[Public-List] RESENT: Mast Beam Variation --what's best?

[Randy Katz]

(The text I wrote is easier to actually find in this version!)

Greetings, 
I've always had a question about the alum. plate repair job for the 
mast beam. The problem force is a downward one. The beams that I 
know of are laminated wood, often with the 40 yr. old glue 
degraded to the point of no return. If one drills holes fore and 
aft through the beam, inserts plates and bolts, wouldn't the 
downward force still be, at least in part, unremedied? 
I don't quite see how the sandwiching of the beam lends as much upward
support as placing posts (or knees added to the existing door 
posts) under the whole thing, including under the alum. plates, 
would. 
The only thing I can figure is that by sandwiching the laminated beam,
by squeezing it really tight between those plates, it would tend 
to be solidified to some degree. 
This is the reason that on my boat I did plates AND hefty knees, well 
bolted. (See our Alberg page at 

http://alberg30.org/maintenance/HullDeck/MastBeam/SimpleGifts/ 

Any comments or thoughts about this would be of interest! 

Thank you, 
Randy Katz 
#249 
Seattle/Bellingham, WA. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
Message: 5 
Date: Wed, 16 Jul 2008 11:45:53 -0400 
From: Mike Lehman <sail_505 at hotmail.com> 
Subject: Re: [Public-List] Mast Beam Variation 
To: Alberg 30 Public List -- open to all 
<public-list at lists.alberg30.org> 
Message-ID: <BAY133-W567C2FCA6DCF29F9F2E9FB78F0 at phx.gbl> 
Content-Type: text/plain; charset="iso-8859-1" 


Althought the appearance of the aluminum sisters to the wooden beam in
the older boats may not be as attrative as the original beam, this fix
was engineered by Bruce Rankin who was a professor of engineering at 
the US Naval Academy. The fix is permanent and there have not been any
failure is 20+ years with this fix.Mike Lehman 
<((((?>`?.??.???`?.?><((((?>`?.??.???`?.?><((((?> > Date: Wed, 16 Jul 
2008 09:13:27 -0400> From: mainstay at csolve.net> To: 
public-list at lists.alberg30.org> Subject: Re: [Public-List] Mast Beam 
Variation> > I would totally agree - the mast beam is subjected to 
immense stress, and as> John commented, dynamic loads in normal 
sailing let alone heavy weather> multiply the load experienced while 
at the dock.> > The beam has to resist the combined loading of all the
shrouds and stays -> thousands of pounds.> > Gord #426> > > > Jeffrey 
wrote:> >> I don't think our mast beams are subjected> >> to all that 
much stress.> >> > > > > You might be surprised just how 
much stress is involved there. That's a> > heck of a compression load 
point loaded in one spot - and it's dynamic> > in any kind of seaway.>
There are documented cases that these have failed at-sea, and 
it's a> > common problem with wooden supports of this kind (see for 
example the> > number of boats in Vigor's "Twenty Small Boats to Take 
You Anywhere"> > that have this as a maintenance issue).> > > > This 
is one structural issue that can affect the safety/seaworthiness of> >
the vessel, and personally I would not do anything less than the> > 
absolute strongest support I could engineer if I had any lack of> > 
confidence in my installation at all.> > ______ 



 1216226795.0