Degreasing oily bilge for GRP repair.

mogmog2

mogmog2

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I need to repair some reinforcement in one of the keel bilges: one of the retro-fitted gussets has partially come away. Presumably because of inadequate preparation...

The bilges are now very oily, following a major engine oil leak.

My uncle came and had a look for me. He is a retired aeronautical engineer specialising in composites, so advised me about the materials and stresses etc. He also stressed the necessity of getting the area clean, but they use Trichloroethylene as (the best) degreaser. However, this is problematic to the average bloke.

After removing the failed tabbing, I intend to remove the original surface. However, he advised that some grease contamination will occur, especially with a grinder, as material is moved around, so meticulous degreasing is necessary, ideally as a wash rather than wiping.

The West guide is a bit lacking in detail and that is the most comprehensive guide I've found.
Has anyone successfully done something with similar conditions (this is obviously different from say repairing a deck or general non-greasy area for which a wipe with acetone would suffice).
Any tips? Thanks.
 
Bobc said:
Any de-greaser or solvent will do it. You can get them at Toolstation.
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I have acetone but was urged to go better than that. On the other hand, I'm not building an F1 car or Airbus...

Have you got first hand experience of glassing, in a bilge?
 
As you might imagine my FV engineroom was messy, but a can of Comma (Gunk just as good) degreaser, brushed on ( I tried a spray bottle but inhalation not nice) later was pristine. Water soluble so pump or drain out. After that obs you will have to grind and maybe a bit of acetone for final cleansing.
 
My advice would be to wipe it as clean as you can get it with upvc solvent from Toolstation (like acetone but not so nasty on your skin or on grp). Then get a mask on and sand/grind the top surface off. This will help you key the area in for laminating and it will also guarantee that all surfaces are clean, because you will have physically removed the old surface.
 
Glassing anywhere long after construction is looking for a mechanical rather than chemical bond. Get rid of any flocoat or other finish, then abrade, but try to scratch and raise the fibres rather than grinding which tends to polish. maybe a dremel type tool? I have used a circular saw dragged across, but very dusty as it all is.
 
Screwfix own-brand degreaser detergenty stuff is pretty good, it copes with the fallout from motorbike chains.
https://www.screwfix.com/p/no-nonsense-heavy-duty-degreaser-5ltr/88668
You want to wash away the gunge, not dissolve it a solvent which then evaporates elsewhere.
Scrubbing with Jif-type cream cleaner can be very effective, if you're left with a sticky layer.
Removing as much as possible with rags etc reduces the amount of oily water to dispose of.

After all that you need to get it dry, then finally wipe over with a solvent like acetone.
Remove any flowcoat.
Abrade shortly before laying on new resin.
 
I imagine that nappies or similar thrown in the bilge first would help with mucky water disposal. I took a hose with trigger down below to wash down selectively after degreasing.
 
Bobc said:
My advice would be to wipe it as clean as you can get it with upvc solvent from Toolstation (like acetone but not so nasty on your skin or on grp).
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I would argue you need as nasty an action on the GRP as you can get. Years of experience on GRP dinghy repairs, bonding fresh fibreglass to old fibreglass is very difficult. This is why when laying up you do wet on tacky. You don't just want a mechnaical bond, you need a chemical bond.

You need to get all the grease off ( a degreaser like Gunk or Jizer, then water wash, then soapy water wash) ... solvent clean and then abrade the surface ... then get in there with whatever solvent you can get your hands on that is most likely to try and disolve the GRP. Acetone is good for this. If you are lucky, it will reactivate the polyester resin, and the new layer will form a chemical bond to the old stuff.

I've seen plenty of GRP repairs where the new layer is only mechanically bound to the substrate and simply cracks off under load.
 
fisherman said:
As you might imagine my FV engineroom was messy, but a can of Comma (Gunk just as good) degreaser, brushed on ( I tried a spray bottle but inhalation not nice) later was pristine. Water soluble so pump or drain out. After that obs you will have to grind and maybe a bit of acetone for final cleansing.
Click to expand...

Yes, Gunk is very good. Sugar Soap also works well.
 
Before laminating new onto old I always give the old a brush with styrene to soften the surface a little.
 
I believe epoxy bonds much better to old polyester, and if you have been looking at West I suspect that's what you have in mind. If so, acetone does leave a residue, and may not be ideal. I would go for a final degrease with isopropyl alcohol (coppercoat advise this agent for their water soluble epoxy coating) after pre cleaning with bilge detergent type cleaners.
 
Degrease with Gunk or similar strong detergent, grind back to clean glass with coarse grinding disc. If the disc starts to clog change it for a new one. Job done.
Personally i like vinylester resin for repairs, it is somewhere between polyester & epoxy in properties & more forgiving than epoxy. Use as you would polyester with peroxide catalyst.
 
I concur with post #8. Screwfix non-nonsense degreaser is inexpensive and has given excellent results in many different applications. When I cleaned the inside of a diesel tank with it, the surface soon became squeaky clean. Highly recommended and great stuff to have to-hand in your garage and boat. What's more, when done, the residue is not at all oily and doesn't look like a petrol or diesel spill when you pour it away.
 
As mentioned by all above, you have to get rid of any oil residue - this is where you start, then grind. In opposite order you risk to shift an oil and dust smear around. Also, in this situation I would not wash with any solvent after grinding as it is too easy to accidentally get some oily residue from outside the prepared area on to it. Finish by sanding lightly with 40 grade.
At this point, before you start glassing, make a 10x10cm 3 ply patch somewhere on the prepared surface. Let it cure properly and pry it off. Does it stick or just pop off? This test will tell you if you will have a good bond. Whether I did a similar job successfully some years ago, does not count, because that was another boat.

If you do net get rid of the oil, it does not help much to turn to epoxy.
Using a Dremel to ruffen the surface just destroys the glass layer you like to bond to, and makes it harder to get rid of trapped air.
 
Jizer is a really good degreaser - brush on and wash off with water. If you use it on bare steel then it starts to rust pretty damned quickly.
 
This is the best degreaser I've ever used - especially if you have access to hot water:

https://www.frost.co.uk/cleaner-degreaser-por15-marine-clean-946ml.html

Agree with the comments about epoxy. It sticks to old polyester GRP better than new polyester resin, BUT, once you've used it, you're committed to it if ever you need to add anything else, because polyester won't stick to cured epoxy very well at all. Polyester is also more tolerant of different mix ratios with the hardener and being used in cold, damp conditions.
 
Personally, I would not use epoxy. Polyester of vinylester resin is perfectly adequate. The strength will come from the laminate, not the resin. Make sure you use good quality woven rovings with a close weave, and make sure the weave is +/- 45 degrees across the split. Avoid using chopstrand, as that just adds bulk with little strength.

The most important things are 1) ensure the new laminate is properly keyed and attached to the existing lamiate, 2) build up your layers getting increasingly bigger as you go, 3) wet out the mat thoroughly (using too much resin as better than not using enough), do the whole job in one go if you can, so that you are lamitating onto wet resin (use a slow hardener).
 
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Chopped strand mat is perfectly adequate for most repairs & good practice is to intersperse csm between layers of woven cloth as this lessens the chance of delamination. It is also important to get the air out & consolidate the laminate with a paddlewheel roller.
Putting all the laminate in in one go with slow hardener runs a high risk of resin running out of vertical areas & puddling, also liable to slump if you go too thick.
 
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