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PostPosted: Mon Jul 07, 2014 8:04 pm 
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Location: Forster, NSW, Australia
Tom, you are wrong... my TI ran into a rocky shore and the aka brace bolt sheared exactly as designed, with zero damage to any other part. The aka brace was then retained by the small tether to the aka, while the other end remained attached to the hull. Fitting a new bolt returned the TI to normal.

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PostPosted: Mon Jul 07, 2014 8:06 pm 
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Location: Adelaide, South Australia
Tom, you certainly have more knowledge than I re the TI/AI however.
I ran into the rear of another TI with my TI. The pin sheered and the Ama folded in.

I can see what you are saying because the inside of the brace fitting pushing on the
welded flange would not give and yes, you would bend the brace. I think what
happenned to me was that when the nylon bolt sheered and the aka started to move
it must have nocked the brace outwards allowing the aka to fold. Unfortunately it
happenned too quick for me to be able to see what occurred.

So what you are saying is right in that if the brace doesn't move, the sheer pin is
of no purpose. My example in practice shows that the brace may move and the
system work as designed. There was no damage to either boat, just my pride.
Of course the wife wasn't too happy about being dunked :wink:

So I will retain the nylon bolt, just in case.

Oh, and I haven't hit anything with the haka in place.

Cheers, Brian in South Australia.


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PostPosted: Mon Jul 07, 2014 8:09 pm 
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Tom, it's OK to say "bloody Australians" and their dam experience.
I still think your theory isn't wrong just that in practice, things are behaving differently. :D


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PostPosted: Mon Jul 07, 2014 8:13 pm 
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Tony, I know those Yanks are sometimes wrong but don't tell them or they may stop
sending us great boats. And we may need them as an allie if there is another war. :oops:


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PostPosted: Mon Jul 07, 2014 8:34 pm 
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Brian, I think we would need something a bit faster for wartime use! :lol: :lol: :lol: :lol: :lol:

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PostPosted: Tue Jul 08, 2014 12:40 am 
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Location: Central Coast NSW Australia
The TI and AI brace bolts are set up differently but both will break when the ama hit an object.
The TI bracebolt end has more room to allow the bolt to snap and separate:
Image

Compare the two in this pic -TI brace above with AI brace below:
Image


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PostPosted: Tue Jul 08, 2014 4:48 am 
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Guys it's not a "theory" it's how it's made and the direction of force versus the direction the shear bolt is made to work.

One puts force directly against the shear bolt. One puts force against the interior shoulder of the aka mount. You may still break something on the TI, although it may be the aka or the aka brace before the shear bolt.


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PostPosted: Tue Jul 08, 2014 5:13 am 
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Tom is right, mostly. On the AI the aka brace is under tension which relies entirely on the shear bolt to stay in place. On the TI the aka brace is in compression with zero load on the shear bolt.

But... if the fit on the TI's aka brace mount end and the aka mounting tab are sloppy enough, then there will be a little bit of force on the shear bolt and you might, maybe, get lucky and have the bolt break and the mounting area come loose, before you break something else. But whereas the system is about 100% sure to work on the AI, its maybe 50/50 or worse on the TI. Same pieces used in the exact opposite fashion.


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PostPosted: Tue Jul 08, 2014 6:31 am 
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Guys, have a closer look. The extra length of the slot on the TI brace ensures that all the load is still on the bolt, as the aka brace is kept away from the aka by the bolt. Once the bolt breaks, there is almost zero probability that the brace will somehow remain resting against the aka.

Tom, did you seriously claim that you have removed your aka bolts from your TI to use as spares on your AI? If so, you are the bravest person I have ever heard of...

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PostPosted: Tue Jul 08, 2014 6:38 am 
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Those are good photos, Stringy, and would indeed create the sort of "sloppy joint" that RHale mentions. But the aka mounting ends on my TI are shorter than what you photographed, they're just like what's on my AI. So that additional space isn't there. The aka bar mounting tab rides very nearly against the inside of the aka brace with little room for the bolt to give way. The clearance just isn't there.

