Tonyb, Bietzpadlin has deep,slack bilges
so I built to fit in the space beneath the floors. I made the shape of the tank of mill finish aluminum flashing. The ends were shaped around 3/4 inch plywood cut to fit the profile of the bilge at the station that would be each end. Just hammered flanges on the cut blanks for the ends and discarded the plywood. Then I riveted the sides and top and bottom to the ends and glassed it with about four layers of chopped strand mat, ground out all the bubbles and patched the holes. Then I cut the holes for the pipes with a hole saw. The inlet pipe is cut at an angle on the end so that if it were a solid it would form a blunt wedge, the flats look at the sides of the tank. That pipe starts at the forward top of the end and touches the bottom aft end. The vent pipe follws the same angle but only enters the tank by about an inch. NO flanges. CSM is wonderful stuff because when you wet it out the fibers will slide over themselves and let you coax the stuff into any shape you want. about 4-5 layers of mats pushed into place with a chip brush and packed with a roller and I had a tank. I let it cure completely, ground off the meathooks and filled it with water to check for leaks and volume. For connections I just glued on the adapters for threaded hose barbs and I had a tank.
