Posted by: Wayne | January 23, 2011

Mainmast glue up

Over the past week or so I have finished glassing the centerboard.  Unfortunately, there are a few bubbles I need to sand out and fill, but I have taken a break from that and returned to spars.

Friday I was able to get the staves cut for the mizzen sprit (the smallest spar on the boat).  I also got the blocking for the mainmast cut.  Then I laminated the mizzen sprit and the head blocking.  Saturday, I did a bit more prep work for the heel blocking and laminated it.  I also cleaned and shaped the mizzen sprit (it just needs a little sanding).

The smallest (current) member of the family plays with the smallest spar.

This afternoon I was able to fit both pieces of blocking to the mainmast.  Then it was time to glue this beast together.  I will let the captions explain much of the process.

Applying glue inside the lower mainmast for the heel blocking.

Setting lower blocking into place into one mainmast half.

Lower blocking ready to marry the two halves of the mainmast. The "teeth" are to avoid a stress riser at the end of the blocking; they are not a torture device.

Upper blocking in place. The "teeth" serves the same purpose as the heel blocking.

Spreading epoxy into the grooves on the mast halves.

And the two shall become one...

Mast head with blocking. The current plan is to have stave "1" forward.

The heel clamped, showing one of the hose clamps used to hold things together. I had a little more room than this when I was working...

The stick. I am tightening the zip ties that help hold the spar together while the epoxy cures. Suffice it to say that ties every 4" or so on a 14 foot spar is a LOT of ties.

As can be seen in the above pictures, I am using my workbench and the box from the table saw.  What isn’t obvious is that after clamping the spar I rotated it so the seam is at the top and bottom.  This should reduce any sag from the lack of full length support.  Also, the head blocking did not get shoved in by mistake.  The design length is 4200mm.  The staves are cut to 4400mm.  After I trim the ends including 10mm off the end of each piece of blocking I will have a 4300mm long spar.  This will still leave me a little bit of wiggle room.

Also not shown is the hole through the entire length of the heel blocking.  I used the table saw to cut a ~5x10mm groove in the middle stave of the lamination before gluing everything up.  I also sealed the inside of the groove and the inside of the mast with neat epoxy.  After clamping the heel block lamination I used some scrap electrical wire fed to clean out the epoxy squeezed into the groove (quite a messy job).  This breather hole should allow any condensation inside the mast to drain out, rather than fostering rot.  We will see if the theory works.

Tomorrow or Tuesday I should be able to clean the corners up and round the stick.  Then I will have 2 of the 6 laminated spars completed.  I will also have the only birdsmouth spar done.  A simple two-part lamination is much less work.


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