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PostPosted: Tue Jul 08, 2014 9:31 am 
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Some new information, and it might save somebody an accident.

I went back and closely looked at all my Aka brace end pieces. They're actually all the same. But the slot isn't cut straight across - it's angled. This makes no difference on the AI, but on the TI it determines if your shear bolt will or even can break, and whether the aka brace will be knocked out of the way, or simply jammed in even tighter. So it appears there is a top and bottom to this piece when it's installed on a TI.

I shot a little movie just now with the piece on both positions. I could break the plastic bolt with the piece in one direction, but not in the other. And in the latter, if I just took the bolt out and pulled back on the aka, the brace jammed solidly into place against the aka brace mount tab. This is the position mine were mounted in. I'll try to get this up on YT tomorrow if I have a chance.

So at any rate, if you want the plastic bolt on your TI to be able to break and the amas to fold back, make sure the mounting piece is oriented so that the long side of the slot is to the inside and the short side of the slot to the outside. Mount it the other way and you'll have a rigid assembly whenever it's under compression.


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PostPosted: Tue Jul 08, 2014 9:45 am 
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Looks like it all makes sense now, and I will check to ensure the plastic ends of my braces are fitted the right way round but Tom you made another intriguing comment
Quote:
So metal bolts on the AI, 4 aka braces on the TI (due to larger sail and greater forces), with either type bolts.

Does that mean that you have rear akas (with aka braces) on both front and back on each side? If so, this is a combo I haven't seen before (and would really be pretty cool in terms of redundancy). If sdo, did you order an extra set of rear akas, or did your TI come with these when you bought it?

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PostPosted: Tue Jul 08, 2014 10:24 am 
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I bought and installed two additional aka braces on the front akas. Standard, all the force falls on the rear akas, just outside the aka brace attachment point. That's why when you see somebody's akas fold up, it always happens at that location and only on the rear akas. The front aka's are free to move.

By putting another pair on the front akas, I have taken at least some of the load/force off the rear akas, distributing it more equitably on both the akas and the hull. I haven't bothered doing this on the AI due to its smaller sail - it was the TI where I was seeing photos and videos of folks having their rear akas collapse.

The only real downside is that if you're solo, you can't fold the amas back without moving fore, or aft, whichever the case may be, to unfasten the other set of braces.

And thinking of it now, if you were to orient the aka braces so that the shear bolt can break, you would still have two in place on each side, which should serve to give you twice the strength as before, but still not an absolute rigid assembly as using metal bolts provides. So you would at least still have some amount of sacrificial breakage in play. Although, I'm sticking with my SS fasteners.


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PostPosted: Tue Jul 08, 2014 10:16 pm 
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Tom Kirkman wrote:
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.


Perhaps ...or maybe the wrong parts have been used? Checking the parts manual there is no mention of a TI brace connector. An AI connector is listed #88991221. There is an obvious difference in the aka brace connectors as shown in the pics I posted and I always understood that gap was bigger on the TI connector so that it should snap on compression as discussed here:
viewtopic.php?f=71&t=49556&p=223030
viewtopic.php?f=71&t=11745

Question for Hobie -What is the part # for the TI brace connector and has there been a running change to this item?

BTW, snapping the brace bolt is not always a recipe for disaster. It has happened 3 times on my AI due to newby collisions and not one has resulted in a capsize.
viewtopic.php?f=70&t=40864

The TI has never had a brace bolt snap. I always sail it with tramps and haka. The way the haka are fitted using a forward hook and rear tube clips there is some freeplay to absorb impacts and I would guess that the tube clips would let go in a major accident, hopefully before any damage was done.


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PostPosted: Tue Jul 08, 2014 10:38 pm 
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Seems to me that just fitting a diagonal rope from the mast base to each padeye on the amas is the simplest and most effective way of strengthening the hull/ama relationship. I only bother to clip mine on when the weather looks like it might get rough, or I am going offshore.

