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 Post subject: rudder pin design
PostPosted: Tue Nov 04, 2008 10:08 am 
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Joined: Fri Jun 01, 2007 11:59 pm
Posts: 94
Location: Danville California/Kahana Maui
After breaking 2 rudder pins this week and replacing them with a nylon bolts since the dealer is out of pins. I was looking at the break point of the Hobie pins. The bottom of the pin seems to receive the most stress but it is the weakest area of the pin. It looks like the failure point is the bottom of the pin where a portion of the pin is removed to allow the tip to compress when being inserted and two little lips to hold it in place. I think the pin should be longer, this will allow a solid pin shaft at the point of maxium stress. The lips are probably unnecessary since the two rudder lines diectly above the pin will keep the pin in place but if that became a problem a small hole could be provided for cotter pin and a threade end for a bolt.
Just my thoughts and "two cents" worth


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 Post subject:
PostPosted: Tue Nov 04, 2008 10:38 am 
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Maybe it would be better installed from the bottom then? another though...

we have been looking into ideas to improve the rudder pins - without sacrificing the rudder housing and or transoms of the boat - We have seen one failure from using solid delrin pins in Maui already. (of course this is mainly only happening to guys who are really pushing the limits of the boat - most users never experience this failure. Even still we provide a spare with every boat - and we recommend our dealers stock spares as well. Sorry that you've had an issue with the pin.
Making sure the rudder is all the way locked down, and also reefing the sail in extreme conditions will reduce the loads causing the failure.


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 Post subject:
PostPosted: Tue Nov 04, 2008 4:48 pm 
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Joined: Wed Dec 19, 2007 4:07 am
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Location: Punta Gorda, FL
Jbernier wrote:
Even still we provide a spare with every boat - and we recommend our dealers stock spares as well.


Is that a new policy? Neither of my boats had a spare, and neither of the demos at our dealership has a spare.

Jbernier wrote:
Making sure the rudder is all the way locked down...


I wonder about this. My wife would routinely pull the down line hard and then stick it in the jam cleat. She didn't want her rudder kicking up while sailing. I pull mine down and make sure it is all the way down, but release the line back inside the hull. I figure I might hit something, and don't care if it decides to pop up under sail (it never has).

She broke two pins, and I'm still on my original one. My boat has been sailed more and harder. As I mentioned in another thread, it appeared that the hinge bound up and the broken pin appeared to me to have been twisted until it broke, not sheared by horizontal force.

It makes me wonder whether the extra tension on the hinge that results from locking the tightened down line in the jam cleat contributed to the failure of her two pins.


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 Post subject:
PostPosted: Wed Nov 05, 2008 12:30 am 
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Joined: Thu Aug 16, 2007 2:25 pm
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Location: Central Coast NSW Australia
Tom, the spare pin is located under the rear hatch lid from (I think) 08 models onward.


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 Post subject:
PostPosted: Wed Nov 05, 2008 7:47 am 
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Location: Punta Gorda, FL
Hey, they do have them! Thanks, stringy!


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 Post subject:
PostPosted: Wed Nov 05, 2008 9:46 am 
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Quote:
I wonder about this. My wife would routinely pull the down line hard and then stick it in the jam cleat. She didn't want her rudder kicking up while sailing. I pull mine down and make sure it is all the way down, but release the line back inside the hull. I figure I might hit something, and don't care if it decides to pop up under sail (it never has).



you must lock it down - it can lift up under load while sailing...that will cause loss of control and might contribute to failure of the pins - or worse.

I recommend you lock it down.


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 Post subject:
PostPosted: Wed Nov 05, 2008 10:05 am 
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Joined: Thu Mar 13, 2008 9:49 pm
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Location: Newport, NH
I never broke a pin until I locked the rudder down (the first time too!) Would not having it locked really create more torque on the hull?


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 Post subject:
PostPosted: Wed Nov 05, 2008 10:43 am 
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Joined: Tue Jun 19, 2007 6:14 pm
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Location: South Florida
Jbernier,

Are you saying that we should "pull the down line hard and then stick it in the jam cleat?" Or are you suggesting more?

Keith


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 Post subject:
PostPosted: Wed Nov 05, 2008 11:44 am 
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The purpose of having a cleat is so that the rudder doesn't lift up while sailing - (which would cause a loss of control) the pin breaking is something that will happen from excessive loading - from either waves (in which case the boat is being pushed hard in extreme conditions) or from impact. These are only small kayaks - and the people who are experiencing the majority of issues are those using it in high winds...without reefing typically. That's not to say there aren't reports of other rudder pin failure - we see them get broken in shipping on new boat shipments...the pins have been specifically designed with a breaking point so that the transom and rudder housings aren't damaged. Its for this reason that there is a compromise in the design. We have not created a transom/rudder housing/ rudder pin combination, that is capable of withstanding everything that mother nature could throw at it.


