It’s just the one sail for the price of two goes against my less is more thing…
I totally get that, Michael. Having two sails and using one at a time does fly in the face of efficiency and minimalism. Here’s how I see the compromise between the isosceles sail versus the two jibs approach.
The isosceles sail has one fewer sail. But it has the complication that the rig must pivot fore and aft. I assume that this is to keep the foot of the sail relatively level, as well as to shift the CE forward—is that right? I assume that there are other compromises in sail shape because of the fact that sometimes an edge of the sail sometimes has to act like a luff and sometimes like a leech.
The tilting rig means that the mast has to be an A frame of some kind. The mast on Flight handles that nicely with an integral A frame and a spreader to windward. But that’s a lot of stuff to have in the middle of a small canoe. You could have a strut to windward that sits on a tube, but now all that stuff needs to be stiffened up as well. It might be possible to have the stay to leeward of the mast, as long as the isosceles sail was to leeward of the stay. Then you could have tilting with out a strut, but it reduces the staying base by a lot.
With my non-tilting rig, you do have one more sail. But because the rig is always up and tight, that sail can just be unfurled or hoisted up the already tensioned headstay. Because the sail does not have to switch bows, you can have the leeward stay well outboard where it does the most good. I’m a little perplexed whether it would help the one sail for each bow rig to tilt. Can’t we put the CE wherever we want based on where we put the tack of the jib, and how long the foot is? And those sails get to be shaped like regular sails—a dedicated luff and leech.
Either rig might make good use of barberhaulers coming from the leeward ends of the akas.
Another worries I have, looking at your drawing, I am afraid the mast is going to interfere with the wishbone before you are as sheeted in as you would like when closed haul…
There are many mysteries of geometry in there. It does feel like a lot of moving parts. It would be hard to get the CE too far in front of the mast upwind. In fact, the remedy to wishbone boom/mast interference is to ease the line pulling the pole to windward (it acts like a spinaker pole, so lets call it the pole), and let it fall off to leeward. That produces more space between the big mast and the wishbone boom, but moved the CE aft and to leeward. Those kinds of compromises worry me. It bears mentioning that Tink’s spinnalug has fewer interference issues like this. But it trades them for luff tension issues. Maybe we could solve the whole problem by just using a sprit boom?
All of this brings me back to the rig I’ve shown here. Always up and tight. With a simple mast that pretty much acts in pure compression. Sails that sailmakers know how to make. Rudders that you can raise and lower from the cockpit without lines. But it does have one sail for the price of two. That bugs me too.
My (limited) personal experience is that any shaft/support sticking out of the hull at a right angle so close to the water line is an absolute brake in any kind of chop. It was pretty bad on my boat (with a lower support for the rudder mount less than one inch thick and less than 8 inch long, so not that much frontal area). Actually it was so bad that I cut the hull in half length wise to add a 6 inch wide section to raise the whole rudder assembly (at the expense of higher stresses on the rudder, of course…).
You need rudders, my friend, rudders…
Amen, brother Laurent. Do you see any good candidates for rudders that emerge from the bottom of the boat besides the Newick/Brown cambered-wing/skeg-and-rudder boards and their sibling, the daggerboard with a ballanced rudder at the tip (no skeg). Any others? I want to be able to pull them up.
Thanks for your thoughts,
Chris
A little Kahana Bay atmosphere.
Hi Chris, glad to see I’ve got you thinking. As for rudders they don’t come much simpler or better than the ones I had in Piawatha especially in a small craft. It consisted of a bent high strength stainless tube having a horizontal leg pivoting in a transverse plastic pipe through the hull sides and a radial arm which plugged into a similar bush in the mid portion of the rudder with a strap around it at the top to form the top mount. The rudder steered about the radial arm and raised and lowered about the horizontal arm. Held down with a light cord and able to kick-up in either direction. I think it is illustrated in my first article.
Best regards
John Pizzey
Hi Chris, I also read with interest the idea of a bendy rig as opposed to a pivoting mast. Sounds appealing looking at it in one plane but I suspect that if you tension the luff to induce the forward bend, the side force from the wind load will bend the mast off to leeward slacking the luff tension which may be a problem with a headsail only rig.
Regards
John Pizzey
Hi again Chris, another really good contraption which was built by my mate John Gross in his one attempt at a proa, (after sailing Piawatha) was a buoyant leeboard which pivoted about a longitudinal axis at the gunnel, had a moulded glass section that extended from its pivot mount to conform to the leeward side of the float, (moulded about the float as a streamlined bulge) and supporting the extended board. When you stopped or went very slow its buoyancy forced it up to float on the surface and its asymmetrical shape pulled it down to an operative position as soon as you were underway. Presto, automatic raising and lowering with no effort on the part of the crew.
