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Why does a canal boat have a S shaped tiller?


Stubones99

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When you think about it, an "S" shape is fairly logical.

If you have a transom hung rudder, all that needs to be done is add a lever. When the rudder is in a tube through the deck, the problem is where to add the lever. If you have a long rudder stock, and just stick a right angle on the top, it's not gonna work or long, as you will be putting a lot of shear on the top bearing and the whole assembly is going to be vulnerable to damage, plus it's going to be a real pain getting the rudder off. So put the initial attachment at deck level, with a vertical component and a horizontal one to form the tiller. It makes sense to keep the vertical bit out of the way of the deck, and, as already pointed out, it's far easier to make a solid joint which will resist torsion when the components are at right angles, ather than in line. So we have now got to a "Z" shape, or a ""C" shape, depending on whether the initial joint is on the front or back of the rudder stock.

 

If you have a forge, it's easier to bend one bit of metal than make two fire welded  joints, so the "Z" becomes an"S".

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7 minutes ago, Iain_S said:

When you think about it, an "S" shape is fairly logical.

If you have a transom hung rudder, all that needs to be done is add a lever. When the rudder is in a tube through the deck, the problem is where to add the lever. If you have a long rudder stock, and just stick a right angle on the top, it's not gonna work or long, as you will be putting a lot of shear on the top bearing and the whole assembly is going to be vulnerable to damage, plus it's going to be a real pain getting the rudder off. So put the initial attachment at deck level, with a vertical component and a horizontal one to form the tiller. It makes sense to keep the vertical bit out of the way of the deck, and, as already pointed out, it's far easier to make a solid joint which will resist torsion when the components are at right angles, ather than in line. So we have now got to a "Z" shape, or a ""C" shape, depending on whether the initial joint is on the front or back of the rudder stock.

 

If you have a forge, it's easier to bend one bit of metal than make two fire welded  joints, so the "Z" becomes an"S".

I can see most of that, except the extra shear on top bearing. The penny will drop eventually :)

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8 hours ago, nb Innisfree said:

Gives more room for the steerer to duck under the tiller when changing sides? 

 

2 hours ago, catweasel said:

Seems reasonable.

Except there is no need to 'duck under the tiller' if the steerer stands on the footboard (slightly ahead of the end of the tiller) as per design / intention. Steering whilst standing alongside the tiller is a modern and quite hazardous practice :captain:

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4 minutes ago, pete harrison said:

 

Except there is no need to 'duck under the tiller' if the steerer stands on the footboard (slightly ahead of the end of the tiller) as per design / intention. Steering whilst standing alongside the tiller is a modern and quite hazardous practice :captain:

Should this gent have know better? :captain:

Mr Joe Skinner.jpg

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35 minutes ago, pete harrison said:

Steering whilst standing alongside the tiller is a modern and quite hazardous practice :captain:

 

Though an exception was allowed if the cabin porthole needed a polish!

 

[Photo Robert J Wilson from "Epilogue"]

 

 

Epilogue_006.jpg

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Would the shape be anything to do with the technology available the time the first metal boats were made - i.e. rivets, big hammers and forges? The S shape would have been relatively easy to create, and avoids the weak spot that a simple right angle would introduce as the stress is distributed around the bend to the substantial square 'ole where it joins the rudder that I can't remember the name of. 

Edited by twbm
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43 minutes ago, Ray T said:

Should this gent have know better? :captain:

 

Yes, and I’m sure he did. That’s a staged picture and maybe the camera lens wasn’t a wide enough angle to capture him on the step. Of course he didn’t steer a motor as a professional boater anyway.

 

JP

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1 hour ago, twbm said:

Would the shape be anything to do with the technology available the time the first metal boats were made - i.e. rivets, big hammers and forges? The S shape would have been relatively easy to create, and avoids the weak spot that a simple right angle would introduce as the stress is distributed around the bend to the substantial square 'ole where it joins the rudder that I can't remember the name of. 

I think this must be the reason, as a sharp right angle must be likely to fail at some stage, along with a vertical fixing to the bearing. 

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4 hours ago, pete harrison said:

the steerer stands on the footboard (slightly ahead of the end of the tiller) as per design / intention.

This also allows you to hold the end of the tiller in your back, while you are lighting your ciggy.  You can also sit on the cabin top and steer quite happily.

CRT Photo - Alice Collins.

Alice.jpg

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"S" or "C" shapes are identical mechanically, both have horizontal top and bottom for attaching to rudder and tiller bar, both have the same mechanical advantage and leverage. At first sight a "C" shape would seem to be easier to make having two 90 degree bends, "S" shape bends are about 120 degrees. But there's a hidden advantage in manufacturing the "S" shape which might explain why it was used...

 

As anyone who's used a tube bender will know, it's easy to make two identical bends in a tube or bar (just do the same thing twice), it's much more difficult to make bends of an exact angle because the metal tends to spring back. With a "C" shape both bends have to be exactly 90 degrees (difficult) if the tiller is to end up horizontal. With an "S" shape so long as both bends are identical (easy) the tiller will be horizontal -- if they're both 115 or 125 degrees instead of 120, the errors cancel out.

