Date: Mon, 09 Dec 1996 13:17:39 -0800 From: marcna Organization: ratdog Subject: COZY: Triaxial Wing Skins I=92m getting ready to skin my wings and I was wondering if anyone has an= y luck with TRIAXIAL glass skins. = Marc Parmelee N425CZ Date: Tue, 10 Dec 1996 07:50:36 -0800 From: marcna Organization: ratdog Subject: COZY: Triax Cloth Nigel Field writes: >Regarding Triax cloth, if you examine a piece closely you will >find lots of space between the fibre tows, much more than UNI. >These act like a sponge and soak up LOTS of resin. Repeat my test >in laying up two identical samples, one of triax and one three >plies UNI and then weigh and test them to destruction. See what >you get. IMO triax only saves time, and if you use the dry layup >method above it saves nothing. The only place you could use it is >on the wing top which call for three plies but the weave >orientation will not be the same as Rutan called for so the >tortional properties will differ. The bottom skin is two plies so >triax just adds lots more weight for nothing. Don't use it, its >arguably weaker and heavier than 3 plies of UNI. Jeff Russell writes: When we use Triax cloth, we always meter how much epoxy for the size cloth used. How do we do that?? Weight of Cloth = Weight of Epoxy. This will guarantee a 50/50 glass to resin count, about what is normal for a hand layup less vacuum bag job. We show in the composite workshops that we teach, how EVERY style of fiberglass has its best place for work ability. Biaxial is a poor choice for a hand layup maybe for a shearweb. Giving its airy composition and it does not like to make a outside bend, air is a bad problem here. If we were to use the same material in a mold. We could now vacuum bag to compress out the extra resin out. Biaxial cloth also likes to make inside bends. Hopefully you can see what I mean about (best place to use). Our molded environment lends the use to this style mostly because of vacuum bagging. A lessen we learned about knitted cloth instead of weaving was no cornstarch was used on the knitted cloth. cornstarch must be baked out of the glass so it will be able to except epoxy resin. When going through this baking process, the cloth losses about 30% of its strength per weight. If you had 9 oz of BID and 9 oz of Biax knitted cloth , I am told it like the 9 oz equivalent of BID (Biax is like going to S-Glass). We have NOT done any load test on these styles, but this is what Hexcel told us their test found. The use of Triax on the bottom skin of a EZ wing has been used on ALL Velocitys, and AeroCanards from day one. Why?? Stronger skin, better compression on the bottom side from crushing foam. Does anyone remember what Burt did and talked about at Big-O last year and the year before?? Skin delamanation on the wings larger than a quarter need to be repaired on ALL EZ's. On the Vari-EZ if this was found on top of the wing by the winglet, The airplane was grounded until fixed. Winglets come off rather quickly with this problem left unattended. Burt used a dime to tap on the wings to find the bad spots. Most were on the bottom of the wing were lifting to set the wing was a issue. I looked at LOTS of Longs and Cozys and could see lots of these spots with just my eyes. The Velocitys did not seem to have this problem confirming what Danny M. told me that it took care of that flimsy skin problem with the Triaxial skins. end Has anyone besides Jeff Russell and Velocity used Triax on the wings, or is the jury still out on this one. Marc Parmelee N425CZ Date: Tue, 10 Dec 1996 23:59:40 -0500 From: Mahan Subject: Re: COZY: Triax Cloth Jeff Russell writes: > When we use Triax cloth, we always meter how much epoxy for the size > cloth used. How do we do that?? Weight of Cloth = Weight of Epoxy. > This will guarantee a 50/50 glass to resin count, about what is normal > for a hand layup less vacuum bag job. Correct me if I'm wrong, but I has always heard that 50/50 was about the very best that a builder could do with a hand layup using bid or uni. How are you able to get 50/50 with a hand layup if the triax has a more open weave? If triax weave is as tight as, say, bid, how do you inspect to see that all plies are wet out? > We have NOT done any load test on these styles, but this is what Hexcel > told us their test found. Could you do some tests for the benefit of the Cozy community? > The use of Triax on the bottom skin of a EZ wing has been used on ALL > Velocitys, and AeroCanards from day one. Why?? Stronger