New bottom paint, old barrier coats?

[kappykaplan]

what's a 'grill block?

A block of stone traditionally used to clean grills. Google is my friend!

 

[Sailfanatic]

Sounds reasonable but i wonder how may boats are soda blasted at high cost every ten to twenty years. After soda blasting comes two or more two part barrier coats then bottom paint that must be applied in a norrow hot coat time frame. Should ablative paint ablate away fast enough to prevent build up?

Ablative paint can ablate enough to prevent buildup, the problem is boats which are only on the water for six months and then get a full coat each year, are likely to accumulate paint buildup...
til flaking sets in. You can see this effect right along the waterline where the paint does not ablate very much.
You can battle this situation by painting the bottom only when a base coat shows, or at least try skipping alternate years.
If you strip your bottom, I would not remove a barrier coat that is in good condition. If you strip a barrier coat you may open up any repaired areas under the bottom coat, requiring you to re-do the repairs. I had this experience on a 36' boat whose barrier coat covered an extensive blister repair. Blasting the barrier off opened the edges of all the blister repairs, requiring re-filling them and extensive sanding. Don't disturb a working barrier coat.

 

[njlarry]

Good advice but how fo you blast off the layers of paint and not affect the barrier coats? If the old barrier coats are ok would it be better to use a primer or one more barrier coat under the new bottom paint?

 

[Sailfanatic]

Good advice but how fo you blast off the layers of paint and not affect the barrier coats? If the old barrier coats are ok would it be better to use a primer or one more barrier coat under the new bottom paint?

The professional who blasted my last bottom could control how deep he went, after doing part of the bottom he called me and reported there was a barrier coat and asked if I wanted it removed, I made the fateful mistake of saying to do so. If the existing barrier coat ends up looking good, I would just paint over it. If its roughed up by the blasting, then add a coat or two of the same material.