Bill, I suspect you know my boat way better than I do. This morning I ground on the keel to hull joint on the rear and still don't see anything too concerning, but I will be reinforcing it.
But what I then did was start grinding the bottom again and worked to the center line and the assembly joint. That joint was very wet. To say that a river runs through it would be an accurate statement. I cleaned off about 8' of the seam and it was all very wet.
I assume these boats were hand laid up and if so with the heavy woven roving used there is a high probability that there are more than a few capillaries from this seam to the core area. Add some hydraulic pressure and you have a tiny and continuous source of water even through 6" of what theoretically solid glass.
I will be filling and then taping with 6 oz. glass this entire seam using epoxy resin. But I plan to leave it open until I don't detect any more moisture. I find it interesting though that the surveyor's meter didn't pick this water up. I don't recall seeing her use the sensor directly on the joint though and this is a very heavy section of glass in this area, not to mention 35 years of bottom paint and gel coat.
As I was grinding through the blisters I was also thinking about the fact that this exterior skin is only about 1/8" thick total. Some of the blisters must go half way through that section thickness so that doesn't leave much glass left to separate the water from the core and polyester resin is porous anyway, so it seems like there are more than a few ways that water finds it way to the core.
