[Public-List] Mast Beam Repair

[John Birch]

The other issue with Resorcinol, which is the glue they used, is that they 
tended to use red oak which has a lot of acids in the wood. Laminating the 
beam with epoxy, over time, I suspect would have the same problems.

If you really like the look of the wood, suggest cutting it lengthwise and 
sandwiching the aluminum beam plates inside ensuring that there is an epoxy 
barrier so the acids in the wood don't eat the beam. I would suggest using 
316 bolts as well.

Just to make sure.

Y'ust my 2 cents.

Best

John

----- Original Message ----- 
From: <crufone at comcast.net>
To: "Alberg, Public List" <public-list at alberg30.org>
Sent: Thursday, January 07, 2010 11:03 AM
Subject: [Public-List] Mast Beam Repair


>
>
> Bill and Rachel,
>
> Thanks for your comments. The laminates are in sheer and this is what 
> caused the original (?) glue to fail over time.
>
> Rachel, as the beam is compressed from above center on the arc it wishes 
> to extend outward a thwratships. This places the glue between the 
> laminates under sheer stress. When the glue fails it allows the a 
> thwartships movement which inturn allows the beam to 'flatten' in the 
> middle ( from the top downward)and the rig to lo se tension.
>
> I would like to mention that I have no disrespect for the aluminum plate 
> sistering fix for this application. To me, the wooden beam is part of the 
> character and interior woodwork/furniture of the early boats which have 
> them in place. For a production boat to have this component last some 
> forty years speaks well enough of it's original engineering. The adhesive 
> has failed not the calculated load bearing requirements of the wooden 
> components. I am not attempting to reinvent the mouse trap as some others 
> have suggested in the past. My intent is to restore the original strength 
> the beam was designed to have without changing it's appearance.
>
> Bill you seem to have much experience in the laying up of laminates. I 
> thank you for coming forward to make suggestions. I hope that I can 
> concact you for further advice when I am at the point of doing the lay up 
> of my mast beam. A couple of other owners who have early boats with wooden 
> beams feel as I do about the appearance factor and are waiting in the 
> wings to see how successful/durable my relamination repair is before they 
> attempt their own repair.
>
> Thank you,
>
> Michael #133
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