Re: CB pivot (was Monel again...)

Gordon (hlg@pacbell.net)
Fri, 26 Mar 1999 16:50:02 -0800


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Apparently, the P15 CB pivot bolt is not as highly stressed as we imagine.
My 32-year-old, 3/8-inch-diameter iron (not stainless or Monel and not 1/2
inch like Dave's) CB did show some wear and some rust but looked like it
would still have probably outlived the boat. It appears to be a plain
hardware-store-type carriage bolt, not galvanized or plated. There is a
closeup photo of the bolt at <http://songbird.com/py/new/CBtext.html>. I
replaced it with a 7/16-inch-diameter stainless-steel bolt, washers, and
self-locking nut. The galvanized board weighed 65 lb and was in excellent
condition. I rewarded its long and faithful service with an SOS-pad
scrubdown followed by a couple of coats of hammertone gray.

My recommendation: if the bolt is not leaking or loose, leave it alone and
don't worry about it.

Harry Gordon
P14 #234, Manatee
Mountain View, CA

>Bernie,
>
>I recently spent a fair number of hours rebuilding the centerboard pivot
>on #1632. I am disappointed to say that it was largly a waste of time. I
>had the same concern about the centerboard riding on the threaded
>portion of a bolt and also the pivot on mine could be wiggled about in
>the holes drilled in the centerboard trunk. I also though it was
>leaking.
>
>Upon disassembly, here is what I found:
>
>The pivot assembly is covered with foam-in-place type foam and then
>glassed over.
>
>Inside is a 1/2" x 2 1/2" bolt, two fender washers and an aircraft
>(nylok type) nut. All the hardware was stainless steel.
>
>There was essentially NO wear on any of the metal parts. There was some
>rusty discoloration of the bolt threads where the nut engaged (crevice
>corrosion?) but the bolt did not appear to be compromised as to
>strength.
>
>What was more of a concern to me was the condition of the holes in the
>cb trunk. There was excessive clearance, most of it in the vertical
>axis, and it is not clear to me whether this was caused by wear or a
>result of fitting the bolt originally. I wanted to get a good seal
>between the bolt and the trunk and I didn't think that would be possible
>if the bolt was free to move that much (approx. 1/16") in the hole.
>
>Sooooooo, I made a 1/2" "pin" by cutting the threaded portion off of a
>1/2" x 4 1/2" bolt, coated it with paraffin, suspended it within the
>loose holes via a piece of wire from above and built up the holes with
>epoxy so that two holes, in perfect alignment, with essentially zero
>clearance were left after I removed the pin.
>
>I made a new pivot bolt by cutting down a partially threaded 1/2" x 3"
>bolt so there are no exposed thread inside the cb trunk, I put it all
>back together with lots of polysulfide sealant and .....
>
>Guess what, my boat leaks just as much as it did before. All this really
>tells me is that my leak wasn't originally the pivot after all. If it
>leaked less, maybe - if it leaked more, maybe. But it's the same old
>leak, about 1/2 pint per hour.
>
>Anyway, Sam Finlay and I had had numerous discussions off-list on better
>ways to design the pivot and really didn't come up with anything that
>didn't require some custom machined parts and even then some compromises
>in strength may have been necessary. I concluded that the original
>design was close to optimal and certainly practical, especially once I
>had figured out how to get rid of the exposed threads inside the cb
>trunk.
>
>But I would be being less than honest if I didn't tell you that the 12
>year old hardware in my boat was in fine condition when I removed it
>despite being used primarily in salt water and that the leak in my boat,
>although I suspected the pivot, appears to be coming from somewhere
>else.
>
>
>Dave Kautz
>P-15 #1632 Tilly Lucy
>Palo Alto, CA
>
>
>
>
>
>Bernie Johnson wrote....
>
>Got to figure out a way to stop that keel clonking around.....
>Keel hinge pin looks really mickey mouse. Looks like the hole in the
>keel plate rides directly on a threaded stud or bolt. Whole damn thing
>is glassed in as well. Bloody thing leaks a bit also...Redesign....need
>a sleeve (teflon?) riding on a smooth diameter (.375 dia. 316 s.s.
>bolt).