Just another thought
John Pizzey
Very interesting stuff, John! I like that the bent tubing is the pivot for the blade and the whole assembly—and that the drag is countered with a line. I also liked the self tacking leeboard idea.
I have some questions about the need to have the rig tilt.
I’m a little perplexed whether it would help the one sail for each bow rig to tilt. Can’t we put the CE wherever we want based on where we put the tack of the jib, and how long the foot is?
The isosceles sail has one fewer sail. But it has the complication that the rig must pivot fore and aft. I assume that this is to keep the foot of the sail relatively level, as well as to shift the CE forward—is that right? I assume that there are other compromises in sail shape because of the fact that sometimes an edge of the sail sometimes has to act like a luff and sometimes like a leech.
Would you help me understand these—especially the first one?
Also, here are some renders of it reaching. I am really getting into this design. Its soothingly simple.
Hi Chris,
I love this boat too! I am also a fan of the single mast, with two jibs. What you are giving up in simplicity with the two jibs (not that much IMHO), you are more than gaining in redundancy. It’s a snap to rig, and it is simple to reduce sail by furling also. The boat is light, and packs up nice and easy, which are all perfect for a beach boat.
I like the shape of the hull and the ama, and I think the concave in the safety ama is really cool.
I agree that rudders are where its at, and with this arrangement, with some bungee to the bow, you can position them to whatever height you want, and they will probably stay put pretty well.
With the CE so far forward on this rig, the forward rudder is probably going to have to do double duty as a centerboard. I wonder if it would make sense to turn the forward rudder all the way around so that the foil is pointed in the right direction?
If you’ve seen The Endless Summer, with the scene of the pacific catamaran surfing down a ground swell, that’s what I’m picturing for this one.
Very cool.
-Kimbal.
If you’ve seen The Endless Summer, with the scene of the pacific catamaran surfing down a ground swell, that’s what I’m picturing for this one.
Absolutely! And thanks. That’s the idea; beach boat. Two people should be able to carry any part, except for the vaka which needs a wheeled cradle.
The CE on this rig can move around quite a bit fore and aft, and a little bit windward and leeward. And the mast can be canted either way, thanks to the leeward stay. Playing with that would be a fun experiment.
I was originally thinking about hoisting jib, but I’m thinking furlers more and more. Quick shunts. Easy, gradual reefing. Proven equipment, But spendy, unaerodynamic (especially the back one) and then there’s the weight of two sails aloft. Hmm.
I’ve only given this canoe about 100sq ft. Half a hobie 16. Same as a GIS. What do you think? Enough?
best,
chris
I would not beat yourself up to much about the two sails, you only have two sails the same as most boats, main and jib. It is much easier to make a jib than a fully battened mainsail or windsurfer sail. Two sails would last longer.
I think I would prefer the sails being hoisted on each shunt and use a flail line like John Pizzey on Piawatha (picture in the-proas-of-john-pizzey-part-2). Systems for launching and recovery of asymmetric spinnakers are well sorted and a joy to use. You probably would not want to scrunch the heavier jib cloth though. I think a single batten for clew to luff might help things. I always have issues with roller reefing not working quite right all the time, I’d worry about the weight and windage of the rolled sail.
IMHO I would add inner stays to the mast and reduce the column length (buckling force function of column length squared) and have a smaller section of mast. It is hard to see but I think you can achieve it without the sail hitting the leeward stay. Would not add any extra termination points or rigging time and savings on mast would I am sure pay for it
Thanks for the Kahana Bay picture your developments are processing well and could lead to lots of fun here.
Tink
Hi Chris, I think “mmburrito” has the answer, in theory, theory and practice are the same…....
The only proof is in the eating .. In this craft where weight shift can be used to good effect I would be happy to try it as you have drawn it. If it doesn’t work as good as you might have hoped there are plenty of fixes available with rudder and centreboard sizes and positions which can be varied without scrapping the boat or making major changes to it. How about small front and rear automatically deploying/raising unidirectional asymmetrical trim boards for a fix if necessary or even a change to a tilting mast. The weight shift for tuning would also show what changes are needed. I would suggest drawing in all the force vectors on the boat in its operating attitude and then make a more educated guess. This should at least highlight any areas of real concern.
