tank access

[andyvou]

HELP!!!!!
As said in a previous post, I have removed the 135 gal tank on my 1983 26ft bertram. I plan on relining. I peeked inside the tank via an inspection plate that also holds the fuel level and was surprised . I assumed the tank, which is in the shape of a low, fat tee, was built like a box----three sides and the bottom formed, baffles glassed in then a top put on. Inside the tank are smooth sides and a metal grid system riveted in place top and bottom. I had planned to cut the top a couple of inches below the top, remove the top, do what I need to do and then reglass the top on. Now I don't know what to do. Can anyone explain how a bertram tank is built and can anyone suggest how to get access to all the areas inside the tank.

Thanks

Andy

[Rawleigh]

I've heard that some tanks had riveted in baffles. The rivets were covered with fiberglass and need to be ground out. The only one i have cut into has fiberglass baffles that are glassed in and bedded in putty at the top. You will need some sort of wire rope saw to cut through the baffles.

[frank price]

Andy,
The tanks were made like a shoe box. One layer of 1/8" glass , then the baffles were riveted in, then the lid glassed on and then another layer of 1/8" glass , totaling 1/4" . The mould was on the inside, as you can see, at least on the later tanks. The early tanks were made with the mould on the outside and rough insides to make the tank look pretty from the outside.
According to Lee Dana, when Richard Bertram was involved in the actual building of the boats, he preferred the smooth outside purely for aesthetics.
I hope this helps. I' ve often thought of doing just what you are with your tank but wasn't sure how to cover the seam on the inside when you re-install the top, since I don't think you have much of a time window to re-coat .
As an aside, I made a stainless waste tank on my last boat(not a Bert) and coated it with por-15.So far, no problems as far as I know.
Frank