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PostPosted: Wed Apr 04, 2012 5:35 am 
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chrisj wrote:
I finally got a chance to try the Raka out on the water today. Winds: 10-15 knots. Experience: excellent. I haven't had a chance to try Hakas yet, so I can't compare, but, as NOHUHU predicted, the Raka certainly gave the experience of sitting high and dry(ish) out over the water. It felt just like sailing a Cat. I stayed on it all day, but, I must admit, when I had to return to my launching spot, dead upwind, I ended up dropping back into the seat and using the Mirage drive. The seat felt cramped by comparison.
One thing I particularly liked was that I could adjust my sitting position according to conditions, so that the amas remained level at all times. What I am not sure about is whether I would be able to hike out far enough to keep the boat level at wind speeds of 20+ knots.
An unexpected benefit: the boat seemed to tack much better. I think it might be a combination of the boat turning better with the bow lifting out of the water a bit and me remaining hiked out for a few seconds after the boat crossed the wind, which seemed to help it fall away from the wind.
Next time, I'll try it in Haka mode, for comparison.


Moving your weight aft is a tried and true way to make a trimaran tack easily. It could also be making your boat make more leeway when sailing upwind. Less bow in the water to push sideways (upwind) means you'll drift a bit more downwind as you go. Not a big deal if you're just sailing for fun.

Speed tip: wetted surface is slow and your sail is fastest when as close as possible to vertical. Adjust your weight to keep one ama in the air or occasionally touching the surface. This will not appreciably increase the wetted surface of the other two hulls, so you'll go faster. Heeling beyond the angle required to keep one ama out is slower because your sail spills more and more air off the top as you heel more, wasting power.


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PostPosted: Wed Apr 04, 2012 6:30 am 
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Tom Ray wrote:
Moving your weight aft is a tried and true way to make a trimaran tack easily. It could also be making your boat make more leeway when sailing upwind. Less bow in the water to push sideways (upwind) means you'll drift a bit more downwind as you go. Not a big deal if you're just sailing for fun
Thanks for pointing that out Tom. That's really interesting. As a matter of fact, I did wonder if I was not managing to point as high at times. I usually use the drive when sailing close hauled, so I wasn't sure if I was imagining it. I guess sailing upwind with the bow slightly out of the water is like sailing without a daggerboard. Next time, I'll try it with the Mirage drive in and the fins down, to try to compensate.

I'm not sure I agree with you about lifting one ama out of the water. Since both amas are slightly in the water when the boat is level, any lifting of one ama will result in a corresponding deepening of the opposite ama and the total wetted area will be unchanged. Not only that, but the actual frontal area which the buried ama presents to the water will increase in proportion to the square of the depth to which the ama is buried, creating a disproportionate increase in the resistance of the water. That's why burying an ama slows the boat so much. I'm no naval architect - correct me if I'm wrong, but I believe the boat will be capable of its maximum speed when it is dead level.

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PostPosted: Thu Apr 05, 2012 3:08 am 
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Chris, I don't know the answer for sure on Adventure Islands. I used to own a Corsair F-27, and on that boat you definitely wanted to keep one ama flying at all times. I used to race on a friend's Multi 23 and the same rule applied. The Multi 23 was actually built to fly one at all times unless heavily loaded, so it was always leaned over one way or the other at the dock. Kind of annoying when you're trying to do something and it shifts to the other ama.

Anyway, on those boats and, I hear, on other trimarans, the additional wetted area of the lee ama is more than made up for by getting the windward one clear of the water.

Adventure Islands may be different. They sit with both amas pretty far in the water even unloaded, so the lee side ama has to be significantly buried to keep the windward one clear of the water. That means the sail has to be tilted, spilling air. Underneath the boat, it also means the daggerboard and rudder are not vertical, so they are spilling water in the same way the sail is spilling air.

I have always assumed that the AI behaves the same way fast multihulls do w/respect to keeping an ama airborne, but it may not be true. You're going to have to experiment and tell us. :wink:


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PostPosted: Thu Apr 05, 2012 4:41 am 
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CaptnChaos wrote:
NOHUHU wrote:
I think you'll like sliding around in the Haka mode. High and dry. The view is outstanding.

You can always jump back in the seat when you want to take a cold bath.

You sure hit the nail on the head NOHUHU. The only downside of switching from haka to haka is the the momentary dip into the "cold bath". Although that may be a positive thing when summer gets into full swing.


What Nohuhu and Jim said!
Well I'm now a Haka convert.
Went out today in light winds (around 10 knots) and had such a great time. The thrill was very much like the first time I ever went AI sailing. What a difference the haka make. Great position -up high, a much drier ride and very comfortable. I experimented a bit with different positions and could actually see the AI's nose rise when I sat further back. Looking forward to testing it out more.
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Steering by foot.
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It's a bit hard to see but I'm standing on the haka in this shot.
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I was only out for 2 hours but I'm sold... so next job make the second one and fit press studs for the cushions.
Oh... and a hiking stick is now a priority as well.

