Hull prep after sand blasting

oxman

oxman

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I have had the hulls sand blasted and am currently sanding down the remains.
As the boat has been on a mud mooring most of its life there are quite a few chips, cracks and dings in the gelcoat below the waterline - so what should I use to fill the holes and then prepare for AF undercoat.

If it makes any difference the hulls are 1970's vintage Prout 35'.

Thanks in advance!
 
If they only affect the gelcoat, I'd be inclined to use gelcoat repair. Plastic Padding do one. I used a car body filler from Halfords on Jissel, but I've since been told by someone who should know, that it's too porous, so it's likely not to hold. It hasn't fallen off Jissel yet, but use at your own risk.

If they go deeper and affect the layup, I'd use epoxy, thickened with one of the various products your friendly local epoxy dealer will be able to suggest. Since you don't need a lot of strength, microballons would be fine, and easier to sand than a lot of the alternatives.

BTW, I hate to suggest extra work and expense but, while the hull's nice and clean, is it dry enough to be worth epoxy coating? That'd give you some extra "osmosis" protection.
 
Thanks Steve - you are right - some of the chips are a little deeper than the gelcoat so probably best to go the whole hog with filled epoxy.

Epoxy coating - I did read that elsewhere - I will ponder it but most obvious problem is time and temperature!!
 
If you do the coating with a solvent based epoxy like International, it is not terribly temp sensitive, dries quickly and you can spray several coats on in a day. Would be a shame to miss the opportunity provided the hulls are dry.
 
G'day Brenden (oxman),

If she has been around since the 70's and has not developed boat pox chances are she never will.

Did you notice any epoxy when blasting? it's much harder than standard resin so will take a bit more to remove. If you did see any it would be a good idea to replace it. As epoxy is much harder it may also provide a bit more resistance to chipping when she settles in the mud.

Epoxy resin mixed with some 'Closed Cell' balloons will be fine for the chips, just make sure she is very dry first. Closed Cell balloons will soak up moisture so are a must below the water line. sanding is also very easy. If you apply the mix with a bendy straight edge you will reduce the amount of sanding, I suspect the blasting will have left a ripple finish so you may end up using a bit more material than you thought, particularly if you fill the low spots.

Hope this helps.

Avagoodweekend......
 
I agree with oldsaltoz on method.
Don't use Plastic Padding or car body filler underwater as it is too porous and will act as a conduit for water to get into the laminate. Likewise, don't use a solvent based epoxy in the chips as solvent will go into the laminate and probably cause blistering to start. Use a solvent free epoxy at least in the damaged areas but that means waiting for the weather to improve as most need to cure at 10C at least.
 
When repairing a substantial hole in Jissel's bottom (an old log impellor that left a 3"hole), I asked about temperature and was told by my supplier that it isn't as critical for epoxy as some would have us believe.

On a decent day on the S coast even now, you can epoxy as soon as the dew's gone and it'll have gone off enough by the time the temperature drops in the evening that it won't come to any harm. Curing will just slow down as it gets cold and pick up again after. Even with a frost overnight, my previous day's work had always cured by the next day.
 
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