Bottom Painting

[GMaurer]

This winter, I'm going to have my boat bottom professionally stripped and painted. The bottom itself seems to be in great shape.
A friend recommended that a barrier coat(s) of 10 mils be applied, before the bottom paint.

Any thoughts on this?

Greg
1988 E28

[Frank Langer]

Greg, there are differing views on this. I think for an older boat (newer than mine, but still an '88), if it doesn't have any blisters by now, the hull is probably in good shape (not to say it won't ever have any blisters), so doesn't need major fix/preventive work. The concern with barrier coating an older boat is that there will likely still be moisture in the hull (there is general consensus that gelcoat is somewhat porous), even if you dry it out over the winter, there will still be some in the spring. The risk is that the barrier coat will trap this moisture in the hull, and potentially cause blisters. On the other hand, some argue that as long as it is mostly dried out (< 5% moisture) ie. if you tape a piece of plastic on the hull, leave it in the sun, and if no condensation shows up inside the plastic over a 24 hour period, it's probably o.k. to consider barrier coating. If you do coat it, ensure the right thickness (I think usually about 10 mls.) to achieve your desired protection.
There is lots written about this, so you may want to do your own reading.
Good luck and let us know what you decide.
Frank.

[Chris Glasspool]

Greg,
Part of the equation on this may be how aggresively you strip the bottom. Staying with the same type of bottom paint, or using a tie-primer might allow you to just get off the rough stuff, and only get glimpses of the gel coat. My understanding is that once the gel coat is fully breached or fractured as in sand blasting, then a barrier coat needs to be applied. Last week someone mentioned walnut shell blasting. If this is possible in your location then it sure sounded to be a fast and efficent method. I can't do this because of dust concerns. - Chris

[Steve]

Get a 3" carbid scraper with the long handle and go for it. Don't bother with the cheap steel ones. You will be amazed how easy you can strip with only a small amount of all-around sanding required. Collect the chips in a tarp, wear full eye and body protection, you'll need it! Its a bit time consuming, but worth it. We barrier coated, agree there is two camps of thought.. time will tell.

Steve e35-3