PS: Thanks Nohuhu and the other haka purists for their contributions in this thread. This has probably been the most significant and valuable mod I've adopted. The sailing is greatly improved and it should double as a camping platform very nicely. I can see huge potential with this and can't wait to try it out further!

PPS: I know it doesn't look anywhere near as beautiful as the fantastically crafted timber haka but it performed so well today that I'm prepared to cop any 'home maintenance/painting' jokes that may arise. It may not be pretty but it is functional! :lol:


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PostPosted: Thu Apr 05, 2012 6:11 am 
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You sold me Stringy! Being in the clydesdale class, I will base it on that industrial strength ladder, but I can hardly wait too now LOL


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PostPosted: Thu Apr 05, 2012 8:39 pm 
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Great to see it coming to fruition Stringy and not a scrap of wood to be seen :wink:. Since we're both testing our setups on Brisbane Water, we should meet up some time to compare notes and to take some photos of our rigs in action.

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PostPosted: Thu Apr 05, 2012 10:24 pm 
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Well done mates! Looks like the age old Haka idea is going viral. Brings a tear to my eye,.. :cry:

Thanks so much for the picts and feedback Stringy. Hope to see video from you guys soon.

Hobies tramps are great for passengers and I really enjoyed hiking on them for couple years, but the Haka (and wing) takes things to the "next" level.

"Kulia i ka nu'u" the Hawaiians would say. (Seek the high ground/strive for excellence).

I might add - enjoy the ride!

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PostPosted: Thu Apr 05, 2012 11:09 pm 
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Well done mate. I haven't really followed this thread for some reason but now I wish I had. Great ideas from all round the globe.

( hope you didn't 'borrow' that ladder from work Stringy )

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PostPosted: Thu Apr 05, 2012 11:44 pm 
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NOHUHU wrote:
"Kulia i ka nu'u" the Hawaiians would say. (Seek the high ground/strive for excellence).

In that spirit, I thought I'd push the envelope a bit further. Here is the Raka sitting in Front of the rear crossbar (I hesitate to call it a "Faka" :shock: ).

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"Why?", you may ask. Well, it retains the ability to hike or sit out, while giving the ability to seamlessly access the drive. I've added my trusty old Ocean Kayak seat, which normally is left folded forward, but can be folded up to provide lumbar support in case of prolonged pedalling (Just to pedal through a tack, I don't think I'd bother). I've tried it out on my dam and it works fine. The proof of the pudding will be in sailing out on open water. The one obvious drawback is the need to duck when the sail is coming across the boat, but that's a feature of most sailboats. At least there's no boom to punish you if you forget. I've reversed the rear akas and strapped them to the seat for stability. If this prototype works well, I may put another set of ball posts behind the crossbar and attach the crossbraces to them.

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PostPosted: Fri Apr 06, 2012 1:06 am 
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Stringy, where did you source the aluminium mesh?


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PostPosted: Fri Apr 06, 2012 2:15 am 
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Cool Chris! I think you'll find that an even better seating position, as long as you can reach the pedals.

Once the sail is leeward you'll be able to slide instantly from center to side. And still retain all your aft storage. On long hauls, that's a bonus

However, when I stayed in the raised center position while beating, I remember being frustrated by the sail blocking my vision more. At times, I think I stole a bit of wind from the sail flow too, so I moved out over the windward rear Aka, or back in the seat when I needed to maintain a tight upwind course. But reaching the pedals will help with this.

Tell us how it works out under sail.

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PostPosted: Fri Apr 06, 2012 2:45 am 
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Wow! Great ideas, excellent execution. Haka, rakas are the way to go. Thanks NOHUHU, Stringy, Jim, Chris, etc.

Keith

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PostPosted: Fri Apr 06, 2012 2:51 am 
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No problem reaching the pedals NOHUHU and I don't have long legs. It's hard to beat the Mirage drive on a tight upwind course, but I found I really didn't like having to get back into the Hobie seat after testing the wing for a while. There are still some advantages to sitting further aft and raising the bow and I might try it in combination with my old PVC rear seat.
As a matter of fact, there's something to be said for having a pair of hakas with a wing running between them in front of the rear crossbar and a seat behind the rear crossbar. Trouble is, all that decking would be a bit hefty, though the Batboat comes close.

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PostPosted: Fri Apr 06, 2012 3:02 am 
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I like Faka position better than Raka.


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PostPosted: Fri Apr 06, 2012 4:15 am 
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This thread sure is growing. Glad to see more converts and the heavy duty ladder designs. I was out all day yesterday with very strong wind and enjoyed the hakas. Sitting on a West Marine cushion made it even more comfortable.

chrisj wrote:
I've reversed the rear akas and strapped them to the seat for stability. If this prototype works well, I may put another set of ball posts behind the crossbar and attach the crossbraces to them.
I'm not so sure about that mod Chris :o . In big wind not having the akas attached might cause problems.

Also, using a leash is highly recommended with hakas. When switching from haka to haka, it provides a nice level of security. Especially when sailing by yourself.

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