Removing an unused through hull.

[WindyWindyWindy]

I have a defunct through hull that currently has an ageing sea cock and a blank on that.

Metal sea cocks don't last forever and nor do the through-hulls they are attached to.

Do I have to take it all out, grind back miles of fibreglass and fill it with fibreglass or does someone do a solid grp through hull blank that I could just bolt in like a normal skin fitting?

 

[Porthandbuoy]

How thick is the hull? The recommended 'grind back' ratio is 12:1. That's 12x the hull thickness NOT the size of the hole left after removing the skin fitting.

 

[William_H]

It is not hard to fill a small hole in GRP boat. Remove the fitting chamfer the edges of the hole both inside and outside. 12 times the thickness of GRP might be a bit much IMHO. Fill a plastic bag with sand or similar and press against the outside of the hull with a prop. Cut out several glass circles that will fit in the hole then more progressively larger to fit into the chamfered area and over the original skin. Saturate with resin. Epoxy is preferred but pollyester is probably ok. Need warmth if it is cold. When resin has partially hardened do the same lay up from the outside. The trick here is that the resin will mingle with the first lot while still chemically bonding so that you get a really good bond of the first plug to the outer plug. Thus when resin hardens you have a shape such that it can not fall out even if attachment to original GRP fails. When it is all really hard you can grind off to fair in with hull. Inside just leave as is. (you can of course start on outside then do inside, the plastic bag of sand gives you something to lay up glass against, plastic easily releasing) ol'will

 

[WindyWindyWindy]

Yeah, it's still a lot of work compared to bolting in a fibreglass blanking plug with a bit of sealant. I can do that in about 20 minutes with a few hours for it to cure.

With your more involved approach would you bother with doing up the gel coat or just sand the epoxy flat before antifouling?

Good tip with the sand bag, I was wondering how I'd do that..

 

[neil_s]

I used 3 mm GRP sheet. Cut a blanking plate for the outside and one for the inside and fill the aperture with adhesive sealant. I used the original seacock mounting bolts. I regret I can't remember where I got the GRP sheet - It's been many years and surveys since I kicked the sea loo out!