Possible cause for tight right steering on Tandem Island.

I have had difficulty turning right on my new Tandem Island when there is any tension on the rudder down control line. If there is light wind then no tension is required once you loosen the rudder bolt so the rudder sits in the slot. However, the rudder will pop out easily when the wind picks up without down tension. The more tension, the more difficult to turn right.

I looked at the rudder design to understand why, and it seems to be caused by the down control line not pivoting over the gray shear pin as it does with the AI. Since the control line enters the rudder off center from the rudder pivot, it acts as a left turn control line. The more tension, the more it pulls the rudder into a left turn. That may explain why it is so difficult to turn right when it is windy.

I made a three photo sequence showing the rudder down line stretch as you turn from left to right. A blue tape marker was placed on the down rudder control line to show how it stretches under the tension of a right turn. This seems to be an intrinsic property of the design so everyone should have the same problem, unless some have a different pivot mechanism on the TI rudder. See photo below to see stretch of down line as you turn from left to right.



Has anyone come up with a temporary solution? The best I can do now is tension the rudder down control line just enough to keep it from popping out. This means I have to continuously adjust this with every gust.

Bob

It looks like you have found out what the problem is. Apparently it is a result of an early modification shown in technical notes where the line feed has been cut away. viewtopic.php?f=68&t=26418
It is high time for Hobie to come up with a proper solution.

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Bo Karlberg
Taby
Sweden
Sail Tandem Island No P1787 in the Stockholm Archipelago (some 40,000 islands and rocks)

It looks like they had the same problem turning left before they cut away the pivot point due to excessive tension on the 2:1 down line. But they just shifted the problem to the right turn now with the same consequences of excessive wear - now due to extreme loads when turn hard right.

One temporary solution might be to route the 2:1 down lines around a cam of the same radius length as the stretch caused by the right turn such that when you turn right there is no increase in the length of the 2:1 down line. It is easier to show in a drawing which I'll do later today. There would be no rubbing or abrasion since there would be no net change in the length of the 2:1 down line as you turn from hard left to hard right.

This curved cam with the 2:1 down line routed on the right side of the cam would sit on the stationary part of the rudder unlike the part they cut away.

Just an idea to consider.

Bob

I also have some idea of feed guide fixed to the hull. I may also produce a drawing later.

_________________
Bo Karlberg
Taby
Sweden
Sail Tandem Island No P1787 in the Stockholm Archipelago (some 40,000 islands and rocks)

Looking for to these design ideas and a drawing or too.

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I'd rather be sailing,
Mark.

Bob, this is my solution to the rudder kicking up when turning to starboard on my AI...I moved the cam cleat on the down line to the rear x beam next to the right side of the seat...ran a larger diam spectra line (it's the white line) through the cleat to the right rear side to the rudder...drilled a 1/4 in hole in the rudder to feed the line through and tied with a figure 8 stopper knot...when turning to starboard the line stretches enough for the rudder to turn...you can see in the pics there is no tension in the factory down line...on a port tack in strong puff it's easy to turn to starboard to maintain a straight course...on a starboard tack turning to port is not a big issue because the pressure on the rudder is pushing against the twist and stow drum helping the rudder to stay down...I've modified my steering that also helps control the rudder...viewtopic.php?f=69&t=27532...I'm guessing it will work fine with the factory steering...so far the new rudder pin is holding up fine...it works great for me...

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CaptRon
"Anything's gonna happen,
it's gonna happen out there"

Rough hand drawing of cam which prevents 2:1 down line from stretching as you turn from left to right.




Good ideas coming so mine may not be as simple as others.

Bob

Ron,

Your approach of attaching the down line below the pivot point and to the starboard side seems to address both the tension issue (since you get more leverage below pivot where you attached it) and the lock-in issue since pulling on the side (for TI rudder) where it has solid backing and not just a small lip as on the port side.

Perhaps there is a way to do this on the TI rudder but keeping the lines internal and above the water line.

Thanks,

Bob

Bob,
Ron and I were looking at doing this on my TI. I will post something if I end up doing it.
Mark.

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I'd rather be sailing,
Mark.

Bob, I was thinking about an internal line also but decided to keep it simple to make sure it worked properly...it works so well I may just leave it like it is...the extra external line does not bother me and is not in the way of anything...please post your ideas on an internal line...I would like to see what you have in mind...

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CaptRon
"Anything's gonna happen,
it's gonna happen out there"

Ron,

The down line would exit the TI the same as it is now but then goes over the rear edge through a grooved roller then down the back a few inches then under a second grooved roller then attached as you have it to the rudder. The 2:1 line passes on the outside of the top roller and the inside of the lower roller and all attachments are above the water line so no slow water leaks.

I haven't looked at my TI yet to see if a bungee could be part of the down line so if the rudder hits a submerged object we avoid more serious damage. Also, we need to center it so there is no left or right bias. Otherwise, we return to the original problem of the down line acting as a steering line when under tension. If there is no way to do it without a bias to left or right then I would prefer my first approach since all it may take is a special screw cam inserted on either the boat or the fixed part of the rudder if there is enough space. The sideways force on the cam may require a support plate in which case a special cam plate with two screws for attachment may be more robust.

Bob

Bob, My Fulmar 19's rudder with a centered down line...it does not "twist and stow" like the AI but works great...I'm not that crazy about the twist and stow feature anyway...I bet the TI rudder could be modified to work like the Fulmar's...

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CaptRon
"Anything's gonna happen,
it's gonna happen out there"

With my new TI, which arrived a week ago, I do not have the problem of the line catching on the rudder pin. I tested this just now in my garage. It may be different with water pressure on the rudder. The pin on my boat is flush with the rudder housing and there is nothing for the up/down lines to catch on. Regardless, I DO have the problem of constant pressure on the tiller to the left (in or out of the water) when applying enough tension to the down line to get the rudder to seat in the "locked" down position. The pressure I experienced on my one and only sail in the boat so far was agrevating and tiresome. I could not take my hand off the tiller (even at a dead stop) without the tiller whipping to the left. Turning right was always a fight and holding her straight required significant, constant effort.

Do you guys experience the same issues?

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Mark
2010 Tandem Island
2010 Adventure
Hobie Cat 14T
Home built sailboat (in progress)

Edmond, OK

You may want to check inside the rear hatch of the TI to make sure knots from different lines are not interfering with each other. On one AI, we needed to shorten a line and add an additional piece of line to get the knots away from each other. I haven't studied mine yet, because I'm not having problems, but I was surprised when I looked in my TI how tightly the lines were rubbing against each other. Looked far more 'busy' than on an AI.

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Hobie Island Sailing since 2006

Mark,

I haven't heard about any line catching on the rudder shear pin so your experience (hard to turn right when 2:1 tensioned) fits mine exactly.

Bob