Hull condition

[treilley]

Hauled the boat for the first time Monday since I bought her in June. Absolutely no signs of blisters. No signs of keel to hull joint and no weeping. I have reason to believe the keel, hull and rudder were faired by a previous owner. If so, I would imagine that a barrier coat was applied also. I plan on walnut shell blasting the bottom paint(10 layers) but I want to preserve any barrier coat. Is there any way to tell if I have a barrier coat by doing some scraping or other type of paint removal on a small test area?

 

[NateHanson]

How is it that you know the number of coats of paint on the bottom, but not whether there's barrier coat under there?

In my mind, walnut blasting requires subsequent barrier coating. While it's a fast and fairly gentle way to remove bottom paint, I wouldn't trust the perfect integrity of gelcoat or barrier coat that's just been walnut blasted.

If the bottom looks to be in smooth, intact, and well-maintained shape, perhaps just sand the bottom and put on new (ablative) paint. I'd only walnut blast if I were planning a total bottom overhaul.

Nate

 

[treilley]

I should have said at least 10 coats. The previous owner applied a coat of paint every year for 9 years he owned it and it had several layers when he bought it. The paint has chipped off in many areas and the bottom is very uneven(from paint not shape). I will be racing this boat and need to remove the layers of paint but keep the gelcoat intact.

I am wondering about the pressence of barrier coat because the bottom is so uniform(other than the thick flaking paint). If the bottom is blister free because the gelcoat is in good condition than I plan on applying AF paint only. If it has a barrier coat than I want to preserve it. The fact that a BC is usually much tougher than AF paint, I should be able to adjust the pressure of the blaster to preserve the BC and then apply my AF right over it. I will probably just carefully remove some layers with a scraper to determine if there is BC.

 

[Loren Beach]

If your chosen method of paint removal would not hurt the original gel coat, then an epoxy barrier boat also would be impervious to the same force.
If the prior owner states that there really is a barrier coat under all that, then presumably he ought to know... otherwise there is probably factory gel coat. The experts that I have talked to say to keep the original gel coat forever, unless severe blistering requires its removal.

Note that if you have gone this long without significant blistering, then whatever is under that paint IS doing its job, and would be best left alone, IMHO.

My .02 worth...
YMMV,
Loren in PDX

 

[NateHanson]

Yes, so paint removal is necessary. However, I'd still roll on a few coats of barrier coat after blasting, personally. It's cheap insurance, and the blasting does slightly abrade the gelcoat.

 

[treilley]

I was looking at the hull this morning and I found a spot where the paint flaked off from power washing and that appears to be gelcoat. It is very smooth and white in color. I cannot imagine power washing removing BC without sitting on one spot for an extended period of time which I did not do.

Now I need to decide whether or not to use BC. It adds weight and also is not as smooth as the gelcoat. I have spoken to a couple of surveyors and they say I should not need it if there is no problem now. They also do not think the blasting will do any harm to the gelcoat. On the other hand, adding a few coats may be the safe way to go. Although, I think you really need to build a certain thickness for the BC to be effective at all.

 

[Frank Langer]

Just a few additional thoughts for your consideration:

1) The makers of the main barrier coats are very specific about correct application procedures and thickness to achieve the desired results, so this is one time you may want to follow instructions carefully if you proceed with it.

2) I have always read that all gelcoat is somewhat porous, and does absorb some water, even if there are no blister problems. Therefore, assuming this is true, if your boat has been in the water, there is a good likelihood that your gelcoat contains some water. A barrier coat would seal this into the gelcoat, which may not be a good thing.

Good luck, whatever you decide. Keep us posted...

Frank.

 

[Geoff Johnson]

Not to mention the moisture that penetrates the gelcoat from the inside and can cause blisters:

http://www.westsystem.com/ewmag/other/ventilation.html


My boat has no blisters, which I attribute in part to the fact that it is out of the water 7 months a year. I am concerned that adding a barrier coat now might simply seal in moisture that would otherwise evaporate. If it ain't broke . . .