Kahana Bay Beach Cruiser
Kahana Bay is a beautiful beach park on the east side of Oahu. Its sheltered. It has a boat ramp and a little pier—but there’s not much surf at the beach, thanks to the big reef that protects the whole east side of the island. But at Kahana bay there’s a cut in the reef so that you can get out to the open ocean beyond. So fishermen love it.
The Kahana Bay Beach cruiser is another attempt to make a simple, beachable, warm weather proa. 22’ LOA with 12:1ish L:B. It has a 6” thick smoot bottom and a fully machined foam ama.
This version has a canted rig, as described by John Pizzey. His argument for a 15 degree cant is really interesting. And I like the idea of the sail hanging in shape in light winds. Who hasn’t heeled a monohull to leeward in light air to get the sails to have some shape?
But this version has a fixed mast and two big jibs are hoisted (or furled) from either end. I like the isoceles sail, but I’m suspicious of the canting rig that makes it work. I’m sure it works great when properly engineered, but I want a little less engineering, at least in this version. So this is an attempt to get the pronounced decrease in heeling moment, in a simpler package. Hopefully using used, recut sails.
The rudders at the end of the akas came out of the mock ups I have been doing in the garage, thinking about how to rig my Wa’apa as a proa. They’re big beefy chunk of wood, high above the waterline, and they’re on the leeward side where all the spray is just a little further away. Torque control measures would have to be better than I’ve shown. I’ve angled the akas to put the rudders where I want them.
Not having a pod or a safety ama is hopefully offset by the reduction in heeling moment of the canted rig. But now that the rudders are there, the front one is interfering with the sail.
Back to the drawing board.
Auxiliary power will be either one or two hobie mirage drives which will also act as drains for the cockpits.
best,
Chris
now with a spinnasurfer rig…
on a reach…
Here’s a closeup of the safety ama…
Developing nicely Chris
Looks good with the Spinnasurfer rig on it, I don’t think, with the right rig adjustments you will need to use the rudders much. Off wind it looks really good and with the angle of the sail I think you should get the bow to lift a little.
I like the two level seating platform, lots options and great for a crowd on board on a hot sunny afternoon.
Safety ama looks good, lots of dynamic lift at the sort of speeds it will come into play.
The bulwark with the curved triangle on top for supporting the rudder looks good. Why have you moved them over to windward? Clash with safety ama? Easier ergonomics, in use and deploying recovery?
I have a very clear vision in my head of many fine days at Kahana Bay….... The snow has stopped and it is just raining and very windy here in the NE UK.
PS still thinking about the Spinnalug, reefing is a must for me, we get four seasons in one day frequently.
TINK
Thanks for your comments, Tink.
It would seem like you might not need rudders at all with the spinnasurfer. Maybe there’s just a daggerboard in the cockpit floor (same well that holds the hobie drive?).
I moved the rudders to windward because they interfere with the rig less, and because using the akas as rudder mounts means that the akas can’t hold up the safety ama. But I’m not sold on the idea. There’s something so neat and clean about mounting them on the akas. And having them to leeward appeals from the point of view of spray.
One of the main ideas behind mounting the rudders on the akas is to raise up the top pivot point to separate the two pivots, without making the lower pivot too close to the water. So on this version I made a little tetrahedral structure out of the breakwater.
There’s no reason you couldn’t reef the spinnasurfer rig. You just need a mast track—like other reefing wishbone boomed rigs. The battens and reef points would be parallel to the foot of the sail.
Chris
Dear Chris
I like the idea of the rudders on the akas, the rudder mounts hitting waves was an annoyance on my TP02 proa.
You have reefing sort out as well.
And I am in big favour of a dagger board and getting rid of the rudders
TINK
I LOVE the paint job! I also love the whole boat. The safety ama is very cool. I wasn’t really a fan of the Pizzey inspired rig (I love the Pizzey rig, just not on this boat) and I think you are getting much closer with the Spinnasurfer - you could use a standard windsurfer rig, perhaps the mast is borrowed from a Sunfish.
It would seem like you might not need rudders at all with the spinnasurfer. Maybe there’s just a daggerboard in the cockpit floor (same well that holds the hobie drive?).
That’s what I’m thinking. The CE is so adjustable that a steering paddle in the Hawaiian tradition would manage perfectly well, and you could butt steer most of the time.
Great work!
The CE is so adjustable that a steering paddle in the Hawaiian tradition would manage perfectly well, and you could butt steer most of the time.
I like it. So here’s my paddle-type steering set up. There are two very paddle-sh leeboards, mounted on shafts that go through the vaka. The shafts have a lever on them, to adjust the angle of the leeboard. There is a brake on the shaft that is operated with a bicycle brake lever. Squeeze the lever, release the brake. That way these can be used to steer in real time, or set hands free to play with the CE of the rig.
There’s a part of me that’s just plain scared of not having a rudder. What’s it going to be like trying to steer it with the sails in confused seas or while surfing?
On the positive side, its pretty damned simple (except for the brake which is TBD). It can be made to kick up. There are no holes in the hull (except for two above the waterline for the leeboard shafts). It should be pretty adjustable and provide nice feel. And there are no control lines for the boards.
On the downside, they’re not as efficient as foils under the hull. Laying them on their sides in the water is not maximally efficient. And the swing of the lever limits where you can put them.
But there is something nice about replicating the paddles against the hulls style steering of Hawaiian canoes with a modern twist.
reaching…
Loving the steering boards, have you thought of linking them, with a simple bar when you lower the aft one front one would go up.
