Gel Shield / Osmosis protection.

AIDY

AIDY

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Anyone got any experience of what's good and what's rubbish to put on the boat before Anti Fouling. I've stripped the hull on my boat back to GRP and am in the process of looking at what I should be putting on the bare hull for Osmosis protection before antifouling.

I've already bought the anti-fouling (International Micron which I've used for years). Do i need to stick with International for compatibility and use there Gel shield 200 which requires 5 coats /forums/images/graemlins/shocked.gif. Or can I use the Blake's alternative which only requires 2 coats. /forums/images/graemlins/smile.gif

Any other product suggestion and tips would be most welcome.

TIA
 
I've used both at different times. I don't think that there are any compatability issues. I remember Gelshield 200, which is a solvent based product, as being considerably easier to apply, 2 coats per day in the right conditions. Whichever you choose, if in the UK, you will need to wait until the weather improves, April at the earliest I would say, unless the boat is undercover. Also make sure the gelcoat is thoroughly abraded. I used a tie-coat, Primocon, under the A/F, but I think International have dropped that recommendation. NB:- I've read opinion that epoxying a boat that has been afloat is of doubtful value unless it still has a very low moisture content.
 
thanks for the responce. I had intended to to wet and dry the gel coat first. Blakes reckon 2 coats for protection and up to 5 for curing osmosis. If the weather stays like this over xmas here Ie.... 11 degree's i had intended to paint over xmas. then A/F in march time. do you think it would be okay left with gel shield on the hull. Or is it a job for gelshield one weekend then A/F the next ?
 
IIRC, there is a max. overcoat time for epoxy onto epoxy, which is fairly short, after which you have to abrade. Don't know how this affects A/F though. Using a tie coat would probably avoid any problem but pehaps best to check with the manufacturer's tech. dept.
 
I don't think you are comparing like products.
Gelshield 200 is a solvent based epoxy. Blakes SFE (if that's what it is) is solvent free.

Successful osmosis prevention is all about getting sufficient film build to give a waterproof barrier coat. A solvent based product will only give about half the dft (dry film thickness) of a solvent free epoxy for each coat. 2 coats of Blakes will give about the same total thickness as 5 of Gelshield but there are other considerations to take account of.

The solvent based epoxy will cure at a lower temperature than the solvent free product and can therefore be used at a wider range of times of year. I think Gelshield 200 can be used at 5C and Blakes SFE 10 or 12C but not sure of my facts so check with data sheets.

Solvent free can be applied "wet on tacky" but solvent based cannot.

Solvent free more likely to suffer from amine bloom if temperature and humidity vary beyond limits during curing. This must be removed before next coat or intercoat adhesion will be severely compromised.

If you are in the UK I really would not recommend epoxy coating at this time of year unless you understand all the complexities or you're prepared to wait for a full cure between each coat, wash down to remove bloom and abrade to provide a mechanical key. It will take a lot of time and effort that can be avoided doing it when the weather is better.
 
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Anyone got any experience of what's good and what's rubbish to put on the boat before Anti Fouling. I've stripped the hull on my boat back to GRP and am in the process of looking at what I should be putting on the bare hull for Osmosis protection before anti fouling.

I've already bought the anti-fouling (International Micron which I've used for years). Do i need to stick with International for compatibility and use there Gel shield 200 which requires 5 coats /forums/images/graemlins/shocked.gif. Or can I use the Blake's alternative which only requires 2 coats. /forums/images/graemlins/smile.gif

Any other product suggestion and tips would be most welcome.

TIA

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Aidy, I am preparing to epoxy my boat at the moment, ready for warmer waters where a boat is more likely to start osmosis.

I think I have now made the decision to use Gelshield 200 for the following reasons:

1. You can use down to 5degrees C, but best applied at 10 or above. (Blakes - most definitley above 10 C.

2. Overcoat time on Gelshield is days or weeks up to 6 months, except Antifouling coat, which should go on the same day as the last coat. (Blakes overcoat within a day.)

3. Tolerant to rain etc in between coats. (Blakes - no way - you must overcoat quickly. - and use a primer coat for the antifouling)

So over a UK winter there will be plenty of days when you will be able to apply Gelsheild, but very few that you would know safely you could do the Blakes.

I understand that Gelsheild is also much easier for the unprofessional painter to do, being thinner and less likely to sag.

I think obver the coarse of an English winter - and that includes April, you are going to be safer with Gelsheild. I would not even think about doing it in dec Jan and Feb! 5C is the absolute minimum 10c is better all round.

You will need to abraid the entire surface - with 180-200 grade, using an orbital sander - available for £30 from Screwfix.

Good luck!!!
 
thanks chris... how did you strip your old A/F did you have it slurry blast ? or are you doing it manually.

I've been using Dilunett paint stripper, putting cling film over the top then leaving for 12 hours then scrapping it off. have you found a better method. It's not a bad method considereing there is 10 years of A/F on there. 2 of us can do half a side of a 40 foot boat in a weekend.
 
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thanks chris... how did you strip your old A/F did you have it slurry blast ? or are you doing it manually.

I've been using Dilunett paint stripper, putting cling film over the top then leaving for 12 hours then scrapping it off. have you found a better method. It's not a bad method considereing there is 10 years of A/F on there. 2 of us can do half a side of a 40 foot boat in a weekend.