Perhaps a running change was instituted to help reduce the situation I've been describing here.

Yes I did remove and replace mine, even on the AI. I tend not to run into things (so far) and due to the heavy winds I often sail the boat in, I would rather not risk a capsize from something shearing. On the TI, I added two additional aka braces to prevent what has happened to a few guys who's shear bolts didn't in fact break, and simply had their aka bars collapse just outward of the aka brace, again, shear bolt intact. Did they have the shorter aka brace mount pieces like mine?


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PostPosted: Tue Jul 08, 2014 6:43 am 
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Simple way to prove out, somebody take the nut off the nylon bolt, then go out sailing, With the AMA partially buried lift the pin out (with pliers because it will be under some strain) and see what happen. Do it on video. I have sheared a lot of nylon pins and the result is always the same, the shear pin breaks, (usually occurs when you bury the AMA at high speed from a big gust), or your traveling pretty fast ( > 12mph) in rough water and you hit a boat wake). The result is always the same, the pin breaks, the brace bar pushes out of the way, if you don't have any additional bracing (ie... tramps, haka's, ropes, etc) then the AMA begins to fold, it pauses for a second as that nylon safety line stretches out, but that then breaks, and the AMA is totally free to fold in. If your unlucky the brace bar falls in the water and is lost (with the spare shear pin still on it).
I suspect it makes little difference whether it's an AI or TI, the result is the same, and the break force is the same.
Or just open your AMA while on the trailer pull the pin out, then push back on the AMA, the brace just pushes out of the way with the pin gone. Pretty simple test.
I just don't want people having false hopes that pin is going hold much of anything, and people are trusting that pin in some pretty rough conditions (a disaster waiting to happen). I've been burned too many times and don't trust the shear pin especially in rougher weather and higher winds. Some backup needs to be in place in my opinion.
Bob


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PostPosted: Tue Jul 08, 2014 6:54 am 
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My TI was delivered mid 2012, and the plastic end of the aka brace is the long one as per Stringy's photo. I have kept the plastic brace pins, but have the diagonal rope "safety straps" mentioned by fusioneng as a back-up. I believe this is a better combination than fitting a steel brace bolt, in terms of minimising structural damage while also lessening the chance of overturning.

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PostPosted: Tue Jul 08, 2014 6:55 am 
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On my TI, I can pull the pin and everything will stay in place, unless and until something moves or shakes the aka brace off the mount. As ;long as it's under compression the pin/bolt isn't doing much of anything other than securing the assembly when the boat isn't moving forward.

That's on what I have. Seeing the photos Stringy took make me believe Hobie either fixed this compression issue with a longer aka brace piece featuring a longer slot, or my boat was assembled with AI aka brace ends.

Either way, I prefer to take my chances on hitting something versus having an ama fold in while under power. So metal bolts on the AI, 4 aka braces on the TI (due to larger sail and greater forces), with either type bolts.


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PostPosted: Tue Jul 08, 2014 7:13 am 
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I have never seen an AI or TI close enough to inspect all the itty bitty parts and pieces. If there are two different aka brace end pieces, one short slotted and one long slotted, then everybody in this thread is right in what they said. It just becomes a matter of what pieces are on your specific TI. I don't think it would be unusual for somebody assembling these boats to put an AI piece on a TI or vice versa if they ran out of one or the other and it was not something that would cause any change in geometry. Are the aka braces the same diameter and will one end piece fit the other? Have there been some running changes to both boats? Best thing to do is take a look at YOUR boat and see what you have and what will happen if YOU hit something.


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PostPosted: Tue Jul 08, 2014 7:46 am 
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This whole argument was my fault for incorrectly assuming that everybody else's TI was fitted with the same parts as mine, which I should have known isn't always the case considering my 2 hole gudgeon and 3 hole hull gudgeon mount. But frankly, my AI and TI are the only AI and TI's I've ever seen in person. Well, you know what happens when you assume...


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