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PostPosted: Thu Oct 28, 2010 10:59 am 
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sammy925 wrote:
The TI AMA's arent really THAT much larger.
"Amas: 4 1/2' longer and with 220 lb. of buoyancy each (100 lb. greater capacity than the AI amas)"... a significant difference. 8)


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PostPosted: Thu Oct 28, 2010 11:31 am 
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It looks like you can move the rear cross member or shorten one of the crossmembers to adjust the toe. I was hoping to use my TI's aka's so the emphasis in the retrofit would be to ensure the TI's akas can fit into the crossmember.

It'll take it out of Hobie's design specs so will have to keep an eye out for the stress points. For example, I broke my pin on my aka supports upon landing a while back. It was a normal calm landing but I experienced a few hard runs previous that probably overstressed the pin. One of the previous runs I had both tramps deployed and caught some lift after getting over a swell. I'm thankful that the plastic pin broke much later and when on shore; but, it revealed a very vunerable stress point.


cliffs2yak


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PostPosted: Thu Oct 28, 2010 1:07 pm 
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The volume of the AI ama is a safety feature for the rig. You can only place so much pressure on it before it simply sinks


I still don't get what issue this is refering to as applied in this TI AMA to the AI hull case. What safety factor is being violated here. Someone please throw me a bone on this.

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PostPosted: Thu Oct 28, 2010 1:35 pm 
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Quote:
I still don't get what issue this is referring to as applied in this TI AMA to the AI hull case. What safety factor is being violated here.


The issue is the stability of the boat when using the TI amas. It is more stable with the larger amas, so you can put a LOT more stress on the mast, receiver, hull connections than was intended.

The safety factor on the AI is the lower volume of the AI amas. They will sink if you place enough wind load on the rig.

I can not recommend something that exceeds original designed specification when damage could be caused.

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PostPosted: Thu Oct 28, 2010 4:09 pm 
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A Hobie disclaimer here is understandable. Although it might hurt Ama sales. :wink:

And my barrister advises I should add one of my own, so:
"Any aftermarket modifications of Hobie products depicted here are the work of a retired engineering genius with an overactive imagination and way too much time and money on his hands. They are not intended as anything other than pure personal amusement. Neither NOHUHU nor Batman Enterprises (AKA "Hawaiian Skunkworks") endorses this or any other modification of any ocean going craft for the sole purpose of achieving more speed, utility or pleasure from said craft. Standard text messaging rates apply, your mileage may vary, call your doctor immediately if your erection last longer than 4 hours."

OK, then.

If the TI hull and various mounting points are substantially reinforced beyond the 2011 AI's, then there is something to be said for the TI having a greater stress tolerance. We know this is designed in somewhere. The TI's length, sail and rudder are much larger. These create greater stresses than an AI would ever experience. Although, if the Akas are essentially the same hardware, then those are not the concern.

I would tend to think that elongated Amas would help distribute and mitigate normal sailing loads. On the Bat Yak, the longer Amas enhanced the AI's tracking, stability and floatation.

The main reason for testing this mod was to add aft buoyancy and make the rear deck seating safer and more effective in Hawaiian waters. Most of the design goals were achieved. Adding more gear capacity or another passenger is an unintended bonus.

Everything has a trade off. As Matt points out, longer Amas add stabilty, but could increase stress on the load bearing points at times. It might also convert that added energy into more forward motion (speed), but the jury is out on this one.

Likewise, burying an Ama may be a "safety" feature, but it also stresses the members. Thus, submerging a longer Ama could produce a larger sudden drag. It might be easier to blow out a shear pin, I suppose. But again, the addition of the Bat Bench (or tramps) controls this. We will keep an eye out for these problems. (My lawyer thanks your lawyer Matt) :lol:

Funny how the first thing we do after bringing our new Hobies home is look for ways to customize them. Sometimes we don't know when to stop. Judging by our passion for hottrodding, I think the Ama genie is out of the bottle now to stay.

That's understandable too. After all, it is called the "Adventure". Not the "Tercel."

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Last edited by NOHUHU on Thu Oct 28, 2010 7:22 pm, edited 2 times in total.

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PostPosted: Thu Oct 28, 2010 6:30 pm 
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NOHUHU,

You my friend are OVER THE TOP. That is one of the best posts of all time. I'm laughing so hard I got tears. Truely a piece of written work. Surely the big dogs at Hobie skunkworks will print and post that one in the lab. I'm with you, and I've said it before. Customizing and taking the craft to its upper limits is what we do. Some guys do guns, some guys do cars. Some guys do Hobie yaks. I'm not asking for a Hobie warranty blessing on this. Just the information I need to take it to its upper limit tolerance that was built in. I truely think that if these stressor concerns were so close to the limit we would have seen it with the standard AMA's
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

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PostPosted: Thu Oct 28, 2010 8:38 pm 
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NOHUHU wrote:
However, if the 2011 AI Akas rake back as badly as the TI's, the resulting geometry may actually toe the Amas together slightly (it would turn better, but sacrifice speed).


