 21, 2003 Share Posted June 21, 2003 I,m asking this as a tyro who knows very little about the subject. A question came up as I was looking at a builder's web site. He mentioned the difference between urethane foam and Styrofoam and noted that the urethane tends to disintrgrate over time. What I want to know is; why not use Styrofoam for the whole aircraft, if it's more durable? Is there a weight penalty for using it? Is the urethane easier to carve for curved surfaces? A more general question is, just how durable is composite construction? I'm under the impression that it's like a composite surfboard, only stronger. Still, I'm wondering, with time, heat and the stress forces on the plane from G-loading in flight, will the foam substrate start to deteriorate, causing problems deep down in the core material, or delamination between it and the glass/epoxy skin, thus leading to eventual structural failure? I'd surely hate to invest many years of my life building this thing, to see it start to deteriorate after five years, becomming a threat to life and limb. I noticed in Nat Puffer's promo.video that Burt Rutan made a big deal out of the superior construction compared to conventional "tin cans". Maybe I'm being a worry wart about this, but what is the story on urethane foam and composite construction in general? I saw something about a destructive test being carried out on an older composite plane. Any thoughts on this would be much appreciated. Quote Jack Kretmar Link to comment Share on other sites More sharing options...
chuckthedog Posted June 21, 2003 Share Posted June 21, 2003 urathane is used in the nonstructural stuff. If exposed to UV it breaks down. Primer and paint over glass thake care of that. It is EZ to form. Styrene is used for flying surfaces, Canard, Wings. PVC is used for bulkheads, strakes, and fusalage. Hope this helps. Quote If the phone don't ring. It's me Link to comment Share on other sites More sharing options...
John Slade Posted June 21, 2003 Share Posted June 21, 2003 Jack, You're worrying too much. Wayne may have said that Urethane deteriorates, but I'm sure he meant to add "when exposed to sunlight and weather". Once encapsulated in epoxy the stuff will last forever. There are lots of EZ's flying that were built 30 years ago with no sign of problems. Aluminum doesnt last that long. We use different foams in different parts of the airplane because of the various properties. In some areas we use very high density foam (Instrument panel) for strength. In others we need a foam that's easily sanded (urethane) for ease of curvature. Styrofoam melts when exposed to fuel, so we don't use it for the strakes. As for not writing in the forum because you havent started - that's ok - dreamers are people too! Seriously - your questions and the answers are relevant to everyone who considers building. Quote I can be reached on the "other" forum http://canardaviationforum.dmt.net Link to comment Share on other sites More sharing options...
LargePrime Posted June 21, 2003 Share Posted June 21, 2003 Jack Kretmar; Now i respectfully request you post over in teh "reasons not to build" thread, because i belive this is a new one. Thank you Quote We know who you are... Link to comment Share on other sites More sharing options...
Wayne Hicks Posted June 22, 2003 Share Posted June 22, 2003 I'm pretty sure Jack is speaking of my website. I should be more careful about what I post to my website because "disintegrate" is much too strong a word. I sincerely apologize if it gives anyone the impression that we are building and flying fragile crafts. I will change the word as soon as possible. Just in my opinion, I've found the fiberglass adheres better to the blue wing foam than to the urethane foam. Of course, there are other foams we use (the PVC foam, for example) that provide even better adhesion than the wing foam. It all depends on the application called for in the plans. I chose to use styrofoam (blue wing foam) for the nose top, canard cover, and canopy deck because I could set it up for hotwiring. It was really important to me to be able to hotwire the entire top of the airplane in one smooth, continuous curve. You cannot hotwire urethane foam without it giving off a noxious gas. Make no mistake about it. Composite construction is strong and very durable. For example, the canard on a Long EZ was tested to 12-plus G's! Just fly the plane like it was meant to be flown - within its design parameters. ....Wayne Hicks Quote Wayne Hicks Cozy IV Plans #678 http://www.ez.org/pages/waynehicks Link to comment Share on other sites More sharing options...
