Tiller handle length

For design of a helm wheel steering system I've seen use of a value of 30 or 40 lbs of force max from the helmsman. That is, max expected effort from the helmsman for the steering system to match the max torque from the rudder.

I have not found a similar value for tiller handle design. I assume it could be the same and the tiller handle being a more straight forward lever to spec to meet the max rudder torque.

I can imagine that with tiller handles that the max effort from the helmsman could vary more widely due to ergonomic considerations.

Any insight into tiller length design would be appreciated. I am curious about what kind of range of max rudder torque I could infer given the length of a tiller handle.

 

Without knowing what size boat is under discussion,its not easy to be specific.It is a well known phenomenon in racing dinghies that a longer tiller adds speed.Why?Well, some sailors seem to have an innate urge to tweak the tiller on every wave that passes and the longer the tiller-the less drag they add each time they react.For a much larger boat with wheel steering it shouldn't be too hard to calculate the equivalent of a wheel system if such a thing is known.It might be more pertinent to consider the rudder design as some have more balance inherent to their design than others.The least balanced tending to be those which are wholly behind a skeg.

 

Thank you. I'm thinking about larger boats. Maybe best to think of 2 ranges of LOA - 24 to 32 ft, and 32+ ft.

Thinking about a better way for boat owners to estimate their max rudder torque than displacement or length. Useful for getting in the ballpark for autopilot sizing. For a tiller steered boat it would be tiller length. For a boat with a helm wheel it would be helm wheel diameter and rudder quadrant/wheel radius (assume 11T cog). Should be easy enough to measure those. Followup would take more details into account.

 

Or simply start a little long and cut it down to what is comfortable.
Length (the mechanical advantage factor) is a function of so many variables...

 

Ergonomics of tillers are a bag full of problems. 40 or even 30# would be tiresome, particularly if you are not in a well placed supportive seat. But if you have a long tiller for leverage it is impossible to have such a seat for the full throw. On small boats the skippers weight needs to be windward and forward. On bigger boats they likely prefer to sit leeward for the view of the jib. The force of a tiller is more tiresome with your arm in compression than in tension (back to windward). On smaller boats you are almost certain to need a tiller extension, and then you have it's kinematics to deal with.
The only sure thing in my opinion is that you are going to want to start with a well balanced rudder.
My ergonomic solution would be to give up on the tiller and run push-pull rods just outside the combing on each side.

 

The torque on the tiller / wheel is purely a result of rudder balance and friction, huge boats with a well balanced rudder can have finger light tiller effort. A small boat with No rudder balance proportionally has a huge tiller effort.

Tiller length I've found is much more to do with the ergonomics of reaching the darn thing, especially when well heeled. On small 18ft boat I converted the boat to twin rudders (the original single rudder was deeper than the bilge keels), I found it became much easier to helm the boat as the tiller was 2ft closer to me , even though the tiller was slightly shorter.

I think the wheel 40lbs is more to do with slop / friction in the system and not really relevant to tillers..

 

Not on a sailboat while sailing.

 

Thanks for the replies. Here's one puzzle I've been thinking about on this issue... The J/105 has a 48 inch dia helm wheel and a 12 inch quadrant. Assuming an 11T cog, that generates a LOT of torque on the rudder post if figuring 40# max input from the helmsman. By my calc that looks like around 10383 in lbs. For a tiller to generate the same torque and have a 40# max on the helmsman it needs to be 260 inches long = 21 feet long. So obviously I am missing a bit here. I've no experience with the J/105. I have heard that in light air the tiller is better but with wind it will give the helmsman a bit to think about. J/Boats could have designed the helm wheel system to have a lot less max input from the helmsman. Say 10#... That would make an equivalent tiller in the 5' range if it had a max input of 40#. That sounds closer to what I've heard about helm and tiller experiences on that boat.

Probably what I am seeing is that helm wheel steering - AND - tiller steering has wide variation in the max input expected from the helmsman to match the max rudder torque estimations.

 

I don't completely follow but it sounds like there is an error somewhere. If I was calculating a tiller length for a maximum force I would start with the sailing condition just before reefing.
wind speed=first reef design speed
boat heel=max normal operating (~20deg)
use these parameters to calculate the force on the rudder then tiller length=rudder force x dist (lift center to pivot)/max tiller force

 

I have never needed to maxout the forse applied to either a tiller or a wheel.

I hold the tiller at whatever length is convenient from where I'm helping.
Other than tacking I keep the movements small.