Correct way to fill in a thru hull hole

[FishStretcher]

I have a thru-hull hole that is just capped off right now, I want to pull the fitting and fix it. It is in a place that will see some forces in a head sea and bang around getting on a trailer.

It the right approach to cut a plug and bond t in, or feather it out and put a bunch of layer of glass on top? Or something else?

[aldo]

I would go for the feathering- check out this site, and the fiberglass repair manual.
I believe it describes the process pretty well.
http://www.westsystem.com/ss/use-guides/

[FishStretcher]

That doesn't seem practical for a thru-hull in a laminate that is 3/4-1" thick. That would be a 18"-24" diameter patch for a thru hull at 12:1 aspect ratio!

[cdavisdb]

The laminate where your head through hulls are is about 1/4 inch

[FishStretcher]

This one looks to be 14" above the keel as you travel along the surface, maybe 10" vertically from the "keel"under the port bunk. I don't know the anatomy of the boat well yet, but I think the head discharge was above it near the waterline- I can see a patch for a larger hole a bit forward and up higher. I hope it is more than 1/4" thick there. Let me see if I can find a picture. If it is a 1/4" then that's a lot easier to deal with though.

edit-

The first photo here-
http://www.classicseacraft.com/commu...3&postcount=37
You can see the old head discharge (?) thru hull, it has been filled since this picture was taken. Plus a little bronze one lower and further aft. That is the one that I hope to fix.

Bottom line is that I need to look at it harder and see what I am up against. Other than a rotting thru hull with a pipe plug in the hose that is attached to it!

[FishStretcher]

I don't know for sure yet how thick it is there, as I haven't pulled the thru hull. The hull changes sound just below that point when you rap on it, so it does seem to get thinner about there and on up the hull. I really was expecting more glass there.

Of course you have had yours apart, I don't know why I thought differently, other than we might be talking about a different spot on the hull. I hope there is more than 1/4" of glass there.

[cdavisdb]

Yes, I did have those thru hulls out, same spot, and you are right, the plugged one is for the head discharge, remaining one is head intake. If I remember right, tabbing from the stringer or keel runs just to or just past the thruhulls. Depending on how your tabbing was done, the hull might be thicker or thinner, but not much.

Seacrafts are built very strong, but light, because Potter and Moesley put glass where it is needed and not where its not. Moesley was and aircraft engineer and understood that stuff. Hull only weighs 3000 lb, That's light for a 25 footer. Don't worry, hull thickness is fine.

The 25 Bertram is built similar, with thin hull sections, but stringers that would do justice to a 40 ft Hatteras. I was astonished at how thin it was when I cut a hole in mine. Still plenty strong, whatever.

[Blue_Heron]

What Connor said x 2. Hull is probably 1/4" - 3/8" where the though-hulls for the head are. 1/2" max.

[FishStretcher]

Well, that makes the grinding easier. Looks like I will have to try some vacuum bagging this spring. I am thinking grind it and wet layup patch half thickness from the inside with a ~1/16" polyethylene sheet backer, then vacuum bag inside and out. Once that cures, grind the outside, wet layup and vacuum bag the outside. That way I can keep the hull shape with the polyethylene backer.

[Normagain]

I'd definitely go with epoxy resin in that application. It will be a much stronger bond and repair. My first boat was a 17' Whaler where someone patched a 2' X 4' section on the bottom of the hull where they had run aground. I didn't know this until one day the entire patch came off while coming in from a day's fishing. It wasn't pretty looking but the foamed hull saved me. I'm sure you could do it right, but no structural polyester repairs on the hull bottom for me.