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| With hakas installed, when you ram an ama/aka, what gives? http://www.hobie.com/forums/viewtopic.php?f=71&t=52085 |
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| Author: | Chekika [ Mon Jul 07, 2014 4:46 pm ] |
| Post subject: | With hakas installed, when you ram an ama/aka, what gives? |
Chekika wrote: I usually have my hakas installed. They would certainly prevent the ama/akas folding back. My guess is the hakas would greatly firm up the ama/aka structure, but, if you rammed into something, would the shear pin break or would something else be put at risk? Keith I asked the above question on another post, but I think it is worthy of its own thread. If you have hakas installed and you ram a heavy or immovable object, what gives? The aka brace shear pin? The hakas certainly greatly strengthen the ama/aka assembly. Maybe the shear pin will not give. Is something else at risk? Keith |
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| Author: | KayakingBob [ Mon Jul 07, 2014 4:59 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
I would think it depends how much 'give' the haka has. If bungee'd or tied, probably would still break the shear-bolt but absorb most of the hit. If hakas are too solid, then the aka bolts, aka hinge assembly or the aka tubes themselves. When Kelly sailed from the Big Island of Hawaii to Maui solo in a TI, he used up all his shear-bolts and then used steel. Surfing down a larger wave and burying an ama, the aka could not take the stress and bent a couple inches from the brace joint. While landing on my trailer, the aka completely broke into two! |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 6:09 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
The AI and TI are different in this regard. On the AI, the plastic shear pin will break. On the TI, the pin plays no role. The force isn't in that direction. You could take the pin out, and the akas will stay in place. The breakable pins serve no purpose on the TI. Unless you're operating the boat in reverse. |
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| Author: | Chekika [ Mon Jul 07, 2014 6:23 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
Tom Kirkman wrote: The AI and TI are different in this regard. On the AI, the plastic shear pin will break. On the TI, the pin plays no role. The force isn't in that direction. You could take the pin out, and the akas will stay in place. The breakable pins serve no purpose on the TI. Unless you're operating the boat in reverse. Wow, that's interesting. Why does the TI brace have a shear pin? What keeps the akas extended if the shear pin is not in? Keith |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 6:48 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
Rearward force. The aka brace on the TI fastens to the rear. The brace on the AI pulls from the front. Look at them and consider which direction the forces come from. You can ram a TI ama into a brick wall at 50MPH and the shear bolt isn't going to fail - the aka brace will. That's what carries the force in that instance. To put the force on the TI aka brace shear bolt, the shoulder would have to be removed from the inward aka brace mount fitting. Otherwise, the shear bolt doesn't do anything but keep the mount from falling out when the boat isn't assembled. |
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| Author: | Chekika [ Mon Jul 07, 2014 6:56 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
All very interesting, Tom. You seem to be saying that the TI aka has no protection (like the shear bolt on an AI) in case there is a serious collision between an ama/aka and a large or immovable object? Keith |
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| Author: | KayakingBob [ Mon Jul 07, 2014 6:59 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
Shear-pins work just as well in both AI & TI, just different designs |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 7:06 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
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. |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 7:11 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
Check at the 6:05 minute mark here to see why: https://www.youtube.com/watch?v=e5janiNE-WE |
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| Author: | KayakingBob [ Mon Jul 07, 2014 7:16 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
The shear-bolt on the AI is on the brace tube, holding the brace connector (hinge) to the tube. The shear-bolt on the TI 'IS' the hinge, with plenty of room for the pin holder to move if overstressed and the pin breaks. |
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| Author: | KayakingBob [ Mon Jul 07, 2014 7:19 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
At 6:05. see that you replaced your shear-bolt (at the hinge) with a (stainless?) steel bolt. The shear-bolt left on the tube is the spare and has no safety purpose, other than a spare. |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 7:20 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
The aka brace on both boats is the same piece, albeit the TI is a tad shorter. Therefore, due to the change in direction versus the same force, the shear bolt plays no role on the TI. This is why if you hit something in the AI, the shear bolt shears. If you hit something in the TI, the aka brace, or the aka itself, bends. I removed the shear bolt on the TI to use as a replacement in my AI. It plays no role in the TI either way. |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 7:28 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
To the original question, if you have the hakas firmly attached to both akas, they will tend to keep the akas from folding backwards. On the TI it won't matter. On the AI, you might still break the shear bolt but the hakas might keep the akas from folding back far enough along the hull, preventing a capsize. |
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| Author: | KayakingBob [ Mon Jul 07, 2014 7:45 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
Tom, I respectfully disagree. Hopefully Hobie engineers will clarify this for us... |
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| Author: | Tom Kirkman [ Mon Jul 07, 2014 7:48 pm ] |
| Post subject: | Re: With hakas installed, when you ram an ama/aka, what give |
If you're sailing along in the AI, and you pull the shear bolt out, the akas will fold back. In the TI, if you're sailing along and pull the shear bolt out, you'll keep on trucking. It doesn't take a Hobie engineer to realize this extremely simple application of force versus structure. Just look at it. |
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