The following might be of interest to new builders. It comes from the
canard newsgroup, which is where Ivan, Andy Draper a few others, and myself
came from a long time ago. Nice to go home occasionally {?:-)
>Hi Mark,
>
>I was just kidding about the bubbles in the epoxy, as I have some bubbles
>too. However, bubbles can be minimized by doing big layups on hot days.
>The warm epoxy sheds the bubbles faster.
>
>Some techniques I have used are:
>
>1. Stir the epoxy slowly. Fast stirring will induce air. It takes at least
>60-90 seconds of stirring for the epoxy to be mixed to my satisfaction,
>and that is with warm epoxy (90 degrees F). Takes longer with 70 degree
>epoxy. EZ Poxy is not real thin, so patience is a virtue. Reverse
direction of the
>stir occasionally, and scrape the sides and bottom often.
>2. Use cups that are a bit on the tall side, or tip the cup slightly
>when mixing. Shallow amounts on the bottom of a cup love to grab air when
>mixing.
>3. For smaller amounts, use a smaller mixing stick, like a popsicle
>stick instead of a tongue depresser. This may require you to take up eating
>popsicles.
>4. West system has a stirrer that goes on a hand drill that induces
>almost no air. It is submerged at all times and will not tear up your cups. A
>battery powered drill works better as it is not quite so fast. Works great
for
>larger batches. However, larger batches are not usually a problem with a
tongue
>depresser either, so, its a wash.
>5. Set the cup down for a minute or two before spreading. Loses some
>bubbles.
>6. Squeegying introduces less air (actually removes air) than stippling.
>Over zealous stippling actually induces air to the layup. Good stippling is
>an art. Stipple slowly and lightly with the broad side of the brush. Also,
>West bubbas make a roller that looks like a roll of quarters for 10 bucks.
>Works great for after the layup is squeegied to your satifaction. Roll slowly
>and lightly to remove any remaining bubbles. I think they call it the
>"Bubble Buster". Works good. Get the small (1/2-3/4 inch diameter), and
use it
>slowly with light pressure. Otherwise it "dents" the glass.
>7. I don't like to layup glass at less than 80 degrees F ambient temp.
>It makes a heavy layup and inhibits bubble extraction.
>8. Vacuum bagging is the best bubble remover. I think I read here that
>submitting your mixed epoxy to a partial vacuum before applying helps
>too. But I do not have the perseverence for that. That's just me. I'm just a
>regular guy that likes to build wings. The vacuum thing makes a lot of
>sense.
>9. Try yelling at your epoxy to scare the bubbles out of it.
>10. Get over it. I have never been able to get ALL of the bubbles out
>that I would like. I have a hunch that it is not necessary to get ALL of the
>really tiny bubbles out, just as many as you can see. Gotta have some
pinholes
>to complain about later during the fill and sand phase. Rechecking your
>work after an hour or two is a good idea. BID glass really likes air. It is
>more like a sponge and springs back up to inhale air after you leave the
>room. That's when I go back to the garage and try to scare the bubbles
out by
>yelling at them. Some light squeegying, rolling, or stippling helps too
>to press the glass back down. UNI lies down nice, if you layup and squeegy
>per plans, along the fiber strands, not against the fiber strands. The wings
>are mostly UNI glass and bubbles are not too much of a problem.
>
>I have found that the hardest thing about building a composite airplane
>is avoiding the spouse after a hard days sanding and getting dust all over
>her car, floor, kitchen, bathroom, bedroom, sofa, pantry, utility room, and
>refrigerator, among other things. That micro gets into everything.
>Remember to duck if things get thrown at you.
>
>Its not just a project, its an adventure. Wings are beautiful things.
>
>Steve
>The Garage Boy in Virginia.
Talking of wings I tried on a new pair today. Bryan Allsop's new 912S XS.
Lovely.
Graham
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