finding hull blisters -boat has been on land for several years

I have a 34' 1978 Silverton that has been sitting on a trailer for several years (yes, overloaded trailer, but I can move it around the yard that way). I'm getting ready to work on the bottom, get it ready for bottom paint. I want to coat it with Interprotect epoxy barrier coat before the bottom paint. Do I need to find any blisters that might be there? If so, how can I find them if they've dried out from sitting out of the water so long?

 

The blisters still would stick out slightly. Spray the hull with high pressure water. This causes loose chips to fly off from the worst blistering.
Then grid off the underbody in roughly 2 ft squares to keep track of where you've already examined. Shine a light askance to highlight every imperfection. Pick open all blisters found with tool of choice.
My method, but you're welcome to it.

Alan

 

Are blisters something you can hear by dragging something over the surface, like a screwdriver or coin, and the blister will sound "hollow"?

 

Thanks Alan. I'll let you know how it turns out. Can you tap on them and hear that they are hollow? I'll try that too. I may wait until the end of hurricane season as the boat is on a trailer now, and I'll set it up on blocks to work on the bottom.

 

Careful gridding makes organizing your inspection easier. They do sound hollow, or dull, lower frequency. Use common sense, and you'll find them. Every boat is different. Some boats are horrible--- very obvious, like a rash.
Those are the ones that have to be ground down completely and built back up again and faired. If you have to look hard for them, that's a good sign, if your boat has any age on it.

 

Blisters will bleed with vinegar smell. Here's the man for it. http://www.yachtsurvey.com/blisters.htm

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