fibreglass repairs

[ghostlymoron]

I've just got a new boat which needs a couple of minor fiberglass repairs. On the corner of the main hatch is one where it has been dropped and split. I've done repairs before - strong but not glamorous - and i want to do a proper job this time. Where can i find information on this and when do you use filler and micro balloons?

 

[Lakesailor]

Have a look at the excellent East Coast Fibreglass Supplies website http://www.ecfibreglasssupplies.co.uk/t-vid_Fibreglassrepairwithwestsystemepoxy.aspx

The tab at the top "Videos" has more and the articles are helpful.

 

[coopec]

ghostly

If I want to learn to weld, fix a leaking tap or do a fiberglass repair I always go to YouTube.

http://www.youtube.com/results?search_query=fiberglass+repairs&sm=12

 

[VicS]

Wessex resins have a lot of useful info... just about everything you need to know ... at least if you are using epoxy resins

There is an old GRP repair manual published by Tyler Boats on http://bluemoment.com/downloads.html

 

[TQA]

West System has a whole lot of 'HOW TO' pages see http://www.westsystem.com/ss/use-guides/

Remember you can always grind it off and have another go!

 

[Avocet]

The main thing to remember with bashed fibreglass is that the damage will go much further than you can see. You'll therefore need to lay up over the back of it (much bigger area than is covered by the visible damage) and then when solid, you can grind back the "pretty" face and re-gel (or fill and paint) as necessary.

 

[ghostlymoron]

Thanks for the links guys. As with most guides, they show you how to do very straightforward repairs in an easily accessible location and my repairs are in tricky spots but I should be able to adapt the techniques and, as TQA says, I can always grind it out and have another go if it doesn't work at the first attempt.
If I clean the brushes in acetone, will it be possible to do subsequent layups with the same brush?
If I'm building up a repair from the bottom, is it possible to leave it slightly indented and paint on some gel coat on the top (visible) side?

 

[Avocet]

Yes, both are possible. I've got "dabbing" brushes that have been in acetone for several years. They're in a sealed container and I just top up the acetone every now and then when it gets low. The wooden brushes re best for that. It's worth bashing a screwdriver into the metal band in a few places so the acetone drains out quicker when you want to use them. Also worth getting one and cutting the bristles down to about half length for extra "poking" power when dabbing into tight corners!

For really tight corners, it's worth getting a pot of short chopped strands. They're just little short pieces of glass about 6mm long. Mix them into the resin to form a paste rather than trying to persuade the chopped strand glass mat to go round tight corners (both internal and external). Also worth having a bit of glass "tissue" to hand. You can sometimes put a layer of tissue over some unruly fibres round external corners when they keep popping up.

A roller or two are essential (and they can live in the acetone bucket as well). It's hard to get too much mat into the mix, and rollers are an excellent way of consolidating it and squashing the air and excess resin out.

Remember that if you're putting gelcoat on from the outside, it will need to have a tiny bit of "wax in styrene" added or it will stay tacky forever!

 

[Iain C]

Couple of tips...

Filler and microballoons will only "fill", you do need a proper glass layup for strength. If you are going round compound curves or into corners use a twill weave, not plain weave cloth. It's amazing what it will go round and not pop up.

Avoid microballoons. They are brown, and when you "hit" them sanding, you'll have to start all over again. Glass bubbles tend to be white. Don't add any colloidal silica to sandable areas as it's very tough to sand.

When you first mix "bog" you will be amazed just how thick it needs to be to not sag. Do an "xmas cake icing" test. If peaks start to droop at all, bung some more filler in. It's almost impossible to overdo it unless you go really silly...if you are using "tongue depressors" to mix, expect to bend/break a few each mix.

I'd disagree with Avocet storing brushes in acetone. Acetone is the solvent you use to remove epoxy and it's remarkably powerful. Play it safe and buy a box of wetting out brushes from East Coast Fibreglass and throw away after use. They are cheap enough and you won't compromise the strength of your layup.

When you do your gelcoat, a layer of thick acetate sheet laid on top of the wet gel will basically give you a mirror smooth finish. All you need to do is feather the edges into the existing gelcoat. Use a teeny weeny sanding block to do this...3/4 inch square is plenty. You only want to abrade the "line" and not any of your gelcoat either side.

Good luck!

 

[prv]

Yes, both are possible. I've got "dabbing" brushes that have been in acetone for several years
[...]
A roller or two are essential (and they can live in the acetone bucket as well). It's hard to get too much mat into the mix, and rollers are an excellent way of consolidating it and squashing the air and excess resin out.

Agree about the ridged rollers - they are essential to making proper GRP. I messed about just stippling with a brush for years and thought that was OK, but the result from properly consolidating with a roller feels very different and I'm sure it's stronger. Getting a better proportion of mat to resin saves on resin too, for a given strength.

