[Public-List] Mast beam.

[Don Campbell]

Gord:
    I do not want to promote products beyond reasonable but West systems G 
Flex is made for adhering to  slippery materials and bonds to various 
materials as well, i.e. metals and wood on one joint. The Gougeon's website 
gives a good summary of what their epoxies do. One of the real differences 
is the amount of shrinkage that occurs in polyester and polyvinyl resins 
compared to epoxy. Epoxy is far far less, 3/32" in seventy feet for their 
wind turbine blades, as an example. G Flex also has a flexibility built in 
so can give a bit without losing bonding capability ads a modulus of 
elasticity of 150,000 lbs/psi.
Don Campbell

-----Original Message----- 
From: Gordon Laco via Public-List
Sent: Wednesday, December 19, 2018 8:11 AM
To: Alberg 30 Public List -- open to all
Cc: Gordon Laco
Subject: Re: [Public-List] Mast beam.

Good morning Greg -

The aluminium plates are the official ‘fix’ for a design flaw that existed 
in pre-400 hull number Alberg 30s.  The original laminated oak beams tended 
to sag and sometimes fail, particularly as the boats aged.  Pre-400 boats 
that don’t have the plates, probably should.   Whitby Boatworks used 
resorcinal glue, which is very good glue, but even that, like epoxy, is not 
permanent when used with white oak.  Unfortunately, no glue is permanent 
when used with white oak.

I do not know what the common wisdom is with regard to rebuilding the beam, 
but on general principals, white oak in lamination is generally considered 
by boatbuilders to be impermanent.  The acids in that wood will destroy 
epoxy or any other glue sooner or later.  Ash glues up better and more 
permanently, but has quite low rot resistance… however, soaked in epoxy one 
might expect protection, particularly if attention is paid to bolt holes, 
which should be soaked in epoxy too.   Laminations of ash and mahogany are 
considered successful, but I don’t know what the strength of such a beam is, 
someone who knows more about this issue should give that advice. Ash on ash 
would be strong.  I made a laminated mast step for my Folkboat made of ash 
and red oak… both not considered good boatbuilding woods due to their low 
rot resistance, but when I got the boat back after she’d been ten years in 
the tropics, some of that time abandoned and open, the mast step was still 
good.  The previous mast step, which was at least her second, had let go 
after the white oak lamination had destroyed its glue and dropped the keel 
stepped mast down onto the keel itself.  In a Folkboat that’s only a few 
inches, but the massive thump, like a giant hammer blow, followed by the 
puzzling circumstance of all the standing rigging suddenly appearing to be 
slack is a good story best told in it’s entirety over a beer.

I throw this question out there… since the metal plates are the fix most 
pre-A30 sailors want, but they don’t look nice, can they not be covered with 
wooden sheathing?

Gordon Laco
www.gordonlaco.com
#426 Surprise



> On Dec 19, 2018, at 6:59 AM, Greg Dawson via Public-List 
> <public-list at lists.alberg30.org> wrote:
>
> Dear all
> This winter I intend to laminate a new mast beam.  Currently we have two 
> very ugly aluminum plates bracing the original beam.
> Does anyone have knowledge of this and if yes what material would you use? 
> I'm thinking of 1/4 inch oak or ash strips to build the laminate. Also 
> what glue would you use in the construction and why.
> Any help appreciated and best wishes to all.
> Greg #348
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