Help needed with fibreglass work

Stingo

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I want to remove an excess head on my boat and would like to plug up the extra holes that the through-hull fittings presently occupy. I have a GRP hull and need some advise on doing the job.

<P ID="edit"><FONT SIZE=-1>Edited by stingo on Mon Nov 5 12:51:04 2001 (server time).</FONT></P>
 
G

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I think the answer is DON'T. Leave the skin fittings in, but blank them off. It's far stronger than trying to plug the GRP. And the Law of Sod says you'll need the skin fitting for something different next season.
 

RobertMartin

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That is not correct. Leaving the skin fittings in does not make it stronger and its totally crazy leaving a hole below the water line... I am doing a full refitt and have moved 3 seacocks so far and will be taking out a least one more.. It is a easy job....
Pull out the boat, take out the fitting, ( you may need to take it out with a hole cutter if its frozen in.) Grind out the edges from the outside, till you get a 12 to 1 bevel. I used thick cardboard lined with greaseproof on the inside to plug the hole and then filled it from the outside with fiberglass cloth and Epoxy. It took about 6 peices of cloth and then 3mm of filler to make a perfect smooth, VERY Strong repair. It really is easy. Then again a shipwright would only charge you about $50 to do it, so its up to you. Do not be put off by others, do what you think is right and you'll have a boat just how you want..

Bobby aka Seawolf..
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Strathglass

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Re: Simplest way

1 Remove all the old skin fitting
2 Make a circular plate of 12mm minimum marine ply about three times the hole diameter with 45 degree taper ( cut it out with a jigsaw )
3 Bolt this plate to the hull using a woven roving gasket well saturated in epoxy resin. ( The hull should be counteresunk on the outside for the bolts)
4 Coat the ply plate and the inner face of the hole with epoxy resin on all exposed faces.
5 Fill the external hole and paint the ply plate inside with epoxy resin / colloidal silica/ microfibres mix.
6 Fair and finish the external surface as necessary.
 

jfkal

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Just a thought. Wouldn't it be better to seal the hole from the inside with one or two layers of epoxied fiber cloth and then start filoling up the hole once the epoxy has cured. Might add extra strength?
 
G

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I have this job to do soon, so thanks for the tips.
I agree with RM that it is not a good idea to leave a sub waterline hole in the boat, so I will remove the fitting.
However I prefer Iain' solution. I do not like the idea of relying totally on the strength of the bond of RM' epoxy plug. I shall follow Iain' bolt and braces solution. In the (unlikely) event of a poor epoxy bond, the hole remains sealed by the bolted plate.
 
G

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Have a look at west systems web site. The do manuals for all kinds of grp work. You'll find them if you do a search for WESSEX RESINS. Sorry I can't remember their full address
 

oldsaltoz

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G’day Stingo.
Blanking a hole is a simple task but do remember the following.
Use only epoxy resin as it provides a better bond. Use all the personal protection gear you can, dust mask and goggles when grinding as a minimum.
The fibreglass matting should be a multi directional type, not rovings.
1 Remove the old fitting and clean the area of any grease, sealant or other material that may contaminate the surface.
2 With an angle grinder start on the inside (I hope you have enough space for this) and grind off any and all paint or coatings around the hole, grind an area about 3 or 4 inches around the hole till clean, now grind a bevel around the hole, you need to take at least a third of the thickness off the edge of the hole, now grind back away from the hole to feather the angle, you should finish up with a slight hollow or dish.
3 Remove any dust with a clean rag and wash the area with a solvent.
4 Cut your fibreglass to shape, you will need one to cover the area you have ground out, and at least two more, make each one about an inch smaller than the last, this will give you a smoother finish and avoid hard spots.
5 Mix a small amount of epoxy resin to start with and apply it the area exposed by grinding, now place the largest circle of fibreglass over the wetted area, apply more resin and using a very small diameter roller roll it till the fibre glass is wet through (Don’t over roll it, about 7 passes with the roller should do it). Now place the next largest circle over the first, apply more epoxy rein and roll as above, then do the same with the smallest circle of fibreglass, at this stage you should try to roll out any excess resin, too much resin will weaken the repair. Do not be tempted to lay up more layers as thick lay-ups generate a lot of heat, this will cause the resin to boil and it will have to be removed and done all over again.
6 Let this go off for about 24 hours, you can then grind off any sharp edges and paint on two coats of resin to protect it, you can give this a light sand and paint job later.
7 On the outside go through the same steps as above but remember you want this to finish smooth, so when placing the fibreglass matting, bend a timber batten over the repair and make sure the fibreglass is about a sixteenth of an inch below the batten when finished. After curing best left for 24 hours, wash the area with plain old water and a scouring pad to remove any residue left by the curing action, give the area a light grind to remove any high spots and to provide a suitable surface for resin, now apply three coats of epoxy resin, if you can not get this on wet on wet, then a wash and light sanding will be required between coats. Then apply at least 2 coats of paint designed to prevent water entering the hull (International Interprotect is one). Now you can apply some filler, micro balloons are easy to apply and very easy to sand, I use an old straight back saw to apply balloons, it bends to the shape of the hull and leaves a good finish, a quick splash of paint and some antifoul and your back in the water.
Avaniceday Old Salt Oz...
 
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