Re: Aluminum shear pins for keel

From: Bill Combs (ttursine@earthlink.net)
Date: Fri Jan 14 2000 - 23:05:16 PST


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> on 1/14/00 2:39 PM, Jim Nolan at panache426@hotmail.com wrote:

> Buy aluminum rod of this diameter from local metal supply (these alloys are
> common). Cut pieces to appropriate lengths allowing for holes for small
> cotter/retaining pins on ends. The pins hold the aluminum dowel in place in
> the keel trunk. The pins go on the outside of the keel trunk, where the
> dowel sticks through it.
>
> I think the aluminum is a better way to go over nylon because it is more
> controlled. The variability of nylon bolts is a bit scary. Also aluminum is
> easier to get than special nylon bolts. Aluminum should be cheaper too.
>
> Make sure you get the proper alloy because some alloys of aluminum are super
> strong. The dowels are better than bolts because the threads on a bolt put
> additional stress on the bolt, so the bolt may yield at a lower weight. The
> dowel has less uncertainty.

I caution you all that, regardless of the material used for the bolt/rod, a
mechanism must be devised to gasket the hole through which it is mounted. In
a goodly seaway, the pressure built up in the keel trunk when the boat moves
downward can create a regular firehose effect. I've seen a solid stream
shoot out horizontally with no bolt inserted and have routinely suffered
significant leakage around the bolt until I applied foam gasket to a couple
of fender washers and compressed them under each end of the bolt.

Regards,
Bill Combs

--
WWP 19 #439 (Aug 1987) "Ursa Minor"
Fort Walton Beach FL
ttursine@earthlink.net
http://home.earthlink.net/~ttursine



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