It looks as if you could sand out each blister and then feather a new patch over each one. If done right, the patches would be invisible, even if varnished instead of painted. But that would be a lot of work. It might be easier to strip the glass with a heat gun and just re-glass the whole thing.

Good luck,

Laszlo

   Thanks Laszlo, appreciate your guidance. Will update as I try to patch blisters and I'm still determined to take a class next year and learn the basics!

I just glassed the interior of my Skerry, and have a number of blisters and wrinkles. I decided to use a heat gun, remove the glass around each problem, and add a patch. But I don't know what "feathering" is. Can someone explain?

Feathering in this case is the process of thinning the edges so that the old and new glass overlap without a visible bump or ridge.

Once the blister is removed, there is a very noticeable edge where the glass stops and the bare wood starts. The first step in the process is to sand away the edge so that the glass tapers smoothly, like a feather, from its full thickness down to nothing. This should be a very shallow taper. If you can manage it, a 2-inch long taper would be ideal. That is, the distance from bare wood to full glass thickness should be about 2 inches.

Once the patch is applied it needs a tapered edge, too. That taper goes from the outside edge of the patch toward the center, the exact opposite of the first taper, just like a scarf joint for wood. Theoretically, if it's done just right, the glass (old + new) will be a constant thickness with no ridge. Reality is always different, of course. That's taken care of during the filling of the weave and fairing.

A couple of hints to make it easier are:

1. Before you apply the patch, outline the area with packing tape. This will give the patch a nice clean edge.

2. Wet out the patch on a piece of polyethylene before applying it to the boat. That way it's guaranteed to be perfectly saturated and as simple to apply as a band-aid.

When you're sanding the tapers, be very careful. This is the rare case where you are deliberately sanding into the glass. Make sure that the epoxy is fully cured. It doesn't hurt to wait a couple of days between application and sanding. Use new, sharp high quality sandpaper and change it frequently. You want it to cleanly cut, not mash, the glass fibers so that the patch won't be visible. Clean the dust away frequently, including wipes with denatured alcohol, so that it doesn't build up and get worked into the glass. And remember that paint will cover a multitude of sins and still win awards.

Good luck,

Laszlo

I don't understand when the patch is sanded. It is applied wet, then it cures, and then it is sanded?