I have a Nacra 450. The 1" OD tube connecting the right rudder to the tiller is bent inward about 30 degrees. The left one is 5-10 degrees. This makes the right rudder turn left (points right) while the left rudder is straight ahead. Judging by the length of the tube that connects the two rudder tubes (the piece the tiller goes to), it seems there should be SOME bend. Or are they supposed to be straight?

I'd like to bend it back straighter (how?), but if I can't, I'll replace it. I was at Lowes today and saw EMT conduit that is about the right size. Would this work?

Thanks,
Danno

This angle is called "Ackerman" angle, and makes both rudders aligned to the radiuses the hulls turn at. The inner hull turns at a different radius compared to the outer hull. The same thing is found on cars, to align the front wheels in turns.

Both tillers should have the same angle (but opposite to each other), and it is quite important to have the right angle. The angle is calculated based on the width of your boat. For a 10 foot Tornado, I think it is 6 degrees of bend.

If you find the correct angle (assume the other rudder have the correct angle), you can just build a jig and bend it back carefully. Otherwise, a good aluminium alloy (that can handle seawater) tube should be fine.

Then bend you describe, will affect both your speed and your tacking abilities..

Danno,

This could be part of your tacking problem. If your rudders are not aligned properly they will provide a good deal of resistance through the water. The rudder arms are supposed to be bent like you show for the reasons that Rolf explained. However, with the rudders pointing straight forward they should be in perfect alignment. Only when the boat begins to turn should the alignment change (due to the Ackerman angle).

With the boat supported on dry ground, draw a level horizontal line on each rudder in the same position (below the casting is usually a good spot). Position one rudder pointing straight forward (site down the hull comparing the rudder blade angle with the bow). Use a tape measure and measure the distace between the back of both rudder blades at your mark. Then measure the distance between the front of both rudder blades at your mark. If these distances are different by more than 1/8" you need to adjust the length of your tiller crossbar to align the rudders properly...this usually means cutting it and redrilling it.

But his rudder arms are bent inward at completely different angles. Wouldn't they still have to be bent in at the correct angle (for Ackerman) and at identical angles?

I mean, he could get the rudders aligned straight by changing the length of the tiller crossbar, but what happens when he is turning, if the rudder arms (tillers) are not bent at the correct and matching angles?

Sorry - I glanced over that bit. Danno, a Performance Catamaran dealer should have the pre-bent rudder arms for about $28 - $32 each. You will have to drill the rivet holes for the castings but I suggest you consider the time you may spend trying to make new (heavier and less corrosion resistant) ones. If you can figure out which one is bent too much, you could possibly just replace one. The rudder arms come with no holes in them so you can place it on the left or the right side.

Thanks, everybody :-)

I'm waiting to see how much the arms cost. Looks like they are 1/16". If I build replacements, maybe I'll get 3/32".

Cheers,
Danno

From memory...I believe they should be 1" O.D. tubing with a 1/8" wall.

Thanks, Jake.

Pretty sure they're 1/16 per my rusty (not trusty) $5.99 micrometer. No matter. I just got done bending it back. Looks like it lines up nice. Too late to measure between the rudders.

Ciao!

Danno, if your tiller arms really are 1/16" you may well want to stiffen them up. We had tubing in a different application that was constantly bending under load. I don't know what the actual wall thickness was but rather than make new ones, after 'straightening' them once again we filled them with expanding foam. The type that you can buy in aerosol cans in most hardware stores. Result - no more problems with the arms bending under load.

I think that the foam actually sticks to the inside of the tube and turns the whole thing into an integral structure. I can't see why it wouldn't work if applied to tiller arms.

John,

That's a pretty good idea with the foam - it will firm up the structure some. Note that this foam can start to absorb water after long term exposure - but for the application of a tiller arm, this wouldn't make much difference.

Thanks, John.

I bought this rig last August, sailed it once, then had knee surgery. While hobbling around in September, I noticed the rudders were out of alignment. I didn't measure, but it seemed worse after a couple trips this summer. So I thought maybe it was getting bent while sailing? But it was really hard to bend it back to it's original shape, so maybe it was my more discerning eye this year.

Still think it's something worth doing though. For sure it got bent somehow to begin with.

Cheers!

It could pose a problem that Nacras have the rudder lift bungees inside the tiller arms.