The other way is a leeboard moving fore and aft which I like, TP03 waiting in the garge uses that, will feed back when I get it afloat. It could be as simple as hooking over the gunwale, just thinking out loud
Re rudders you can always have a fall back plan and retro fit
TINK
Michael may not be feeling my Pizzey-sh rig, but I keep coming back to it.
The big advance in this version is that it is stayed to leeward. Because there’s no booms or yards to shunt, just two good old jibs that furl or hoist from each end, there is actually room for a stay. Now I can step the mast wherever I want and have a well supported rig, even caught aback. I’ve taken advantage of this freedom to move the forestays to the windward side of the vaka. Now the jibs drop onto a deck. It makes more room for the leeward stay and shifts the CE of drive a little to windward.
Downwind, there’d be a barberhauler coming from the leeward tip of the forward aka, which moves the sheeting point forward and to leeward.
The rudders are good old newick/brown type. But because the uncluttered cockpit is just 7’ long, there’s no need for control lines to raise and lower them. They don’t even need tiller extensions.
There’s something soothing about how simple this is compared to a lot of the cockamamie rigging schemes proanauts come up with…me especially! There are 6 strings; two sets of sheets, halyards and barberhaulers.
The canted rig that depowers faster is a very compelling idea. But there’s no reason why we couldn’t rig this boat with the mast upright or even canted to windward. That leeward stay buys you a lot of flexibility.
It’s just the one sail for the price of two goes against my less is more thing… but I still think it’s a cool boat. I saw an interesting proa rig in an AYRS publication that featured an isosceles sail, set from a central, free-standing mast. The mast was super bendy so that by pulling the forestay tight, the mast tip was bent forward, allowing the head of the sail to move fwd, and basically doing what the Pizzey rig does but without a canting rig - the bend created the movement in CE, and also tensioned the rig like a bow.
I this case, I imagine that a windsurfer mast stuck into the top of an alu mast might work, stay the rig to the top of the alu mast, and let the upper section bend fwd under tension from the forestay.
I saw an interesting proa rig in an AYRS publication that featured an isosceles sail, set from a central, free-standing mast. The mast was super bendy so that by pulling the forestay tight, the mast tip was bent forward, allowing the head of the sail to move fwd, and basically doing what the Pizzey rig does but without a canting rig - the bend created the movement in CE, and also tensioned the rig like a bow.
I remember this rig appearing on TV in the UK. It was on a beamy double ended hull (looked like a lifeboat) with the mast in the centre. The sail had two luffs and the required tack pulled to the respective bow and as said the mast bent. The idea of the boat was that it would be simpler to teach people to sail and they would not hit their heads on the booms. The idea never caught on with sailing schools.
The rig has legs though, I can see the mast canting fore and aft against bungie stays with back stays to limit the canting, one isosceles ‘jib’ with two luffs.
I will look for a picture in my AYRS stuff
TINK
The CE is so adjustable that a steering paddle in the Hawaiian tradition would manage perfectly well, and you could butt steer most of the time.
I like it. So here’s my paddle-type steering set up. There are two very paddle-sh leeboards, mounted on shafts that go through the vaka. The shafts have a lever on them, to adjust the angle of the leeboard. There is a brake on the shaft that is operated with a bicycle brake lever. Squeeze the lever, release the brake. That way these can be used to steer in real time, or set hands free to play with the CE of the rig.
There’s a part of me that’s just plain scared of not having a rudder. What’s it going to be like trying to steer it with the sails in confused seas or while surfing?
On the positive side, its pretty damned simple (except for the brake which is TBD). It can be made to kick up. There are no holes in the hull (except for two above the waterline for the leeboard shafts). It should be pretty adjustable and provide nice feel. And there are no control lines for the boards.
On the downside, they’re not as efficient as foils under the hull. Laying them on their sides in the water is not maximally efficient. And the swing of the lever limits where you can put them.
But there is something nice about replicating the paddles against the hulls style steering of Hawaiian canoes with a modern twist.
I love the rig, not so much the pivoting leeboard.
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…
The rig is really appealing. What I like compared to Tink lug rig is the fact that the luff tension is taken care of by the “tilting spar” and the sail with not impact on the mast what so ever. Depending on the geometry you start with, you can increase or decrease the amount of swing of the CE from one tack to the other. I am not sure you will be able to bring it forward to middle of the boat though. In your (beautiful, as usual) models, I would guess that the CE is pretty much in the mid transverse plane.
So you will need rudders, my friend, rudders…
So now, the negative points about the rig (I am French, I have to complain).
Added weight up high, you have now two long spars pointing pretty high, not so good. (Coming from a guy who had a 30ft aluminum mast on a 20 ft proa, and now has a schooner rig, it’s pretty funny, isn’t it?...)
But (at least) one of them can be a windsurfer rig, if you do not want reefing capability; it’s pretty light, actually.
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… Maybe a solution to that would be to have the mast with the foot as much as possible to windward, and tilted to the leeside. But then, when you swing the “bottom pivoting sprit” (how am I supposed to call that thingy???) from one tack to the other, the tack of the sail will get dangerously close to the water… Maybe by attaching the “bottom pivoting sprit” on the leeside rather than the mast could solve this…
So many possibilities…
Cheers,
Laurent
There is a rig in AYRS Catalyst from say… 10 years ago that Chris is well on his way to re-inventing. If all my crap wasn’t all packed up right now I’d go hunt it down. The rig was tested on a sailing dinghy, but it would make a perfect small proa rig. It even won an award that year.
The rig has legs though, I can see the mast canting fore and aft against bungie stays with back stays to limit the canting, one isosceles ‘jib’ with two luffs.
I like that idea. The bungies would keep everything tight and in control while the sail swapped leading edges and the mast pivoted forward to the new bow.