To be super cautious, it would also be possible to run another set of diagonal ropes from the ring fitting behind the front seat to the same padeyes. That way the ama would be restricted in moving either forward or aft, yet the weakest part of the aka (just outside the aka brace) would not be under threat.

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PostPosted: Wed Jul 09, 2014 4:40 am 
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One of the first things I considered was a rope "brace" just as you describe. Because we so often beach the TI and climb in and out of it, and the guys aren't as limber as they were a few years ago, the ropes would be something for them to constantly have to step over, get tangled in, etc. Maybe they would have gotten used to it, but I just added the extra aka front aka braces. More work for sure, though.



.......


Stringy,

Flip the pieces around and see if the slot on one side isn't longer than the other. I thought mine were shorter but I was looking at the side with the shorter section of slot. I now suspect there is only one piece and how long the slot is depends on which side you're looking at. So then it becomes a matter of how the part is oriented, up or down, as to whether you can or can't break the bolt, and what happens if you just took the bolt out.


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PostPosted: Wed Jul 09, 2014 7:25 am 
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This has certainly been a stimulating discussion. Since I use hakas on most of my trips and all camping trips, it appears that they will (1) prevent the aka/amas from collapsing and (2) strengthen the ama/aka structure. The hakas may prevent the brace shear bolt from doing its job, but they may also strengthen the akas so that they do not bend/break as easily. I don't think the question is answered: if using hakas and a collision occurs, what gives? Maybe only time and experience will tell.

This discussion (Stringy's observations) seems to further strengthen the view that these boats are difficult to capsize, even when a shear bolt gives. Fusioneng who has "sheared a lot of nylon pins" doesn't talk about capsize. I'm not a fan of SS bolts in the aka brace.

Keith

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PostPosted: Wed Jul 09, 2014 8:11 am 
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Keith:
Yes I have sheared quite a few nylon shear bolts, but the firs week I had my first TI I saw the potential AMA folding problem back in spring 2010, and added my safety rope, it's been on the boat ever since. So when I do shear a pin I just pull over and switch it out, no danger of the AMA folding in. I have never had an AMA fold in and have never capsized.
Everyone knows my TI is massively modified (hardened for offshore) so my circumstances are different from most. With massive sails (265 sq ft), twin outboards, planing hull, and hydrofoils (I only put the foils on once in a great while just for fun) this puts a lot of extra stress on the TI, plus adds considerably to the speed ( I currently top out at around 20 mph). As a result of the higher speeds I'm breaking things a normal wouldn't break. As a perfect example if I'm barreling along at over 15 mph in rough water and hit a boat wake wrong, or a gust suddenly buries my AMA, the force of the water pushing on the AMA shears the nylon bolt. My stretchy nylon safety rope prevents the AMA from folding. This is highly unlikely on a stock TI.
Because I have massive sail area that little 1/4 stud in the bottom of the hull is not designed to take the extra stress, so I had to re-enforce that area in the hull and add the rear stay line, again I doubt there is a problem with a stock TI.
So my circumstances aren't necessarily the same as everyone else's.
The EC rating on the TI is a 'C' rating meaning it's not certified for rough offshore conditions from the factory, my opinion is if someone plans to take a TI offshore they need to be aware of the potential safety issues, and modify their boat as needed to suit the conditions they plan to sail in, that's all. My opinion is taking a stock TI out into over 25 mph winds and over 3 ft chop can put you at great risk, especially if you are oblivious to the potential problems that can occur in those conditions, it nice to have fun, but don't put your life in danger just for fun.
Bob


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PostPosted: Wed Jul 09, 2014 9:31 am 
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Tom Kirkman wrote:
No, they do not. They serve no purpose in the TI, unless you're moving in reverse. Look at the direction of force vs the position of the arms.


I had the pin break in my TI when a wind shift and gust started the boat to pitch pole. As I watched the whole bow go under water the pin in the port aka broke causing the ama to swing back alongside the main hull leading to a roll on its side and then capsized.

