Gelcoat Application

slangley · 26 September 2003, 11:17

Hi All,

I have decided to do a bit of maintenance work to my boat. When I bought it, although in fairly good condition, it has quite a few scratches on the under side.

I was told that the best way to make it look nice again is to use Gelcoat and spray it on. I have been looking up information on Gelcoat and it seems it is the right stuff but I have also heard rumours that it is not just a case of spraying it on like paint. Apparantly, there is a thing called the 'Orange Peel' effect.

Is this the best stuff to use to respray the bottom of the RIB. I intend to flatten the scratches with filler and there are a couple of holes I want to make disappear from things that were bolted into the RIB by the previous owner.

Can anyone give me some good advice either on using Gelcoat to do this or perhaps suggest and easier, economical and good alternative.

I will probably change the colour of it so will probably do the inside afterwards to make it all look nice.

You help would be much appreciated.

Steve.

MikeS · 26 September 2003, 16:32

Gelcoat (which is the outer, hard layer of any GRP moulding) is a thixotropic (thick and sticky) resin, so it doesn't run out of the mould during manufacture. Consequently, I don't think you could spray this onto your hull. The best way to refurbish any GRP hull is to fill any scratches, holes etc. with a suitable gelcoat filler, sand very smooth, then spray with a two-pack polyurethane paint. This stuff is very hardwearing (it's said to be harder than the original gelcoat) and very shiny. For this reason (and the fact that it gives off some very toxic vapour when sprayed), it's probably not a DIY job. If you get runs or brush/spray marks in it, it's very difficult to rub them out. However, there are approved application centres for the main brands (e.g., International, Awlgrip) where they have all the right equipment and will make a boat hull look like new.

Andy Stevens · 27 September 2003, 01:40

A lot of people use a small foam roller (not a fluffy one) to apply the gel coat. You can put two coats on, the last coat has another liquid added too called..cant think at the mo. It ensures the top coat isnt sticky. I did this to my boat, came up really nice, its a bit tought than 2k paint.

ribraff · 27 September 2003, 11:09

I have had very good results from spraying on crystic topcoat, it is available from Scott Bader. You will need to add pigment to get the colour you want and use acetone as a thinner. The good thing about this application is that if you do get any runs you can wet and dry them out and buffing with a 1000 grit and then a 1200 will give excellent results.
Spraying on gelcoat is a bit harder in my view but if you do go down this route you will need to add wax in styrene... this is what stops the top surface from being sticky

jwalker · 27 September 2003, 11:53

Not wanting to discourage you in any way, but you will need to seriously abraid the whole of the hull surface if you intend to apply gelcoat. If you intend to paint it, 240 grit wet-or-dry will do fine. Don't use car body filler to make the hull good, it absorbs water.
To fill the holes, chamfer their edges and file them inside to give a key. Tease apart some chopped strand mat into a fluffy pile. Mix up some resin and stir in as much of the CSM as seems reasonable. Stuff this into the hole and stipple it with a brush to get rid of the air. You might like to seal one side of the hole with tape first. When it has hardened, file/rasp/grind it flush.
If applying gelcoat, it will set shiney (provided you use the paraffin wax in styrene, commonly called Solution"MW") but it won't be flat. If you use a foam roller to apply it, it will have a finish that is very orange peely. The finish will be better if you use 50% gel + 50% normal resin, but, nevertheless it won't be flat. If you use a short hair roller you'll get a much smoother surface but it will need to be thinly applied and it'll require a few coats but it will still have a texture. The solution "MW" MUST only be in the final coat or it will prevent subsequent coats adhering. Personally, I would want to sand it down afterwards and then go through a polishing process.
However, it is the case that a smooth matt surface produces less friction than a nice shiney one. You may be happy to consider this.
Finally, if the scratches are not too deep, gel coat will probably fill them without recourse to a filler.

Andy Stevens · 27 September 2003, 13:09

I didnt get any orange peel with the roller, laid it on a bit thick and it floated out.

Didnt mention the prep, if its not keyed it will fall off for sure!

jwalker · 27 September 2003, 16:34

Quote:

Originally posted by Andy Stevens
I didnt get any orange peel with the roller, laid it on a bit thick and it floated out.

OK.

MeMe · 29 September 2003, 14:15

If you're not in a mad rush why not wait another couple of months and get a professional job done. Once the dealers have done all their winterizations and are kicking their heels as no one is buying new boats they still have to employ their mechanics and technicians and are often crying out for work just for the sake of keeping people busy. A quote received today can often be halved when there's snow on the ground !! If you get my drift.

slangley · 29 September 2003, 15:48

I am not in a mad rush but would like to do it myself for the experience and satisfaction. If I mess it up I guess it is rub down and start again.

I have spoken to a few fibreglass companys that deal with this sort of thing and it seems the best way forward is to completely rub it down to get rid of the last wax surface and then apply with a roller, the last coat being with a wax solution added. Then rub it down until it is smooth.