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I had the boat slurry blasted. I think it is worth it!!!! its a hell of a job to get the old stuff off if well bonded.
 
Out of interest how much did you pay for a slurry blast ? I looked into it and decided not to after a few reports on taking the top layer of gel coat away. A friend who had it done found particles all over his boat for weeks after /forums/images/graemlins/grin.gif

Dilunett seems to work well. your meant to apply with a brush then jet wash it off.
 
Not sure who your local chaps would be in La La Land but in Portsmouth the chaps at ARC slurry blasted my 36ft long keeler for £550.

Just one point to add to the good info that has been given....If you are going to epoxy the boat it really has to be looked at as a fairly major under taking .. if only because the problems caused if it goes wrong. I epoxied my last boat which was a new build ( in the garden job) 29ft, and I wouldn't even think about doing it outside in an English spring time let alone winter.

However maybe thats just me being cautious ! FWIW I did 5 coats and just kept going round and a round with my father in law mixing and cleaning rollers as i went. Actually an easy job as i found that the previous coat had just had time to 'tack off' to the correct amount by the time i got back the the start.

I used SP System and it was about 15 years back so can't remember whether it was solvent or solvent free.

It was all in the prep and getting the correct low humidity on the day.

I'm just having my present boat done as a precautionary job whilst I am having the topsides painted and the painter is checking the moisture levels and will have it rubber stamped by a surveyor to ensure that this is correct before starting the job...he will also move the boat into a big tent to paint and epoxy, after letting her dry out all winter.

Good luck, Nick
 
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Not sure who your local chaps would be in La La Land but in Portsmouth the chaps at ARC slurry blasted my 36ft long keeler for £550.


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La La Land is currently chichester /forums/images/graemlins/grin.gif thank's some good info here as usual.
 
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I've stripped the hull on my boat back to GRP and am in the process of looking at what I should be putting on the bare hull for Osmosis protection before antifouling.

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If you are down to bare glass, then you will have exposed some ends of or the fibreglass strands. It is vital that they be properly sealed; the end result may be wicking as a minimum or a bad case of Osmosis.

The fact that some strands may be exposed will help the drying process required before sealing the hull.

Given that ens are exposed I would be looking at 5 coats, wet on tacky of epoxy resin, applied with a roller and tipped off with a brush. But only after Hull moisture has been confirmed and the conditions for application are confirmed.

After all coats have been applied the hull should be washed starting at the top and working down, rub with a plastic kitchen scourer (scotchbrite) till the running water no longer forms beads, this ensures all the residue left by the curing process has been removed.

Ony after washing as above should you do any sanding, and this sanding is only to remove the very high gloss left by the resin. a 200 grit is fine, just remove the gloss and wash down, let it dry and you are ready to apply an epoxy primer.

We use a high build primer, mist coat first, then a full coat, then a second full coat, it dries very quickly.

This is ready to antifoul when you are, be it days or months, just a light sand and wipe down and apply.

Hope this helps

Avagoodweekend......
 
I'm interested in this discussion because I've stripped off all the old AF and would love to epoxy coat the hull. However, the local surveyor has run his meter over the hull and tells me that it will not dry out unless I remove the gel coat, hot vac inside. etc. So, all you guys who are contemplating epoxy - do you know that your hulls are dry enough, or is this surveyor being particularly cautious?

Also, a few months ago, PBO ran a piece about how it is possible to epoxy treat a hull with osmosis by painting with International paints, simply filling the blistors or, if there are too many, just sanding the hull smooth and then painting.

I was intrigued by this, so called International's technical people. They told me that this was all possible if I could get the moisture reading below 15. I'm not sure which meter this should be on, or whether this might be possible on an older hull, drying outside in the UK.

Any thoughts on all this?
 
G'day Cspirit,

Your surveyor is correct, drying is prolonged if the old gelcoat is still in place, by removing the old gelcoat you will also be able see and defects in the layup including wicking and osmosis.

Look for dark areas, grind them out, look a small darker brown dot or line and keep grinding till it has gone, this is the stain left by the hollow glass fibe the moisture has travelled up.

Also look for lighter whitish spots, these are areas that did not get wet out properly when being built, grind till you see normal colour and no tiny voids.

You can speed up drying by heating the inside of the boat 24/7.

Hope this helps.

Avagoodweekend......
 
willow i would be interested to learn more. how much are you paying for 2.5litre can ? and what A/F are you intending to slap over the top is it compatiable with international range.
 
It's all on the Shepherd Marine website with prices and full data sheets. Smallest can is 5 litres; that's one reason it's cheaper, they don't mess around much with small packs for the yacht market, Jotun are in the commercial market. Overcoat with their Vinyguard interlayer (that's vinyl based; most other makes seem to use chlorinated rubber for this interlayer, I don't have the technical knowledge to know which is better, if either) then follow with their own or any other a/f. I'm using their top grade SeaGuardian.
The guy there - Malcolm - is very helpful on the phone. I ordered on line and it all arrived next day.
The HB sticks like s**t to a blanket and is very tough to rub down. It doesn't brush on as smoothly as SeaJet epoxy.
Mike
 
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