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fiberglassing experiment

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kzimmerman

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I thought that some of you on here might like to know a bit about different "resins" that I have used to fiberglass things, and a new one that I've never tried. I'm building a Cosmic Interceptor, And I'm concerned about the fins, as they are big, with very little joint area = breakage. So, I set about fiberglassing the fins into place, but couldn't decide how I wanted to do it. I took 3 pieces of balsa about 3x4 inches, and some junk BT that I had laying around. I scratch build a lot, have amassed a large collection of random BT. I glued the fins on using either titebond 2 or 5 minute epoxy, depending on the laminating resin used. I used 3/4 ounce cloth, from fin tip to fin tip, including all around the BT. Here's the resins, with some observations.
1.Thinned Titebond 2, approximately 75/25 titebond 2/water. It was difficult to work with, as it did not want to easily wet out the cloth, and it tended to drag the cloth around as you squegged it. I believe this was due to the surface starting to tack up before the wood/cloth joint. I also noticed after a 8 hour window of "drying" that it wanted to delaminate at the fin/tube joint. I'm gonna let it "dry" overnight, or cure, don't know the window for either. Finishing it looks to be moderately difficult, and weight wise it's in the middle.
2. 5 minute epoxy thinned 75/25 with alcohol. Have to move fast! Cured up quick, layed up easy, doesn't want to delaminate. Appears to be the strongest so far, but I'm gonna let the other ones sit for a while before I pass judgement on this, as they are both air dry. Finishing appears to be be fairly easy, sanding a little and then primer. Negative is weight. I'll try to use a proper laminating resin on the actual rocket (I think theres enough west systems left).
3. Polycrylic. Foam airplane trick, strong but much lighter than epoxy. Seems Fairly strong, but letting it dry some more to see if it gets better. Easy to finish, a very small amount of sanding and primering. This was the easiest of the 3 to laminate, wet out the cloth very easy, squeegeed out to a very even surface. My favorite so far, assuming that it is strong enough.

Please note, I didn't have an FFF on hand, so didn't try that.

More results pending the finishing of my morning coffee. Can't make any kind of qualitative strength measurements before the consumption of an adequate amount of coffee!
 

kzimmerman

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I meant to say FFW, not FFF, eg: future floor wax. Also, I think I might further experiment using litespan for the cloth, and laying up the west system in addition to the other resins listed. Any other suggestions? Taking requests now! I won't do polyester or vinlyester resins though, they are nasty to work with and I don't like them. Also, I'm doing this experiment in the hopes of upping the engine size a bit too. A steady diet of CTI F's and possibly a G, depending how the F's go. Theres other mods in the works, build thread coming soonish. Looking at the G 84 green and G65 White longburn. Possibly the G100 skidmark (that would be awesome, but makes me very nervous!)
 
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blackbrandt

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If you want a good cheap epoxy, go with US Composites. You can get a half gallon for like $40, and they have smaller sizes as well. Don't mix water with your epoxy, it will mess with the cure. Stick with a laminating epoxy.
 

Cabernut

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Those "tie-fighter" fins on the Cosmic Interceptor really do break easy. On mine, the fin snapped upon landing on hard dirt. As a solution, I added balsa-strip fillets and it seems pretty solid now. I wouldn't fly it on more than a small F(F44?).

What are your plans for glassing it? Just the weak parts of the whole thing?
 

kzimmerman

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I thinned the epoxy with alchohol. Works really well, water won't even dissolve it. Yup, steady diet of f's. We'll see what the weight is upon completion.
 

kzimmerman

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I pushed on the fins a little this morning. The surprise was that the polycrylic was stiffer and stronger than the epoxy. I'm gonna do some west systems to compare, also to compare to the 5 minute with alchohol, maybe I should have used a slower setting epoxy to give the alchohol more of a chance to evaporate.
 

kzimmerman

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So I laid up another sample using west systems. It was only marginally stiffer than the polycrylic, but was heavier. So, the polycrylic gets the nod for the interceptor build. Build thread coming soon.
 

cavecentral

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Not familiar with the polycrylic. I've used US composites fast 4:1 with good results if 2oz-10oz cloth making tubes / nosecones. Never heard anything bad about West for the same uses except that it costs more than US composites. BSI 20min finishing epoxy is ok too for smaller applications. I added 2oz cloth to a paper tubes and did some repairs with it. It seems good for what you are doing. A bit pricey for making larger tubes from scratch.

Unless the polycrylic is better, I'd try the BSI since it is a small piece.

I wouldn't thin the epoxies. The lamination ones are what you want. The thicker ones have filler. Thinning them doesn't makes sense since it was thickened vs. starting with an unthickened resin.
 

kzimmerman

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Thinning them is a fairly common way of doing it. It actually doesn't thin the finished product, as most of the thinner evaporates out before the epoxy sets, theoretically. It just makes it easier to get a thinner coat on. The polycrylic is an acrylic based finish used in woodworking a lot, kind of like the polyurethane finishes you see on furniture a lot. The main benefit to using the polycrylic is weight reduction, and it is much thinner than laminating epoxies, so it is easier to get a smoother finish. It also is not sticky, so your tools don't tend to drag the cloth around as much. It is not a strong, but it is plenty strong enough for most midpower or lower applications, I don't think I would try to glass up a HP rocket with it!
 

dford

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Is it too late? Pro Set 125\229.
Issa nice

Please don't thin
 

TopRamen

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I'm about to try some Polycrylic on some glass cloth, but for a home application not a rocket thing. I'm going to test it on a small area first, so I'll grab a set of balsa fins and do those too while I do the housey thing.
I have some Evirotex Lite epoxy that is going to be used on a house project with cloth too, and that will get experimented with, as it is affordable in large quantities. Like the Polycrylic, I get a discount on that at a store I once worked at, so that is why I say it is "Affordable in large quantities".
 

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