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 Post subject:
PostPosted: Wed Nov 05, 2008 12:04 pm 
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Joined: Fri Jun 01, 2007 11:59 pm
Posts: 94
Location: Danville California/Kahana Maui
Good news I lifted the hatch on my 2008 AI and there was a new rudder pin, so I removed the nylon bolt not to be used as a back up until I can order a handful of pins since the maui dealer is out of stock on the pins.
The winds here off West Maui can be strong but they are not extreme on a normal day when pins are snapping. I think the transom rudder and pin componants could be "beefed up" a little to allow for wind gusts and wave action, just my thoughts
These are great machines, everyone who sees them are always very curious and amazed at their capabilities, thanks Hobie


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 Post subject:
PostPosted: Wed Nov 05, 2008 1:37 pm 
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Location: Punta Gorda, FL
Jbernier wrote:
you must lock it down - it can lift up under load while sailing...that will cause loss of control and might contribute to failure of the pins - or worse.

I recommend you lock it down.


Noted, but I don't think I will. Mine seems to stay down just fine without locking. The down line pulls from the top of the rudder assembly, which has to contribute at least a little to friction in the hinge if it is under tension.


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 Post subject:
PostPosted: Mon Dec 15, 2008 8:10 pm 
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Joined: Sat May 31, 2008 3:44 am
Posts: 17
Location: Brisbane, Australia
Herewith are some metrics on my three pin breakages (so far) which may be of use to Hobie designers or other AI sailors:

First sailing use was 27-04-08.

All 32 sailing uses were in Moreton Bay which does get quite choppy and about another 10 trips were non-sailing (hull only using pedal or paddle) in various locations. Sail was usually furled accordingly when winds reached 15 Knots, Dagger Board was always installed to full extent, and pedals were always installed but mostly, when not tacking, fins were held against the hull.

During each trip, I recorded only the maximum boat speed and the maximum BOM recorded wind gust for my area (my maximum boat speed, in most cases, correlated with time of maximum wind gust).

FIRST PIN 30-09-08 ... 21 sails (estimated approx 4 hours average)
Ave Max Wind speed 12.40 Knots
Max Wind gust 18.00 Knots
Ave Max Boat speed 6.20 Knots
Max (brief) Boat speed 8.20 Knots

SECOND PIN 28-10-08 ... 7 sails (estimated approx 4 hours average)
Ave Max Wind speed 14.71 Knots
Max Wind gust 19.00 Knots
Ave Max Boat speed 7.81 Knots
Max (brief) Boat speed 9.20 Knots

THIRD PIN 15-12-08 ... 4 sails (estimated approx 3.5 hours average)
Ave Max Wind speed 19.75 Knots
Max Wind gust 27.00 Knots
Ave Max Boat speed 8.43 Knots
Max (brief) Boat speed 9.20 Knots

Cheers, and hope the info is useful :)


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 Post subject:
PostPosted: Mon Dec 15, 2008 9:42 pm 
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Joined: Wed Dec 10, 2008 8:53 pm
Posts: 232
Haha, nice, looks like an obvious correlation with speed and pins breaking to me. Maybe if you intend to really run the boat over 6kts it would be best to just automatically replace the pin every trip or every 2 or 3 trips for safety....

What did you use to measure the wind speed and gusts?

J


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 Post subject:
PostPosted: Tue Dec 16, 2008 3:00 am 
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Site Rank - Deck Hand

Joined: Sat May 31, 2008 3:44 am
Posts: 17
Location: Brisbane, Australia
JollyGreen wrote:
Haha, nice, looks like an obvious correlation with speed and pins breaking to me. Maybe if you intend to really run the boat over 6kts it would be best to just automatically replace the pin every trip or every 2 or 3 trips for safety....

What did you use to measure the wind speed and gusts?

J

Yes, that would be a good way to minimise inconvenience but I've now learned how to use the paddle as a rudder to slowly get back to shore :D (I'm not game to try to replace the pins on the water).

Fortunately there is a local BOM (Burea Of Meteorology) automatic weather monitoring station right in the middle of the area I sail so, as long as I remember the time of day I was sailing, I can look up what the actual wind speeds were on the internet when I get home :)


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 Post subject:
PostPosted: Fri Dec 19, 2008 4:15 am 
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Joined: Fri Nov 21, 2008 3:39 am
Posts: 863
Location: Bairnsdale, Victoria Australia
I've twice been on larger yachts that have broken either the rudder box or the pintles on down-wind runs under kites. Both times the boats were rounding up basically out of control putting the steering under enormous load. Something is bound to give as it did on those two occasions. Not locking the rudder blade firmly down is also asking for trouble in heavier airs as any lifting will cause far more unwanted pressure on the steering. Good on you Mr. Hobie for having a weak redundant pin system.
My advice would be to reduce the sail area early and trim so as to allow some air to escape, ie let the main out a little...Pirate


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