Kensho
Kensho is a Japanese word for knowing one’s own nature. Its not enlightenment, but it is an insight.
Kensho looks a lot like Sweet Rhode Island Red, but it is an all new boat, drawn from scratch, very robustly, so that I can easily manipulate all of the aspects of the design without blowing up the model. This is a model that can be used to make parts. As I carefully redrew the canoe, I reconsidered many of the details. Its a start. Pending model testing, this might just be a real canoe some day.
Kensho is 24’ long, 22.5” on the waterline. The L:B of the vaka is 16:1. Displacement is close to 1200 lbs. Sail area shown is 120 sqft. Draft is 19” with the rudders up, 22” with them down, at full displacement.
The akas will slide into glass sleeves at either end. I’m very happy with the new ama to aka attachments. The large radius on the inside of each machined plywood triange provides a sharp leading edge, along with a one sided (no flip) machining strategy. Also, the outsides are flat, for more fiber contact.
The ama is machined foam. It’ll have a 1/4” stringer down the middle, lengthwise. Maybe there’ll be transverse “bulkhead” type stringers near the attachment points. Maybe the connective triangles will just be glassed to the skin, with appropriate glass reinforcement. On one hand, I worry about compression. On the other hand you might be able to skip 8 half bulkhead/stringers and the associated assembly complexity.
The cross section of the rudders are 1.2x the rudders that are on my current, 16’ canoe. I wanted to put a little more paddle in the water on such a long boat. They’re built from 1” thick halves, not .7. You can see the inner spar that supports the platform sticks out to accept the rudder retrieval lines. Pulling on those lifts and folds the rudder over. You can see the hole for the rudder torque line near the front. That’s the one that limits movement aft when it is deployed. It’s tied to the forward (on that shunt) aka, for a fairly horizontal run. A mechanical fuse provides kick up when you hit something. The forward edge of the rudder is sharp above the waterline, to reduce spray. I think these rudders are kind of close. But I wonder if they are deep enough with 22” of immersion. Maybe more with the rearward weight shift.
The platform still needs a little love, but it’s close. The spacing and/or deletion of some of the holes is still in process. I made it more simple than before, but hopefully strong enough. It’s a piece of 3/4” ply that gets lightly glassed on both sides, masked, and then has the perforations machined. That way we can epoxy all of the endgrain, and pull the masking off without making the whole thing as much of a drippy mess. There are two longitudinal spars underneath—the leeward one holds the rudder retreval lines. But I said that.
It’s shown in its upwind configuration—rudders raised, butt steering.
The fore and aft position of the mast is NOT achieved by stays that go to the top of the mast. Those lines will go from the akas to a point a foot or two above the deck of the pod, on the mast. It’s an attempt to get all of that loose spaghetti out of the air during and after shunts. The ww/lw position of the rig will be by a masthead stay to windward, and a leeward “traveler” that attaches at the same height as the fore/aft stays. The lower rigging will put some bending loads on the mast, but I think its a good trade off to get two stays out of the air. The mast will pivot on a ball, beach cat style. The rig will be adjustable ww/lw and fore/aft, for any course. Or at least that’s the plan.
I’m trying to combine a bunch of small discoveries into a simple, cohesive, canoe that respects its Marshallese heritage, but belongs in the 21st century.
Anyway, now to the model building phase.
Some more views
Another very nice design.
How effective do you think the asymmetric hull will be? I am wondering if this should be a standard for chine proa hull designs. Do you know if there is experience and comparison to say that asymmetric hulls are a preferred way to go?
The perforated platform is going to make the user look like he was attacked by a giant squid. How about two 8” boards lashed to the top of the aka, separated by a gap of 16”, with a third board as a footrest, somehow attached to the aka 16” below the top of the two upper boards?
The fore and aft position of the mast is NOT achieved by stays that go to the top of the mast. Those lines will go from the akas to a point a foot or two above the deck of the pod, on the mast. It’s an attempt to get all of that loose spaghetti out of the air during and after shunts.
I’ve been using this idea (sort of) on my proa, in an even simpler form. My mast steps on the bottom of a Wa’apa like hull, and there is a loop attached to the gunwale which you step the mast through.
I’m thinking for a boat this size, the babystays might be more in the way than normal stays. How about a continuous line from the bow, up through a sheave on the masthead and back down to the other bow. Then you put a couple of stoppers on this line to limit rake. Is this similar to what you mean by leeward traveller as well?
-Thomas
The ama is machined foam. It’ll have a 1/4” stringer down the middle, lengthwise. Maybe there’ll be transverse “bulkhead” type stringers near the attachment points. Maybe the connective triangles will just be glassed to the skin, with appropriate glass reinforcement. On one hand, I worry about compression. On the other hand you might be able to skip 8 half bulkhead/stringers and the associated assembly complexity.
