Prep for bottompaint

clayhubler · Posted: Thu May 27, 2021 1:54 am Post subject: Prep for bottompaint

I'm going to reapply bottom paint on Hammerhead. The current paint is some kind of ablative paint, and it comes off easily. Since I don't really know what kind it is, and it doesn't seem to be adhered especially well, I'm going to scrub/ sand it off back to the gelcoat.

From my research, once you are down sanded gelcoat, you should do 2 coats of epoxy barrier, and then 2 coats of ablative. I am going to use the Pettit Hydrocoat.

I have quite a few areas where I have patched holes on the hull and transom, and consequently there is no gelcoat there. Currently only west system epoxy thickened with fairing compound.

Do I need to gelcoat these areas??? Or does the epoxy barrier coat effectively 'seal' the repair?

Thanks!

PaulNBriannaLynn · Posted: Thu May 27, 2021 12:19 pm Post subject:

I think your spot on with your planning. I wouldn't bother with the gelcoat, unless you don't want bottom paint at all. The epoxy should seal off the repairs. I don't sand all the ablative paint off. Ill usually blast with a pressure washer all the loose bits off, and then sand down and rough up the stuff that does not come off pressure washing. The ablative will adhere well to any exposed epoxy repairs or previous ablative paint sanded down. The epoxy bottom paint is a good idea if you are going to prep it all the way down to that level. Considering the extensive work you've already done on that boat, what's a little sanding to prep for a barrier coat at this point!

thataway · Posted: Thu May 27, 2021 2:30 pm Post subject:

Definitely remove all bottom paint, if you are going to put on epoxy layers. The epoxy is a far better water barrier than gel coat.

The reason for the barrier is to prevent osmotic blistering of the hull. Some would argue that they don't occur in colder waters. Unfortunately not true. But the incident of blistering on C Dorys is very very unusual.

After the bottom epoxy coats (you ant at least 20 mil), then wash well to removed any epoxy amine blush, and lightly sand--then the ablative paint.

clayhubler · Posted: Thu May 27, 2021 5:03 pm Post subject:

I assume west system epoxy is suitable for the barrier coat, even though Pettit sells an epoxy barrier coat that they recommend for use with hydrocoat?

thataway · Posted: Thu May 27, 2021 8:52 pm Post subject:

I have used West Systems for the barrier coat. You want to try and get 20 mil.