If the shape you're making has internal corners, you will want one of the narrow "wheel" type rollers as well as a cylindrical one.

Completely disagree about the brushes - life's too short for cleaning cheap brushes, and perfectly good ones for fibreglassing can be had for pennies (about 20p each for a dozen at a time, from memory). I bought six dozen last time I stocked up. If everything starts getting awkwardly sticky in the middle of a layup, chuck the brush and gloves into the bin-bag, break out a new set, and carry on. Same with disposable plastic pint glasses for mixing, and disposable plastic pipettes for adding catalyst or wax, and for "injecting" gelcoat into old screw-holes.

I only buy quality brushes, and clean them, for varnishing.

Pete

 

[pcatterall]

Can you get the items indoors as finding the right outside temps can be an issue. Don't buy owt as I have spare stuff here.

 

[ghostlymoron]

I can bring the hatch in but I need to repair a crack in the gunwale which will have to wait for a fine day. Thanks for the offer PC I only need tiny quantities so would appreciate any left overs.

 

[MYStargazer]

Not knowing anything about GRP to start with, I found these surprisingly enlightening...

Fiberglass Repair http://www.boatus.com/boattech/casey/fiberglass-repair.asp

Blister Repair http://www.boatus.com/boattech/casey/blister-repair.asp

Polyester or Epoxy Resin? http://www.boatus.com/boattech/casey/polyster-epoxy.asp

Resin Boat Talk http://www.boatus.com/boattech/articles/resin-boat-talk.asp

 

[Avocet]

You don't really "clean" the brushes, you just get the worst of the resin off them and chuck them back in the bucket. It's easy!!!

Oh, and a box of latex (surgical" gloves is well worth investing in.

Also, if laminating, get a "wetting-out" board. Just a board. Paint resin on it and then get the bits of mat on the board, Paint the resin on them quickly, and then lift them (you have to be quick!) on to the job and roll them. It's better than trying to wet them out on the actual thing you're trying to stick them to.

 

[Iain C]

A sheet of very thick glass is even better. And you can clean it afterwards with a razor blade or scraper.

 

[William_H]

If you do go in for cleaning brushes with acetone for polyester resin then grind off the paint on the handle. If not the paint dissolves making an 'orrible mess. Use methylated spirits as cleaner and solvent for epoxy resin. Fibre glass repairs as OP has described are really easy. As said grind out damaged glass to good GRP. The biggest problem is finishing the job. If it is non skid rough that will be difficult to replicate. If it is smooth that is much easier. Gel coat should be applied to uncured resin to get a chemical bond. Unfortunately it is very difficult to sand down uncured resin as it just clogs sand paper. So a better alternative might be let it go hard then sand then finish with polyurethane paint. of course gel coat on hard cured f/g will probably adhere Ok and will be cheaper if you already have the resin. just need pigment and wax. good luck olewill

 

[ghostlymoron]

If you do go in for cleaning brushes with acetone for polyester resin then grind off the paint on the handle. If not the paint dissolves making an 'orrible mess. Use methylated spirits as cleaner and solvent for epoxy resin. Fibre glass repairs as OP has described are really easy. As said grind out damaged glass to good GRP. The biggest problem is finishing the job. If it is non skid rough that will be difficult to replicate. If it is smooth that is much easier. Gel coat should be applied to uncured resin to get a chemical bond. Unfortunately it is very difficult to sand down uncured resin as it just clogs sand paper. So a better alternative might be let it go hard then sand then finish with polyurethane paint. of course gel coat on hard cured f/g will probably adhere Ok and will be cheaper if you already have the resin. just need pigment and wax. good luck olewill

Do you mean that gel coat is just resin, pigment and wax? What's the formula?

 

[prv]

Do you mean that gel coat is just resin, pigment and wax? What's the formula?

I assume that Will meant "gelcoat" when he said "resin" in that sentence. You'd add the pigment to gelcoat make it match the existing colour, and add wax to gelcoat to prevent a tacky surface if it's curing in the air rather than a mould. Gelcoat with wax added is sometimes called flowcoat.

I dare say you could make gelcoat from resin by adding the right additives - mostly thickeners so that it doesn't run down a vertical surface when you paint it on. But it is conventionally bought ready-made.

Pete

 

[MYStargazer]

When repairing exterior gelcoat, is it possible to cover gelcoat in cling film to cure, or do you have to use flowcoat?

 

[prv]

When repairing exterior gelcoat, is it possible to cover gelcoat in cling film to cure, or do you have to use flowcoat?

You can cover it. I would use cellophane rather than cling-film, though, as the latter is likely to give a wrinkled finish whereas the former tends to stay smooth (as long as the surface is flat or only curved in one direction).

If you're planning to sand the new gelcoat, then you can get away without either as the tackiness is only right at the surface and is quickly removed.

Pete