Forego the bulkheads, since you are machining the foam you can carve a nice 1/8” or so soft edge recess in the foam and start your layup with a layer of glass followed by a layer of coremat. Once the outside skin is glassed your connective area will be nice and rigid spreading the compression loads (if any, it’s lightly loaded) over a large area.
Nice boat, can’t find anything to make a gentle suggestion on 😉
Would be nice to sail in company with such a boat, Nomad’s coming.
Cheers,
Skip
The final phase of alchemy is Rubedo, which might also be called a “knowing of your true nature”.
Rubedo is a Latin word meaning “redness” that was adopted by alchemists to define the fourth and final major stage in their magnum opus.-wiki
It seems as if you have distilled the same basic paradigm over time, again and again, and that the end result is a craft of refined design that really suits you. It’s been fascinating to watch the process unfold, and thanks for sharing it.
it’s a beautiful boat, Chris. Could it stand a bigger sail? Is this meant to be a gibbons, with the yard ends switching from tack to head on the shunt, or more like a Sunfish rig?
Dave
How effective do you think the asymmetric hull will be? I am wondering if this should be a standard for chine proa hull designs. Do you know if there is experience and comparison to say that asymmetric hulls are a preferred way to go?
I don’t know is the short answer. Its the same number of planks as a flat bottomed dory, which I like. It has a lot in common with Marshallese canoes, including the flat keel section with a fairly cutaway forefoot, which I like. Models will tell me more.
The perforated platform is going to make the user look like he was attacked by a giant squid.
This I actually do know about. I made perforated seats for my Wa’apa (see the thread “Hello, Malolo”) and they are light, sturdy, comfortable band look bitchin.
I’ve been using this idea (sort of) on my proa, in an even simpler form. My mast steps on the bottom of a Wa’apa like hull, and there is a loop attached to the gunwale which you step the mast through.
I love this system. I considered a lot of options in how I would rig this, but in the end, I decided to pursue the simplest fully adjustable set up I could figure out. And this is it. I also considered slots, hinged masts. A loop (like you described) and a loop that starts at the leeward edge of the pod (for less ww/lw translation in a shunt). I might be over thinking it, but I have a little experience with rig balance from Palindrome. Its key to getting it all to work, I think. I’d love to be proven wrong by a simpler set up!
Forego the bulkheads, since you are machining the foam you can carve a nice 1/8” or so soft edge recess in the foam and start your layup with a layer of glass followed by a layer of coremat. Once the outside skin is glassed your connective area will be nice and rigid spreading the compression loads (if any, it’s lightly loaded) over a large area.
Nice boat, can’t find anything to make a gentle suggestion on wink
That’s more or less what I was thinking about the glass; a ring frame under the connectives. Thanks for that! I’m sure some gentle suggestions will arise as this progresses!
Would be nice to sail in company with such a boat, Nomad’s coming.
That would be a blast.
It seems as if you have distilled the same basic paradigm over time, again and again, and that the end result is a craft of refined design that really suits you.
Thanks a lot, Michael. High praise coming from you! This boat is a hodgepodge of ideas from other designs, but that refinement has been missing. I think I’m starting to find it.
By the way, the other design I’ve thought about bringing to fruition, Scampi, needs just what you said it does—6-10 more feet to justify the complexity. I didn’t like that at the time, but after some simmering, I see you were right.
it’s a beautiful boat, Chris. Could it stand a bigger sail? Is this meant to be a gibbons, with the yard ends switching from tack to head on the shunt, or more like a Sunfish rig?
It might just. Its a boom less gibbons rig. The problem is that as the yard gets longer, the mast goes more upright and the CE moves back. Ditto for lengthening the “foot” that is perpendicular to the middle of the yard.
I like the idea of the Hobie Adventure Island type batten—but symmetrically with one on top and one on the bottom, both battens converging at the center of the yard. It would give the rig two fat heads, keep the CE forward, and still accommodate reefing around the yard.
How much sail would you want to fly Dave? The 160 ft feels like a practical maximum for a daysailer like Kensho.
Thanks for your thoughts, everyone!
chris
Could it stand a bigger sail?
Here’s that Hobie Kayak style, round batten sail. It gives a fat head (at both ends) to the sail, and still allows the sail to reef around the yard. The set up adds 30 square feet, for a total of 150. And best of all it does it without moving the CE back.
I also simplified the perforations on the platform.
But the sail is really happening now.
Could it stand a bigger sail?
