by GreenLake » Sat Apr 09, 2016 10:20 pm
Talbot, just use 3M High Strength Marine Filler next time. It is glass reinforced, so no need to wet out anything (unless you really need to apply larger patches - more about those below). It's Polyester (or perhaps PolyVinyl) so there's no big chemical or hardness difference to your gelcoat. I found the sanding behavior reasonable. I've used Marine Tex, but my recollection is that the 3M product was a tad "stiffer" during application.
I usually prefer epoxies for repairs, but this filler is an exception. It's worked really well for me, esp. on CB repairs. It definitely can be used to "build up" an edge, not just to fill an indentation.
For sanding epoxy and epoxy-based products. If you can get to them during the green cure phase, then using a sharp scraper or a blade is your best bet to quickly level drips, sags and similar accidents, so later sanding does not need to remove a lot of material.
If I needed to apply an actual patch, I would laminate it on a level surface on top of a sheet of plastic, and then transfer the final patch like a sticker. If you tape the edges so no air can get in, it won't pull away from the repair (or prop it up with something like a foam pad).
If you use SystemThree GelMagic (their "glue") rather than their laminating epoxy, you get the advantage of a less runny epoxy, but one that is still able to wet out most fabrics. You may be able to do the same with some thickening of West System, but, as you know, I'm partial to the pre-mixed stuff (and it's well-stocked around here).
~ green ~ lake ~ ~