Possible design flaw in Tandem steering?

Our Tandem is experiencing the exact same deployment issue Anakritis described. The rudder won't seat into the tongue and groove and positive lock into the clip.

We experimented with different drum bolt tension settings. As the rudder approaches the full down position, it is experiencing some kind of resistance.

Starting new thread: TI rudder down line snapped
http://www.hobiecat.com/community/viewtopic.php?f=71&t=26172&start=0


Rudder, after applying downward pressure, unable to seat in the tongue and groove.

_________________
Marc K
2010 Hobie Tandem Island
Boynton Beach, FL

Anakritis, nice detective work! I compared your system with mine (which functions well). It appears that you have a warped rudder housing, as your 'witness' marks testify. My system has no such marks, and bumps into the pocket nicely, whereas yours is evidently binding where the marks are, pointing to a misaligned rudder housing. I suspect that's the hang-up, so to speak.

I also owe a humble apology to TIDALWAVE for criticizing his remedy. Based on Anakritis' analysis, TITALWAVE's correction appears to be a good interim solution to a similar problem.

Thanks to both of you for your diligence and problem solving skills!

Anakritis has this pretty well figured out.

We do have a tolerance issue. This may be design, tooling, materials, swelling of the parts (water is absorbed by nylon and can change tolerances), cooling, warping... in any case, even on the production floor, the parts have a contact point causing the rudder to spring away from the full down position when the drum bolt is tensioned as in the original Twist-n-stow systems.

This is corrected here by loosening the drum bolt. This allows enough play to allow the parts to seat properly in the down position. But... this also allows the blade to move laterally while rotating down. This may cause the blade to hit square on the latch if loaded from the right side and prohibit full down position from being easily achieved.

We will be looking closer at this to determine the corrections required fix the tolerance issue.

In the meantime...

Loosen the drum bolt until the parts seat easily in the full down position.

The rudder will require a couple of simple techniques for easier use.

As you lower the rudder... pedal or sail forward and turn slightly to the left. This will help the rudder reach the full down position by pressing the blade to the right while rotating down.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Anakritis...you have displayed the exact problem I recognized a couple of weeks ago just
after your first mention of loss of starboard control.
I didn't have photos to show the 'minimum' extent that the clip was touching the rudder.
I have essentially the same 'wide' gap between the rudder housing and the rudder at the clip.
Even when dropping the rudder while on the trailer, sometimes, the clip gap is so wide that
even a slight touch with one finger will cause the rudder to pop out of the clip! And this
is with the drum tightness set as recommended by Hobie. I have tried to gently push on the rudder to close the 'gap'...the rudder will usually move back opening the gap.
It was mentioned that some rudders won't clip in correctly if the Tandem is moving.
I also have found that the same situation.
Now that I have been sailing for a couple of more weeks...I NEVER try to drop the rudder while underway...the rudder will not consistently lock correctly. Even with the drum tightness set as required, I let the tandem come to a halt before I try to drop the rudder. If I don't, I know that it is just as likely that I will have no starboard control. It is easy to discover if the rudder isn't clipped...before I try to sail, I pedal a short distance and see if I can turn right. If not...I stop and raise and lower the rudder and try again.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

A temporary fix…
I started measuring the errant fit of the rudder and decided that I could easily compensate for the error with a Poly washer, some shim stock and a pair of scissors.
The problem here is that there is excessive gap between the groove and tongue and there is a 2 to 4 degree angle between the rudder and the tongue (top to bottom). So a person has to move the rudder over by placing Polyethylene washers in the drum and then shim the bottom rudder mount to compensate for the angle.

Gap and angle prior to shimming…


I placed a second poly washer (8mm) in the drum and spaced the drum out accordingly.

Note the new drum spacing (exposed line)…


I cut two polyethylene shims, drilled holes in the shim for the screws (5mm thick tackle box dividers) and and inserted them in the lower rudder mounting position…


Now the rudder seats flawlessly… (note how the lower mounting screws do not protrude as far as the upper mounting screws)


Now with these two modifications the rudder seats correctly each and every time you deploy it.
It also resists side loading and stays put. I will get it under sail sometime this week to test it, but as of this time the rudder deploys correctly every time.
I am afraid this is only a temporary fix as having the drum spaced out this far will certainly produce loads not expected by designers. The threads and the drum bolt are not fully engaging the entire thread surface and neither are the lower rudder mounting screws.
If a person were to keep this configuration new longer screws and bolts will be needed.
The only permanent fix is to have a properly designed system that has correct design and fit tolerances.
Hope this helps!
Peace.

Hobie's twist and stow (T&S) rudder system has been in production for several years. Yesterday, we visited a dealer to study the T&S rudder system of their Hobie kayaks in the showroom. None of kayaks with T&S rudders we tested clicked into the clip properly. The rudder doesn't clip, but instead, relies on the rudder down line and the cam cleat to hold the rudder down in the water. For a kayak which is peddled and paddled at lower speeds, this is probably sufficient. But for the Tandem at our higher sailing speeds (and pressure), the strength of the rudder down line may be insufficient to keep the rudder down.

Hobie is shipping express mail to my dealer a new rudder unit too. Thank you, Hobie.

Anakritis. Please keep up posted with the results of your tweaks with the washers and shims. This weekend, we had a wonderful family vacation sailing the Tandem, using a strong rubber cord to tie the rudder down in the water. Also, please keep up posted with the results of your new rudder unit when it arrives.

