Having just finished off a new birdsmouth stick, I made some adjustments to the usual arrangements. I was replacing a stayed aluminum mast with a wooden freestanding stick, that was also to be fully rotating. I wanted a better shape than the typical round or oval section so I went with a teardrop shape. This gives the advantage of a 3"x3.5" oval, but has better "penetration" into the wind, is lighter than an oval and inherently stiffer than a round one.
This one had to live in a tabernacle, so I used the symmetrical stave layout, because I could keep the flats on the sides, which would grip inside the "U" shaped tabernacle sleeve better (more surface contact area). Above the gooseneck the mast is rounded normally and has an external track for guaranteed sail location and leverage to rotate the mast.
I talk about symmetric and asymmetric stave arrangements all the time, so I've posted this image of the differences. The asymmetric stick is easier to make, because the notch is centered and pretty easy to cut. It's harder to round off though. I like to use the symmetric arrangement, because it's easier to round the corners and I can keep the octagon if I want to, like on the inboard end of a bowsprit. I also find the symmetric staves are easier to close up any gaps too.
Boy would I like to try one of these, just for the challenge. Unfortunately “challenges” for me end up being expensive with all the practice runs.
Most find birdsmouth pretty intimidating, until they build one. Once everything is cut, they seem to click together and fall in line.
I glued up six of them at a Scamp Camp. They were already milled and ready to go. All I had to do was build a jig to hold them straight while they set up. We used heavy duty zip ties to hold them together which worked quite well. By the time I got to the last couple masts, I was laying the birds mouths up and holding the staves together with a couple C clamps, then painting the goo into the grooves with a brush. I got nice even coverage on all the staves in a matter of a minute or two. I laid them up in the jig, snapped them together, zipped them up and wiped the spooge down to coat the outside. I capped the ends and that was that. It was a little bit messy, but I didn't waste any goo to speak of and the whole process only took about ten minutes.
I think that for me the hardest part of making a birds mouth mast would be the math getting the dimensions right. It took me the better part of an afternoon to get the jig right, but it was going to be used repeatedly, so it needed to be robust and bang on. Cutting the staves should be pretty easy with a good table saw once everything is set accurately.
I don't plan to make a birds mouth mast for the CY, at least not at first. I will make a box mast instead as per the plan. I want to sail it next summer so I won't get fancy the first year, but I can't see not making one as time permits.
Al
I can work up stave and mast dimensions for you on any typical mast, with just a little input from you, if desired.
Thanks Paul,
As I age I find that my already pathetic math skills are deteriorating to the point of being non-existent. Not long ago I was trying to calculate the volume of some of the compartments on the CY when I realized that I had forgotten how to do long division. I think I need more coffee.
I still haven't come to grips with tapering the staves for a birds mouth spar yet. My current thinking is to clamp them all together and plane the taper into them all at once. I would like to keep the next mast full dimension up to the point that the gaff jaws top out then taper to the mast head. If I do this, it will make adjusting the lacing for the luff much easier.
Otherwise, I agree with you that making birds mouth spars is no big deal. I would also like to repeat my contention that hollow mast and gaff makes a noticeable difference in how well weekender sails. With my octagonal hollow mast I am getting a better leading edge on the main, and the hollow gaff makes the whole deal feel more stable.
Al
AGe is a wonderful contrivance of fate isn't it. You know, they have these new fangled gadgets now, called pocket calculators. I know, I know, learning new technology and all, but they're damn handy, especially when you brain fart away half of the few remain cells. I do taper the staves by clamping them together and planing them all at once, usually with a tapered ramp to get the taper right. I just ride the infeed sole on the ramp, until I can't remove any more material. Yep, lighter spars makes better sailors and I've been preaching it for years. I just made a carbon gaff for an old coot and he loves it, except it makes weird noises he says.
dammit, now you guys have me wanting to try making one.
Do it Keith,
When I try new stuff I always use cheap ( remember me?) construction lumber as a first attempt. The masts I messed with were all Sitka spruce, and pretty spendy. When I do up my first proof of concept mast try I will probably rip up a 2X4. When I do up one for the CY, I will probably use Arokolu pine which is pretty flexible but kind of weak. I used it for the cooper layup gaff, and when glued up, it is quite strong.
Paul wasn't kidding when he talked about getting the weight out of the rigging. It took me a while to get it, but I'm in the choir now.
Al
Oh, I believe it. Getting 10 pounds out of the top is probably better than sticking 100 on the bottom, of one of these boats at least. I'm just worried about doing a crappy job. Sometimes I have to try a few times, but on the other hand if I "practiced" on worthless wood and got it riht the first time, which is possible, it would be annoying to have to do all that work again. I'm not *that* fond of building things, you know. I do it because I'm stubborn. If my conscience would let me just buy things like everyone else, I would. An example is model planes. I build the labourious way, with little balsa and basswood frames, steamed, bent and laminated outlines, doped tissue covering, etc. It takes me like a year to build one. They fly pretty good and I'm always pretty proud of the outcome. The other day, though, I bought a kit that built up in two days, for a little flying-boat made of waterproof artist's foam-board. It flies great and is kind of a guilty favourite to be honest.
I would never buy a hollow mast though, because I know I could build one. But I hate building things. I always cut myself and it takes a really long time to clean up afterwards and I doubt I save any money either. But I do it, because I'm stubborn. You see therefore why this stuff annoys me.
When I want to have something, my brain, which sounds a lot like my Dad, says "you can have one if you make it". So then sometimes I say "f#$& it, then." And then the Dad/brain voice says "see, that's why we don't have nice things- because you're lazy." And so then I get horribly burned, or I get stitches, or I destroy the garage, trying to make something. And I get all weird and obsessed about it too, which is frustrating. Then when I'm done, no-one can stand all the boasting. It's quite the process.