[Public-List] Mast beam.

[americo silva]

something to consider is the orientation of the laminates
in stead of horizontal try thinking about vertical laminates
much more strength with fewer laminates
but with more wood waste which is probably why Whitby did it that way

On Wed, Dec 19, 2018 at 8:11 AM Gordon Laco via Public-List <
public-list at lists.alberg30.org> wrote:

> 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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