Excelsior, an Atkin 'Cruising Canoe'

With 120 SA she will move briskly, and the flat bottom and plumb bow will make her pound to windward unless heeled sharply. That will transfer stresses to the sheer planking of the rather bluff bow. 1/4 ply will have sinilar weight to the specified planking but will be less stiff and flex more. It may be wise to use laps of generous width and add reinforcement forward.

I'm looking forward to seeing this one - I don’t recall having seen a canoe with a galley before

 

Not a problem; I spent years reading plans in the construction trades. I view them as pictorial layouts of information, rather than as miniature patterns. I'll definitely be lofting this boat full-sized before building her.

Do you think it might make a noticeable difference if I'm singlehanding from the after cockpit, and toss the hundred pounds up towards the bow for trim?

I'm a little leery about eliminating frames, because the boat is flat-bottomed and slab-sided. It doesn't have much in the way of compound curves to give the planking rigidity. And since I'd have to build molds anyway for glued lapstrake, I figure I might as well go the extra mile and build frames instead...

That's what I was considering; nice to have you confirm it.

I've also been considering an unstayed version. The old sharpies I've been studying had sprit booms on unstayed rotating masts, and the arrangement seems to have worked just fine. I suspect there are stays on this particular rig to stiffen it for a little more racing speed, rather than because it can't do without them.

Of course, I'll have to figure out what to do about holding up the boom tent, if I have sprits instead of booms....

Thank you for the offer on mast scantlings; I'll send you my email sometime today.

 

It seems to me this boat was specifically designed to sail heeled, rather than flat, and that for that purpose she has less initial stability than most flat-bottomed boats. But a little extra strength forward can't hurt.

I'll invite you aboard for a drink and a meal, after she's launched.

 

I agree with the comments about the rigging. My first thought on looking at the article was "Why not use a sharpie rig?" You could even use existing sails from a Laser or whatever. I've forgotten the name of the variants but I know Lasers come with different sized sails for varying crew weights, so having a smaller mizzen for balance would still be possible.

 

Cruising Canoe

Troy, just for the hell of it I thought you might find this interesting. I've been
thinking a lot lately about twin masted "slightly high performance gunkholer".
I wish you well with this boat-lots of fun.
This is a bit on "on-deck" movable ballast used to race but it could be adapted,(maybe) to a boat like yours:

 

I can certainly understand the "sheer terror" aspect of such a system - expecially if you were a little off on your timing when you released the sliding ballast.

Or were you talking about the terror it struck into the hearts of Herreshoff's competitors? Either way, it sounds like something fun to look into. Thanks for bringing it to my attention.

 

Actually, I don't think she has enough sail area, though I haven't studied her lines well enough to be absolute.

NoEye, it has a sharpie rig, though the proportion of main to mizzen isn't what is typical. If it was me, I'd use a 65 sq. ft. main and a 60 sq. ft. mizzen. I suspect Billy was going for windward ability with the longer main luff. This would mean windward drive isn't quite as good, but from a reach and back, she'll have enough foil separation to rocket along, assuming a reasonable WS/SA or SA/D.

From experience I can tell you Billy used this type of ballast purely as trimming weight.

One of the lovely things about glued lap is it acts just like there aren't any laps when it's cured. In other words once the goo is hard, the lapstrake planking sides act just like it was one big *** piece of continuous plywood. "You don't need no 'stinken compound curves" to make it strong, it is naturally. This said, you could work in some arc in the bottom and topside planks if desired.

I don't think Billy was very familiar with unstayed rigs. He was wise enough to stick with what he knew. A boom tent would be attached to the boom and a topping lift used to position the boom, just like any other boom.

 

PAR, I meant "sharpie rig" as in "unstayed with sprits instead of booms". The classic New Haven sharpie rig. Simpler and cheaper and just as effective for messing about.

 

Which is what PAR was talking about too, in his earlier post. Cat-ketch or periauger (sp?) rig with unstayed, rotating masts, jib-headed sails and sprit booms. So far, the voting seems to be unanimous in favor of it....

 

My point was that it's a big-assed thin, flat piece of plywood. Although I guess it isn't, really. It does have a pretty good curve in it, even if it isn't a compound one, and it's held at the edges by deck and bottom.

 

Bingo . . .

I have to agree with Billy, the knockabout rig would make a faster boat.

 

I'm nowhere near as experienced a judge as you, but I'm not sure I'd concede she's under-canvassed. I've drawn the stations and profile to scale from the table of offsets, and there really isn't as much boat there as you would think. Although it's about 5' 4" on deck, the widest beam at the chines is only three feet. Maximum draft is only six inches below the lwl, and it's a double-ender with both stems at the lwl. That isn't a lot of displacement.

It also has a fairly typical sharpie bottom: pretty much a straight slope in the first third; most of the rocker in the middle third; and a straight run up from there to the stern.

Between the rig and the bottom, it's almost like Mr. Atkin was playing with the idea of designing a sharpie rather than a canoe, but wasn't quite ready to admit it to himself. So he wound up with something in between

When it comes to the stayed rig with conventional booms, it has also occurred to me that he was designing what he hoped would be the start of a development class, to help young sailors learn the ropes. So maybe he wanted to give them some ropes to play with....

 

The WS/SA ratio will offer a good idea of how much "canvas" she carries. Calculate the immersed area of the hull in sq. ft., then divide the sail area by this figure.

On such a narrow hull, you should expect to hike in modest wind strengths, which may make the string steering interesting. Also from experience in cat ketches, you'll want to have crew or your normal steering position will be on top of the mizzen deck. In a tiller steered boat, this means a hiking stick and you on the rail.

An eyeball estimate of her displacement at 6", considering here construction might be as much as 1,000 pounds. This gives her a SA/D of 20, which is much more then the average cruiser, but well under what a modern racer would enjoy, though likely what Billy considered safe. This also means her 100 pounds of ballast is 10% of the displacement and another ballpark figure Billy might have used for trimming ballast. This also is in keeping with my guesstimate of her wetted surface/sail area ratio (I'm guessing about 50 sq. ft. surface area) making for a 2.5 WS/SA and not especially impressive, but not a slouch. Built lighter, everything improves.

About the sail area. On one of my recent 17' cat ketch builds, naturally with more beam/length ratio, the dry hull weight was about 350 pounds, so with a crew and on a shorter length and 30% lighter then my guesstimate of this old Atkins canoe, my build carries the same area, which is partly my base for suggesting she could use more area.

 

Troy, if using the same sail dimensions, the main mast with a 20% wall, birdsmouth style should be 3" at the base with a continuous taper to the 1.75" head. If made of Douglas fir, will weight about 15 pounds, including epoxy, but 12 pounds if Sitka or 11.5 if white spruce.

The mizzen is 2.375" to 1.375" and just under 8 pounds if Douglas fir or a tad over 6 if Sitka or about 6 pounds if eastern white spruce.

These would be cruising spars, racing spars can be as dainty as practical, but to give you an idea if you wanted light racing sticks, the mizzen would be about 2" x 1.125" and would weigh a touch over 4 pounds if spruce. Naturally, you snap these like twigs in heavy air or if you had a big load and were hit by a gust, but they'd be light, which is fast.

 

Or if you want them lighter but still strong, a bit of carbon tape isn't that expensive. From memory the Gougeon's used to get pretty good results mixing carbon and timber.