Working with fillers

[Jorgeahl]

I'm restoring an old Sunfish. I'm doing this as a learn-feel-good-project. I keep having problems with the red putty filler. I'm using 320 grit wet sanding, 20 to 25 min after aplication on screw holes and gelcoat spidercracks. Instruction says its ready to sand in 15 to 20 min. The problem is that in some of the holes (1 out of 15), the putty comes of the middle. Is the grit too coarse? Should I repeat application until I get good results? When should I stop sanding? I've search quite a while for filler aplications in the net but they never seem to mention the sandpaper grit

Hey! Apreciate your help!

[captsvm]

Jorge,

If you are using a polyester catalyzed filler, (such as Bondo), you may be mixing too small amount of the cream hardner and need to wait for longer period of time for the catalyzation to cure, or add more hardener to the resin.

If your using a 1 part putty, (such as 3M acrylic filler), you can't fill larger voids with just one application. Fill it gradually, no more than a 1/16" deep per application, allowing 15 - 20 minutes between applications.

Regards,

Patrick