Can't speak for the fleet but my 2011 AI doesn't have toe or rake issues. The tramps fit perfectly square when deployed.

It is easy to figure the additional buoyancy of the TI amas and the forces applied to the hull and connectors. What we would need and guess we won't get the the engineered tolerances for failure.
We can always modify and then destroy one kayak but that still won't tell use what the design limits are... just the point of failure of that one kayak. Without the baseline specs we won't know if the modification was the cause of failure or if that one hull is defective.

I can see how burying a TI ama on an AI hull would raise some serious questions. Parts flying everywhere... a water based version of a yard sale.

So who has a new 2011 for testing

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PostPosted: Thu Oct 28, 2010 9:02 pm 
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sammy925 wrote:
Jerry D (dosjers) has both. I know if I had them I would have done it already. That would have been my first operation as soon as I got the TI home. Hey Jerry, can you help us out?? :D

I'm not exactly sure what you want me to try.

Let me know so I can give it a try.

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PostPosted: Thu Oct 28, 2010 9:26 pm 
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If you are up to it, can you give us your impression of how the TI Amas fit (or don't) on the AI Akas?

Photos of the AI vs TI Aka collars and end caps, for comparison?

How limited is the Aka folding range with this hybrid setup?

(We're getting you in pretty good shape, hauling that trailer out all the time,..) :D

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PostPosted: Fri Oct 29, 2010 5:18 am 
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NOHUHU wrote:
(We're getting you in pretty good shape, hauling that trailer out all the time,..) :D

I'm starting to wish I had an aluminum trailer now instead of the galvanized steel version.

We are going on a kayak trip tomorrow so I'll be pulling the boats out today and stripping them down to the kayak mode. If I have the time I'll try to swap amas and take some pictures.

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PostPosted: Fri Oct 29, 2010 6:01 pm 
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OK. Here are the pictures you asked for:
[img]http://i755.photobucket.com/albums/xx196/dosjers/DSC_00012.jpg?t=1288399616[img]

View from the front.
[/img]http://i755.photobucket.com/albums/xx196/dosjers/DSC_00023.jpg?t=1288399688[/img]

View from the rear.
Image

Attempt at folding the amas in.
Image

The amas appeared to be straight when the supporting strut was connected to the boat but they sure didn't want to fold up.

Even though the larger amas will work on an AI I wouldn't suggest using them. The akas on the AI were not designed to take the loads of the bigger akas and you could do some serious damage to a boat.

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PostPosted: Fri Oct 29, 2010 7:52 pm 
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Thanks for the photos. So the Aka end caps and collars are the same?

Since the 2011 AI has the same Aka to Xbar connector as the TI, using the TI Amas, believe the point of failure (if any) would be the Xbar to hull mounting points at the 4 SOC cap screws. Either the screws pulling out or cracks in the hull.

On the earlier AIs, guess the Aka connector pin would shear due to increased lift due to the additional buoyancy.

Yet, before that happens on any year AI... shouldn't the shear bolt fail first?

Still worth a go. Really need a TI to borrow some parts.
The TI Ama on an AI hull is the first and only mod that my wife likes so it has to have merit.

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PostPosted: Sun Oct 31, 2010 6:44 am 
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Just keep in mind none of the failures will happen until there is enough wind to cause sufficient load on the leeward ama to break something. At that point you will probably be sailing at around 7 knots or more when all hell breaks loose and you dump your boat when the akas fail.

Don't forget to wear a life jacket.

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St. Johns, Florida
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PostPosted: Mon Nov 01, 2010 8:59 am 
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I wonder if the vertical height component of the Ama is different ( TI > AI ) and being on ground, that may be what caused the difficulty on closing the Aka's ?

If so, it would put an immediate increased stress on the X-bar when on water.

... sometimes you start with a silk purse and after playing end up with a sow's ear

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PostPosted: Mon Nov 01, 2010 1:54 pm 
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There are differences in the distance between crossbars of the AI vs TI, so the distance between aka holes in the amas is different. This makes the folding an issue (Geometry) when you swap the TI ama onto an AI. This also causes a toe-in when you hook on the aka brace. The afta aka would be square to the boat... so the forward one is not. In addition there is a difference in the depth of the aka holes in the amas. The TI ama has a deeper aka connection hole. The aka collars are riveted in a different height... so the AI aka will not fully seat down into a TI ama (without moving the collar). Then the difference in volume which allows more load to be placed on the rig before the boat would capsize.

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