THE HAKA BENCH SEAT - AN ALTERNATIVE TO TRAMPS

NICE!

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Hobie Island Sailing since 2006

Thanks, Bob. It's been fun, and I hope the daggerboard will slow the leeway going to windward. Trimaran's have a lot of wind resistance compared to a weatherly monohull. That's another reason I want to perfect my haka's. the tramps catch too much breeze as the boat heels.

The first week the tramps were sold in Hawaii, two different friends flipped their original AI's cutting over a wave when the tramps acted as additional sails. The new Islands with their extra weight don't seem to be as much of a problem, but I do prefer haka for all but maybe snorkeling off the boats with little wind with friends.

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Hobie Island Sailing since 2006

Very nice work on those Haka Mike and I like the innovation of the daggerboard slots.
Looking forward to your results.
You are you using ama 'keep out' lines or the like? I imagine the haka mounted daggerboards would add extra pressure to the brace bar pin.

Thanks Stringy. OK what are ama "keep out" lines? I have preventers on each knuckle insert so that the aka's cannot dismount. The hakas themselves are inboard up against the outer casing of the knuckle, so they don't tend to move inboard at all. However, I was out today in open water going to windward against 1-2 foot chop (the half height). What is happening is that I have way underestimated the side force generated by the daggerboard.

The hakas are pinned to the akas only by shock cord. So the side force is literally twisting the windward edge of the hakas up off the akas. I'll have to fasten them more securely.

With so much wave action today, I really was not able to selectively test the boats performance with the dagger in and then dagger out--mainly because the dagger was impossible to remove except in the middle of a tack. I'll have to make the inner trunks over again and put graphite in the epoxy coating so that I get slippage when torqued.



However, the board has to be doing something, because the lateral resistance is creates is obviously very large at 4-5 knots boatspeed.

Mike, "keep out lines" are a description of rigging up lines which help to avoid over straining your aka brace bolts.

In your situation, with that huge amount of force being generated by that big daggerboard, I believe you will need a couple of complimentary solutions.

1. Run diagonal lines from the hull to the outer ends of the akas, If you run two lines at about 90 degrees to each other, and they are not stretchy, you will maintain both your akas in place even if the aka brace pin should fail. (normally people would make these lines out of rather stretchy material, as there primary use would be to soften the impact of a broken brace pin, but in your case, you want rigidity).

2. I would suggest that as well as tying down your haka to prevent it twisting, you add lateral parts underneath to physically lock the haka between the akas. This will add to the rigidity mentioned above. (You can cover the parts touching your akas with thin closed cell foam or rubber to prevent scratching the aka surface).

Your daggerboard mod sounds exciting, as quite clearly you ARE generating the side force you were hoping for, and it will be interesting to see the results when you get the opportunity for some side to side comparisons.

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Tony Stott
2012 Tandem Island "SIC EM" with Hobie spinnaker

Thanks, Tony--obviously yes to tying down the hakas to the akas.

One of the benches is fasted to the forward aka with padded 1.5" vertical boards on both sides of the aka pipe. This version prevents the ama from folding back while the haka is attached. It does not prevent it in the same way as lines would. A collision would break a pipe or worse. But I don't beach launch or sail in surf, so I'm not so worried about that. I don't know what kind of pressures the "two board" haka attachment puts on the knuckle insert....

The other haka I have left the ama free to swing back if the brace pin fails....

I still don't like the amount of play in the knuckle assembly sailing upwind or on a reach across slightly stacked up waves. It just seems like a recipe for excessive wear (which I can see happening) and metal fatigue. However, if I glued the knuckle insert into the Xbar, the small rotation necessary to lift the folded ama into the trailer cradle would disappear, and I would then have to modify the trailer. And that glue job would only fix one of three points of looseness in the joint (the insert, the vertical pin, and the rivets). I really loved the original AI1 single vertical pin version of this joint. The new one mounts and dismounts easier, and I guess is easier to replace (not sure about that), but all that jumping up and down in the joint just scares me in the sort of bay chop I mostly have to sail in.

the waves in the picture are not breaking or showing white caps, but they are steep in places and close together, and they really give those loose joints a workout. I've experimented with the idea of lines extending downwards to something like chainplates in the hull just below the waterline to stabilize the joints, but I don't think that would work. You can tie a line from the upper part of the 90 degree bend in the aka underneath the boat to the same place on the other aka. Crank that line up bar tight and you still get the movement in the Xbar-knuckle joint. I don't think the rotomolded hull has enough stiffness to make this tentative solution work.

Mike, I actually have similar concerns, but for a very different reason. My haka has a built-in mount for my two stroke outboard, so the forces applied in my case will be in the opposite direction compared to your dagger board, but equally impacting the aka joints
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A not-so-MacGiver solution might be to load up the joint by applying tension via bungee cords. I can't envisage exactly how, but if there is enough pressure on the knuckle, it will sit (mostly) at one end of the slack rather than moving around and possibly causing wear. (thinking out loud... could rubber inserts go >inside< the aka joints, in the spaces at the sides of the inserts.

On my hakas, I have lateral pieces 2 inches high at both ends, with 10mm yoga mat padding under the haka and between the akas, so my haka is a tight squeeze (obviously yours would be slightly different with the aka brace leading forwards). My padding effectively stops all fore and aft movement of the aka hinges.

Still thinking... you could rig up a line from the outer front aka to the bow, and back to a cleat in the cockpit to counteract the drag from the daggerboard. You could either tension it, or at least feel the forces being generated by the daggerboard. I think I will need to set up something similar at the back aka for my outboard

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Tony Stott
2012 Tandem Island "SIC EM" with Hobie spinnaker

Tony--I see your concern.

