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PostPosted: Mon Jan 12, 2009 2:28 pm 
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geocacher wrote:
I haven't looked back through the recent posts to see which one it was but someone mentioned having to put a pin in which was very tight. Even so tight as to be unable to be pushed in by hand.

It's unlikely that a pin put in like this would rotate in the hole, so any movement would have an abrasive effect on the pin over time. It would also stand that under sailing load any binding between the mechanism under load and turning the rudder, weather helm etc would transfer a twisting load onto the pin in alternate directions.

As we all know the best way to break plastic rod is to twist it back and forth, as if it has any flex in it it will bend rather than break if you just bend it to snap it.

There should be no real bending load on the pins, just shear forces and twisting if it sticks.

Dave


Well my replacement was a tight fit. I do not think that meant it was suffering any twisting torque, but it was tight enough that I could not push it home the last inch or so. The break on the pin at the bottom is fairly clearly shear stress. But it also gets damaged after the first bit shears, so the top end is badly twisted.

Regarding why would these break. Well there is always the possibility you hit something underwater. Unless the rudder makes some noise at that time, and I don't know if it would, you would not know. But sailing a cat, you sure knew when you hit something and the rudder kicked out. I do not really think I hit anything in the water, but you can't be 100% certain. And of course, the break can occur later, after the pin has started to fail, and this would explain why they may seem to break when the conditions are not as stressful as they were a few minutes before. But the more that are reported, the more the evidence moves to not being quite strong enough. But we certainly don't want the boat damaged either.

Geoff.


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PostPosted: Mon Jan 12, 2009 8:30 pm 
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Darwinian wrote:
Astro wrote:
i have gone through 3 pins so far the first went in 35 knot conditions so no surprise there...however the other 2 broke in rather benign conditions and were not under real stress at the time...


This does not make any sense at all. Why would pins just break when hardly under any stress at all. I can understand breaking a pin if your rudder hits something, like the ground, but just popping one in calm water? How on earth is that possible?

Ron Patterson

my thought on that is that pins over time are stressed and fatigue to a point where not a lot of pressure is required for them to break...

both easy breaks occurred heading in one direction and not when jibing (spelling) or tacking, the wind would not have been more then 8 knots at the time

anything to improve this area is much appreciated since i have lost some confidence in the AI when heading offshore and/or in windy conditions...and these happen to be what i like to do most with mine

any thoughts on reinforcing the transom??


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PostPosted: Mon Jan 12, 2009 8:59 pm 
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Astro wrote:
any thoughts on reinforcing the transom??


How about standing the kayak on its tail and pouring in about a quart of fiberglass resin?

Ron Patterson


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PostPosted: Mon Jan 12, 2009 9:17 pm 
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Darwinian wrote:
Quote:
How about standing the kayak on its tail and pouring in about a quart of fiberglass resin?

That is done in fiberglass sea kayaks. In the AI you might have to worry about the control lines running through that area. If you reinforce that area and then use a stronger pin, the question is: what is the new weak link in the system, i.e., what is going to break now in a collision with the rudder?

Keith

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PostPosted: Mon Jan 12, 2009 9:31 pm 
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Chekika wrote:
Darwinian wrote:
Quote:
How about standing the kayak on its tail and pouring in about a quart of fiberglass resin?

That is done in fiberglass sea kayaks. In the AI you might have to worry about the control lines running through that area. If you reinforce that area and then use a stronger pin, the question is: what is the new weak link in the system, i.e., what is going to break now in a collision with the rudder?

Keith


Not necessarily. The issue is getting a slightly stronger rudder pin solution. If that means reinforcing the tail, that's a good idea. The pin must always be the weak link, can't debate that. With the current design, you have to provide for hitting something hard going forward. Unless you design a rudder system like the Hobie Cats, that kicks up when it hits something. But they still could destroy the hull if you reversed into something and had unbreakable stainless steel pins instead of the original plastic ones.

Quote:
my thought on that is that pins over time are stressed and fatigue to a point where not a lot of pressure is required for them to break...


Unless we can prove we are all hitting fish or submerged objects, that is probably the case. But seeing as one has a huge big dagger board just ahead of the rudder, that seems very unlikely to me.

Geoff.


