Fiberglassing- a discussion

[Tom M.]

 Andy, those grooved rollers are used to force the heavier cloths and mats used in boatbuilding etc. into corners and such after the resin is applied, so not suitable for our purposes. As for cleaning the foam rollers, no, I don't bother.
Jack, epoxy resin will be much stronger than WBPU, slightly heavier, and considerably harder to sand. It's the 2nd coat of epoxy (the one to fill the weave) that is really hard to sand so you could compromise and use WBPU (thickened with talcum powder or micro balloons) here instead.
  If a straight balsa structure, a great way to fill the weave is with a thinned coat of auto body putty/glazing compound. Thin to a heavy creme consistency with laquer thinner or acetone and just brush on a heavy coat. Drys really fast and sands easily- downsides are the very strong smell and you'll have red dust everywhere, so best done outside in warmer weather (after Andy has put away his snow pants). Don't try this with an underlying foam structure as the solvents will find their way through any areas not well-coated with epoxy and eat the airplane. The jet (now deceased) pictured had balsa sheeted wings that I glassed and then used this method on- works well and is very lightweight as almost all the putty mixture is sanded off.
  Tom