1st time bottom painting...Need little help

[Carl Wonderful]

So apparently the previous owner used Pettit Vivid. I have 1 gallon of Pettit Hydrocoat.

Should I just sand the hull down to the bright blue...Or the white? Pretty sure the dark is bare fiberglass?

Ive attached pics of the sanding in step so I could see each layer but not really sure what I'm looking at or how to proceed.

Please include step by step if you can... because I'm new to this and a classic overthinker,lol.



Thanks!!!!

 

[Davidasailor26]

My guess is the white is barrier coat. Definitely no reason to go through that. If the bright blue layer is well adhered - no flaking or chipping - I’d probably just rough it up, get the debris off and to fresh blue. The hydrocoat should be compatible enough with that.

 

[Captain Larry-DH]

My guess is the white is barrier coat. Definitely no reason to go through that. If the bright blue layer is well adhered - no flaking or chipping - I’d probably just rough it up, get the debris off and to fresh blue. The hydrocoat should be compatible enough with that.

This is good advice. Hydrocoat is compatible with the Pettit Vivid. Just a scuff sanding with 80 or 100 grit then paint.
Tip - Hydrocoat (and most other bottom paint) will adhere better if you use thin coats. Thick coats are more likely to flake or chip. Avoid the temptation to slop it on thick with the hopes of it wearing longer. The opposite is true. Use a short nap roller (1/4”).

 

[Carl Wonderful]

Sounds good! That's what I was hoping to hear.

So no need to clean with anything before sanding?

So for cleaning after sanding... what are my options?
-Rag with Acetone?
-Shop Vac?
-No cleaning?

------

Couple last things.....
Do I need to worry about those parts that I sanded down past the barrier coat?

Is Barrier coat and gel-coat the same thing?

 

[Davidasailor26]

So no need to clean with anything before sanding?

Nope. The only time you clean before sanding is if you have something like wax or amine blush on the surface that you don’t want to drive into the surface with sandpaper. That’s not the case with regular dirty antifouling - any dirt will just powder off.

So for cleaning after sanding... what are my options?
-Rag with Acetone?
-Shop Vac?
-No cleaning?

I’d at least shop vac the loose dust, and probably wipe down with a solvent. Pettit recommends their brushing thinner as the solvent. If you don’t have that but do have acetone or dewaxer those would be close enough for me, but your mileage may vary.

Do I need to worry about those parts that I sanded down past the barrier coat?

I wouldn’t. It doesn’t look like you got to the fiberglass laminate, so on spots of that size I don’t think it’s worth trying to recoat anything.

Is Barrier coat and gel-coat the same thing?

Not really. Gelcoat is a pigmented polyester (on most older boats) or vinyl ester (on some newer boats) layer applied over the fiberglass to make it look nice and even. Polyester isn’t perfectly waterproof - over years of water exposure it can allow some water to seep into the lower layers, forming blisters. Barrier coat is a few layers of epoxy applied over the surface to make it waterproof and prevent blistering.

 

[Carl Wonderful]

Nope. The only time you clean before sanding is if you have something like wax or amine blush on the surface that you don’t want to drive into the surface with sandpaper. That’s not the case with regular dirty antifouling - any dirt will just powder off.



I’d at least shop vac the loose dust, and probably wipe down with a solvent. Pettit recommends their brushing thinner as the solvent. If you don’t have that but do have acetone or dewaxer those would be close enough for me, but your mileage may vary.



I wouldn’t. It doesn’t look like you got to the fiberglass laminate, so on spots of that size I don’t think it’s worth trying to recoat anything.



Not really. Gelcoat is a pigmented polyester (on most older boats) or vinyl ester (on some newer boats) layer applied over the fiberglass to make it look nice and even. Polyester isn’t perfectly waterproof - over years of water exposure it can allow some water to seep into the lower layers, forming blisters. Barrier coat is a few layers of epoxy applied over the surface to make it waterproof and prevent blistering.

Beautiful! That's exactly what I needed. Appreciate your info and walking me through it all. Its been a real mind-bender trying to get a handle on the logistics and compatibility of all this stuff. Much, much appreciated!

 

[Art12050]

All good advise above. Petit makes very good products. I’ve been using Petit Odyssey for several years with very good result.

 

[VenturED]

I'm no expert, but the white coating doesn't look like gelcoat...unless it is a very rough layer done after the hull left the mold (in cases where later repaired), so it looks like some kind of non-slip coating like Awlgrip. There appears to be a tape line adjacent to the black area...

The dark patch looks a bit like the resin layer beneath the gelcoat...but it is hard to tell from the photo viewed on my phone. Perhaps the swirl patterns is from sanding or glass mat in the first layup layer? If so, and yu are through the barrier coat, shouldn't that be touched up with barrier coat before any top/antifouling coats?

I have some gouges in my V21's gelcoat that appear to have been puttied and will need to do something with...since it lives on a trailer, I'm thinking just a few coats of polyurethane would be enough...

Show us how it turns out.

 

[marcham]

Concur, I only see fiberglass/resin, then gelcoat, then various paints.

As for how to paint, just follow the paint manufacturer's recommendations. They have instructions on what can go over what and what prep is required (wash, light sand, heavy sand, complete removal).....

If you don't have blisters, carry on. If there are a few small ones here and there, it would likely be worth it to sand down all the bottom paint, apply barrier coat, then new antifouling. it's much easier/cheaper to fix it when it's a small problem than once you get hundreds of blisters to repair.