Sunday, November 13, 2011

By Michael

Our brand new RuleMate 2000 GPH bilge pump is wet and
corroded inside. Check out that circuit board! It was defective
in that the wire grommet wasn't properly seated. West Marine
says I can return it for store credit when we're in the States
next summer. Ironically, if the pump hadn't been submerged
in the water from our leaking tanks, we may not have
discovered this problem until we really needed the pump.
A lot has been happening around here lately and yet we are still in the same place and our prospects for getting out of here by the end of November are tentative. There are three things holding us back: chain plates, port lights, and water tanks.
The Chain Plates
I installed and bedded (sealed) the two new chain plates for the upper stays. The bedding compound I used is a popular 3M product called 5200, a polyurethane sealant with astounding adhesive properties. In fact, it adheres so well that ten years from now—when I go to remove and inspect these plates—I will likely curse myself for using this stuff. But no water must get into the joint, not a drop. Stainless steel, generally immune to the rusting and corrosion that plagues other iron-containing alloys, is subject to crevice corrosion and pitting corrosion. Both of these types of corrosion are apparent on the chain plates we removed.
Of course, corrosion weakens the metal. As I explained in recent posts (here and here), this could be really bad.
So pretty, I hate to re-install the teak
trim that hides it.
In our case, water found its way through the existing bedding compound, through gaps probably only a few micrometers wide. Some of that water remained in the crevice where the chain plate passes through the deck, and some found its way further down, behind the chain plate. In both cases, this water sat stagnant and over a long period of time broke down the oxide film that stainless steel needs to remain corrosion free.
I am going to wait five more days for the 5200 to set before I attach the new upper stays. At this point, I will remove all four of the chain plates for the lower stays. (I can’t remove the lowers sooner because they are holding up the mast while the uppers are not attached.) If the lowers are okay, I will reinstall them. If they are corroded too, we will wait for new ones to be fabricated.
The Port Lights
We can sail away without installing the port lights. But I don’t want to. The existing port lights don’t open and you can’t see through them as they are opaque. The new port lights are beautiful stainless works of art that provide additional visibility and ventilation. Installing them at the dock will be easier than doing so at anchor and the sooner we get them installed, the sooner we clear these boxes out of the cabin. Windy isn’t as adamant about doing this before we leave, so we’ll see.
In this picture, you can see the pitting corrosion on the back of the old chain plate and in the
background, the rust staining on the fiberglass against which the plate was held for 33 years.
Water Tanks
They leak, both of them, a lot. We have decided to replace them here in Banderas Bay. This will be a big and disruptive project. These leaking stainless steel tanks are actually replacements of the originals. These were made in San Carlos, Mexico in 2008 using a thicker wall to prevent just the problem we are having now. Apparently, either the metal used was flawed or an inferior grade or the tanks were installed in such a way that crevice corrosion, pitting corrosion, or some form of electrolysis attacked them. Interestingly, I don't see any evidence of rust staining in the bilge where the water runs out from under these tanks.
Once they are out, we will have a better idea of what is causing the leaking. To get them out, I’ll remove the dinette, the flooring in the main part of the cabin, the holding tank, the floor joists, and finally the tanks. The floor joists are attached to the hull beneath the settees with fiberglass tabbing. The tanks are glassed to structural members down low. I will cut all of this away and then learn all about glass and epoxy when I put them back in.
We strongly considered two other options for storing potable water aboard: building integrated fiberglass/epoxy tanks and using flexible water tanks. Though each promises a less disruptive solution to our problem, neither matches the permanent (in theory), non-toxic solution of new stainless steel tanks.
I don’t have an estimate from him yet, but I was very impressed last week when I visited the machine shop of Hilario Gonzalez in Puerto Vallarta. Several people have recommended several machine shops around the Bay, but Gonzalez’s name came from a few independent sources I trust. He will likely make our new tanks.

I will write more about this project as it progresses. I start tomorrow.

There is no promise I could not have exacted from Eleanor and Frances in exchange
for letting them have one of these pups. Unfortunately, the answer was no.


  1. Michael,

    For the water tanks... I would not go metal and I would not go with integral. Metal breaks down and gets destroyed by a host of problems and integral ones are good but asking for trouble if something bad ever happens. I suggest looking into polyethylene tanks. You can probably find someone to mold them up to spec pretty easily.


  2. Although this all sounds like an endless amount of work, knowing you, you are thriving on the work and the mystery . . .

  3. I, too, was going to ask if you had considered polyethylene tanks. Sounds like such a lot of work to get those metal tanks out. You'll be able to build a boat from scratch when this is over.


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