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PostPosted: Thu Jun 13, 2013 12:48 pm 
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Joined: Thu Jan 10, 2013 12:55 am
Posts: 80
Location: Riverside, S. California, USA
I recently took my TI to Black Canyon on the Colorado River, just south of Hoover Dam (great place!). We started downriver, and sailed 11 miles up the canyon, with good wind. The next day, we took down the mast, peddling with the current. In the afternoon, upriver wind came up so strongly that it was difficult to make headway peddling, even with the current. We put up the mast, and, with the sail deeply reefed, tacked back and forth in the narrow canyon, making somewhat better time, and with less effort than we could do peddling. But, the sailing was pretty hairy, with strong wind, inconsistent in both force and direction (and effects of current). Suddenly, we discovered that the right rear aka had completely disconnected. The brace was still in place, and the tramp held it more or less in position, but the hinge pin (5/16" diameter SS pin in the "knuckle" on which the aka folds) had completely fallen out. Fortunately we did not capsize. After peddling more, with little progress, we dug a 1/4" diam aluminum tent pole out of our gear, and put it in place of the missing pin. This worked for a while, till the tent peg sheared off (my 200 lb mate was out on the tramp). We put the remaining part of the peg (only sheared at top point) in again, bending it to stay, and peddled onward, until we again tried sailing, without putting weight on the tramps, and with the sail even more reefed. This got us back successfully.
The temperatures on this trip were extreme: 110°F (43°C) air (plus very intense sunshine heating everything black to painful temperatures), and 55°F (12°C) water (glad we did not get a long swim, since we were dressed for the air temp). Thermal expansion/contraction may have contributed to loosening the pin.
I have contacted Hobie about this, (they say it is rare...) and I can replace the pin. Apparently (I have not checked this out fully), the pin is held in place with a screw accessed through a cap on a usually-hidden part of the knuckle joint. This is an item I would not have imagined needing in my repair kit, but I will carry a spare or two from now on. When I get part number, I will follow up for those interested. (or maybe Matt will chime in).
I am also thinking about taping around the knuckle, so that the pin cannot simply fall out, as mine did. I am concerned this might contribute to corrosion though, as I sometimes sail in salt water. Inspecting these pins (and the screws holding them in) frequently for any slippage or looseness is probably a good idea.


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PostPosted: Sat Jun 15, 2013 3:57 am 
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Joined: Thu Aug 16, 2007 2:25 pm
Posts: 1977
Location: Central Coast NSW Australia
Thanks for alerting us to this potential problem bb.
First I've heard of it.


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PostPosted: Sun Jun 16, 2013 12:34 am 
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Joined: Thu Jan 10, 2013 12:55 am
Posts: 80
Location: Riverside, S. California, USA
The hinge pin situation turned out to be worse than I thought. When I looked behind the plugs on the 3 akas that had not lost pins, all of them had the screw sheared off.
The construction of this joint is as follows: The casting that sticks into the aka crossbars (I will call it the proximal casting) has a vertical hole going through it, which is designed to be the stationary part of the hinge. The casting at the inside end of the aka (I will call it the distal casting) goes above and below with vertical holes that line up with the aforementioned hole, and is the movable part of the hinge. There is a plastic (fiber reinforced nylon?) "kneecap" piece that fits onto the proximal casting , which also has a vertical hole. Through all of these holes is the vertical hinge pin. What is supposed to hold the pin in place is a screw which passes horizontally through the pin's midsection, and screws into the "kneecap". Thus, the pin is also supposed to be stationary, held to the "kneecap" which in turn is held to the proximal casting. The distal casting then rotates around the fixed pin.

What happened on my boat, apparently, is that the pin froze onto the distal casting, probably by galvanic corrosion. For its first two years, the boat was used just on salt water, and stored bayside, covered, maybe without rinsing, maybe without much use (I don't know, it was not mine then, but it looked pretty new when I got it). Once it was frozen, moving the joint to put the amas out would put a lot of force on the screw. if the seizure was stronger than the screw, the screw broke off. But, since the pin was frozen to the distal casting, it could not readily fall out, even though the screw that was supposed to hold it was broken and rattling around loose under the plug. Finally something loosened on one of the pin-casting seizures (perhaps from thermal effects) and one of my pins fell out.

Look at these hinges on your boat. You can look behind the soft plastic plug in the "kneecap" to check the screw (you need to fold the aka to do this), or you can just examine whether the pin stays stationary while the distal casting moves around it. If the pin is moving with the distal casting, you may have the same situation I had, which is a catastrophic failure waiting to happen, which is entirely hidden from casual observation.

If the screws are broken off, you have a somewhat difficult repair on your hands, because they thread into the plastic casting, and the broken off SS screw end will be difficult to remove from the softer plastic without enlarging the hole too much to take a new screw. And you have to free up the frozen pin.

I will probably lubricate the distal-casting pin joint regularly, to prevent this recurring, and check the screws for tightness from time to time (don't know if they are put in with threadlock, though it would seem like a good idea). On new akas, the fit seems loose enough that it is hard to imagine it seizing, but I don't know how mine were originally.

Hobie could not have been more helpful to me in resolving this problem quickly.


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