Line Steering

The tiller extension seemed like a good idea, but it busted out the first time it I took it sailing. I suspect that the tiller hung up on the aft hatch and busted when I pushed on the extension. So I've decided to run a line around the perimeter to amidships and back to the rudder. That way I'll be able to steer the boat from anywhere in the aft half of the boat

I used the 2/1 pulley set up to decrease the sensitivity of the steering. More line pulled for the same rudder deflection compared with just a direct connection.

The red disks are the tops of pulleys that just direct the line around the boat. I left them open so I wouldn't have to string the line through a bunch of pulleys to rig the steering. This way after rigging the aft pulleys and T-bar I just loop the line around the perimeter pulleys.

The 2/1 setup turned out to be difficult to actuate. So I went to a 3/1 setup to try to gain some mechanical advantage.

In response to an E-mail that I sent to the smallsailboats group on yahoo, Russ Ashworth pointed out:

"A more effective method to get mechanical advantage is to increase the length of the T-bar. This also reduces the loads on the pulleys and so reduces the friction and thus the force required to move it. In fact doubling the length of the bar and using no pulleys will reduce the force required compared to now. Depending on the friction in the pulleys increasing to 3/1 might not gain you much."

He is right. :( This is a situation that can be described by two sayings:

"I couldn't see the forest for the trees"

and

"Just because you can do something doesn't mean you should"

 

I had become so focused on turning pulley wheels out of plastic, and making pulleys that I didn't take a real critical look at what I was doing. I suspect the friction in the pulleys is what is causing the high operating forces. A longer T-bar would have been MUCH faster and simpler. I forgot KISS. :(

 

Guess what the next modification is likely to be.

 

Another problem that showed up during testing was that with the lines rigged this way, steering was counterintuitive. If you pulled on the port line the boat turned starboard and visa versa. Even though I knew how the steering was set up, while sailing I kept turning the rudder the wrong way. I will have to devise some sort of crossover to reverse the action of the lines

 

Here is the next variation.

 

 

The T-bar is about twice as long, and mounted on the Center Line of the rudder pivot. The lengthened T-bar would probably have been adequate, but I love to complicate the issue, so I reinstalled the 2/1 pulley system. It works quite well.

 

 

Hard'a starboard

When I pull on the starboard line, the boat turns starboard

 

 

Hard'a port

When I pull on the port line, the boat turns port.

Thanks to the 2/1 pulley system, and the extended T-bar, it takes about a 2 foot pull on the line to go from center rudder to the stop.

Since nylon rope stretch when wet, one end of the line is fixed, and the other is fastened to the aft belay pin. If the line gets too loose underway, it is an easy thing to take up the slack.

 

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