Just as 'JWalker' said really. I have ordered up the stuff so I guess I will have a go. You never know, I might get lucky.

thewavehumper · 29 September 2003, 16:04

How old is your Hull?

slangley · 29 September 2003, 17:41

It is approx. 1990. Overall, it seems Ok. I plugged the water ballast system and there wasn't any leaks from underneath BUT, because of the things that the previous owner has bolted to the deck, there are 6 or 7 holes in the deck that water does leak through.

The only problem underneath is the number of scratches ( some done by me in a storm ). I really want to do it for cosmetic reasons.

thewavehumper · 29 September 2003, 18:18

I have recently did this to my beloved, and sadly now sold, Avon 4.7. we fixed the scratches with Gelcoat with a tiny bit of filler and got a colour match by mixing red, dark red and yellow pigment. Mix the pigment after the filler has been added to the resin.

When it's dry rub it down through the grades and then give it all hell with a polishing mop and Rubbing compund moving on to Farecla polish afterwards. The results I got where really quite stunning, Well I though so anyway!

slangley · 30 September 2003, 09:45

I hope my one comes out as well as yours. Since you have done it before maybe you could answer a question for me. Before I can apply the new Gelcoat, I must abrade the old Gelcoat. Do I have to take the whole of the old gelcoat off or do I just rub off the top surface of it. If I have to take it all off, how will I know when it is all off, is it when the colour disappears entirely?

jwalker · 30 September 2003, 10:43

Just make sure you have completely broken the surface. This is to form a key. The new gelcoat is only going to adhere by mechanical grip. Use 60 grit production paper. Buy it at a motor factors. While you are there, buy 25 litres of gunwash (standard thinners). Use this to clean resin brushes, rollers (It's better, overall, than acetone.), paint brushes, remove grease stains from clothing, clean your boat tubes..... lots of uses you'll find for it. Costs about £12 + the dreaded vat.

slangley · 30 September 2003, 10:55

Many thanks for all your help. I have ordered all the stuff I need from http://www.cfsnet.co.uk . I will get some Gunwash and I intend to start next weekend. I assume that for the initial sanding, it is ok to use an electric sheet sander.

I have bought a few books now which seem to be pretty good. The sequence I intend to go through is as follows:-

Clean hull with acetone/gunwash

Initialy sandown using 60g sandpaper with an electric sander to break the surface.

Fill in holes with a resin based filler with embedded glass fibres.

Fill in scratches with Gelcoat filler.

Level off by hand using sandpaper 600g.

Apply a coat of un-waxed Gelcoat using short pile roller and leave for about 3 hours.

Apply a second coat of un-waxed Gelcoat using short pile roller and leave for about 3 hours.

Apply a third coat with wax and leave for about 2 days.

Sand down by hand going through the grades starting at 240g down to about 1200g and then rub and polish with Farcela G3/Advanced Liquid.

Finish polishing.

I will let you know how it all turns out.

Many Thanks to you all.

Steve.

jwalker · 30 September 2003, 11:31

Yeh, pretty much, but leave out the 600grit. You want the old surface to be as course as possible. It increases the surface area enormously, therefore, there is more surface for the new resin to stick to. Gel coat is very thick and it does not flow well. It is just laminating resin with a thixotropic agent added to prevent it flowing. You wont need to wait 2 days before starting the polishing process. In fact, if you wait 2 days, the gel will be pretty hard by then and your polishing arm will feel it! The rubbing down and polishing will be a labour of love. I'm not sure about the sander. I sometimes use one but I almost always go back to a cork block with the paper wrapped around it. The rubber block with the jaws at either end is sometimes used. It's a bit softer and flows over undulations a little better. Andy Stevens reckons he got the gel to flow out to a smooth surface and I can't argue with that but I've never managed it.

Oh yes, I forgot to mention, mask off the tubes and wear clothes which you don't mind ruining. Some resin will fly from the roller as spatter.

Jelly · 30 September 2003, 12:23

JW
Question, I was told on near vertical surfaces to tape a piece of thick plastic / acetate over the gel repair
a, to stop it slumping and
b, to stop the air getting to it so it wasn't going to have a sticky surface, once it has gone off.
Was this because it was just gelcoat and no wax?
When you buy gelcoat as a product does this normally come with the wax added?
Many thanks
James

slangley · 30 September 2003, 12:27

The Wax you purchase seperately to the Gel Coat. It is very cheap ( mine was about £3 for enough to treat 10L ). You add it to the last coat and that will stop the air getting to the Gel Coat so it can cure properly.

Jelly · 30 September 2003, 12:43

Many thanks for that.
Jelly

Mike C · 30 September 2003, 18:43

Can I just say that this has been one of the most useful threads for ages.... (That’s not to say they aren’t all fascinating but you know what I mean)

It has answered a lot of questions I have wondered for years. I will now save the thread to my computer for the next time I get a scratch! (Not the flea variety)

Thank you gentlemen!

Mike C