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Aka Connection to Crossbar
http://www.hobie.com/forums/viewtopic.php?f=75&t=13167		 Page 1 of 2
Author:  Slaughter [ Wed Jul 22, 2009 3:12 am ]
Post subject:  Aka Connection to Crossbar
Just wondering what the acceptable amount of play is in the pin connection between the Aka and the crossbar. Just noticed on the weekends outing that the front left connection joint has a bit of wear and had a bit more play than I have noticed before. If I connect the Aka without the Ama, and then measure the vertical movement of say the rubber collar boot that goes into the Ama, would someone mind doing the same to see if I have a problem and have anything to worry about ?
Author:  Yakaholic [ Wed Jul 22, 2009 5:26 am ]
Post subject:  Re: Aka Connection to Crossbar
Slaughter wrote:
Just wondering what the acceptable amount of play is in the pin connection between the Aka and the crossbar. Just noticed on the weekends outing that the front left connection joint has a bit of wear and had a bit more play than I have noticed before. If I connect the Aka without the Ama, and then measure the vertical movement of say the rubber collar boot that goes into the Ama, would someone mind doing the same to see if I have a problem and have anything to worry about ?


I cut down self adhesive felt pads (like the ones put on chair legs) and attach then to a flat spot in the aka arm. Felt pad fills the gap between the x-bar and the arm.

Image

This does several things.
It eliminates any rattle caused by the aka arms against the xbar, especially in chop. It reduced the amount of wear because it reduced the metal to metal pounding. Finally if the felt is tight in the gap it reduces the "play" and up/down travel of the aka arm.

The felt needs replacing after a 1/2 dozen outings or so but its easy and cheap. Others have used indoor/outdoor carpet as a hinge shim also. I used carpet but found the felt better.

Image


As far as how much play is too much - can't answer that. More play means the boat will heel slightly more as it looses a bit of support from ama. Play in the hinge translates to quite a bit of travel by the time you get to the end of the aka arm where the endcap ama attachment is located. My theory is that wear like this is accelerated like any metal part that has play and subjected to stress/vibration. A replaceable bushing would be one possible design change.

My approach is that even when new the aka hinge would benefit from padding and extend the life of the metal. A proper sized and shaped replaceable rubber shim would be perfect for the job.

BTW if you use felt you will have to compress it some with a hammer - if it is too thick you will never get the aka arm pinned in place.

Play in the aka arm should not make the boat unsafe or unusable IMO. The felt as a hinge shim does a great job in quieting the arm and reducing play.
Author:  Slaughter [ Wed Jul 22, 2009 5:59 pm ]
Post subject:  Re: Aka Connection to Crossbar
Thanks Yakaholic. I ran out of time to measure the amount of play last night. I just wanted to reduce this play so that the wear won't accelerate and your solution looks pretty good. Is this a common issue ? I havent heard anyone else talk about it. I also noticed that at the top of the Aka where the pin bends, the hole is deformed to oliptical. A removeable bush or a sacrifical pin would be an improvement but in the interum I'll look at adapting your ideas. Thanks mate.
Author:  Astro [ Wed Jul 22, 2009 7:27 pm ]
Post subject:  Re: Aka Connection to Crossbar
hey Yakaholic

what have you used to attach the felt...looks like flat head nails to me
Author:  Yakaholic [ Wed Jul 22, 2009 7:41 pm ]
Post subject:  Re: Aka Connection to Crossbar
Astro wrote:
hey Yakaholic

what have you used to attach the felt...looks like flat head nails to me


The felt pads use a peel and stick self-adhesive, any hardware store will carry them they are used on furniture legs and can be cut down as needed. They are easier than the carpet & pin solution

The carpet is attached with plastic pins used typically in the auto industry to attach plastic panels and dust coves and stuff under the hood. Ace Hardware has them - panel pins I believe they are called.

You may have to adjust the thickness of the carpet under the pin or the thickness of the plastic head itself if it too tight.

