View Full Version : Push-pull vs trad sweep design tillers
12-13-2005, 12:16 PM
This question is more for design theory than immediate application, as I plan on a traditional tiller design for my dory.
I've sailed small boats with the push-pull design -- a small post comes sideways out of the rudder head, then the tiller is loosely attached to this post at 90 degrees.
Is this design just awkward to use and unfamiliar to most of us, or is the handling always going to be inferior to a traditional sideways sweep design? Some boat designs go to GREAT lengths to avoid the push-pull tiller, the recent thread on the Green Island 18 had the below pic of that tiller design:
12-13-2005, 12:50 PM
One consideration is that a long tiller allows more subtle adjustment of rudder angle. You have to move your arm a long way to move the rudder much, and this makes it easier to steer smoothly and not overcorrect. With a push-pull arrangement, the effective tiller is the arm sticking out the side of the rudder. Itís almost always shorter than a conventional tiller, so a small movement of the stick will give a fairly large rudder movement. The force required on the push-pull mechanism is also proportionally larger.
12-13-2005, 01:13 PM
Most dories are so narrow at the end that you'll not want to sit back where a right sized tiller would reach and you really don't want a wanking long tiller as it clogs your space and offers but limited steering range. Even the short tiller gives but limited range in many dories. Swampscotts notwithstanding.
Especially with an off-set rudder as you'd have in most double ended dories, and athwartships tiller will be long enough and still be inboard. This is a wonderful thing upon which to hang a nice long light stick for the push/pull.
If the rudder is too large for that leverage or if you want even greater convience, steering ropes that go over a wheel at the rudder head work very well.
You need the wheel to get the right geometry that will stay tight. The line that contacts the wheel should pass around the foreward side of the wheel if you want the natural feel like a horizontal wheel if you have both ropes in hand, and still quite natural that for either side, pushing the rope ahead turns the bow away from that hand, pulling back (like reining in a horse) turns toward the line.
You'll want something better than 1:1 advantage so have the steering rope end with a small block.
The ropes you'll handle go from some point on the gunnel, back to the block, forward around the boat to the other block, and then forward to the gunnel.
The rope should be fat enough that it's comfortable to pull. Little blocks and fairleads keep the steering rope along the sides and let it cross the boat up by the mast.
A cam cleat on each side about even with the normal steering spot and a bit above the natural run of the steering rope makes a nice way to pin the helm. Have the cleats aimed to resist a strain from the stern so that the weather cleat will be all you need to hold against the weather helm you should have. You'll use both cleats to freeze the helm when rowing or towing. This one feature which really can't be conveniently duplicated with a tiller, is worth everything.
12-14-2005, 04:07 PM
Well, there's the extra unwanted slop in the connections and several more places for something to go wrong. Ball joints might fix the slop thing. Due dilligence might overcome the latter.
As said above, the more you have to move the tiller for a given rudder angle change, the less twitchy the steering - a good thing ;)
12-14-2005, 07:13 PM
My limited understanding is that push-pull tiller arrangements have their place in some relatively small, narrow-beamed boats due to the difficulty involved in sitting on one side or the other to use the tiller, especially if one is seated down low. I had a heck of a time trying to steer my Whisp with a sweep tiller while seated on the bottom of the boat and so just made a push-pull version which I believe will work better in my situation. One problem I encountered is that the transom is raked so much that the side arm fastened to the rudder blade doesn't stay level when moving the rudder left and right. This presented a problem in fastening the end of the push-pull tiller to the side arm. I'm experimenting with a "piece of rope through the end of the tiller and the end of the side arm" arrangement and will see how this works.
Larger boats may need the greater mechanical advantage available with a side to side tiller for a larger rudder and don't suffer so from moving one's weight around from side to side as one changes sides when tacking. There is obviously more to the story than this, as some beamy double enders use push-pull tillers as is noted above in another post.
[ 12-14-2005, 08:21 PM: Message edited by: Steve Lansdowne ]
12-15-2005, 10:41 PM
This is the flexible joint I came up with for my CLC Skerry. The Skerry steers very nicely with this set up, and I can ship and remove the steering extention in just a few seconds.
The black and white line is quarter inch bungee.
The retention pin lives on a short leash so that it cannot be dropped overboard.
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