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PostPosted: Mon Jan 12, 2009 10:50 pm 
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Mickey and I just got back from a most enjoyable kyak today before it got too hot. Took some photos with my new camera and had a great morning. They are a great little versatile vessel but that is another story. Anyway I decided when I got home to check out my rudder pin for wear so while it was convient I pulled it out and checked it for wear. This is a near new boat and pin which would have been used no more than six or eight times. I was surprised how much it had already suffered and thought you might like to see it so I took advantage of my new camera once again.
Image
Appears a lot going on near the end so I zoomed in on that part. The rudder box seems to be cutting away or compressing already forming a deep ridge line.
Also while we were peddling on the water I observed and took a video of Mickey's rudder which was wobbling laterally in the water to the extent that it was visually obvious when close up. Mickey checked mine which was the same. I have already said I believe some of these pin failure may be due to the regular pounding the pin gets from this constant vibration caused by the variance in hole sizes between the rudder box and the brass transom insert compared with the nylon rudder pin.When I got home I measured all three on my boat:
Rudder pin = 7.6 mm
Transom brass insert = 8 mm
Rudder box ( no inserts there) = 8.4 mm
I believe these light pins are doomed to failure under these conditions regardless of the weather we are going out in. That would be one reason why some pins fail under normal operating conditions. Remember my pin is not two months old.
Q. Why cant the tolerances be closer between the fittings? I have had a close look at the lifting mechanism and can see no reason for the need for slack to allow it to operate correctly. That seems a furfy to me.
Q. Why is not the rudder box holes that take the pin not protected from wear with brass or stainless inserts like the hull?......Pirate


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PostPosted: Mon Jan 12, 2009 11:07 pm 
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Yeah that pin looks destined to fail. Good catch.

Geoff.


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PostPosted: Tue Jan 13, 2009 1:02 am 
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oh...just another point, i have taken to carrying large cable ties just incase i run out of pins on extended trips...they may restrict some steering but like the pins will fail if required..


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PostPosted: Tue Jan 13, 2009 3:32 am 
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On a slightly different but related bent...

I haven't heard of anyone complaining about regularly breaking aka brace bolts (the nylon one) yet there are two spares on the boat - one on each brace, and another two in the spare parts kit.

Yet the pin that seems to suffer regular failure by reputation is the rudder pin and there's only one spare.

Go figure?

Dave

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PostPosted: Tue Jan 13, 2009 12:57 pm 
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geocacher, I have only seen one aka brace bolt fail, and that was when an out of control AI hit a dock. It was exactly the kind of thing for which they designed that shear pin, and it worked perfectly.


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PostPosted: Tue Jan 13, 2009 2:36 pm 
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Astro wrote:
oh...just another point, i have taken to carrying large cable ties just incase i run out of pins on extended trips...they may restrict some steering but like the pins will fail if required..


More to the point, I could see this being easier to fit when on the water, and the wind is howling.

Geoff.


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PostPosted: Tue Jan 13, 2009 8:29 pm 
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Geoff wrote:
Astro wrote:
oh...just another point, i have taken to carrying large cable ties just incase i run out of pins on extended trips...they may restrict some steering but like the pins will fail if required..


More to the point, I could see this being easier to fit when on the water, and the wind is howling.

Geoff.


good point, next trip out i am going to practice offshore replacement of the pin to see if it possible to do it without going for a swim

any ideas??


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PostPosted: Tue Jan 13, 2009 8:34 pm 
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Tom Ray wrote:
geocacher, I have only seen one aka brace bolt fail, and that was when an out of control AI hit a dock. It was exactly the kind of thing for which they designed that shear pin, and it worked perfectly.


That's great Tom. I had no doubt it would work. You do get my point though... we get four spare ones of these & one spare rudder pin.

As I've said before. I've not had an issue with either and I'm not worried about it - though the photo of the worn pin is interesting as M & P have only had their boats a few weeks longer than I have had mine. They are retired though and have all the time in the world to sail them.... :)

Maybe if they returned to the workforce they'd wear out less rudder pins... :wink:

Dave

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PostPosted: Tue Jan 13, 2009 8:44 pm 
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Pretty easy to change as long as the waves aren't too big. Biggest problem is when it breaks, most of the time the rest of the arm falls off the ball and sinks. I've removed the spare shear-bolts and attached a light line that keep the cross-brace from leaving. I carry my spares in my toolbox in the bag on the back of the seat.
Image

Also, I find it easier to replace the wire ring used on the pin that attaches the cross-brace to the aka with a cotter pin. A lot quicker to attach than the ring. (The newer boats have bolts for the paddle holder.)

If you sail with others like I do, it's even easier to carry a spare of the whole cross-brace, and just replace it whole. Then fix before the next outing.

Kayaking Bob


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PostPosted: Tue Jan 13, 2009 9:20 pm 
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Good point Bob. I am going to do that trick too....Pirate :wink:


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