Glassing in through hull hole

P

Peter

Well-Known Member
Joined
31 May 2001
Messages
345
Location
cumbria
Visit site
Got a couple of redundant through hull fittings, currently not causing any problems, both capped and no issues. I was thinking of removing the fittings and glassing over the holes to tidy things up and remove a potential leak. First question is how to do as I haven't done anything like this before, not bothered about the glass fibre work but working on holes in hull and the potential for a cock-up so slightly nervous on this one. Looking to use a standard polyester resin and GF mat and epoxy finish the outside, hull is a "standard" GRP laid hull. Or do I leave well alone as not causing me any problems now.

Peter
 
Peter said:
Got a couple of redundant through hull fittings, currently not causing any problems, both capped and no issues. I was thinking of removing the fittings and glassing over the holes to tidy things up and remove a potential leak. First question is how to do as I haven't done anything like this before, not bothered about the glass fibre work but working on holes in hull and the potential for a cock-up so slightly nervous on this one. Looking to use a standard polyester resin and GF mat and epoxy finish the outside, hull is a "standard" GRP laid hull. Or do I leave well alone as not causing me any problems now.

Peter
Click to expand...

I would also leave it, or use epoxy if you really want to go ahead. You must ensure that if there is any core to the hull, you scrape some of it out to make a void, and also fill that void- ie, you dont just plug the hole. This ensures that there is almost no way that water can penetrate into the core.
But I would just leave them.
 
Peter said:
Got a couple of redundant through hull fittings, currently not causing any problems, both capped and no issues. I was thinking of removing the fittings and glassing over the holes to tidy things up and remove a potential leak. First question is how to do as I haven't done anything like this before, not bothered about the glass fibre work but working on holes in hull and the potential for a cock-up so slightly nervous on this one. Looking to use a standard polyester resin and GF mat and epoxy finish the outside, hull is a "standard" GRP laid hull. Or do I leave well alone as not causing me any problems now.

Peter
Click to expand...

If the fittings are in good condition I'd leave them. I should imagine these through hulls have seacocks fitted??? Just check that they are not suffering from dezincification corrosion.

If you do decide to remove, remember that filling the hole entails quite a bit of work from both sides to an approx diameter of 8". If you are not happy about this get someone to do it who's fully conversant with this sort of repair.
 
saxonpirate said:
If you do decide to remove, remember that filling the hole entails quite a bit of work from both sides to an approx diameter of 8". If you are not happy about this get someone to do it who's fully conversant with this sort of repair.
Click to expand...

Without wishing to push the OP in any direction, I'm curious to know what's entailed in this as well ? Are there any websites around detailing the procedure for glassing them over ?

Thanks,

Boo2
 
Filling a through hull hole

It is relatively easy. Assuming you have a solid f/g hull with no core.
You take to it with a grinder and you chamfer off a circle around the hole to a depth a 1/3 total thickness and out to about 1 radius of the hole. Now do the same on the inside. Clean with acetone.
Cut circles of f/g to fit nearly the outside of the chamfer then graduating in with several/many bits the same size as the hole.
Get a plastic bag full of sand and either press it against the outside with props or lay it on the inside of the hull.
Splash lots of resin over the hole and ground area. Lay in the circles the same size as the hole then slightly bigger then a bit bigger etc until the hole is filled and level with outside hull. Let it go hard but don't leave it too long. You should be able to remove the bag of sand and do the same from the other side. The plastic bag should release from the resin easily. Make sure the next inner patch is well attached to the last inner (hardened) patch with no air bubbles. You need enough layers of f/g to match the original hull thickness. ie quite a lot.
By having the polyester resin fairly green you get a chemical bond of the 2 patches. The bond to the hull will only be mechanical. However when all is hard you have a patch that can not be removed even if there is no bonding to the old hull because it is bonded one patch to the other and larger on both sides.
When it is all hard grind the outside down to fair and coat with epoxy or whatever. yes you can use epoxy for the whole patch but not necessary.
I filled my log hole many years ago and can't even find the repair now. Certainly much more reliable than a brass sea cock. easy peasy olewill
 