dust Posted June 22, 2003 Share Posted June 22, 2003 comments made about the process and the materials really have to be watched. Wayne, i'll use you previous post as an example (you are more than welcome to search mine for similar words and point them out) Wayne wrote Just in my opinion, I've found the fiberglass adheres better to the blue wing foam than to the urethane foam. Of course, there are other foams we use (the PVC foam, for example) that provide even better adhesion than the wing foam. It all depends on the application called for in the plans. Let us ALL asure you the glass sticks just fine to all of the foams speced. All of the fiberglass layups are plenty strong enough and no layers need be added or foam changed All metal parts are strong enough. ETC, ETC If you build this plane, per plans, the cozy, it will not need to be engineered by you, it is already well enginered. If a change need be made, Nat puffer will inform you in the quarterly newsletter. Nat is very conservative and does not want cozy's falling out of the air. For example, recently one cozy builder/flyer found a bent rod end for a control surface. Althou no problem ocurred in that or any other plane, he published a mandatory plans change for everyone to change the rod end for the next size up. A ten minuite fix and maybe a 4.00 part. Done, no FAA, No forum needed, thats just the way that he does business. Sorry wayne, I'll see if i can replace your example with one of my many slips Enjoy the build Quote maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build i can be reached at http://www.canardcommunity.com/ Link to comment Share on other sites More sharing options...
LargePrime Posted June 22, 2003 Share Posted June 22, 2003 I know this plane is really strong. Overbuilt is appropiate I think. But that didnt stop me from thinking "I wonder if i should build out of PVC foam???" I think it is natural to think like this. I also think it is unnessary. Jack, dont worry about the plane. Enjoy the build. And KNOW that you have chosen the safest and most successfull homebuilt available. Quote We know who you are... Link to comment Share on other sites More sharing options...
John Slade Posted June 22, 2003 Share Posted June 22, 2003 I think you've hit on an important point here. The average airplane builder (if "average" can be used in that context) isnt satified with just knowing "how". Most of us want to understand "why" as well. Nothing wrong with that. Quote I can be reached on the "other" forum http://canardaviationforum.dmt.net Link to comment Share on other sites More sharing options...
dust Posted June 23, 2003 Share Posted June 23, 2003 We have a tradition in our shop, when a new slave, i mean helper, comes along or when we used to allow gawkers, we had a small bulkhead that was 30"x 3" x 1/4 inch thick instead of 32"x3"x 1/4 inch thick,another story of trying to be too perfect, and we hand this piece to all and request them to break it. It weighs close to nothing and two 200 lb men can NOT break it. They can bend it but they can't break it. If we taped on a rib(a technicle term), they wouldn't be able to bend it, To me that is the "why", grab a piece and see for yourself how strong it is. Go help someone build for a day and see and "do" how easy it is. Go fly one and the flying will amaze you. Our shop is open to all for the doing enjoy the build Quote maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build i can be reached at http://www.canardcommunity.com/ Link to comment Share on other sites More sharing options...
Jack Kretmar Posted June 23, 2003 Author Share Posted June 23, 2003 Alright guys, Im convinced! Composite construction is strong and durable. Cheeze, the reaction of you cozy stalwarts is phenominal! You know; the very day I posted my question on the website, I caught a T.V. show on gliders and sailplanes. One of the craft featured was a super slick (in the literal sense of the word) composite sailplane that could go up to 146 mph. and do all kinds of aerobatics. I figure, any plane that can sustain those kinds of g-loads must be pretty strong. By the way "largeprime", I didn't mean to rile you up. I could just see the hair on the back of your neck, bristling from your indignation as you're thinking, "Who is this dufus to ask such a silly question?' Sorry about that. I like to ask lots of questions, and sometimes that irritates people. I'm looking for reasons to build, not excuses not to. Also Wayne, I was talking about your site. I'll bet you got some email from other builders, saying, in effect, "What are you trying to do? Scare this guy off before he's even built a bulkhead?" Seriously, I'm impressed with the ingenuity, know-how and diligence of all the builders. I'm particularly impressed with your site, Wayne. No offence to anyone else, but your techniques for building the tub and for lining up the wings and main spar together,answered a number of questions I had. But be assured that if and when I go with this, I'll be stealing ideas from everyone. Well, it looks like I'm rapidly running out of excuses not to build. Unfortunately, gentlemen, there's one that's not so easy to overcome, but I hope to remedy that in the future. And no, John. I'm not planning to take ten years to build this plane! Quote Jack Kretmar Link to comment Share on other sites More sharing options...
