Possible design flaw in Tandem steering?

Thank you Tidalwave - just the info I needed. I think I'll pick up the parts just in case the bungee doesn't work out e.g. not enough force in windy conditions or enough force but only with warpage risk as you mentioned.

I suspect the warpage is more of an issue when the force is applied laterally and asymmetrically(e.g. locked down in storage with rise of pulley under it) rather than symmetrically and longitudinally as through the blade force of a knife when cutting. Easy to warp a knife sideways and very difficult when cutting. Just the same I store it in the water at the dock in the detached state (less stretch) and rudder in down position but not in groove to minimize sun and warpage damage. I'm also considering an adaptation where it has a bistable clip that can switched from low tension in storage to higher tension in use by a simple flip of the clip. That would reduce warpage risk and also preserve the bungee's stretch from deteriorating over time.

Bob

I used one of the Aka brace nylon nut&bolt. Thumb nut is a good idea - think I will go that route. It is easy to drop the socket wrench when in the water....

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I'd rather be sailing,
Mark.

TxYackMan:
The probability of dropping the tool in deep water is directly proportional to its price and difficulty to replace.

LOL yes!

Having a handful of nylon wing nuts in boat, priceless.

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I'd rather be sailing,
Mark.

Bobco,
You raise some valid points re the lockdown/unlock pin.
Now that the bungee solution has appeared I feel like I am in a time warp for sure!
My head is spinning.
Everything old is certainly new again.
viewtopic.php?f=75&t=8107&hilit=bungee
Just as with the AI I'm sure Hobie will get this sorted.

Well the slingshot cord I used lost its power as it became permanently stretched so I'm trying a bungee from homedepot that another member used successfully.

More later,

Bob

Hi Bob.

We tie the bungee to spectra, and wrap the spectra line behind the rudder pin bottom and up over the rudder pin head attached to the hull.

The purpose of the spectra line is to hold the bungee up on the rudder pin and prevent the bungee line from slipping off the rudder pin bottom.

In our earlier design, we wrapped the bungee around the back of the rudder pin. This introduced a problem. The bungee was so bulky behind the rudder pin, that it prevented the rudder from swinging to its full port and starboard sides. The thinner spectra line eliminated this problem.

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Marc K
2010 Hobie Tandem Island
Boynton Beach, FL

Re: fixes to help the rudder stay in down position.

Just another suggestion...
Why don't you simply attach a static line (or small strap) to the rudder with a metal snap? One end can be attached to the hull (in a convenient place) while the snapped strap would have enough tension strength to hold the rudder down and still release in the event of shallow beaching.

Mark K,

I didn't think I needed the spectra line since the slingshot cord when stretched was thin enough and sticky enough to stay put on the fixed part of the rudder. But once it lost its strength through fatigue, I then realized I needed to have a non-stretch and thin cord like spectra line permanently attached as you did and then simply hook the bungee on each time with use. I found the same bungee cord you had at Home Depot and I tried to find spectra line at Lowe's, and two different sports/fishing stores locally but to no avail. I did find 100 # braided fishing line but it was too thin and I feared it might cut into the rudder shear pin.

The Hobie dealer is 3 hours away (round trip) so I was looking for a local source. Any ideas as to where to get the 500# 0.053" diameter spectra line that is used on the boat now - but from a local source and is spectra line designed to be in water all the time as the bottom of the fixed part of the rudder is constantly wet as wind waves splash it?

Otherwise, I may try to use fish line inside a nylon sleeve or some other line that retains its strength when wet as I leave my boat tied to the dock all summer.

Thanks,

Bob

Hi Ben.

I simply borrowed some old spectra line from the first Tandem rudder that was replaced several weeks ago.

Slightly thicker line that you might be able to pick up at Home Depot should do. Or flat cord, similiar to those found on digital camera straps. We just want to make sure that the line doesn't hamper the rudder's ability to rotate from side to side.

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Marc K
2010 Hobie Tandem Island
Boynton Beach, FL

Mark K,

Why did you replace your Tandem rudder? If because of the rudder problems, and you presumably got a rudder replacement without those problems any more, then why do you need the bungee?

Thanks,

Bob

Excellent questions, Bob.
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Q: Why did you replace your Tandem rudder?

A: We discovered that the Tandem's black bungee cord that is used to stow the rudder on top of the hull was too tight and distorting the rudders. The bungee distorted two rudders, until I finally discovered it to be cause of the distortion. We have since cut the bungee cord and tied a bowline at the end. Now the bungee contains 1/2 the tension and should not distort the 3rd rudder.

Hobie has resolved the issue with all new Tandems. Jim C. informed me that all new Tandems contain longer bungee cords.

We suggest that all earlier Tandems should "cut the cord" to lengthen the line and reduce risk of rudder distortions.

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Q: Why do you need the bungee?

A: At lowers speeds (< 5 knots), rudder downline tension is unnecessary. A good rudder that locks in the down position shouldn't require any rudder downline tension to keep it down.

At higher speeds (5-10+ knots), rudder downline tension must be applied to hold the rudder down. But rudder downline tension causes steering imbalance. See the forums for excellent postings and photos explaining this issue in great detail.

Until Hobie engineering resolves the downline and steering imbalance, we will continue to install the bungee when expecting to sail at higher speeds.

The bungee resolves all these issues.

1. No rudder downline tension required.
2. Perfect steering balance is restored.
3. High speed sailing is a pleasure!!!

We sail the Tandem several times a week. Florida Keys, ICW, rivers, lakes, Atlantic Ocean, everywhere. With the bungee installed, there is no concern about the rudder popping up and the helm is perfectly balanced.

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Marc K
2010 Hobie Tandem Island
Boynton Beach, FL

Mark K,

I'm still surprised that Hobie didn't send you good rudders so you don't have to use the bungee at higher speeds to hold it down. I'm guessing that they only sent you the movable rudder blade and not the fixed part of the rudder.

One hypothesis I have is that most Tandem rudders have the problem but many just sail light winds so don't know it yet.
Thanks,
Bob

I also found the bungee cord holding the rudder on deck too short to go over the rudder without creating unhealthy pressure on the blade . That was before i discovered that if I let one part of the cord go under the rudder and the other over it there would be just the right pressure to hold the rudder blade in place.

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

I used the spectra line coupled with the $1.49 adjustable bungee from Home Depot.

I put loops on the ends of a 15'' piece of spectra line. Then I ran the spectra line over the top of the rudder housing, brought the two ends down on opposite sides of the rudder, then crisscrossed them under the rudder by the base of the rudder pin. That put a loop on each side of the rudder about an inch or so from the leading edge. I then used the adjustable bungee to connect the two loops together and hold the rudder down.

The good part. It allowed me to get my new TI on the water and sail. The line over the top of the rudder keeps everything from slipping off and the rudder never popped up. The boat is a lot of fun and has great promise. I didn't cleat the down line at all.

The bad part. It was difficult to hold the boat in the surf and hook this up by myself. I may have had too much tension on the bungee as the steering was very stiff. The second day, I skipped the spectra line and just used the bungee, easier to hook up alone. The 24' bungee is long enough to go over the rudder and still crisscross at the bottom. But it is thicker than the spectra line and that also made the steering a little stiff.

This weekend I am going to drill a hole in the rudder and bolt it down as mentioned here. I'm interested in how the steering will be without a bungee holding it down.

Love the boat but can't wait for Hobie to come up with some permanent fix.