GRP renovation

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prescott56

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Watcha,
What's teh best way to clean/renovate hulls.
On GRP cars and vans I have always t-cutted then a product called "protec" which sort of seals teh GRP then good wax polish. Not sure how this will work with salt water...
Any recomandations?

Regards
 
It depends how bad the gelcoat is. I did my 30 yesr old gelcoat last weekend after being advised by a profesional car/boat restorer who works at my office. This is the process I follwed.

1. Clean the hull thoroughly with a good boat cleaner. You can use a scotch pad on tough areas as you'll be polishing out scuffs later. You can use some fine wet & dry sandpaper (1200-1500) to get any nasty bits if you want. Dont worry too much about really stubborn stains at this point as they will polish out. You just want to get the hull as clean as possible and remove and residual waxes etc.

2. Get a proper polishing machine. These can be found quite cheaply, but make sure it is designed for the job. The orbital ones aren't up to the task and many 'polishing' machines are just re-badged angle grinders, which rotate far too quickly. You want a machine that has a range of about 600-3000 rpms.

3. Use a strong cutting compound with a foam bonnet on the polishing machine. You need a good compound for this, not just a t-cut. Something that is designed to remove any suffs you made when cleaning/sanding. It should say on the bottle what grade of scratches it will remove, 3M Fast Cutting Compound(will remove 1200 scratches) or Farecla G3(will remove 1500 scratches) are good ones. Work over th whole hull with this compound and the polishing machine set at a low speed (aeound 800rpm).

This will remove the top layer of the gelcoat and any stains that the washing didn't get. The aim here is to get a uniform colour all over the hull. Although you can buff to a shine with these compounds dont worry about leaving residue behind at this stage. If the foam bonnet gets too sticky you can put a little water on it, you can also wash the foam bonnets if they get too clogged up.

When you have completed this stage wash off any resdidual polish and and inspect the results. You should be able to see quite clearly if you've missed any areas as the freshly polished gelcoat will be a slightly brighter colour. After this stage the hull should look really clean and uniform in colour, although it may have swirl marks from the polishing and wont be especially shiny just yet.

4. Use an extra fine compound/polish with a lambswool bonnet on the polishing machine. Something like 3M Extra Fine Rubbbing or Farecla G3. The aim here is to get the hull to a deep shine and remove any swirl marks left by the first cutting process. You want the machine running a little faster for this stage, around 1500 rpm. Again you can add a little water to the bonnet if it gets sticky.

After this process the hull should be very smooth and all the swirl marks should be gone. Wash off any residual polish with water once you are done.

5. Get a good quality wax that has UV resistant properties. You need to do this as soon as possible after the polishing as it is the UV that degrades the gelcoat. Dont use the polishing machine to buff the wax as it's too powerful and probably just remove it. You can use an orbital polisher for this process if you have one, but I did mine by hand.

I did this on a 28'er and it took me a weekend, one day to clean/cut one day to polish/wax. My hull was dull, chalky and quite badly stained in places, especially just above the boot stripe. The results were absolutely amazing. The hull is now uniformly white again, and reflects like glass.

I'll take some pics next time I'm down and show some before/after shots.
 
Thanks for that, SvenglishTommy....eeeeerrrrr...what you doing this weekend :-)
The hull is not a disaster area, so I think I'll go with the Farcela G3, then a good wax.
Was looking at 100% Carnauba wax, have used this on old cars with great results.
Any comments welcome.
Regards
 
lol, this weekend I am going to Florence, far away from anything boaty :P

If you're just going to do one of the compounding stages use the G10 or another very fine compound. If the hull is in ok condition and colour is uniform and stainless after cleaning then you can skip the G3 and go straight to the G10. The G10 gives the nice shiny finish, but it doesn't cut like the G3.

If you do use the G3, it is really worth going over it again with the G10, you can see the difference in finish as you go.

Why not give the hull a good clean first, then try the G10 and see if it gives you the finish you want, and if not resign yourself to the 2 stage process.

As far as the wax goes, I wouldn't use Carnuaba wax. It's too hard and will be a pain to apply. It's great for your car but you really want the UV protection more than the super shine you'll get from Carnuaba. A liquid marine wax will probably be your best bet, easier to apply and better protection.
 
WARNING

I did the same as Tommy 2 years ago on our Seeker31 with fantastic results, but be warned, sanding the hull even with 1500 grade wet and dry you are reducing the thickness of the gel coat and it can be easy on thin gel or a repaired hull to go through to the laminate

I also recommend this as I tried to Tcut the neglected hull and this made no difference, just be really careful and use lots of water.

You can get the buffers from Machine Mart for about £60 ish and the compound, foam heads and paper from Partco.

3M sanding blocks are Ideal for the sanding (Flatting) the hull.

P.S. Don't forget to remove any spray hoods, dodgers, sails or any other absorbent materials from the boat, as the compound goes everywhere and will stain. Check for the position of other things like the guy next doors Jag as I covered that in compound and it was parked about 30ft away!

Good luck
 
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