Fixing a Hole in the hull

[MarinUS]

Dear fellow sailors;
My OMC Saildrive
needs to be removed from my S2- 8.0 B sailboat because it’s old (1983 model and I just don’t trust a gas engine below deck.
The plan is to stick a 9.9 four stroke outboard on the back.
My question is; how many layers of fiberglass I need seal the hole where the saildrive lower unit protrudes through the hull. The plan is to use epoxy.
Next question:
Should I seal it from the inside, or from the outside?
Thank you.
Marck.

[Chotu]

First, how big is the hole?

Second, you need to make a scarph joint all-around the hole. Inside and outside.

The thickness of this patch should be the thickness of the hull so the repair doesn't look horrible.

Take a grinder disc and "dishpan" out a little taper all around the hole, inside and out. Keep on applying layer after layer of glass, inside and out.

When you are done, the middle of the hole will be slightly thicker than the hull. The edges will look very thick and will protrude from the hull. Grind these flush as well as the middle of the repair flush and you have yourself a hull as good as the day it was built.

[MarinUS]

Originally Posted by Chotu

First, how big is the hole?

Second, you need to make a scarph joint all-around the hole. Inside and outside.

The thickness of this patch should be the thickness of the hull so the repair doesn't look horrible.

Take a grinder disc and "dishpan" out a little taper all around the hole, inside and out. Keep on applying layer after layer of glass, inside and out.

When you are done, the middle of the hole will be slightly thicker than the hull. The edges will look very thick and will protrude from the hull. Grind these flush as well as the middle of the repair flush and you have yourself a hull as good as the day it was built.

The hole is approximately 5” x 9” , I images the thickness of the hull is 1/4” or so.
I’m might be tempted to use polyester resin and not epoxy.

[44'cruisingcat]

If you don't want to use epoxy, use vinylester, not poly. Better secondary bonding, (but not as good as epoxy) and more waterproof.

Little difference in the price.

[nortonscove]

Originally Posted by MarinUS

The hole is approximately 5” x 9” , I images the thickness of the hull is 1/4” or so.
I’m might be tempted to use polyester resin and not epoxy.

Use polyester and just sand and wash the ground out area with acetone prior to applying the first layers. Go with three layers at a time with minimal time to allow for hardening. If you allow a layer to fully kick to where it looks glassy just scratch it up some and acetone wash it again.

You could also apply a thin sheet of fibreglass over the hole from inside and work out to the bevelled edges of the hole outside. This would allow for several additional layers unseen on the inside but with a little more assurance and surface adhesion.

[Compass790]

Don Caseys book the sailboat maintenance manual would be good for you. Shows how to do that job in detail.
i personally would replace the gas engine with a diesel but outboard ok if you are in sheltered waters

[MartinAdelaide]

Boatworks Today on Youtube has some very god videos is such repairs.

[Dymaxion]

If external curvature allows, a piece of formica laminate could be secured to the hull and you could work up the patch from inside. How thick is the hull where you are patching? May take multiple stages to get thick enough layup without overheating when curing.