From my side, I don't think there is that much drag from the daggerboard trying to rotate the ama backwards. It is a high aspect ratio, perfectly shaped windsurfer board--lots of lift until it stalls, and very little drag. The strong life is trying to rotate the leeward aka and ama downward, which probably counteracts the push upward of the buoyant ama. Once the haka's are stabilized so as not to rotate themselves off of the akas, the daggerboard/haka assembly is trying to break the aka, which I don't think it can in any way do.

I've rigged up lashings to hold the hakas in place (since I'm not at home near my shop). If it doesn't rain too much today or tomorrow, I should get another sail with the daggerboard working. The boat certain turns a lot sharper with the daggerboard down.

I'm on the Eastern short of Lake Ontario for another 10 days, then back to Philly. Where are you located??

I'm in Forster, a holiday town about 170 miles north of Sydney Australia. My local lake is 74km2 in area, but a flip of a coin (and direction of wind and tide) determines whether I sail amongst the oyster leases in the lake, or head outside to the ocean. What a lovely decision..

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Tony Stott
2012 Tandem Island "SIC EM" with Hobie spinnaker

Mike - Do you have a tracker? A GPS or phone app like navionics should clearly reveal any advantages in pointing or speed with the 2nd dagger. Test it on both tacks and share if you can.

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The Wind Is Your Friend...

Field reports, Mike?

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The Wind Is Your Friend...

Just showing my haka, with labeling after a friend asked how things worked (that'll teach him!) My little outboard is not directly attached to the hull. Videos to come (no-name Chinese 3.5 hp water-cooled two stroke). In theory the motor midships should always see the prop underwater no matter the sea state.

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Tony Stott
2012 Tandem Island "SIC EM" with Hobie spinnaker

Quite the rig. Gets the Haka utility prize for the 1st motor mount, I think.

Funny though- I don't see a label for the seatbelt/leash. With a motor AND a big kite, there's nothin but you to stop her!

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The Wind Is Your Friend...

I originally bought tramps for my 2014 TI, but was not happy with them. Hakas seemed like a much better alternative. I spent many hours reading various posts on this forum, full of great ideas, but I wanted something simpler than wood, and I didn't like the spine board idea. I kept thinking, "what's light and strong?" and finally hit on it - bamboo! A quick look online found several suppliers of bamboo, and I ended up buying 25 8-foot pieces of 1 1/4" bamboo for $120. I did spend some time on the internet reading about bamboo construction, and learned that splintering is a problem when you cut it. I used the recommended method, which was to tape around the bamboo with masking tape, and then cut with a hack saw. Very easy. Then I used a table-top belt sander to just smooth and taper each cut, so that there are no splinters. I also read that drilling bamboo will cause it to split, and using any kind of nails or screws is not recommended. Construction was quick and easy, except for a minor diversion trying to hold the pieces together by lashing. I was never a Boy Scout, and I couldn't get the lashings tight enough. Then my husband suggested using zip ties, and my problems were solved.

I chose a 5' 9" length for my hakas, only because that's what would fit into the bed of the trailer that I use to transport my TI. They could be longer if you want. I used 10 bamboo poles for each haka, and had plenty of short pieces left over for the cross-pieces. After I cut the pieces to length, I laid the 10 pieces out, and used bungie cord wrapped through them to hold the whole thing together temporarily.


Then I zip-tied the cross pieces, using 2 zip ties for each pole, and 3 cross pieces for each haka, one at each end and one in the middle. 60 zip ties for each haka, total of 120 zip ties. I used the black zip ties with 75 lb. test, so I'm pretty sure that they will hold together.


Once I had the end cross pieces attached, I pulled the bungie cord out, then added the middle cross piece. The bamboo poles are not completely smooth, but I put the end cross pieces on the top and the middle cross piece on the bottom, and that seemed to work well to even the whole thing out a bit, and make it pretty stiff. The bamboo itself is extremely strong, it's just a matter of holding everything together and not having too much "play" in the haka. I attached the hakas on the akas using bungie cords that use carabiner-style clips instead of just open clips, which should be a lot stronger (found at either Lowe's or Home Depot?). One cord on each aka, and then I just zip tie the bungie to one pole of bamboo to prevent loss. They are quick and easy to put on and take off.


Each haka is about 14 inches wide, and each weighs about 10 pounds (4.6 kg). Obviously if you made them longer they would weigh a bit more. They are quite comfortable to sit on as is, although you could add some sort of seat or padding if desired. I also have done nothing to "finish" the bamboo. Most people don't recommend putting any kind of finish on bamboo, so we'll see how well they hold up over time. I haven't put any padding between the akas and the hakas, but I have seen no evidence of wear on either side. I did remove the holders for the kayak paddles from the akas so that the hakas will sit flat on the akas. I keep the hakas in pretty close to the hull, but you could move them as far in or out as you want. There is just enough room to get a paddle in between the hull and the haka, but I only use a paddle for getting in or out of docks/shore, so usually the person in the stern can take care of that. After quite a few hours of use, I did cut a few zip ties on one end of one haka to adjust the cross piece a bit, and I pulled a few zip ties tighter, but otherwise I have made no changes to the original design.

My first sea trial of my new hakas was on Lake Erie in 20 mph winds and 3 to 4 foot waves, and they worked great! Sitting in the front I was still very wet, but not nearly as wet as I would have been if I had been sitting down in the seat, where waves were regularly completely filling the cockpit. And having the weight out to weather definitely helped the boat sail better and kept the leeward ama from submarining. I have since used them for a week up in Georgian Bay (Lake Huron), and for a picnic sail with two friends on a nice day on Lake Erie. I hope to do some camping in the future, and I think it will be easy to lash things to the bamboo poles. As a last note, I also think that they look great, and have gotten a lot of comments on them from bystanders.

Sea trials in Lake Erie:


A nice day in Georgian Bay: