Sunday, October 21, 2012

Back to working on projects

This is a boat project post.  Its what I'm doing now.  No interesting recent sailing news.

My comfortable home, taken apart a little...

Since returning to Seattle on August 14th, my main occupation has been working on boat projects.  Its now Oct 21st and the beautiful summer Seattle has had has moved along to make way for the weather that follows summer.  From time to time I like to recap what I have worked on over the past little while in order to make myself feel better about any progress that's been made.  So.  Over the past two months, I've worked on:

  • cleaned the boat inside and out.  Mildew had started to form on many of the interior surfaces during the latter part of my Hawaii->Seattle passage.  Cleaned this up
  • changed the engine oil and transmission fluid
  • polished all the boat's exterior stainless steel.  Unless you rinse it in fresh water from time to time (via either a dock hose or rain) it just starts to rust.  It was.  Now its back to being in good shape
  • varnished all my exterior teak
  • compounded and waxed the hull
  • cleaned all my sails (put them up, washed them down, let them dry, re-stowed.)
  • inspected the rig (all good as far as I can see.)
  • figured out why my zinc's were being eaten so quickly and fixed it.  More on this later
  • took out my water maker as there was a small leak between the membrane housing and the stainless steel body it was attached to.  Sent it back to Katadyn.  Katadyn fixed it under warranty, no questions asked, and returned it to me 6 weeks later.  I paid for the shipping one way, they paid the other.  Good service
  • brought down my wind indicator and returned it to Raymarine (who had bought Tack Tick.)  They replaced the unit under warranty and have returned a new unit to me.  The new unit is installed and works.  I hope it keeps its charge longer than the old unit, I'll report when I find out (which probably won't be for quite some time...)
  • decided on a floor finish I'll use to refinish the cabin sole (Daly's FloorFin.)  Tested the finish on a board along with another product and subjected them to some abuse.  It looks good.  More on this later
  • took out the galley sink and re-installed it 3" higher.  More on this later.
  • took out my galley stove (a Force 10) as the two gimbals it swings on were not properly adjusted (my fault from years ago) and were wearing.  More on this later
It seems like much more than this was done, but I haven't logged all of my projects and some of them have faded from memory.  I'll expand on a few of these in more detail.  I'll talk about the sink project in a separate post.

The watermaker leak.  It was small, but there shouldn't be any leaks at all.

The zinc's

My boat has two zinc's, one on the max prop and one at the base of the gudgeon (which is located at the base of the skeg (which holds the rudder.))  Something changed in my preparations for departing on my first cruise which caused the zinc's to be eaten much more quickly.   By the time I left Sept 2011 on my first cruise, the zinc's were lasting 6 to 8 weeks.  This came as a surprise to me.  I was not plugged into shore power at all during my entire stay in Hawaii, and yet the zinc's were lasting 6 to 8 weeks.

I read up on galvanic corrosion and bought a reference zinc (a half cell) that can be used to measure the potential difference between grounded metals onboard with the seawater outside.  In a nutshell, all connected dissimilar metals immersed in seawater form a battery, and the less noble metal is consumed in a electrochemical reaction.  Since many dissimilar metals are connected (through hulls, the engine, the prop shaft, the prop, grounding plates, etc) and are also immersed in seawater, you need to provide a metal that is the least noble so that it can be consumed rather than one of the other pieces (the engine, prop, etc.)  Zinc is a metal that is very low on the noble scale for metals and is what many boats use to protect against galvanic corrosion.  So anyway, after buying the zinc half cell, I could measure something so that when I started changing things I could measure to see if what I just did made a difference.  The initial number, the bad number, was 390mv which was too high.  (This measured the potential difference between my boat's ground a the reference zinc half cell in sea water.)

One of the changes I had made to the boat before leaving last year was that when installing the SSB, the fuel tank was also out of the boat and I saw the keel bolts exposed and decided to incorporate the 6,200lb lead keel in the SSB ground plane.  This in effect joined the keel to the boat's ground plane and meant that the zinc was not only protecting the engine, prop shaft and everything else, but it was also trying to protect the lead keel as lead is much higher up the noble chart than zinc.  When I cut the ground strap to the keel I measured the ground potential again and it fell to 160mv which according to what I read is a good number.  390mv was high, 160mv is within a safe range.  So its a bit of a mystery, but I believe the boat should no longer consume the zinc so quickly.

[Update Oct 23rd]

It was pointed out to me that the SSB RF ground shouldn't have been coupled with the boat DC ground.  i.e. cutting the connection to the lead keel shouldn't have affected the boat's ground.  I agree with this, the two should be separate.  I have been planning to do some work on my SSB system anyway and part of this was to remove the keel ground - so rather than try to figure out how to properly incorporate the keel now I just removed it from the ground and solved two problems at once.

The reason I planned on removing the keel from the RF ground was that when I installed the copper ribbon to the keel bolt, I didn't glass the ribbon in or otherwise protect it from corrosion in any way.  Oops.  This means that it is slowly corroding and at some point would no longer provide a connection.  I didn't want to be leave Seattle next year with a decent RF ground only to have it slowly degrade over the next few years and end up trying to fix it while I was in the tropics.  So I cut the connection now and will solve the RF ground problem now, in a more permanent manner.

[End of update]

The cabin sole

Over the past three years, the cabin sole's finish has gone from marginal to worse.  I decided to fix this while I'm in Seattle and have made a start on it now.  I first applied two different floor finish products to a board and tested it for a little while.  I got it wet and tested the finishes traction.  I scuffed it up, scratched it and tried to re-apply the finish to see how easy it would be to fix up problems in the future.  Daly's FloorFin appears to be the better product and is super easy to work with.  It was easy to get an initial clean smooth finish and is also easy to touch up later on.  I'm planning for the day when I accidentally drop things on the sole and scar the finish, as that's what seems to happen.  FloorFin touches up very easily.  I've learned that planning ahead for maintenance is an important part of any project, as on a boat, something you fix doesn't seem to stay fixed forever.

I used a heat gun to strip the old finish off one small region of the cabin sole - the area underneath the nav table.
Starting to strip the old finish - a bare patch on the upper level has been scraped out.
After taping and sanding, I applied three coats of FloorFin.

Old finish on left, new on right.

The grain of the wood is much more clear now, the wood looks much richer.  I haven't yet continued the project from this initial test, but after I get through the work I'm going to be happy with the result.

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