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)
Osmosis in integral FG water tanks
Hi, Steve - I have a few thoughts I can share with you. And I''m sure you are posting a similar thread on the HR owners site http://www.classic-hrs.com/ altho'' you might also consider posting on the UK site http://www.hroa.co.uk/discus/ as there are a number of Nab 35''s/HR 35''s over there.
It sounds like HR added some fiberglass panels to the cabin sole since our 1975 Rasmus was built; we could pull up individual wooden floor panels and expose the entire subfloor, bracing, tank access, etc. And our experience does answer - sorta - one of your Q''s: our hull had zero blisters even tho'', when I pulled the tank''s one large access plate off (fiberglass panel, gasketed & bolted all the way around), I did find some minor blistering on the tank''s gelcoat (which only makes sense). So...at least at that point in the boat''s age (15 years), tank blistering hadn''t (yet?) caused a problem. OTOH I can tell you I just spent time with a shipyard owner who told me this is one of the issues they face when peeling and Hot-Vac''ing blistered fiberglass hulls. They look for concentrated blistering in areas where the integral water tanks exist and, if they find it, then they go after the tanks as well. (You might look closely at some old photos you have or otherwise reflect on what hull blistering you found before starting your project. If you didn''t see this localized, increased evidence of blistering, you could consider skipping tank repairs totally). It''s also important to remember a yard is motivated by two things you are not: they have to warranty their blister repair job for 5 years and so want to eliminate as much localized failure possibility as they can, and more work means...well, more work and more billing. Even a reputable yard such as I''m referring to has no disincentive to recommend add''l work. You can afford to be more discriminating in whether to commission exhaustive tank work or not.
Personally, I think your lengthy description of the difficulty of accessing all of the tank has answered your own question. It sounds like you''ve been very thorough in your hull treatment process, and I can appreciate you want the overall quality of the repair to be retained. But afterall, it is a boat...and not a terribly expensive one, either. And you own it presumably to sail it, not work on it (altho'' my wife would laugh at ME for saying that). Were I in your shoes, I would go about the business of opening the portion of the tank I can reach sufficient for a good repair, dry out the tank and execute a repair on the starboard side of the tank, thereby limiting the *potential* for moisture penetration to only one side of the hull. And as an added sanity check, consider for a moment just how little hull area is adjacent to the remaining tank area - it''s very small relative to the overall surface of the hull.
WRT your question about bladder tanks, when we left Annapolis for the Caribbean, we felt we needed more than the 50 gals of water in that one tank (no, it wasn''t 60...) and so we chose to add two bladder tanks. This is one of the best things I did to the boat for cruising purposes, altho'' that may not be in your plans. I put a 10 gal bladder under each cockpit locker''s sole (removed the ply sole sections and slipped the bladders under the transverse supports). This uses space otherwise unused and puts the weight right where you want it. I ''T''d a supply hose from each tank into the central main fill hose to the main tank, planning to use gravity to allow the bladders to drain into the main tank, installing a ball valve for each supply line. I did not put effort into installing fill hoses on each bladder as I thought I''d fall back on those bladder tanks infrequently, so I had to gain access to the bladders each time I filled them. As it turned out, this worked well for us but it''s an inelegant approach which I''m embarrassed about a bit in retrospect. The bladders could not be totally filled (due to encroachment of the transverse supports on the swelling bladder shape) but we probably got an extra 18 gals of water aboard using this approach. I realize this isn''t the purpose for which you asked your question, but mention it in case it is of use.
You no doubt know the 80/20 rule. IMO you''re now working the last 1-2% of the blistering issue and I encourage you to do what you can to wrap up the project. I don''t think water tank contamination will be likely given the thickness of your hull, you can remove water from the tank when the boat is left idle (winter, or lousy sailing weather periods), and you can seal at least some of the tank, anyway. In short, worst case: you will have a small problem that will take an extended time to appear and you can take other measures to mitigate it. Best case: there is no problem.
Good luck to you.
Osmosis in integral FG water tanks
Thanks for your detailed and thought-provoking reply.
I have owned this "classic" for 22 years, am happy with her and hope to keep her for another 10 years of sailing. Twelve years ago, it became clear that the hull was high in water-content. Small "weeps" of white would show up on the hull after haul-out. A surveyor checked the hull and advised that there were no structural blisterings or delaminations, that the thick layup of the HR would probably last as long as I wanted to keep the boat, and that I should just do minor epoxy "cosmetic" repairs of the "weep" spots each year -- keeping an eye out for bigger problems developing. That''s what I have done for the last 12 years -- with no structural problems becoming apparent. As you say, it is just a boat.
This last year, I decided to start on a semi-major refit, starting with the epoxy barrier coat. Over the years, I have done all the work on the boat myself (except for the engine overhaul done in 1993) and enjoy working on her as well as sailing her.
When I took the bottom paint completely off (changing to a different bottom paint system), it became clear the gel coat was shot and the resin in the laminate was being washed out.
Again, no major blisters or delaminations -- just resin-starved fiberglass mat. So I removed the gel coat and rebuilt the whole bottom: dremeled out the larger voids, sealed and filled them, then two coats of epoxy sealer on the entire bottom, two coats of epoxy filling/fairing on the entire bottom, six coats of epoxy barrier coat, many new thru-hulls and seacocks, three coats of bottom paint. It was only about $3000 in materials but 5 weeks of hard and satisfying work.
I had hoped someone out there might have a "magic bullet" for shutting the door on that last part of the 80/20 rule! I appreciate your thoughts, though. Maybe I''m being a bit too concerned with the ingress of water from the fresh-water tank. As you say, it is a small part of the hull surface and I probably can effectively reduce that by nearly half if I repair the starboard side of the tank as best as possible. If I cut an access hole under the settee area and build a fiberglass cover similar to the starboard ones, I could probably repair 60 to 70% of the tank surfaces.
Probably good enough for another 10 years!
Again, thanks for the sanity check!!
I have a 1974 rasmus and I wondered what became of your water tank problem? And how has your bottom barrier coat held up? I am in the middle of a complete redo and want to know as much as I can. Also, my boat has a gouge that has been filled down the bottom centerline from the bow waterline to the bottom of the keel. I can't figure out what has caused it. Couldn't have been done during manufacture, do you think? It's about 5/16 inch deep and a 1/4 inch wide and I am concerned I may need to grind back some glass and relaminate for strength purposes. Any ideas. Thanks for any info. Pat Sixbey
This thread is over two years old.. and likely not to get a response anytime soon. Please don't revive old dead threads, as it is considered poor net etiquette.
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