Should Twin Rudders have “toe in”?

[Quickstep192]

I had occasion to kayak around my J/95 while it was up out of the water in the lift and noticed that the rudders appear to have some toe in (for lack of a better term).

I can imagine that when heeled, the rudder on the heeled side would end up being parallel with the centerline, but I still wonder if it’s normal for the rudders to have some toe in.

 

[slug zitski]

Yah

typically the designer supplies a table for optimum angle when adjusting the tie rod

 

[Trevor B]

Yes when you have consistent helm, windward or leeward, and no when the helm is neutral.
ideally it's adjustable for long distance racing.

 

[slug zitski]

Weather helm , heel angle are the consideration

typically it’s the designers best guess

some of those speedsters have a system to adjust while sailing

 

[Lost in Translation]

The interesting thing for a keelboat with twin rudders is the heel of the boat as others note.
When heeled upwind, you ideally want the windward rudder (which only will have a small portion immersed) be in line with the angle the boat is tracking. That means some toe-in.

When sailing flat downwind, you will ideally want the twin rudders to both be parallel as the leeway angle is reduced and you want to minimize drag.

Another dynamic is Ackerman angle and toe-in has some impact in that. That's another whole area of twin rudders similar to cars. There is a lot to twin rudders.

 

[slug zitski]

The interesting thing for a keelboat with twin rudders is the heel of the boat as others note.
When heeled upwind, you ideally want the windward rudder (which only will have a small portion immersed) be in line with the angle the boat is tracking. That means some toe-in.

When sailing flat downwind, you will ideally want the twin rudders to both be parallel as the leeway angle is reduced and you want to minimize drag.

Another dynamic is Ackerman angle and toe-in has some impact in that. That's another whole area of twin rudders similar to cars. There is a lot to twin rudders.

Yah

I have a mate who commissions and tunes up Owen Clarke speedsters

he is frequently tweeking rudder angles and going on about heel angle, fore and aft trim, wetted surface …

those boats are technical

 

[Lost in Translation]

I used to tune my catamaran to have the windward rudder stream water equally on each side when close hauled. I thought it was a touch faster upwind and felt better. In those days we would flip up a leeward rudder downwind if flat or sail heeled downwind too.

Now we foil as much as possible with the boat level and the rudders are set to straight. Now the big deal is to have the windward rudder pulling down and the leeward rudder lifting up.

Twin rudders are very interesting and very technical for sure. One big benefit of them for any boat: large heel angles don't cause the rudder to let go like they do for more traditional rudder single rudder designs.

 

[Zonker]

Yes +toe in and should be adjustable easily.

 

[longy]

E-BAR | Fourth Cape

The E-BAR controls toe in/out adjustment of rudders onboard twin rudder boats, this trimming minimises drag and maximises control.

fourthcape.com

 

[Roleur]

E-BAR | Fourth Cape

The E-BAR controls toe in/out adjustment of rudders onboard twin rudder boats, this trimming minimises drag and maximises control.

fourthcape.com

Pretty common in the SF3300 fleet.

 

[beercanned]

Our Open 5.70s have twin rudders and we (mostly) set them up with 1°-2° of toe in.

Some skippers are sensitive to it, others are not. YMMV.

 

[longy]

Do you have it?

Pretty common in the SF3300 fleet.

 

[Blur]

Our Open 5.70s have twin rudders and we (mostly) set them up with 1°-2° of toe in.

Do you know if there's a tuning guide for this or do people do it by feel?

We got an Open 7.50 to play with, and the twin rudders are one of the things we need to understand (as well as the spreaderless rotating wing mast and articulating sprit😀)

 

[JMOD]

on the J99 you can adjust the toe in. look at the wake, if you see a lot of water turbulence on the lifted rudder, twist it, until its gone.

 

[slug zitski]

on the J99 you can adjust the toe in. look at the wake, if you see a lot of water turbulence on the lifted rudder, twist it, until its gone.

Yah , that’s the fast way to get 95 percent

for a long distance race it’ seems straightforward , around a race course its mysterious

I see tunning guides…like standing rigging adjustment, light med , heavy

since I don’t have much sailing time on those boats I don’t know the game

and since those twin rudders pick up junk fast… step one is to have a system to clean off junk from the rudder

 

[Monkey]

I can’t help but wonder if a touch of toe in also helps tracking in the same way most vehicles run a degree or two of tow in on the steering wheels to track better. I know heel angle messes with that concept.

 

[Quickstep192]

on the J99 you can adjust the toe in. look at the wake, if you see a lot of water turbulence on the lifted rudder, twist it, until its gone.

Can you provide a little primer on how to adjust? I’m guessing the J/95 shouldn’t be too much different.

To me it looks like access will be my biggest issue. Getting into that area involves going through openings smaller than me.

 

[Roleur]

Do you have it?

We do, but only at the end of the season, so it functions, and it is calibrated, but we haven't progressed to a "tuning guide" yet, other than more toe-in as leeway increases.

 

[Lost in Translation]

The e-bar set up is really cool. So is the J/99 solution.

Any sailboat makes some leeway, so the idea of toe-in is to put the windward rudder, which can't get much grip anyway, in a position that minimizes drag. The amount of leeway varies depending on all heel, speed, wind angle, etc.

I've heard some insist that boat rudders straight all the time, zero toe-in or out. Sometimes I've seen people recommend the 1 to 2 degrees of toe-in just to make sure that the rudders aren't toed out.

I wonder if toe can be used downwind on a fast keelboat to put some downward pull into the stern and put the bow up?

One of the new IMOCAs, Charal 2, is using the windward rudder to try to control flight without a rudder elevator. They call the configuration V Rudders and are working to use the windward one as an elevator / trim control for flight.

CHARAL 2 vs. MALIZIA 3 |

 

[slug zitski]

The e-bar set up is really cool. So is the J/99 solution.

Any sailboat makes some leeway, so the idea of toe-in is to put the windward rudder, which can't get much grip anyway, in a position that minimizes drag. The amount of leeway varies depending on all heel, speed, wind angle, etc.

I've heard some insist that boat rudders straight all the time, zero toe-in or out. Sometimes I've seen people recommend the 1 to 2 degrees of toe-in just to make sure that the rudders aren't toed out.

I wonder if toe-out can be used downwind on a fast keelboat to put some downward pull into the stern and put the bow up?

One of the new IMOCAs, Charal 2, is using the windward rudder to try to control flight without a rudder elevator. They call the configuration V Rudders and are working to use the windward one as an elevator / trim control for flight.

CHARAL 2 vs. MALIZIA 3 |

Normally the helmsman can feel the drag of the windward rudder.

if you had a system to adjust the tie rod length while sailing you could instantly neutralize it

im not sure how they tune for level sailing , both rudders biting