William_H said:
It is relatively easy. Assuming you have a solid f/g hull with no core.
You take to it with a grinder and you chamfer off a circle around the hole to a depth a 1/3 total thickness and out to about 1 radius of the hole. Now do the same on the inside. Clean with acetone.
Cut circles of f/g to fit nearly the outside of the chamfer then graduating in with several/many bits the same size as the hole.
Get a plastic bag full of sand and either press it against the outside with props or lay it on the inside of the hull.
Splash lots of resin over the hole and ground area. Lay in the circles the same size as the hole then slightly bigger then a bit bigger etc until the hole is filled and level with outside hull. Let it go hard but don't leave it too long. You should be able to remove the bag of sand and do the same from the other side. The plastic bag should release from the resin easily. Make sure the next inner patch is well attached to the last inner (hardened) patch with no air bubbles. You need enough layers of f/g to match the original hull thickness. ie quite a lot.
By having the polyester resin fairly green you get a chemical bond of the 2 patches. The bond to the hull will only be mechanical. However when all is hard you have a patch that can not be removed even if there is no bonding to the old hull because it is bonded one patch to the other and larger on both sides.
When it is all hard grind the outside down to fair and coat with epoxy or whatever. yes you can use epoxy for the whole patch but not necessary.
I filled my log hole many years ago and can't even find the repair now. Certainly much more reliable than a brass sea cock. easy peasy olewill
Click to expand...

I would never ever suggest someone tackles a job under the water-line for their first ever attempt at glassing and their first ever attempt at glassing alone.
 
William_H said:
It is relatively easy. ........ easy peasy olewill
Click to expand...
I will have a a hole fill in the near future. Can you come and demonstrate what you mean. :D
We could take some pictures of you doing it to post back on here.

PS bring some warm clothes ... its pretty chilly around these parts from now on until next spring.
 
The OP states,
"First question is how to do as I haven't done anything like this before, not bothered about the glass fibre work but working on holes in hull and the potential for a cock-up so"

This would seem to indicate that fibre glassing has been done by the poster, and is looking for guidance on the methodology to be used for hole filling.

Perhaps the OP would like to clarify this.
 
oldsaltoz said:
The OP states,
"First question is how to do as I haven't done anything like this before, not bothered about the glass fibre work but working on holes in hull and the potential for a cock-up so"

This would seem to indicate that fibre glassing has been done by the poster, and is looking for guidance on the methodology to be used for hole filling.

Perhaps the OP would like to clarify this.
Click to expand...

Okay I see that after reading it again, it is not clear if he has or not.
 
for the 3 under water through hull holes i had in my boat a well respected grp company did this job for £50, no messing about for that kind of money.

i disagree with those posters of leaving the un-used through hull fittings. why want to take the risk?

my boat doesn't have any under water through hull fittings left what that gives me peace of mind.
 
If the fittings are sound, and capped internally with screw on blanking caps, and not just left with seacocks on them, I would leave them alone. If they have seacocks I would remove them and fit caps. My own boat has a 38mm through hull that was a heads outlet before a holding tank installation necessitated moving the outlet. It is sound and capped, and I have no plans to remove it.
 
bitman said:
my boat doesn't have any under water through hull fittings left what that gives me peace of mind.
Click to expand...

Go on then, how does that work? (Or do you sail a dinghy? ;) ) I always rather liked the idea of a keel-cooler for the engine on a steel boat, but what about head and galley intakes and drains?

Pete
 
Demo in UK

VicS said:
I will have a a hole fill in the near future. Can you come and demonstrate what you mean. :D
We could take some pictures of you doing it to post back on here.

PS bring some warm clothes ... its pretty chilly around these parts from now on until next spring.
Click to expand...

Sorry Vic it is a religious thing. I will never visit UK in any time but UK summer. I might even manage it next UK summer. I have fiddled with f/g for a long time even done a few courses in f/g work. I never thought it difficult. The trick is to try a few simple projects first. You get the feel for hardening times cleanliness before whacking on resin and general rolling air bubbles out.
I really doubt you could compromise the integrity of the ship by DIY hole filling.
Meanwhile must rush going down to the sea for a swim. 33 degrees max today.Nice. olewill
 
As William_h posted the idea is to make a 'yoyo' type patch. The inner and outer patches laid up whilst the materials are green enough to bond together. I filled 3 through hull fittings that are now undetectable from outside and can only be seen from inside because I know where to look.
 
Last time I used resin as a filler I thought it was going to catch fire it became so hot. It would probably expand and crack the fittings too.

Good idea, I thought so too, learnt from that one.
 
Filling in a an old thru' hull fitting is not rocket science, the aim is to end up with a capstan shape that will push or pull through.

I always start glassing on the outside first and finish just below the the surrounding level of the hull, then stick a bit of stiff plastic or better an off cut of peel ply over the area.

Than move inside and repeat the process. After curing, remove any high spots with a grinder fitted with a 40 grit disk and clean the area with Acetone then fill with closed cell micro balloons.

The outer repair should have 4 coats of epoxy resin applied to reduce moisture ingress.
 
You must log in or register to reply here.

Share this page

Top