Shiver me timbers, but I'm going to be in the position this fall of
building a mast for the new (old) sailboat I've acquired for next-to-
nothing. The boat is sound, but the mast is glued together and
threatening to come apart in many places. The boat is an old 1968 C
scow from Johnson Boat works in White Bear Lake, MN. The mast is about
22', and from what I can see, it's a kind of torsion box design with
lots of hardware holding it together. The box probably makes up 3/4 of
the total mast, and the last 5 feet are probably solid wood as it
tapers to the end.
Any reason I can't duplicate it with new lumber, put the hardware in
the exact same spots and be confident that it will hold together for
Anyone on this list ever done this? [For what it's worth, I also plan
a pilgrimmage to the boat maker to quiz anyone I can find there with
some history and woodworking sense].
None at all but don't count on the hardware to hold it together, do a *good*
glue job, Resorcinol or epoxy. Hollow masts are common and 22' isn't very
big. Never built a hollow one myself, always solid (some laminated but
solid). Here's a starting point...
use it for a mandrel and make a carbon fiber tube by wrapping it around. you
can get prepeg fiber tape for not very much. do a thick buildup in the
places where you need the attachments, but you won't need any of the
hardware that simply holds it together. you'll just need to vacuum bag it
when curing. after you're done, you should be able to lift the tube with one
hand, it will be so light.
Sailed a lot of scow during my teen/college years... A, E, M20.... You
could more easily post to a scow sailing forum and buy a aluminum mast
for cheaper than building the new one (time IS money). But if you
have more time than money....
Reminds me of the CF mast that Harken built for one of the brother's A
scow - three cf tubes joined by alu triangular sections (point
forward) and a track for the mainsail boltrope mounted to the rear of
the triangular sections. Folded like three of them expensive suckers
before they gave up on the concept.
Get clear straight-grain quarter-sawn spruce, in the longest lengths you can
find. Get it as soon as you can and put it down to season, sawn into about
1"-thick planks. If it's green, plan to give it at least another six months
if you can spare the time, or better a year, which would be just about right
for one-inch thick stock. Kiln-dried wood could be usable sooner. If you
can't find full-length stock, learn to do good long scarf joints. Epoxy
would do a good job of gluing it up, probably better than resorcinol for
someone new at it. I like West Systems, myself, but there are others.
That C scow is a powerful boat, and it'll want a well-built spar. So you
should do your research. There's a lot of information available in books on
boat building. West has a good manual on using epoxy for boatbuilding tasks,
and it'd pay to study it.
A pleasant project - I envy you the opportunity to do it.
P.S. you might also take a look at the old stick. Depding on its condition,
it's possible that you might be able to get it apart, clean it up, and
re-glue it. That wouldn't be a bad approach if the condition would allow it.
For sure you'd end up with a spar that met the original specs.
My father repaired his cracked spruce Nite (iceboat) mast via a
similar methodology. This may be your best route. Spread the crack,
used some powder-based water-mix glue, positioned the mast to cause
the glue to flow into the crack and taped it tight with packing tape.
Worked like a champ and still in use decades later.
Wooden boat had an article on spar building. Go to
http://www.woodenboat.com/wbmag/idx/index.html and look for
"Sparbuilding, Hollow". I believe it's in issue 149, July/August 1999.
The technique uses a bird's-mouth joint. Basically you rout a 90-degree
rabbet in one edge of each plank with the rabbet set at an angle
appropriate for the number of planks in the spar (e.g., 45 degrees for
an 8-sided spar). You glue up the planks with the square edge of one
plank settled in the rabbet of the adjacent plank. Glue 'em up all in
one session, round off, install hardware, and yer done!
Crude plank illustration:
square edge |_______________________< rabbeted edge
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