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PostPosted: Wed Jul 09, 2014 10:14 am 
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We covered that - look at which side your brace end long slot is on. One side and the joint will be loose enough that the pin can break. Other side and it can't break. If you take it out the aka brace just jams in under compression and keeps the amas out.


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PostPosted: Wed Jul 09, 2014 5:04 pm 
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Remember though, that if the aka brace end is upside down (ie. the long side of the slot faces outwards), taking out the aka bolt will not prevent the brace disconnecting from the aka should the force applied be anything except compression. So the aka bolt should never be removed.

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PostPosted: Wed Jul 09, 2014 5:37 pm 
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Very true, I was just illustrating that the bolt plays no role as a "breakaway" device in that particular scenario.

No matter what, AI or TI, upside down or not, you have to have something in there to keep the pieces together.


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PostPosted: Thu Jul 10, 2014 1:57 am 
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Chekika wrote:
This has certainly been a stimulating discussion. Since I use hakas on most of my trips and all camping trips, it appears that they will (1) prevent the aka/amas from collapsing and (2) strengthen the ama/aka structure. The hakas may prevent the brace shear bolt from doing its job, but they may also strengthen the akas so that they do not bend/break as easily. I don't think the question is answered: if using hakas and a collision occurs, what gives? Maybe only time and experience will tell.

This discussion (Stringy's observations) seems to further strengthen the view that these boats are difficult to capsize, even when a shear bolt gives. Fusioneng who has "sheared a lot of nylon pins" doesn't talk about capsize. I'm not a fan of SS bolts in the aka brace.

Keith
I'm enjoying this conversation too, particularly Bobs. Only wish it was in the Haka thread.

I can add that the TI3 is one boat with TWO sets of Aka braces. The 2nd and 3rd Akas are supported with the compression style joints. Akas are tied together with overlapping Haka benches too. Also, a custom brace connects the 2nd and 3rd Akas.

Image

So there are a couple layers of reinforcement as well as multiple sacrificial points of failure. Together, it all feels good and is working as intended. Other than surfing, we do NOT bury the Amas.

I'm sure we'll exceed the "limits" some day, but when we do, I suspect the pins will shear and the Hakas will prevent things from unraveling suddenly. That's been my experience with the AI.


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PostPosted: Fri Jul 11, 2014 3:33 am 
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Tom Kirkman wrote:
Stringy,
Flip the pieces around and see if the slot on one side isn't longer than the other. I thought mine were shorter but I was looking at the side with the shorter section of slot. I now suspect there is only one piece and how long the slot is depends on which side you're looking at. So then it becomes a matter of how the part is oriented, up or down, as to whether you can or can't break the bolt, and what happens if you just took the bolt out.


You are right Tom. On closer inspection the TI brace end is angled:
Note where the slot starts here close to the brace tube:
Image
The other side of the slot is about 1cm from the tube:
Image
My TI brace end is about 4cms long whereas my AI brace end is just under 3cms long and definitely not slotted at an angle. The parts are clearly different and designed to work either in tension (AI) or compression (TI).
If your brace ends look both the same something has changed. I wonder if the smaller AI end is now angle slotted so that it fits the TI as well. Problem with that is that it would change the angle on my TI aka bars. :?

It would be good to have the Hobie part numbers for AI and TI brace ends.
Anybody there from Hobie to answer this? Matt....anyone? It's not listed in the spares catalogue that I can see.


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PostPosted: Fri Jul 11, 2014 6:40 am 
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Very interesting. My guess is that only one part is used now, the later angled slot piece. This works on either boat by simply orienting it in a certain position on the TI. Obviously it doesn't matter on the AI. I just checked and measured mine again - they are the same piece on both my AI and TI.

To get the right geometry with the same longer piece, all Hobie has to do is alter the length of the aka brace bar itself. And even then, it might not make enough difference to be any sort of practical factor.

It shows once again that there are a lot of running changes made to Hobie boats to continually improve the product, although it can make it difficult to discuss these issues when we're not all working with the same parts and pieces.

.............


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