Polishing GRP, simple questions from a first timer

Fascadale

Fascadale

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The time has come to try to clean the stains and discolourations off the hull of my 35 year old MAB

From reading various threads I understand that I need a polisher that will run slow and some sort of cutting compound. (and time and patience)

I've never done this job before so here are a few really simple questions

Will this do as a polisher ? Is 900rpm slow enough ?

What cutting or polishing compound do I need ?

And where can I get it?


Thanks
 
It is difficult to get a powerful one that is any slower than that.
I have tried a smaller one running at about the same speed on GRP, but suggest the one you show will be OK provided you keep it moving so that it does not have too long in any one spot to heat up the surface. Problem with using a big polisher on a boat hull is that they are heavy and you may well be working at an uncomfortable height. Another point to bear in mind is that the motor is at its least efficient at the slowest speed, so be prepared to stop at intervals and let it cool down, and your arms recover from holding it.
 
26 foot?

Wimp.

Do it by hand.

A machine may be tempting, but the possibility of burns and even the edge of the mop grazing the gel coat when you lose concentration make a handraulic solution more satisfactory.
 
"Problem with using a big polisher on a boat hull is that they are heavy and you may well be working at an uncomfortable height"

I can't offer an opinion on the polisher but I have seen a good tip to overcome the arm strain - attach a length of shock cord from the rail to the tool. It takes a significant proportion of the weight, but doesn't impede movement.
 
A bit of oxalic acid in some wallpaper paste plus a bit of food colouring so you can see where you have put the stuff on. Paint it on with a brush, leave a couple of mins and hose off. It cleans grp really well. Wear gloves and goggles.
 
I use a similar (but larger) tool and it works fine. From recent experience I would use a cleaner first to remove the worst of the stains. I used a cleaner based on Oxalic acid. There are rubbing compounds made for the marine market but like most things 'boaty' they are pricy. I always use the ones sold for cars. Brown brothers are a good source. I normally go over the whole hull with the finest and then use a coarser one, if required, on any stubborn marks. It is very important to use good quality polish after cutting. Some people don't like silicon polish on GRP but I have had good results. When the job is done, it is very quick to add more coats of polish and I think the more coats the better. On my last boat, which was only 22ft, I could polish the whole thing in a couple of hours. I did this at least twice a year plus a really good clean and polish once a year when she was out of the water. Beware using the polisher near antifouling, it can pick-up and mark the adjacent gelcoat.
Allan
 
Yes that is slow enough, but it must be possible to fit a compounding mop.

You need to use a closed cell foam compounding mop, with a cutting compound, which you keep wet. They come in different grades for different grades of compound

Find Farecla's website for details of their range of compounds and mops. Compare with what 3M have to offer.

You'll probably need a medium and a fine grade compound.

Wax polish afterwards to seal the surface

Do it a bit at a time. It is quite hard work but the results can be spectacular. I polished a dull pink hull back to shiny red and it looked so good that people though it had been spray painted. I took two days to do a 19 footer.

BUT wash the dirt off first and I would also do clean with Y10 or similar if it is badly stained

Farecla or 3M should be able to tell you stockists but I actually used a compound aimed at the vehicle refinishing trade and bought it from a car paint suppliers
 
I bought a Metabo (?spelling) from AdrianB at Clean and Shiny.
http://www.cleanandshiny.co.uk/index.php?act=viewDoc&docId=2

They know everything about boat cleaning.

It goes down to 700 rpm and that's more than enough to deal with old GRP surfaces, as it's a very tough machine.

They have a very wide range of compounds too, and the knowledge to advise you.


It's not the cheapest machine on the block, but by golly it saves the arm muscles and so much time.
 
I have a 30 year old 26ft as well. If it is like mine anything you do is a vast improvement. So give it a go by hand first using the compounds suggested.

Only worth having a concours hull if the rest of the boat is up to the same standard in my view.
 
I'm sure that polisher would do the job, but at 4.3Kg you'd need arms like Popeye for prolonged use. There are plenty around at half that weight and believe me, it would be worth shopping around for one of these (all IMHO of course).
 
And here's the recipe...

50 grammes of Oxalic acid crystals per litre of hot water.
A small amount of wallpaper paste - not much at all.
Food colouring of your choice, but blue looks good!

Don't let it dry, otherwise the glue goes hard.
 
[ QUOTE ]
but at 4.3Kg you'd need arms like Popeye for prolonged use.

[/ QUOTE ] I have not tried it but I have seen it suggested that the answer is to suspend the polishing machine from the guard rail.
 
I purchased a Silverline polisher to polish the boat this winter. Did a bit of research beforehand and decided--after taking advice--that it wasn't worth spending the £180 that a "pukka" Bosch would cost. Washed the dirt of the hull first and then used a blue sponge mop with Farecla G3 compound, it's important to use plenty of water, both on the foam mop and the hull as you are polishing it. Used speed setting no2 (around 1000rpm) and when you have finishd use a wet sponge and a wash leather to remove any excess compound left on the hull.
I then used a white foam head (dry) at speed setting No4 to give the final polish---the results were spectacular, a twenty year old boat with a very dull and oxidised gel coat looked like new. I agree with the point about the weight of the polisher. Either bring a mate along and take turns or do what I did and rig a small block from your guardwire and suspend a container of water from one end of the rope, your polisher from the other. You should be able to adjust the water content so that the polisher has "zero" weight.
 
Try paints4u.co.uk for cleaning gear and compounds. Don't like the idea of suspending a machine tool from the boat, if it 'bites' or 'kicks back' you need to be able to get it clear of you; suspended from the guard rail sounds dicey to me.
 
[ QUOTE ]
Try paints4u.co.uk for cleaning gear and compounds. Don't like the idea of suspending a machine tool from the boat, if it 'bites' or 'kicks back' you need to be able to get it clear of you; suspended from the guard rail sounds dicey to me.

[/ QUOTE ]


Better than suspending from the guard rail is hanging it on the main halliard with some doubled up lengths of shockcord.
Adjust the halliard so the polisher hangs at about gunwhale height, then with little effort you pull it down and polish, you get much more coverage before you need to adjust the halliard than if you hang it from the guard rail. If you drop the polisher (and you probably will sooner or later because they are very heavy and your arms go to sleep) then no damage is done.
Keep the polishing surface wet, I found that a small plant sprayer is ideal for this, hang this from your belt with cord, and spray the hull as you go. If you put a bit of washing up liquid in the water it seems to help. Water and electricity don't mix so do be sure that you have a earth leakage trip device on the power lead. If you are working on tressles and they are as rickety as those in the yard I use, it's not a bad idea to wear a harness and clip on a halliard in case you miss your footing and fall.
 
Think that most of the points have been covered, but can rec. Farcla G4 and Autoglym Polish, Just completed a 15 yr old 40'....T/cut wouldn,t look at it! squirty bottle of water used liberally cuts down on the risk of burn! and if you cut back well, you will find that you can do the polishing bit by hand! /forums/images/graemlins/smile.gif
 
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