Hobie Forums
http://www.hobie.com/au/en/forums/

Matt--what may happen in a collision with a rigid aka/ama?
http://www.hobie.com/au/en/forums/viewtopic.php?f=70&t=54573		 Page 1 of 1
Author:  Chekika [ Mon Apr 27, 2015 4:17 pm ]
Post subject:  Matt--what may happen in a collision with a rigid aka/ama?
Matt, there has been some discussion on the "2015 AI Capsize" thread and privately through emails, about using SS pins in place of the brace shear pin. I have suggested the rigid akas, either via a SS brace pin or hakas rigidly locking the aka, may lead to damage to the boat in case of a collision. Some have said, "What damage are you talking about?" Well, I can only speculate, which doesn't satisfy the critics of the plastic brace shear pin.

Can you please tell us what damage may occur to the boat in case of a collision when the akas/amas/brace have zero give?

Keith
Author:  KayakingBob [ Mon Apr 27, 2015 4:29 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
Well, I've seen sheared off ball brace screws;
and aka "elbowed" near where the brace connects
falling apart, luckily, not until landing,
as a few results.

None were my boats.
Author:  Chekika [ Mon Apr 27, 2015 4:45 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
That is the kind of real life report we need, plus Hobie's input, otherwise, there is no reason not to go with an SS brace pin. My people are saying they would rather take the chance with rigid aka/amas rather than have a capsize like I did.

Keith
Author:  mmiller [ Mon Apr 27, 2015 5:02 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
Aka, brace, brace ball, crossbar or ama damage I'd think.

Same considerations for rudder pins. We use plastic so we don't fail the transom.
Author:  fusioneng [ Mon Apr 27, 2015 8:36 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
Keith:
I have broken quite a few of the sheer bolts as everyone knows ( nearly always speed related). I have also had several collisions with other boats, docks, bouys, basically you name it I've hit it ( lol). (keep in mind I'm out there most weekends and the stuff just adds up over the 5 yrs I've been running TI's). The surf off Sarasota gets pretty bad quite often (everyone on the WT knows this all too well), and we do a lot of beach landings thru surf, a few times it didn't go as planned and the boat got sideways on me where the boat crashes into shore sideways. Maybe I've just been lucky but what usually occurs is the boat gets sideways hits the sand, the AKA nylon bolt breaks, then as the AMA is folding in (sometimes forward sometimes backward) as my little safety rope gets more tension it simply snaps (it's only 200 lb test nylon stretchy line). Then the AMA folds in completely (usually taking out all my tramp straps (the clips pop like a zipper one at a time)), once the AMA is against the hull and can't fold in further it is just going along for the ride at that point. Maybe I'm just lucky but I have never bent an AKA bar (well not doing that anyway), and I have never broken off the little ball on the hull. Every time I have hit other boats, docks, bouys etc the sheer bolt just breaks, the AMA pushes back about halfway as tension grows on the line, then just pushes my boat back without doing any other damage (like a giant shock obsorber).
My opinion is the nylon sheer bolt is one of the best features on the TI, my only complaint is I wish they would lose the threads on the bolt, and just have a 1/4" pin (no threads, or just threads at the very bottom (and of course the side hole) so when it breaks it's pure shear rather than at the minor diameter of the thread (which is under 3/16), this would make it more similar to the rudder pin (that works on sheer). I'm pretty sure it would still be weak enough to prevent further damage, but frankly most of my broken sheer bolts have been done by helpers trying to help load the boat or get the boat into shore by grabbing the AMA's, everytime before I can get the words out "no please don't help" there is a pop sound (there goes another sheer pin), with a solid plastic pin ( or a 5/16 plastic bolt), or go to delrin (which is stronger), I doubt it would still pop just by pushing the boat by the AMA. I am out of sheer molts right now so I can't try this, but if someone braces their AMA out, then pulls on the AMA with a fish scale, they can measure how much force it takes to break (i'm guessing its around 30-40 lbs with the current design, with a solid pin that would over double). Also the hole in the AKA bar itself is very large, if you dropped a rubber grommet in there (around the bolt) the sheer force would increase quite a bit (the rubber grommet was probably in the original design (at least that's how I would have designed it), but I'm suspecting once it went into production, the rubber grommet was eliminated (making everything much weaker (no longer in sheer). Either that or my rubber grommet was lost at sea long ago (many many pins ago LOL)

I simply do not agree with replacing the sheer bolt with a stainless bolt, the resulting damage can get very expensive very fast ( I know it's just money), but that's not the main issue in my eyes, the bigger issue is if you have a stainless bolt in there, and something does break (either the ball breaks off, brace breaks, or the AKA bar elbows, the boat might not be sail able. And you would likely need to order parts to be able to get back out on the water again (which can sometimes take a couple months for some of you).

If you want to prevent the AMA from folding in from a wave or speed, just add the crazy little safety line, then let the system work as designed in the event of a real crash, you want to make sure the safety line is weak enough to break in the event of a real collision in my opinion.
My two cents
Bob
Author:  Totch [ Mon Apr 27, 2015 9:40 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
As I was out sailing down in the ten thousand islands in South Florida this weekend, I started looking at the aka brace and contemplating this issue. It occurred to me that the aka brace handles are pointed right at my kidneys. I would much rather the sheer bolt break than have the ball sheer off the hull.

The other possibility I saw was bending the aka brace handle (probably toward the hull given the angles and forces involved).
Author:  Buckaroo [ Sat May 09, 2015 4:42 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
Has anyone definitively tested the aka shear bolts to identify the material as nylon ? I see a lot of posts referring to them as nylon, mine included, but don't see a statement from anyone at Hobie confirming this.
I'm interested to look at the material properties of the specific bolt being used.
Thanks

Chris
Author:  tonystott [ Sat May 09, 2015 7:01 pm ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
Cutting right to the chase, I reckon it is easiest to just assume Hobie has chosen the correct material for the brace bolt, and it is designed to break at a certain level of force, in order to prevent other, more serious damage to the vessel.

Given the above scenario, what we then need to do is find a way to SLOW DOWN the ama folding in, to give us time to, for example, furl the sail, turn into the wind, and or move crew weight to prevent capsize.

How do we slow this down? Adding a diagonal line from the central hull back at an angle to the ama will, if non-elastic, absolutely prevent the ama folding in to the hull. If this line is either made from elastic material, or includes some bungee-type material, it will soften the collapse, importantly buying time for the prevention of a capsize.

Probably the ultimate "safety line" should have a finite breaking point so it will snap before any damage is done to its own mounting points, but this scenario is unlikely to be reached, given that there is unlikely to be enough continuing forward inertia after the initial collision.

My $0.02
Author:  Buckaroo [ Sun May 10, 2015 4:24 am ]
Post subject:  Re: Matt--what may happen in a collision with a rigid aka/am
I'm convinced that the safety lines are needed and they are already on my boat. I'm just curious about what bolt material was chosen out of the wide range of available materials.
thanks

Chris
Page 1 of 1 All times are UTC - 8 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/