Listen to Terry. Filled resin has no place in this repair.

Terry Spragg wrote:
Chris wrote:

Howdy all,

I've got some visible cracks at the bottom of my hull on my 16ft
runabout. This past summer when using the boat I was getting a bit of
water in it after having it sit for a while in the water (the bilge
pump easily took care of it). I'm now thinking that these cracks may
be the cause and water slowly seeps into the boat.

Now, my question about how I should attempt to fix this giving the
following considerations 1. It's an old boat. 2. I use it a 4-5
weekends a year. 3. I don't want to spend a lot of money as its not
worth it.

My ideas have been the following:

1. The ugly job
- rough up the area around the crack and put a few fiberglass
patches on it (poly resin & cloth)
- paint over it

2. Cleaner job
- grind out the crack and a bit of the area around it (make a V)
- fill with fiberglass resin, or epoxy resin using a filler
- not sure if a cloth patch on top of this would be necessary.
- paint over it

What do you guys think given the considerations?


Close, no cigar. Grind the Vee on the outside, feathering out 5 times
the thickness of the glass, leave it rough. Wash it with acetone.
Laminate several layers of glass, starting with a narrow strip, covering
with wider strips until you fill up the Vee. Smooth and paint /
gelcoat. Wet the glass, but try to use more glass and less resin.
Squeeze the bubbles out (don't mix the goo too vigorously, just
thorougly) using a serrated roller made from 2 sizes of washers loose on
bent threaded rod with locked nuts. Clean tools with acetone.

You should also do the same on the inside, or could just lay a couple of
wider strips on the roughened inside, where you can, washing the cleaned
inside with acetone before laminating.

You will find polyester strong enough, if you get enough thickness and
surface area covered and well bonded. Epoxy would be stronger, but is
overkill, and will make the question of refinishing the exterior gelcoat
into a can of worms, because poly gelcoat doesn't stick to epoxy, so you
would need to redo the entire hull with epoxy paint to achieve a Bristol
appearance.

Polyester Gel coat is just catalyzed polyester resin with pigment and a
little thickener, like silica gel, or, I am sure others have their
favorites. You can brush it on with several / many thin freshly mixed
coats applied while the hull is still tacky and buff it flat and smooth.
It is self levelling, especially if you can turn the boat so you are
painting on the level. If you get a good colour match (on the bottom?
who cares?) you won't be ashamed of it. Don't use bondo, it just isn't
as good as it could be, with automotive fillers, etc.

Are you sure the cracks go right through? If so, gring the crack a
little beyond the torn glass. You may only want to redo the gelcoat, if
that is as deep as they go.

Water collects in boats, even condensation can get inches deep, and rain
could be getting in, too.

Terry K