Image

All aka arms AFAIK come with 2 holes to use for mounting

Image

An industrious person could tap these holes to screw on a more permanent rubber bumper of sorts. Think of a car's shock absorber; they are not bolted metal to metal but have a solid rubber bushing on the shock mount. A hard rubber piece shaped to fit the gap in the hinge, flat where it bolts to the aka and concave where it mates with the xbar would work great.
Author:  Slaughter [ Fri Jul 24, 2009 12:04 am ]
Post subject:  Re: Aka Connection to Crossbar
Good stuff mate. Guess what I'm do'n this weekend ?
Author:  Yakaholic [ Fri Jul 24, 2009 6:26 am ]
Post subject:  Re: Aka Connection to Crossbar
Slaughter wrote:
Good stuff mate. Guess what I'm do'n this weekend ?


Yes, in your experiment of attaching an aka arm, grabbing the end and moving it up and down to check for play. Notice the gap in the hinge as it narrows at top and bottom as you move the aka arm up and down. Grab anything and shove/wedge it into the entire hinge gap then check for play - it is all but gone; the aka is solid.

The trick is finding the right material and also something the will stay in place and still let you pin on the arm easily enough.
self stick felt pads can be purchased in large squares and the cut to fit with a razor.
Author:  Slaughter [ Fri Aug 07, 2009 5:09 am ]
Post subject:  Re: Aka Connection to Crossbar
Well I finally sorted something out with the play in this connection and I must admit, I'm pretty pleased with the result.

I first cut 4 pieces of rubber 6mm thick, to a length of 65mm, and width 15mm, to fit inside the top and bottom lugs on the Aka. Photo shows finished rubber sculptured and glued to Aka with contact adhesive.

Image

You know that round stone wheel that came with your Dremel, and you have always wondered where you will ever use it ? well........

Image

.........it took me about 10 minutes to scallop a groove longitudinally up the rubber centre. Sculpturing, fitting, resculpturing, refitting etc until the pin could be pushed through the connection. Before I made this modification, I measured 35mm of vertical play in the Aka at the plastic collar that fits into the Amas. After the modification, no play at all.

Image


I tried it out on the Broken Bay outing at the weekend, and the new stelth-ness of the AI helped up slip past Japanese U boats in America Harbour undetected.
Author:  stringy [ Fri Aug 07, 2009 6:06 am ]
Post subject:  Re: Aka Connection to Crossbar
Very impressive Slaughter- looks like a great solution! 8)
It was certainly quiet last weekend! :wink:
Thanks for posting.
Author:  arno [ Sat Aug 08, 2009 12:40 pm ]
Post subject:  Re: Aka Connection to Crossbar
After about 10 outings of 3-4 jours, I have the same thing as Slaughter.
One question : where to find a small pad of rudder of about 6mm thick ?
Or else, why not just 12mm thick, drill a hole through it and then cut it in halves and you're done in two minutes ?
Author:  Slaughter [ Mon Aug 10, 2009 2:13 am ]
Post subject:  Re: Aka Connection to Crossbar
Sounds just as good Arno. I'm sure there is more than one way to get a good result. We use the rubber that I used at work so I 'borrowed' some. ( I'll give it back ) :lol: . The dimensions that I mentioned fit the connection perfectly. Hope whatever you do works out for you. Please post some photos when you have something worked out.
Author:  TIDALWAVE [ Mon Aug 10, 2009 7:44 pm ]
Post subject:  Question to Matt...
Has there been any talk within the company on using the 'knuckle' connections (aka-to-crossbar) used on the proto-type tandem AI's as an 'upgrade' for next year's single AIs?
Author:  Slaughter [ Tue Aug 11, 2009 2:45 am ]
Post subject:  Re: Aka Connection to Crossbar
I've heard of the knuckle joint Tidalwave but as far as I'm aware, it's only a rumour, unless anyone else knows otherwise.
Author:  Sun Coast Sail [ Fri Aug 28, 2009 3:32 pm ]
Post subject:  Re: Aka Connection to Crossbar
I just had my locking arm pop off and sink to the bottom of the drink. I had a strong head wind push me up against a dock. It must of hit the on the right spot as the bar disappeared instantly as the aka hit the piling. Is this a warranty item?
Author:  mmiller [ Sat Aug 29, 2009 8:57 am ]
Post subject:  Re: Aka Connection to Crossbar
It is designed to release if you hit something that might damage a major component. Just the shear bolt usually goes, but some instances of the release handle also popping off the ball have been recorded.

This is not considered warranty in this case. Some others have posted ideas about using lanyards for the strut.
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