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Fiberglassing wings and planes

Discussion in 'General Aircraft Chat' started by cncmachineguy, Apr 27, 2010.

  1. cncmachineguy

    cncmachineguy Member

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    Odenton MD
    I am starting this post in hopes of creating a good knowledge base on this subject.

    Let me start off with where I am at. Alex and I spent some time messing with glassing foam over the weekend. We were using 1.5oz glass mat with different "resins"

    In case you don't know, I was told by the fiber supplier that mat is weighted by the square yard and cloth is by the square foot. Now incase I have the two terms backwards, for me mat is the pretty grid pattern stuff, while cloth is the random direction stiffer stuff.

    We tried several "resins". they were Polycrylic (some waterbased stuff in the polyurathane isle), regular polyurathane, and west systems epoxy.

    We tested these on both dow FFF and the green lowes foam. here are what we found:

    The regular poly didn't work out so well, takes forever to dry and doesn't feel real strong.
    The polycrylic worked better, dried a little faster and was a little stiffer.

    Both of the above products allowed us to pull the 2 layers of glass back apart without too much effort.

    The west systems epoxy works excellent, still takes too long to dry for my liking, but much stronger when done. Prolly heavier too :(

    None of the tests ate into the foam at all.
    I may have gone into it with the wrong expectations, all my glass experience is with 2 layers of 1.5oz cloth and regular polyester resin. Needless to say, these layups should be 9 times stronger then what we were doing.

    I didn't try polyester resin as i read on Eriks site it will eat the foam, nor did I try the Zap finishing resin as I don't have any.

    I am hoping to get some discussion for my benefit and the benefit of all. Lets take the mystery out of glassing. :)
  2. rcav8r

    rcav8r Moderator Staff Member

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    I also did some "testing" a few years ago. I built an 8' C123 out of foam. I wasn't too thrilled about glassing using zpoxy ( or any of the sloppy 2-part systems) due mainly to how sloppy they are to work with. I'm like Charlie Brown with a pen when it comes to epoxy.
    I ran a test with 2 coats of zpoxy, and 3 coats of polycrylic using .5 ounce cloth and some scrap foam as the base as the plane was made out of it.
    I did 1 square foot of each. Weight advantage was slightly to the poly. I forget the exact numbers, but it was close.
    I then gave each the thumb nail test after it cured for a day. I was surprised to find that it was actually harder to push my thumb nail in to the poly than the zpoxy. Not by much, but still a noticeable difference. Zpoxy seemed to be a little more pliable.
    I gave each the break test. Neither one really stood out, but definitely harder to break than the untreated foam. I guess someone with more ambition could set up a test with weights to get some numbers on it.
    With all that said, I used 3 coats of poly over .5 ounce cloth. The weave was filled rather nicely. Not baby butt smooth, but close enough for me. Could very easily fill with weave with some corn starch mixed into a coat of poly. After all the real one was really rough looking when you were up close. Strength has been OK. It still has a bit of hangar rash, but I'm sure it would have gotten that with the zpoxy also as after all it is a huge foam airplane, and foam airplanes have a habit of getting bumped into everything possible.

    All of this was with only once coat. Actually last night I covered the headrest for my Pronto ( first complete wood kit cut on the phlat printer ;), well except for the headrest ) with 2 layers of .5 once cloth and poly. I'll see how it looks when I get home tonight.

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