_________________
Marc K
2010 Hobie Tandem Island
Boynton Beach, FL

That is a very interesting find.
I have three Hobies, a revolution, Adventure and a Tandem Island. Both the Adventure and the Revolution fit snugly in the clip when deployed. Additionally literally every Kayak I inspected at the dealer functioned in the same "snug" fashion, with the exception of the Tandem Islands.

You are very correct when you say that Islands certainly need a snug fit to augment the down line.

I will post results of the test as soon as I am able.
Peace

Loosen the drum bolt or replace the inner washer with one slightly thicker... does the same thing.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

I respectfully disagree.

Loosening the drum bolt will only increase the gap distance and will not provide a solid position on the bolt shaft and will allow the drum to slide along the shaft preventing a solid and repeatable action.
Inserting a thicker washer or multiple washers prevents sliding and gives a smooth repeatable action, and what is more, loosening the bolt does absolutely nothing for the rudder being askew of the slot. To correctly remedy the problem a person MUST correct this condition as well.

The entire unit demands attention. A re-design or at least an engineering dimensional change.
I was able to temporarily cobble-knock a proper and reliable operation with minimal effort, fixing the problem permanently will be just as easy.

Hobie has a great opportunity here to address the issue with an easy and cost effective fix. If the Hobie engineers are worth their salt they will come out with a Twist and stow unit that is superior and better that what they have now.
I will be the first to say here that the existing twist and stow (at least mine) is a poor excuse of a first attempt for the tandem. From what i have seen earlier models work much better.
Come guys, fix this thing and fix it right.... your customers deserve the quality Hobie is known for.

Viewing 15 boats on the line today... only one boat required a thicker washer. That removed the spring-back action and the rudder easily locks. It is not a design issue perse. It is looking more like a warpage or tooling inconsistency issue. They are still looking at the issue of course. We have a few ideas. One is to add a simple ramp that will allow the rudder to align with the lock area as it comes down rather than bump hard. The fact that many are using this without issue... and some start to have issues later suggests that it does work, but can come out of adjustment in a few ways.

The current solution of the looser drum bolt and simple rudder handling technique will work. We will continue to evaluate.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Well it appears as though I recieved a Twist and stow that was a bit of a "perfect storm" of sorts.
If your tooling (mold or die) is incapable of producing parts within the acceptable quality control limits you necessarily have a design problem... You either correct the design of the part to make manufacturing possible or you change tooling design to make the process capable.
Telling people to simply loosen the bolt is irresponsible and fails to address the problem.... and make no mistake about it, SAFETY is the problem. Why not define a proper interim fix that does not require sloppy "techique" that will deploy the unit after multiple trys and even then does not guarranty safety at speed.
I am speaking from experience here. I tried simply loosening the bolt, coupled with your "technique" and it only worked occasionally and even then was easily pushed aside by side loading.
I think owners will find that the more solid temporary modifications I described to be a more effective fix.
We are all waiting for Hobie to do the right thing. We don't want a half-assed repair, not even the one I described. We want a dependable properly designed twist and stow rudder, we paid for it already!
Those who have the defective (and they are clearly defective) twist and stows simply want a unit that functions to specification and does so safely. This should be a no brainer after your customers hand you nearly $5000 a copy for your product....

Therefore my comment

Please allow us the opportunity to work though the issue and discover if further correction is needed. In the meantime, If you have a rudder that simply can not be adjusted properly as we describe, contact your dealer for help or a replacement. As I noted yesterday... only 1 in 15 assemblies on the production line required more than minor adjustment to the drum bolt to work properly.

Please understand that a loose drum bolt, on a properly molded unit, IS proper adjustement and not a "half-assed fix". Over tension binds the system. Some lateral play in the drum is expected as is the case with every Twist-and-Stow rudder.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Hi Roadrunner and Matt Miller.

The Tandem is my first purchase of a Hobie product. Please help me understand how the Tandem's Twist & Stow mechanism is designed to work.

By loosening the drum bolt, the rudder will easily seat into full down position in the groove. This is fully understood. No need to reiterate.

When under sail, the TI will sail faster and the rudder will be subject to stronger forces than any other Hobie kayak designed to date. How is the rudder designed to remain fully down in the water?

On all the Hobie T&S systems I have observed, there is a wide gap between the rudder housing and the rudder at the clip. It is not a snug fit. There is a lot of wiggle room. Is this by design?

Several theories.

1. The rudder is designed to be held down in the water by the rudder down line. This is how it works on all the Hobie T&S kayak I have ever seen. For all of Hobie's slower kayaks, this may have been sufficient. Are these lines strong enough for the TI? My down line snapped already while under sail in the deep water of a small flat lake. Max SOG: 7.5 knots.

2. The rudder clip is located on the port side of the rudder casing. The rudder is designed to be pressed against this clip by the down line pulling the rudder towards port. This is due to the down line exiting the transom on the port side of the transom. This places constant pressure on the rudder to turn to port.

3. The rudder is designed to fit snug into the rudder groove behind the plastic locking tab/clip.

Thoughts?

_________________
Marc K
2010 Hobie Tandem Island
Boynton Beach, FL

Ok, I will remain silent and await a new twist and stow.
I will say that at 1 in 15 yields a .6 Cpk (6 in 100, 93% yield, 3 sigma) and most certainly indicated your suppliers are out of control. unless that is Hobie does not inspect the parts upon reciept, which would indicate that.... well, I think you understand.