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Stubones99

Why does a canal boat have a S shaped tiller?

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Why is the tiller on a canal boat shaped like an S, where the tiller attaches to a collar at the top of the rudder stock, with the tiller arm going off the front, then bent upwards and backward to go over the pivot point of the rudder stock, then back forward? I see canal boats that have a pocket in the back railing to accommodate the forward part of the tiller arm at the base of the tiller, when it seems that if the whole collar and attachment point  exited to the rear and then had two 90 degree turns, the same effect could be done, without having a tiller pocket.

 

Is it done to get the tiller out of the way of a possible collision from astern?

Screenshot 2019-04-19 09.19.48.png

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Is a good question.

 

I don't know but I suspect there will be a reason other than it just looks better than a vertical bar with a 90 degree bend at the top.

 

I too always notice how the joint where the tiller bar slides on is roughly over the centreline of the rudder stock, and wonder why this would need to be. 

 

So basically, I'm asking the same question as you!

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As there is no mechanical advantage having that shape tiller the only purpose of the backward swoop of the Swan neck that I can see is to provide a bit of weight over the rudder to act as a counterbalance. 

 

Just a guess though. 

Edited by carlt

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But why would a bit of weight over the rudder to counterbalance it be needed? 

 

I think to counterbalance the rudder sticking out the back, exra weight would actually need to be forward of the rudder stock. 

 

I expect someone will be along sooner or later to tell us the original reason, and it will all make perfect sense!

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If it was shaped like an I it would have no leverage.

If it was shaped like a Y the people in the boat behind you could lean forward and steer you out of their way.

Shaped like a d or a b could be useful as it could be called into service as a replacement if your rudder dropped off.

I used to have one shaped like an H but I couldn't get BBC2 with it.

V was popular for a while but offended the meek

W offended them twice as much

So Z and S were given a go.

  • Haha 2

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5 minutes ago, Mike the Boilerman said:

I expect someone will be along sooner or later to tell us the original reason, and it will all make perfect sense!

It appears you were wrong ;)

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Don't forget that there have been exceptions.

Example: W J Yarwood & Son's built "Royalty" boat Edward.

 

v0_web.jpg

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1 minute ago, alan_fincher said:

Don't forget that there have been exceptions.

Example: W J Yarwood & Son's built "Royalty" boat Edward.

 

v0_web.jpg

 

The narrowboat swan neck is the exception.

 

I don't recall seeing such a shape on any other type of boat.

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1 hour ago, alan_fincher said:

Don't forget that there have been exceptions.

Example: W J Yarwood & Son's built "Royalty" boat Edward.

 

v0_web.jpg

 

I didn't realise the tiller hinge has such historical authenticity.

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1 minute ago, tree monkey said:

Does having the longer tiller give a mechanical advantage maybe?

No because the leverage depends on the horizontal distance from the rudder bearing to the handle which is the same even if it is just at right angles. 

 

I believe it was devised by mischievous working boatmen so that when leisure boaters hang their rope over the tiller pin it is dangling perilously close to the prop. 

  • Greenie 2

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Too many ales to think straight but what if the tiller is set back at a slight angle the bent bit acts as a self centering mass for the tiller. 

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1 minute ago, mark99 said:

Too many ales to think straight but what if the tiller is set back at a slight angle the bent bit acts as a self centering mass for the tiller. 

But the weight of the rudder is probably significantly greater, and would presumably provide that effect anyway?

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Well maybe it adds to the self centre force. I notice mine coincides (projects) with end of rudder so its a practical at a glance measurement of where the rudder ends/starts. Nothwithstanding correct rear fenders should protect you.

Edited by mark99

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The swan-neck form allows the tiller bar to start "further back" (actually beyond the back of the boat) so giving a longer lever in a confined space, more room, and less radial sideways movement for the benefit of the steerer.

 

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Ok mechanical advantage? Longer movement per rudder degree? Posts crossed.  ;)

Edited by mark99

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Just now, mark99 said:

Ok mechanical advantage? Longer movement per rudder degree?

As I said before...there is no mechanical advantage because the actual lever length is the same. 

 

If there was any mechanical advantage the design wouldn't be restricted to tiddly little narrowboats. 

Tiller steered wide beam barges have straight rudders despite being a lot heavier to steer. 

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I was literally studying this while manoeuvring Vulpes this afternoon; the pontoon’s at Netherwich basin now bear testament to this.

 

As carlt says it’s not about mechanical advantage. What struck me was the joint at the tiller hinge. I wondered if the origins of the tiller shape lay in the ability to make a mechanically sound and reliable joint between rudder and tiller. This is far more easily achieved if the tiller and rudder post are perpendicular at the join. If the tiller post was vertical (and the tiller an inverted L shape) then there would need to be an in-line joint between tiller and rudder post. Even in the picture of the Royalty class above the style of joint is common. Of course the tiller doesn’t have to be a Z shape but that may just have been aesthetics or perhaps just because it’s probably easier to put abrupt bends in the metal than gently curve it.

 

I like the idea of the outer bend of the tiller signifying the extent of the rudder or maybe some other feature. May not be correct but a nice idea all the same.

 

JP

Edited by Captain Pegg

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I have a semi trad and when I come out of the back on all fours because the tonneau is still on the swan neck allows a little more space before I bang my head on it. 

 

Cheers Graham

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I reckon it is that shape so when butty runs up the back it doesn't hit it and the stem post of the butty will go in to the bend.

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With another ale I do agree the mech advantage is not there. I did read somewhere it helps even wear on the rudder tube/bearing. I thinks its re  enhanced balance and self centre-ing. Plus it looks better!

Edited by mark99

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If the radius  of the two curves of the s are the same there is no mechanical advantage surely. As to the butty theory we rarely hit the tiller generally the bow hit the fender first.

I think it’s because it was a casting and may have needed minor adjustment to get the tiller bar level. Easier to do by adjusting two radius, because that means you can raise or lower while keeping the tiller bar parallel to the water.

 

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19 minutes ago, Graham and Jo said:

I have a semi trad and when I come out of the back on all fours because the tonneau is still on the swan neck allows a little more space before I bang my head on it. 

 

Cheers Graham

That is known as lulling you into a false sense of security. 

More evidence of working boatman mischief. 

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