BYYB Forums

I've been playing with new ways to build hollow masts and spars.

The most common way is to take a couple of 2x4's, channel out the middle, maybe with a big cove router bit, glue together and then shape it. The only problem with this is the mast isn't all that light, the 2x4 stock often has lots of internal defects, knots, pith pockets, etc. which weaken the mast.

Shown is another 2x4 method, but with 3 hunks of stud stock. This particular mast is 3 5/8" in diameter, which means a 2x4 wouldn't work (3.5" wide), so a cocked the 2x4 blanks at 120 degrees.

It's all table saw work, with simple cuts, except the one with the rounded hollow, which could be roughed in with saw cuts and finished with a sanding drum on a drill. Just run the 2x4 through the saw at the angles you need for the mast diameter.

This brings up the need to taper the mast, which is done before hand on the first perpendicular cut. You're basically shaving one side of the mast at an angle, so snap a line a cut to it. I usually eyeball this on the table saw, freehand, but a circular saw will do too. This particular stick has multiple tapers, 3 5/8" to the hounds, then a different taper to 2 3/8" at the head. This means a transition to the new angle, which again I freehand, sort of round over the angle change across a foot or two.

Tested to destruction, a 36" long 20% wall (both types) sample, broke along the grain lines, not the glue line, so there's enough meat to make it work. The only problem with this method is it's not self aligning like a birdsmouth mast. To it's credit, it's only 3 pieces and simple cuts. I even roughed in the 8 sided outside on the table saw, making rounding easier.

After fooling with it a little more, I've come up with a self aligning method (lower left). It does have a few more cuts, but these are related to hollowing out the inside more than anything else. The notch will make it easy to assemble and offers a fair bit more gluing area. The internal hollow is cocked a bit to eliminate a couple of additional cuts.

Very cool Paul,

I am going to make a new gaff for my weekender this winter, and I plan to make it hollow.  I like doing things on the table saw, so this will be fun. 

Al

A gaff is a pretty small spar, so you're not going to save much weight, though any weight reduction this far up in the rig is beneficial. Instead of birdsmouth or one of my weird setups, I'd recommend a simple box section, with a top and bottom stave the width of the gaff and two spacers between them so they create a gap down the middle. Built like this you'll half the weight of the gaff, while still having enough stiffness. Of course round over the top as much as practical, but lightly just ease the corners on the sail side of the gaff, so this edge acts as an end plate for the top of the sail.

I think the best gaffs are aluminum or carbon. Aluminum is easy enough to do, but carbon will force you to sell off a kid to two. I just built a 4 pound gaff that's 10' long (white spruce). To save weight, I used an aluminum "U" shaped bracket inside the jaws, which was surrounded with more spruce. The aluminum saves a lot of weight, compared to the typical hardwood jaws and also allowed me to make the jaws smaller, for less windage. If I was really industrious, I'd laminate a really thin spruce veneer over an aluminum tube and do the aluminum jaws thing again. Tough, predictable, likely not to split or crack and light. A faux wooden paint job over the aluminum gaff would be even lighter.

Yeah I have thought about a lot of those things.  It would be something of a problem to have the gaff break while underway and farther from the landing than I want to row. 

The mast I built for my sailing canoe is nothing more than two 3/4 X 1 1/2 pine boards with a channel ripped into each and laminated together with the channels making up the hollow center.  It is remarkably tough and light.  For an unstayed mast it can take a lot.

I also make hollow bent shaft canoe paddles.  I laminate 1/8 inch strips with strategic cutouts in them into the bent shaft.  Its kind of a hockey stick deal.  People don't believe how light they are.  They are also strong enough that I haven't been able to break one in thirty years of trying.  I suppose I could make the gaff with a system like that, but it is a lot of work.  I think the biggest weight saving I will get will be in cutting down that giant block of wood that makes up the jaws. 

Oh well, I have all winter to think about this.  Right now I am adding a bridge deck to my weekender and am consumed with how to set that up to be water proof with top access.  This is the part of boat building that I like the most. 

Al

I never cut up a solid gaff jaw. I laminate them. If you want it to look like a big hunk of wood, rip strips from a single piece of whatever, then stack them in the same orientation they where when cut. This way, when glued together, the grain likes all align and match, looking like a single hunk of wood. Old trick, works great.

Some day, I'm going to cold mold a gaff or boom, spiral wrapping thin veneers around a mandrel of some sort. This would be the ideal, all wooden spar, if a pain in the butt to do.

I'm getting ready to make a mast and the attached stave layout is what I'll use. It's a 4 stave arrangement, which are notched so they'll "nest" together for easy assembly. All the cuts can be done on the table saw, so it'll be easy to do. I'll cut the stock from four 2x4's, though a lot of waste, a cheap way to get a stick. The cutting guide is also shown. There's more cuts than a birdsmouth, but less staves and an easier alignment, plus you get a real octagon, which is easy to round and it's easier to glue 4 pieces than eight.