John Slade Posted June 23, 2003 Share Posted June 23, 2003 there's one that's not so easy to overcome Ahha! The old "secret" reason-not-to-build-trick. but I hope to remedy that in the future. "in the future" doesnt cut it as a deadline. Pick a date. Quote I can be reached on the "other" forum http://canardaviationforum.dmt.net Link to comment Share on other sites More sharing options...
Wayne Hicks Posted June 23, 2003 Share Posted June 23, 2003 Dear Jack Kretmar: You've made my day! I'm glad you get benefit from my website. I can only take some credit for the hinge technique for joining/gluing foam, and the upside-down jigging technique for assembling the fuselage in Chapter 6. I'd be stretching the truth if I claimed to have invented foam clecos (drywall screws) :-) Almost all the other techniques were borrowed (stolen?) from other builders! I believe the quote is, "Good artists create; great artists steal!" That it truly the benefit of following the builders that go before us. I'm only happy to return the favor. ....Wayne Hicks Cozy IV Plans #678 Quote Wayne Hicks Cozy IV Plans #678 http://www.ez.org/pages/waynehicks Link to comment Share on other sites More sharing options...
LargePrime Posted June 24, 2003 Share Posted June 24, 2003 As a hackel-less member of the stupid question club I was far from bothered. In fact I have asked about all the same questions you have asked. I never thought to ask the "urethane tends to disintrgrate" question. It was wourthy of note, in my humble opinion, in the "reason not to build" thread. The formailism of the request was an attempt at dry humor. A form underappreciated here i think. The destructive test i am aware of was a 21 year old Long ez that RAF tested to destruction. The spar/wing broke at 7.5g's. This was a huge disapointment for many. The canard was good for 14. Last I heard RAF was investigating to see what exactly the issue was. Please note; This is honest information provided publicaly by a homebuilt aircraft company that hasent sold a plan in 15+ years (correct me if i am wrong) and only gets royalties from Nat Puffer. 30 years from now with all we have learned and current tech (epoxy et. al.) what will a cozy break at? I dont know. But if it's not better, and I am still around, The beer is on me. Quote We know who you are... Link to comment Share on other sites More sharing options...
Wayne Hicks Posted June 24, 2003 Share Posted June 24, 2003 Uhmmmm, hold it..... RAF recently performed destructive tests on a VARI-EZE, not a Long-EZ. The wing structure of the Vari is completely different than the Long EZ, so the 7G static failure does not apply to Long-EZs and Cozies. However, RAF's testing did uncover a bolt corrosion issue potentially affecting most of the designs that are of RAF heritage. The issue will be discussed fully in the next issue of the Central States Association newsletter. For those of you unfamiliar with the CSA, CSA is THE quintessential organization still publishing technical newsletters for the canard community. The CSA publishes this 32-page newsletter 4 times a year. Find out more information at http://canard.com/~csa/ ================ Wayne Hicks Cozy IV Plans #678 Quote Wayne Hicks Cozy IV Plans #678 http://www.ez.org/pages/waynehicks Link to comment Share on other sites More sharing options...
John Slade Posted June 25, 2003 Share Posted June 25, 2003 Thanks for reminding me, Wayne. I haven't seen a CSA newsletter in a while, so I just sent a check for renewal. For those interested in canards, allow me to expand on Wayne's description of the CSA newsletter.... Get it! Seriously - if you were only allowed one airplane publication, this would be the one to get. But then, that's just my opinion.... Quote I can be reached on the "other" forum http://canardaviationforum.dmt.net Link to comment Share on other sites More sharing options...
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