26 October 2011

The keel-hull joint.

This was the single most problematic fault with the condition of the boat as I got it and, as it turns out, one of the most easily remedied.  Sometimes the dumbest fixes are the best ones.  (See the post on ‘Reverse-Mooyock Technology’.)  The PO had perceived either cracks or actual leaking in the keel/hull joint and was able to arrange the the yard’s Travellift to hold up the boat so he could loosen the keel bolts and apply new bedding compound.  Unfortunately he did not know his ‘caulk’ from his ‘bedding compound’ and apparently went into the marina store and asked for ‘caulk’.  Now caulking is used on wooden boats, to provide a watertight seal between planks that may not planed perfectly straight or do not meet perfectly together. The secret is that the compression of the swelling planks squeezes against the caulking and makes it watertight.  (I have heard stories of Barnegat Bay garveys that don’t use caulking at all; the yellow-pine planks swell terribly, jamming edge-to-edge against each other, from the first minute it’s in the water and after about three days stop leaking altogether.  This is why yellow pine is NOT code for house construction; and it's why pressure-treated deck lumber, which is yellow pine, changes dimensions over time.)

The PO should have asked for bedding compound which is meant to be phenomenally strong under tensile loads, opposite loads pulling apart from each other.  The often-infamous 5200, properly applied to clean surfaces, will hold 700 pounds per square inch.  It's meant for holding on lead keels.  Don’t even consider ‘caulk’, polysulphide, silicone or other such nonsense for this role.  Unfortunately my boat’s PO didn’t know that.

After too long a time worrying about how to fix this, the solution hit me almost literally on the head.  I bought some lengths of little 1/2” steel pipe intending to have the boat jacked up and then set down with those pipes lying between the hill and the keel, propping it up so I could reach in there, scrape it clean and rebed to reassemble the boat.  One day adjusting the jackstands I realized that all this worrying was idiotic-- the boat without the keel weighs
only about 2200 lbs.  So I loosened all the keel bolts, taking the nuts up to the top of the threads leaving about 7/8” to work with, and then under the boat I went about screwing the jackstands up.  I even put a prop under the sloping forward edge of the keel to keep it from toppling over (which would be catastrophic; for how would I pick up the fallen keel with the boat still on stands above it?).  Every day I went down and turned the stands another turn or so.  One day I was turning the stand under the bow with my back to the boat and and I heard a rubbery stretching noise behind my head.  I turned about and saw the ugly caulk parting from the keel-- the boat had risen about 3/4” from just the stands alone.  Once I got everything aligned it was a very simple matter to pick out all the residue to put in new 5200.

I scrubbed and sanded and scraped till I had two very clean surfaces in surprisingly good condition.  But I couldn't understand why the opened slot between the hull and the top of the keel kept appearing to be more in front than in back.  I kept adjusting the stands and still could not account for it till a fellow yard rat suggested, ‘The keel’s probably falling over.’  Sure enough it appeared that
the keel was probably leaning forward, in spite of the prop, and just walking the boat forward on all the stands.  How far would it go?  I wouldn't wait to find out.

‘Right,’ I said
to my daughter there.  ‘Tomorrow we get the 5200.’

I bought two fresh tubes, and the joint took that and all the rest I had lying about.  I just pumped in as much as the opened gap would hold.  Then we let down the jackstands and about half of it oozed out.  That got all nicely puttied over the whole seam area.  I made backing plates of G-10 and installed them in the bilge, leaving a space between the keel bolts for water to run back to the pump.  To preserve the threads from the 5200 (which would have barred any future adjustment) I wrapped the threads in masking tape.  Since then it’s been adjusted a few times, mainly to satisfy my worry, and it’s been fine.

One day my cousin Dave had to move the boat to the other side of the yard.  I didn’t know this was going to happen and when I heard I dreaded finding some disaster about my keel-bolt fix. The hull’s flexing under the load of the keel when it was picked up had caused my new cabin-sole joists to part from the hull-- but the keel-bolt nuts hadn’t even been torqued up properly and the 5200 held the whole thing on for the jaunt across the yard.  So-- no more worry as to that.

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