Fairing compound lesson

Builder's Forum
1

OK, so used the MAS microballoons for the first time to fair out a goof on my part on the SUP.  I didn't get the sides and tailblock quite right, creating some hollows near the stern. So, I used some fillet mix to reinforce the corner on the outside, filling some of the hollow but wanted to fair it up into a nice curve with the rest of the sides.

The microballoons w/ some wood dust added made a very smooth compound.  Much nicer to work than the fillet mix.  However, I didn't count on the sag I got in the deeper part.  Boo.  I caught it at the gel stage and scraped the droopy part flat with the squeegee but will have to put in another layer.  I'm assuming I need to wait for it to set to what I call "al dente" (can just dent it with fingernail) before trying to refair.  I was hoping to do a hot coat to avoid the extra time of cure, sand, clean.  Has anybody out there "hot coated" with microballoons?  I'll make it a bit stiffer next time, anyway.

2

i have hot coated with micro-balloons for almost the exact reason you cited.  no problem overcoating/putting another layer on when 'al dente' .   its actually stronger than waiting if you have a non-blushing epoxy.

fwiw, i often use clear packing tape over smaller repairs that are on the vertical to prevent sagging or turning the piece to an orientation where gravity will be less likely to cause sagging.

h  

3

   Yep, second coat went on fine.  I was surprised how much microballoon filler will go in a small amount of resin before becoming nonsagging.  It was also thinner, so sag was not an issue.  Now sanding prior to the glassing step.  I did stain the hull and was going to try to finish it w/ varnish, but this and other goofs has me headed toward painting.  I know painting better anyway!