Here’s that Hobie Kayak style, round batten sail. It gives a fat head (at both ends) to the sail, and still allows the sail to reef around the yard. The set up adds 30 square feet, for a total of 150. And best of all it does it without moving the CE back.
That’s a little slice of genius, that is. I really like it! And 150 sf better suits this boat than 120. You asked my opinion of maximum? Maybe 160-180 sf. 150 is just fine for starters! So you reckon this is a significant improvement over the Dierking/Gibbons rig?
I also simplified the perforations on the platform.
But the sail is really happening now.
[aside] Turn the pod over. You can do it! [/aside]
Dave
That’s a little slice of genius, that is. I really like it! And 150 sf better suits this boat than 120. You asked my opinion of maximum? Maybe 160-180 sf. 150 is just fine for starters! So you reckon this is a significant improvement over the Dierking/Gibbons rig?
Thanks! Is it a significant improvement? Dunnow. It has some neat aspects though. Keeping the sail taught along its luff while you roll it up is one. The battens might eliminate the need to re lash the heads when you reef. And the fat heads might feather/spill off in gusts.
Another guess I’m making is that the boomless version of the D/G rig depowers better when you blow the sheet. I’ve read some scary accounts of the boomed ones flying around when they were supposed to be off. The boomed version is probably more efficient. But if you are going to go boomless, the sheeting angle from the stern is pretty ideal.
As for the pod—I have several I’d like to try in models. This one has a pretty flat run. It’s that pesky leading edge I’m struggling with.
On a reach, with the rudder down.
more reaching and rudder.
Another guess I’m making is that the boomless version of the D/G rig depowers better when you blow the sheet. I’ve read some scary accounts of the boomed ones flying around when they were supposed to be off.
I was told a story of racing a Farrier trimaran with a boomless main in a stiff breeze. On a reach, there was this zone of death in which releasing the sheet first powered up the main, because it got so much more camber. The problem could have been fixed if there had been a wider traveller, but that solution will not be available to you. However, I don’t know whether there will be a problem. Crab claw sails should have exactly the same trait, and I never heard of any such thing. I don’t know what makes the difference.
Also, I think you’ll need a two-part sail, with a slit in the middle, otherwise the halyard will get in the way of rolling up the sail.
Regards
Robert Biegler
Thanks! Is it a significant improvement? Dunnow. It has some neat aspects though. Keeping the sail taught along its luff while you roll it up is one. The battens might eliminate the need to re lash the heads when you reef. And the fat heads might feather/spill off in gusts.
I like all those. Do you think you can roll the batten right up into the reef? That’d be a very neat trick.
Another guess I’m making is that the boomless version of the D/G rig depowers better when you blow the sheet. I’ve read some scary accounts of the boomed ones flying around when they were supposed to be off. The boomed version is probably more efficient. But if you are going to go boomless, the sheeting angle from the stern is pretty ideal.
A lot of guys who try boomless get disappointed by sail shape or set, or what-have-you. Few try a club (call it an oversize clew-board; sounds less violent!) The club allows many more options for sheeting angle and lead, at the price of a (modest sized) chunk of hard stuff banging around. Only if you need it, mind you.
Dave
I was told a story of racing a Farrier trimaran with a boomless main in a stiff breeze. On a reach, there was this zone of death in which releasing the sheet first powered up the main, because it got so much more camber. The problem could have been fixed if there had been a wider traveller, but that solution will not be available to you.
Don’t know if this was mis-translated to you or perhaps there are two separate issues, but the “zone of death” applies to all multis with a biggish rig when sailing fast and deep (offwind). Nothing to do with camber, the problem is the boat is sailing in an apparent wind much lower than the true wind. Eventually, however, the boat becomes overpowered even in this “reduced” wind. The first—and often last—thought is to steer deeper, but even dead downwind, one can be overpowered—and start stuffing the bow(s) in. At this point you cannot bear up because the apparent wind will increase dramatically, you can’t let out the sails (which are likely up against the shrouds by this time), you cannot reef because the sail is fully powered up AND against the shrouds, and over you *will* go. This is a very real issue for racing multis.
There are only two solutions as far as I know. One is to reef very early, in anticipation of the above. Note that this needs to happen very early, while there’s still just 12-15 kts across the deck and you think you are out for a nice afternoon’s sail in your wicked-fast boat. Forewarned is forearmed—KNOW your true wind at all times.
The other is to use an unstayed rig (or solid wing) where releasing the main guarantees the sail will de-power completely, 100%. Almost no one’s ever done this (beaten the “zone of death”) with an unstayed rig—none to my knowledge—but presuming it works, one could drive the boat much harder away from a freshening breeze, knowing the “zone” won’t be there, waiting for you.
Dave