A problem with my bottom!

[Brian_B]

I need advice on my bottom. My Starlight 35 was hauled out yesterday for the winter.
The power wash took paint off about 10% of the underwater surface right down to the glass fibre.
It looks in good shape, smooth with no blisters.

How should these bare areas be treated before we anti-foul again in a few months?

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[woody001]

glass fibre? you saying there's no gel coat?

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[snowleopard]

Not uncommon to have clear gel coat on the bottom. If the paint came off, you may have a bit of wax mould release agent still on the hull. It needs to be removed by de-greasing with e.g. acetone (wear gloves) followed by wet sanding.

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[malcp]

Snowleopard is right, Starlights do have clear gel coat below the water line (at least the MK1s do). Treat as stated above and then what I do is put on a coat of Interprotect epoxy primer and follow this with the antifoul. Rub down to key primer first. I find this works well.

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[Brian_B]

I'm not sure about wax mould release agent as the boat's 12 years old.
I think you are right, it 's clear gel coat but I didn't know if some sort of primer should be applied before the anti-foul?

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[Brian_B]

Malc

I think that's the answer. She is a MK1. I think de-grease and coat with primer is the way to go.

Thanks all

BB

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[geoffatstanpit]

Wow! Where do you get a scrub-off with a gadget that'll do that. The one at the yard where I lift out (3000psi) doesn't even get the barnacles off (gets them nice and clean though!)

Geoff

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[boatmike]

If the power wash took the antifoul off it is as snowleopard said probable that the boat was never properly prepared for antifoul in the first place and release agent won't necessarily dissapear on it's own especially when it has been painted over even after 12 years. If these are big areas I would consider removing all old antifouling,(sounds as if it will not be difficult) degrease thoroughly, then wash with detergent and lightly abrade all over with 400 grit before re-coating.
You are very lucky to have a clear gel coat on the bottom. any inperfections or osmosis will be clearly visible through it (the main argument for not pigmenting gel coat on the bottom) You can paint antifoul direct to the abraded surface or use epoxy first to give added protection. A good plan is always to use a hard racing coat of something like Trilux as a first coat in a contrasting colour (I use black ) before overcoating with cruiser type antifoul of your choice so that you can immediately see if there are areas where the antifoul is wearing off faster.... There are primers that are sold but frankly I don't think they do a lot and they are seldom used professionally.

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[Brian_B]

Mike
I went back and looked at our survey prior to purchase. This states that a primer has not been used and it's been anti-fouled straight onto the clear gel coat.
The surveyor implies this is no bad thing as it makes inspection easier and without a primer the hull 'dries out' more quickly.
Your advice is much appreciated. We'll be cleaning up the hull and not applying primer before we paint the bottom in a couple of months.

By the way, for anyone who's interested we used Blakes Tiger xtra in white this year and it did a very good job. After 9 months in the water and not as many miles under the keel as we'd hoped for, the bottom was just covered in a green/brown slime that came off easily, no weed or other growth.
We'll be using the same paint but in red next year.

BB

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[boatmike]

No probs. The surveyor is correct in that most "primers" are solventless epoxy. My own feeling is that if you are going to use epoxy go the whole hog and apply the full recommended 6 coats of "Gelshield" or something similar which acts as a positive and effective barrier to stop moisture getting in. The problem as he implies is that thin coats of epoxy primer don't really stop water getting in but certainly slow down the drying out process when the hull comes out of the water.
My own boat which I built myself was cleaned and abraded before 8 coats of Gelshield, followed by two coats of black Trilux topped off with two coats of Micron. Belt and braces perhaps but designed to enable me to leave the boat in the water with only a quick scrub and re-coat between tides (she is a catamaran with 2ft 10in draught).
Don't forget to degrease and wash BEFORE abrading as abrading alone will only re-distribute the release agent. It's persistent stuff!


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[Brian_B]

Thanks Mike

Will do.

BB

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