RE: Aluminum shear pins for keel

From: Eric Johnson (etj@nwlink.com)
Date: Fri Jan 14 2000 - 14:22:21 PST


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> It turns out that some aluminum alloys have about the same shear
> strength as
> nylon bolts.
>
> It appears that a 5/16 bolt is easy to get through the hole for the keel
> lock down on the P-19.
>
> An aluminum dowel/rod of 5/16 diameter used as a shear pin to
> yield at 1000
> lbs of shear would have to have a shear rating of 13,000 psi.
> This yield is
> 2.5x the weight of the keel, and less than the weight of the boat.
>
> The following alloys have the required shear:
>
> Aluminum alloy 6061-0 shear of 12,000 psi
>
> Aluminum alloy 6063-T1 shear of 14,000 psi.

<snip>

Great research, jim!

A couple thoughts:

* wouldn't using aluminum be inviting galvanic corrosion? Perhaps an
undersized steel pin would work better.
* Is there even one documented case of a P19 turtling with the board down?
Even the one case we know of where the P19 was knocked over with daggerboard
up, did it even turtle?

Psalm 2:9 seems appropriate to this discussion: "You shall break them with a
rod of iron, and dash them in pieces like a potter's vessel" :)

 -Eric Johnson 1988 P19 #461 "Victoria", Bothell, WA (daggerboard held down
the old fashioned way, with gravity :)



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