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Should I raise the amas on my AI?
http://www.hobie.com/forums/viewtopic.php?f=69&t=43938		 Page 2 of 2
Author:  NOHUHU [ Tue Aug 28, 2012 4:25 pm ]
Post subject:  Re: Should I raise the amas on my AI?
:lol: :lol: :lol: That seems prudent! We'll wait,..
Author:  Slaughter [ Fri Aug 09, 2013 2:24 am ]
Post subject:  Re: Should I raise the amas on my AI?
chrisj wrote:
I am planning to sail the boat from the quarterdeck with no amas, but I was waiting for summer - for the water to warm up a bit :roll: :roll: :roll:


OK, Chris, a summer has now come and gone. What happened ?

( don't know I missed this thread ).
Author:  fusioneng [ Fri Aug 09, 2013 5:37 am ]
Post subject:  Re: Should I raise the amas on my AI?
Chrisj:
Interesting stuff, I have a TI and have always contended that the AMA's should have been designed so they sit 1 foot further out so the boat would be 12 ft wide vs the current ten ft wide. Lengthening the AKA's would also raise them a little. I wonder if the AI would also benefit from a wider stance.
Bob
Author:  chrisj [ Fri Aug 09, 2013 6:26 am ]
Post subject:  Re: Should I raise the amas on my AI?
Slaughter wrote:
chrisj wrote:
I am planning to sail the boat from the quarterdeck with no amas, but I was waiting for summer - for the water to warm up a bit :roll: :roll: :roll:


OK, Chris, a summer has now come and gone. What happened ?

( don't know I missed this thread ).

Russ, life turned seriously pear-shaped soon after I posted that and I only got to go sailing two or three times all summer, so I have yet to try it. I'm hoping to get more opportunities to get out in the boat in the next few months.

fusioneng wrote:
Chrisj:
Interesting stuff, I have a TI and have always contended that the AMA's should have been designed so they sit 1 foot further out so the boat would be 12 ft wide vs the current ten ft wide. Lengthening the AKA's would also raise them a little. I wonder if the AI would also benefit from a wider stance.
Bob

Bob, what benefit do you envisage in a wider boat?
Author:  tonystott [ Fri Aug 09, 2013 6:46 am ]
Post subject:  Re: Should I raise the amas on my AI?
I can try and answer that Chris.. The wider stance offers greater resistance to heeling, without any increase in drag from the water. Added bonus is greater tramp area. Interestingly, that giant french trimaran I posted in the America's Cup thread had a width equal to its length, so theoretically and AI could have a 50% wider beam! But I think that the design would need just a few changes if the amas were each almost a metre further out from the main hull!
Author:  fusioneng [ Fri Aug 09, 2013 7:52 am ]
Post subject:  Re: Should I raise the amas on my AI?
Chrisj:
I couldn't have described it any better Tony. At least on my TI if I am on a reach in 12 plus mph winds, the AMA submerges under water, so I have to reef the sail 1 turn. If the boat were wider this wouldn't happen.
When I got my first TI I started with a 35 sq ft jib, it turned out to be too much sail so I had to cut it back. If you look at the specs on most of the other tri's out there like the Windrider 17 (which is 12 ft wide), they are all much wider, in my opinion there would be no downside to the change, actually being 2 ft wider would be nice because you could have Haka's and the tramps installed together.
Bob
Author:  chrisj [ Fri Aug 09, 2013 2:05 pm ]
Post subject:  Re: Should I raise the amas on my AI?
OK, so if you increased the effective width of the boat by 1/6th, you would increase the upward leverage which each ama exerts by 1/6th and reduce the submerged volume of the ama by about 1/6th. I can see that being of benefit in the newer AI, with the larger rudder, because it does not suffer from weather helm in higher winds. In the case of the older AI, which had considerable weather helm, I think the benefit would be less, because the drag of the leeward ama mitigated the weather helm to some extent, so lessening that drag would require either compensation with the rudder or reefing the sail further. I've never sailed a TI. Do they have much of a tendency to weather helm?
Author:  Slaughter [ Fri Aug 09, 2013 4:18 pm ]
Post subject:  Re: Should I raise the amas on my AI?
Fully understand about the trialling Chris.

With a wider stance, is there a tradeoff ? In some way, with every design mod, there is always a tradeoff but the only downside I can see is the weight gain from the Akas being a bit longer and the aesthetics. It would look ugly.
Author:  siravingmon [ Sat Jul 12, 2014 10:10 am ]
Post subject:  Re: Should I raise the amas on my AI?
Hi Chris,
Have you had time to use your raised Ama's much this season yet? I'd be interested in hearing a long term report or from anyone else who's done something similar.
Do the raised Ama's mean your AI tends to bury its nose more down wind than before?
Author:  chrisj [ Sat Jul 12, 2014 4:42 pm ]
Post subject:  Re: Should I raise the amas on my AI?
Hi Simon,

On further experience with the raised amas, I have to say that they are really only advantageous in light winds and sailing from the quarterdeck. The reason is that the boat needs to be kept level to keep both amas out of the water. I can do that by sliding from side to side. With the higher centre of gravity of the quarterdeck the boat feels quite wobbly at first, but once you get the hang of it, there really is a marked improvement in light wind performance. In heavier winds, I can't hike out far enough to keep the downwind ama out of the water, so the benefit is negated. Because I am using the Quarterdeck, I don't have a problem with the nose burying, as I can just lean back to lift the nose - that's an advantage of the quarterdeck even without raised amas.
In zero wind and pedalling from the standard seat with the sail furled, there is less resistance and the boat moves faster. I also have a set of unmodified akas and crossbars, so I just switch between them at the beginning of the day, depending on the likely conditions.
Stringy achieves a similar effect sailing his AI with no amas attached and using a smaller sail. He seems to achieve speeds comparable to an AI with amas and a full sized sail.
Author:  siravingmon [ Sat Jul 12, 2014 10:59 pm ]
Post subject:  Re: Should I raise the amas on my AI?
Thanks Chris,

I have a couple of smaller sails and I'll be trying the monohull solution first when my AI arrives next week in any case. I suppose balancing in light airs will be easier without the amas..

Where I am, however, the winds often gradually go from 0 in the morning to 15 knots by the afternoon then back to 0 by early evening, at least in the summer, so I do like the ability of your solution to make the best of all conditions.
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