skin, better > compression on the bottom side from crushing foam. Wouldn't the third bottom ply add weight, too? Are there any weight comparisons between a uni built Cozy wing and one (or an Aerocanard wing) built with triax? > Does anyone remember what Burt did and talked about at Big-O last year and > the year before?? Could you tell those of us that weren't there? > ... bad spots. Most were on the bottom of the wing were lifting to > set the wing was a issue. I looked at LOTS of Longs and Cozys and > could see lots of these spots with just my eyes. How could lifting the wing at the winglet to set the gear cause compression damage on the bottom of the wing? The bottom glass would be in tension. Are you referring to someone pushing up on the bottom of the wing itself? Everyone I know pushes up on the bottom of the winglet, realizing that pushing up on the skin itself is a no-no. > The Velocitys did not seem to have this problem confirming what > Danny M. told me that it took care of that flimsy skin problem with > the Triaxial skins. The third ply would seem to be added to allow for pushing up on the bottom of the wing, not for flight load reasons. Marc Parmlee writes: > Has anyone besides Jeff Russell and Velocity used Triax on the > wings, or is the jury still out on this one. Haven't heard of any Cozy's Long-EZ's built with triax. Laying the glass down one ply at a time lets you examine the first ply before you put the second ply over it (and the third ply over that, on the top). Yes, it takes longer, but a very small percentage longer of the total time to build the aircraft. Fred in Florida Long-EZ N86LE Date: Wed, 11 Dec 1996 09:19:25 -0500 From: Phillip.Johnson@kan.lmcda.lmco.com (phillip johnson) Subject: COZY: Triax Cloth Marc Parmelee Writes: > Has anyone besides Jeff Russell and Velocity used Triax on the > wings, or is the jury still out on this one. Yes I used it on the top surface of the wings. I did some test samples and they came out lighter than the equivalent UNI. A friend of mine did the same tests on a Dragonfly and came to the same conclusion. For the wing lay ups, I did these a couple of years ago so only qualitative data is available, I found that I used significantly less than 1.5 times the resin used on the bottom surface, now remember that the top surface is approximately 10 to 20 larger than the bottom because of the asymmetric aerofoil and only two plies are required on the bottom. The surface finish is more coarse because of the nature of the cloth weave , or rather lack of weave, and clearly requires more filler to complete the job it may be here that I will pick up extra weight. My wings complete with all fitments and fittings came to 78 & 80 lbs. These figures include a mass of extra coax, for both Coms antenna's and a marker beacon antenna. The weights also include the leveling boards so I guess that the true weight is a few pounds lighter than those specified. When I did the lay-ups I also wrapped the top and bottom surfaces over the shear web face between BL 31 and BL 67.6 i.e. the exposed face of the spar because this is where the stress is concentrated. I noticed a couple of weeks ago that some builders gave some wing weights one of which was a three place. As I understand it the three place uses thinner spars and does not require the wrap around at the inboard end of the spar, nor does it include the large UNI panel in the region of BL 69. My feeling is that the biggest weight difference results from variability in the foam and the amount of micro used in the foam joints. I would use the Triax again. Phillip Johnson Date: Wed, 11 Dec 1996 13:18:01 -0500 (EST) From: "George A. Graham" Subject: COZY: Biaxial Cloth I used the biaxial cloth on the inside of my turtledeck. After the layup, I was so upset that I called Wicks who gave me the Hexell tech help number. The problem was the huge empty spaces in between the fibers, it looked to me like I could use gallons of epoxy to try to fill in the pattern. The guy at Hexell said that those cloths work better for vacume bagging or mold work. Some day you'll get to see the mess it made, there is no way I'm going to try to "fill" that in, that would take more fill than the rest of the airplane ! The good news is that it is not in a critical area. I really should have tested it first. That is the ugliest mess I've made, maybe some type of headliner material or something will stick to it. George Graham Eracer #206 Mazda Rotary Engine (716) 874-3277