[Public-List] Mast beam

Glennb brooks.glenn at comcast.net
Thu May 30 20:18:29 PDT 2013


Jeff,

My boat, Dolce is a pre-liner boat, built in 1968.  when I bought the boat the mast support beam was partially delaminated on one side - several laminates, varing lengths up to 1/3 length of the beam were separated.    I sailed the boat for two seasons this way then replaced the beam spring time of my third year when the delamination became worse.  I mention this because the beam was serviceable even when partially delaminated.

Rather than put in the aluminum plates described on the alberg30 site, I opted to saw a bigger one piece  4x6 beam out of purple heart.  This required a 4 x 12 beam to start with, as the crown of the beam extends the height of the beam vertically something over 9" top to bottom.  I reinstalled the sawn and shaped beam by glassing in the ends and thru bolting to the  plywood bulkhead.  Same method as the original.  I went oversize on the beam because I wanted a stout, permanent ocean service fix.  Probably overkill now, but I never need worry about mast compression!! purple heart varnishes up nicely and is good structural-load bearing material.

The biggest problem I found is that the forward edge of the cabin top curves downward and forward at the upper forward corner of the beam, hence I found I had to round and shape the forward corners of the beam and forward edge to get a tight fit up against the cabin top.  

Where it did not fit snugly, I injected a bunch of 5200 to fill the gap and act as a load bearing surface between the beam and the roof top.  This seems to have worked well as I have no compression on the door frame etc.

Had I to do it over now, I wouldnt hesitate to cut laminate strips out of oak or some other nice hardwood and epoxy a beam together as you are thinking about doing.  sawing a whole one piece beam also works well but uses more material.  (I never have liked the idea of bolting up aluminim plates over damaged/delaminated structural beams. The damaged beams will only continue to delaminate and fail behind the aluminum- eventually becoming nothing but a loose pile of laminate material wedged together by some metal.  Just doesnt seem like a seamanlike fix + wood compression beams look great when varnished.)

If you really wanted to reinforce the load bearing beams, you could put in beefier vertical posts, maybe knees up against the  beam, bolted and glued to the bulkhead.  this would certainly carry the load better. You wold probably need to install loading pads on the hull, to receive the bigger beams, as you wouldn't want small hard spots on the hull to receive the additional  downward compression loads larger beams would deliver.  However I've found the alberg cabin top and bulkhead is extremely robust and strong to begin with, so perhaps the extra vertical supports are overkill.  On the other hand Yves Galinas, of Jean du Sud fame recommends making up a removable vertical mast support beam to wedge in place under the mast when sailing in heavy weather.  So your call depending on what kind of sailing you might eventually decide to do.

The most work went into picking away at the original fiberglass beam ends and shaping the beam to fit back into the space.  The project is definitely doable.  But worth the extra effort when done right!

Good luck,

Glenn
Dolce 318

Sent from my iPad

On May 30, 2013, at 2:24 PM, Jeffrey <fongemie at gmail.com> wrote:

> Hi everyone,
> 
> I'm diverting the conversation here talking about a pre-liner boat (sorry)
> but I also need to do something with my boat's mast beam.
> 
> https://plus.google.com/photos/115571802364472829939/albums/5182769471833731569
> 
> I keep thinking that I want to rip it out and laminate a new one to the
> same curve. One thing I'm a little unclear on is exactly how the beam
> transfers the load onto the hull. If you look at the my images in the link,
> the fiberglass tabbing to the cabin side can't do much, or the bulkhead
> that it is bolted to. Seems the support posts must be doing all the work,
> but they don't even sit squarely under the beam. What the heck holds up my
> mast?
> 
> Jeff Fongemie
> #116 Seagrass
> 
> http://picasaweb.google.com/fongemie
> 
> 
> 
> 
> 
> 
> 
> 
> On Thu, May 30, 2013 at 4:57 PM, Kris Coward <kris at melon.org> wrote:
> 
>> 
>> I also get a bit of a dip on 583, but it's enough to cause slight
>> problems with the doors. I've been tempted to address mine by either
>> re-hanging the hanging locker/vee berth door a smidge lower, or sanding
>> off the top 1/8" or so, but I already confound that door with the filler
>> cushions always in place in the vee, so that fix is quite far down my
>> to-do list.
>> 
>> -Kris
>> 
>> On Thu, May 30, 2013 at 04:44:54PM -0400, David Gilbert wrote:

 1369970309.0


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