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Osmosis in integral FG water tanks
I own a 1972 Hallberg Rassy RASMUS 35.
I have recently completed a major epoxy barrier-coat repair to the entire bottom of the hull. The gel coat was in very poor condition and had to be completely removed. The hull had a high moisture content and I let it dry for a year before doing the epoxy repairs. I am satisfied with the exterior repairs.
However, an inspection of the integral freshwater tank revealed numerous very small blisters on the inside. These may have been originally caused by migration of water from the outside of the hull. Water may have also then been migrating from the fresh water tanks into the hull.
Now that the hull is dried and repaired, it is this second possibility that I wish to prevent. I am concerned that filling the fresh water tanks "as-is" will lead to moisture getting right back into the hull laminate.
Unfortunately, the design of the Rasmus is such that I cannot get access to the entire inside surfaces of the tank. The two inspection ports only allow limited access to the starboard side of the tank. The shape of the tank would make it very difficult to sand and epoxy-coat even the starboard side. The internal baffles block all access to the port side of the tank. The baffles are glassed in.
To get access to the port side of the tank, either the baffles would have to be cut out or additional inspection ports would have to be cut into the fiberglass flooring under the settee area and in the bottom of the shower sump area. Cutting out the baffles would still leave the port side of the tank VERY difficult to reach for cleaning, sanding and epoxying. The floor of the shower sump appears to be a raised floor above the tank top.
I am also considering flexible bladder tanks. The baffles would need to be removed. I would still be left with a very difficult (if not impossible) task of securing the bladder tanks down on the port side.
I am looking for any information that can help me make a decision as to how to resolve this whole issue. If anyone out there has faced and solved this problem, I would greatly appreciate any feedback. Has anyone installed bladder tanks? Has anyone sanded and epoxied the inside of the fresh water tank? Anyone cut out the baffles? Anyone added port-side inspection plates in the settee area? What about in the head floor? Is it a "double" floor? Do the baffles provide any structural stiffining to the floor and hull? Would cutting them out weaken the floor/compression post/bulkhead? Has anyone used any kind of "spray-in" coating to seal the inside surfaces of the tank? I want a solution that is structurally sound, relatively easy to implement and that is "potable water" safe.
I know some of these questions are specific to the Rasmus but would appreciate any feedback.... Thanks.
Rasmus 35, 1972 (hull #135)