Best regards
John Pizzey
IMHO I would add inner stays to the mast and reduce the column length (buckling force function of column length squared) and have a smaller section of mast. It is hard to see but I think you can achieve it without the sail hitting the leeward stay. Would not add any extra termination points or rigging time and savings on mast would I am sure pay for it
That’s interesting. I had been thinking about adding 3 diamond wires—since there’s no mast track to interfere with. But adding lowers is an option I hadn’t thought of. I could probably get away with 3 more—fore, aft and windward. The leeward stay area would get too crowded. Maybe they’re good for hanging little storm sails on super windy days as well!
The Kahana Bay Beach cruiser feels like a LOT less boat to build than Scampi. Not as pretty. Not as comfortable a cruiser. But a nice little canoe none the less. Its sort of a Gary Dierking boat with a few twists.
Maybe I’ll stretch Scampi out to 28 feet…
I’ve been contemplating scampi vs. Kahana Bay Beach Cruiser (KBBC). They’re really different boats and they look it.
I’ve been thinking that maybe scampi was a bit squished lengthwise at 24’. It looks pretty bulky compared to the smaller 22’ KBBC. The rig on this Scampi is an easily handled, reduced version of a basic beach cat with about 180sqft. The KBBC has about 115 sqft (twice, unfortunately). I’ve drawn it with no leech—assuming furlers, which is attractive. But a cool option that just occured to me was that you could have a fully battened jib with chord built into the shape of the battens. Since you don’t have to tack, you don’t need Skip’s bendable batten!
Scampi’s BOA looks a bit much in comparison. And KBBC’s safety ama looks too whimpy!
Hi Chris,
I really like the KBBC right now, I could see that as my next winter project! (and lets be honest, probably the one after that as well).
I might have an idea for how to turn that into a 1 sail boat without too much compromise. I’m sure a picture would help, but I’ll try to sketch it with words:
If you had a track along the leeward rail between the crossbeams, and had the tack of the jib attached to the track so that it could slide back and forth along the track, you could have one jib to use on both tacks without too much fuss. This is similar to a crab claw, except it is a more efficient shape for going upwind. The track could be curved so that it described an arc around the top of the mast, and would keep the forestay tension tight. This would also serve as the leeward mast support. If there were problems with the car binding on the track if the forestay tension is too tight, you could adjust the tension of the windward stay that goes out to the ama - ease it before a tack, and tighten it again after.
For reaching and running angles, the jib could have a boom, or be fully battened, or have a wishbone, but it would be nice to have something that would work with a furling system.
Again, you could play with jib and mast rake angles to give you neutral helm, and even with the tack location on the track. This might work even better on one of he early versions where the crossbeams were wider at the main hull than at the ama.
I wonder if there should be some design criteria for the safety ama, like it should have enough buoyancy so that it can just float the whole rest of the boat when it is fully submerged? If the cockpit is self-draining, maybe it can be smaller. From looks alone, this one looks pretty good to me, especially with all the dynamic lift you’ll get with that concave section.
My biggest question with this type of boat (beach cruiser) is how does one person right the boat after a capsize? If I’m going to take my kids out on this, I need to be able to get it back up if it flips over.
-Kimbal.
The other cool thing about a jib-only boat like this is that when you are charging down the ground swell, you can gybe over to Atlantic proa mode, and probably be more stable with a better sheeting angle. No shunting required!
-Kimbal.
If you had a track along the leeward rail between the crossbeams, and had the tack of the jib attached to the track so that it could slide back and forth along the track, you could have one jib to use on both tacks without too much fuss. This is similar to a crab claw, except it is a more efficient shape for going upwind. The track could be curved so that it described an arc around the top of the mast, and would keep the forestay tension tight. This would also serve as the leeward mast support. If there were problems with the car binding on the track if the forestay tension is too tight, you could adjust the tension of the windward stay that goes out to the ama - ease it before a tack, and tighten it again after.
Ah yes, the tack of the jib on a car rig. I’ve thought about that too. It could bend in the plane parallel to the deck, or it could bend in the plane between the mast and the keel. Or both! It could also be straight as long as there is a way to adjust luff tension, which should be doable. It does seem to offer lots of CE variation options. The thing I don’t like about it is the track. It’s a spendy item. I need to look into the relative cost of two furlers v the track—not that those are the only options. The other thing I don’t like is a loss of luff tension when shunting. Lots of folks have talked about how nasty that can get in rough conditions. But it can be mitigated by the curving the track in one or two dimensions solution.
It is a very cool option.
This render is of the permanently shaped batten/two sail solution. The battens would still be bendy, but camber can get emphasized where it should be, since we have the opportunity. The stays are all in the wrong paces now, because the backstay no longer works with the semi rigid sail. But you get the idea.
The result has a hint of JS Taylor.