[Public-List] Mast Beam Variation

[Jonathan Adams]

My beam failed after this year's NOOD. It was a new (less than 20 yrs) laminated wood Beam, and I think the wood went not the glue. The problem was that due to the curve, the lamination has to be done correctly so that the strength of the wood is maximized if it is not, the beam will split along that portion of the lamination where the grain does not align well with the stress.

The length of this thread may be due to the fact that some boats had laminations that were well formed - where the stresses were well aligned with the strongest points of the lamination; while others may not have been done so well.

I have the alloy beams and big half inch bolts - I feel better :) this way. If I wanted to keep the wood, just replace a few internal layers of lamination with the alloy plates.

JA
Laughing Gull
197


----- Original Message ----
From: Jeffrey <alberg30nh at gmail.com>
To: Alberg 30 Public List -- open to all <public-list at lists.alberg30.org>
Sent: Thursday, July 17, 2008 7:26:00 AM
Subject: Re: [Public-List] Mast Beam Variation

Have there been any failures of the beam? Any while the lamination was
still strong? It would have to be early in the boats life to determine
that I guess.

Not to say the aluminum plates are not a good idea, but wouldn't it
stand to reason that if the wood itself was in good condition, then a
new lamination using an epoxy glue likely last another 40 years? Or,
even a new laminated beam using oak and epoxy?


-Jeff








On Wed, Jul 16, 2008 at 10:12 PM, Lawrence Morris <morris.lc at verizon.net> wrote:
> It is not the epoxy that fails it is the wood that fails inevitably.
>
> Larry
>
>
> On Jul 16, 2008, at 6:49 AM, Jeffrey wrote:
>
>> Larry,
>>
>> I would bet (in my opinion) that a lamination done properly with a
>> good modern adhesive would last a very long time.
>>
>> T-88 by System Three would be a good product to use:
>> http://www.systemthree.com/p_t_88.asp
>>
>> It is designed as an adhesive. It's even FAA certified..people build
>> airplanes with the stuff.  I don't think our mast beams are subjected
>> to all that much stress.
>>
>> -jeff
>>
>> On Tue, Jul 15, 2008 at 10:17 PM, Lawrence Morris <morris.lc at verizon.net>
>> wrote:
>>>
>>> How about sandwiching the AL plate in side the beam  if you are going to
>>> remove it.  Relaminating is just setting your self up for a future
>>> failure.
>>> It is a weak design.  The AL plate is a permanent fix.   Sometimes they
>>> go
>>> slowly sometimes suddenly
>>>
>>> Larry
>>
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Jeffrey Fongemie
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