My boat is made with fiberglass tanks for potable water. It is coated with CeRAM Cote 54, which is an epoxy-based coating specifically designed for potable water tanks.
How large are these tanks... if they're more than 10-20 gallons, you really need to have vertical baffling inside them to help reduce free surface effects and sloshing. I would cut the metal top off completely, rather than try and clean the metal to get a good bond. One real reason you don't want to deal with trying to bond the metal to the fiberglass is the difference in their expansion and contraction characteristics.
That may also be a problem for the tank itself. One possible solution is to place a layer of foam down inside the existing tank, and then laying up the fiberglass tank over the foam. The foam would help prevent the metal tank contracting from damaging the tank and help support the fiberglass tank when the metal tank expands.
Trying to install a tank into an existing tank, that probably has internal baffling, will probably take more time than cutting off the lid, gutting the tanks and then laying up the new tanks.
Finally, unless your boat is homeported on the island in question, you may not have to pay customs duties on imported tanks, since they are going to a yatch in transit. Generally materials to yatchs in transit are not considered imported...since the yatch doesn't stay in the country in question.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
If you're new to the Sailnet Forums... please read this To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Still—DON'T READ THAT POST AGAIN.