May 2, 2010

Don't drink the water continued

After tearing into the water tank, I discovered - blech.  Rot, and lots of it.  The tank has 4 internal baffles, considerable overkill for a 7' long tank.  Each one of the baffles had a cleat on top to support the tank top.  And each baffle was starting to show signs of moisture damage.  The cleats (a 1"x1") were mostly spongy and totally soaked.  Obviously they hadn't been coated with enough epoxy because the baffles themselves were in much better shape, but all wet.
 

The suction point for the tank is not quite at the bottom - Maia and I had to bail out the few gallons left after the pump sucked dry.  

Then we find this mess (at both ends of the tank).  These end bulkheads keeps the water in the tank  - and these were very spongy.  I'm surprised they weren't leaking.  The solution is to tear away all the old rotten or spongy wood and apply a plywood doubler patch over the squishy area.  Then coat liberally with several coats of epoxy.  It has to be multiple coats to make sure no pinhole leaks occur.



Out comes my favorite tools for this endeavour - a 1" chisel and a hammer.  It allows you to (carefully) peel off the tabbing from the wood baffles and the hull without damaging the underlying laminate.  It is also a lot less messy than an angle grinder.  If I was working on this tank with nobody aboard the angle grinder would have come out, I would have tented off the rest of the boat with plastic in the work area and had at it.  But we are living aboard and the noise, inevitable glass dust escaping, and general unpleasantness of grinding glass means the slower chisel is the way to go.  I got good enough by the end that I was peeling off strips of mat tabbing a foot long.  
The hull internal laminate is in good shape by the way - a few osmotic type bubbles but nothing to worry about really.

You can see the white patches of mat where the baffles were located.  Each baffle took about 2 hours to totally clean off.  New baffles are sitting on the foredeck with the first couple coats of epoxy on them.  Di is coming home tomorrow.  Better keep at it...

11 comments:

Seven C's said...

familiar with that wood chisel and fiberglass! A lot of work to replace the baffles in the first place, but they should last many, many years when you are done.
I hope to resume working on our boat soon and get it sold soon. Or if not sold, install a roller furler and start leading more lines aft at the least.

boatbaby said...

Dayum! That is quite the undertaking! nicely done Ev!

arb said...

Good work Evan!

Jeff said...

If that's your drinking water tank, consider getting some food safe coating for it instead of epoxy. I was going to build my water tank like that as well, and I learned that the epoxy that you generally use for boat building isn't safe for drinking water tanks.

I really enjoy your blog!

Jeff

Diane, Evan and Maia said...

Hi Jeff,
The problem with epoxy is the hardener contains BPA (the chemical in plastic that made the news so much last year.) It's pretty ubiquitous. The best option we're finding is to go with a resin rich mixture in the hope of binding up all the particles. My guess is there are very few completely safe coatings out there and our otpions are pretty limited in our location.

Did you find any alternatives?
cheers,
Diane

jeff said...

Yeah, I hear you about it being hard to find info out about what's safe. I did find a drinking water safe resin, but I ended up just buying a prefab tank. I'll see if I can find that stuff again. You could do all your work as is and coat it with this stuff and be ok.

btw, I just spent a week sailing with Richard Woods, the designer of your boat. :)

jeff said...

ok, I didn't find an actual product, but another boater that did something similar. It was a couple years ago that I was researching it, and now I remember that this was the same place I got my information back then.

http://www.atomvoyages.com/projects/watertank.htm

I've also heard of putting boiling water in to heat it up make sure it's fully cured before adding drinking water. When I talked to my suppler about that method, he said there's still no way to mix it thoroughly enough to make sure nothing will leech into the water, but it sure can't hurt.

Diane, Evan and Maia said...

Yup, we're planning to hard cure in the heat before using the tanks. The epoxy we are using was considered tank-safe less than two years ago and the BPA leaching levels should be fairly low. It's not ideal, at all. But nothing is on a boat. I'm pretty sure the prefab tanks (the plastic ones at least also will end up with BPA or other hormone disrupter issues, it seems to be the fact of plastic.)

Cool about Richard. How's he doing?
Diane

jeff said...

Yeah, I hear you about the plastic tank being not so great as well. I'm unusually paranoid about these things, so that doesn't help. :)

Richard and Jetti seem to be doing well. We had a great sail from Green Turtle Cay in the bahamas back to Florida.

karen said...

Hey! wanted to say thanks for getting updates to our parents - we are in Nuku Hiva safe and sound!! just checked your blog and Matt wanted to put in a word about your water tanks since we made ours out of plywood/fiberglass/epoxy too. Don't know if it's too late but Matt read a West bulletin sent out a few years ago saying that the West system epoxy mix should have a modified ratio in order to make it healthy/safe. The mix should be 6:5 resin:hardener (slightly resin rich). You should post-cure it at an elevated temperature using a worklight or other heat source. When mixing, West System recommends two mixes - i.e. mixing the stuff in a second bowl before application to ensure complete homogenaity (sp?) and reduce any possible toxicity of the epoxy. Anyway, he has the document and we can email it to you if you want to look at it (need your email though!). Our watertanks have sooo much epoxy on them because they were one of the first fiberglassing jobs the guys did, so hopefully we won't have to re-visit this issue anytime soon! but we feel your pain. - Matt & Karen (S/V Syzygy)

karen said...

um, ok, so i totally didn't read the other comments first! haha sounds like you guys are on the right page, sorry for the repeat advice! hope all goes well!