Building a mast

[BobFilipczak]

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

10 years?

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].

[dadiOH]

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...

[Joe AutoDrill]

I can't help you with the design other than to suggest possibly wrapping it in criss-crossed fiberglass / epoxy when it's done...

BUT... I want to see photos of the progress if you can. Neat project!

[charlie]

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.

[FrozenNorth]

That was a flagpole if we are thinking of the same episode.

[D'ohBoy]

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.

D'ohBoy

[Upscale]

Norm did a show I saw where he built a mast out of sections if I remember rightly. The op might want to look into that.

[Upscale]

My mistake, I think you're right. Apologies to the OP.

Guess I'm getting old and my memory is going.

[Lew Hodgett]

RE: Subject

Take a look at Fred Bingham's book, Practical Yacht Joinerey, he covers building a wood mast, step by step.

Lew

[Tom Dacon]

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.

Good luck, Tom Dacon

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.

[D'ohBoy]

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.

D'ohBoy

[scritch]

Wooden boat had an article on spar building. Go to

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