 

I'd bet that this was the reason, it would probably have been obvious to anyone who actually bends metal bars or tubes... ?

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3 minutes ago, IanD said:

"S" or "C" shapes are identical mechanically, both have horizontal top and bottom for attaching to rudder and tiller bar, both have the same mechanical advantage and leverage. At first sight a "C" shape would seem to be easier to make having two 90 degree bends, "S" shape bends are about 120 degrees. But there's a hidden advantage in manufacturing the "S" shape which might explain why it was used...

 

As anyone who's used a tube bender will know, it's easy to make two identical bends in a tube or bar (just do the same thing twice), it's much more difficult to make bends of an exact angle because the metal tends to spring back. With a "C" shape both bends have to be exactly 90 degrees (difficult) if the tiller is to end up horizontal. With an "S" shape so long as both bends are identical (easy) the tiller will be horizontal -- if they're both 115 or 125 degrees instead of 120, the errors cancel out.

 

I'd bet that this was the reason, it would probably have been obvious to anyone who actually bends metal bars or tubes... ?

As anyone who has worked steel knows, you can bend it any way you want, just apply a little heat. If you've built the boat out of steel already, the tiller is just a bit of fluff... Yes, steel springs back, but it also springs back on everything else. You just bend it over what you want, accounting for the spring back. If it's not enough, do a little more and check your work.

 

If you can't make two bends in a rod or pipe and end up with what the customer wanted, you need to find another career. 

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5 minutes ago, Stubones99 said:

As anyone who has worked steel knows, you can bend it any way you want, just apply a little heat. If you've built the boat out of steel already, the tiller is just a bit of fluff... Yes, steel springs back, but it also springs back on everything else. You just bend it over what you want, accounting for the spring back. If it's not enough, do a little more and check your work.

 

If you can't make two bends in a rod or pipe and end up with what the customer wanted, you need to find another career. 

But why make life harder for yourself by using a "C" shape when you can make it easier by using an "S" shape? Anyone doing metalwork for a living not a hobby will always choose the easier way, all other things being equal, because time is money...

 

Also it does look more elegant, but I suspect ease of manufacture trumps elegance if the two conflict with each other -- fortunately they don't here ?

Edited by IanD
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18 minutes ago, IanD said:

But why make life harder for yourself by using a "C" shape when you can make it easier by using an "S" shape? Anyone doing metalwork for a living not a hobby will always choose the easier way, all other things being equal, because time is money...

 

Also it does look more elegant, but I suspect ease of manufacture trumps elegance if the two conflict with each other -- fortunately they don't here ?

If you have a steel gunwale surrounding the stern like I've seen on some boats, you have to cut out an area to allow for the front of the S shape where it connects to the rudder stock. This would be far more complex to have to make an inset pocket, to match the outer curve of the gunwale steel (like the initial post photo). Simply doing a C shaped tiller would have meant they would not have needed to make the pocket co clear the lower end of the S curve tiller.

 

While there may be other reasons, I think the primary reasons are to build in a "stop" to keep the tiller from being pushed hard over far enough to hit the prop, plus a little bit of "that's the way we do it" thrown in for good measure. Why change if there is no clear advantage.

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14 minutes ago, Stubones99 said:

While there may be other reasons, I think the primary reasons are to build in a "stop" to keep the tiller from being pushed hard over far enough to hit the prop, plus a little bit of "that's the way we do it" thrown in for good measure. Why change if there is no clear advantage.

No!

See previous posts.

The rudder has a raised tip, and that limits how far it can swing round, or at least that is the case on virtually all boats where this design evolved.

 

There is absolutely no need to use the actual tiller to limit travel of the rudder, and it is only in exception cases that it ever does.

 

You may wish to believe your explanation, but it isn't matched by the actual reality.

Edited by alan_fincher
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44 minutes ago, Stubones99 said:

If you have a steel gunwale surrounding the stern like I've seen on some boats, you have to cut out an area to allow for the front of the S shape where it connects to the rudder stock. This would be far more complex to have to make an inset pocket, to match the outer curve of the gunwale steel (like the initial post photo). Simply doing a C shaped tiller would have meant they would not have needed to make the pocket co clear the lower end of the S curve tiller.

 

You are rewriting history here. The S or Z shaped rams head became established practice very early in the development of motorised carrying boats almost a century ago. None of those boats had any steel gunwale, railings, dodger, perch seats, canopy supports or similar paraphanalia that one finds on some modern narrowboats and so the issues you raise simply wouldn't arise. The S/Z shape has simply been copied from working boats by modern leisure craft builders in recent years. Surely the real question arising from your observation is why modern non-traditional boatbuilders continue to use the S/Z shape when it conflicts with all their other bits and pieces.

 

p.s. At the weekend I saw a modern steel cruiser-style narrowboat with a fixed steel dodger around the stern and the bottom of the canopy fixed along its top edge. The Z shaped rams head passed through a slot in the canopy and also through a hole in the steel doger - the latter was fitted with a large flexible rubber gaiter - presumably to keep rain or wind out.  Talk about unnecessary complication!

Edited by David Mack
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45 minutes ago, Stubones99 said:

If you have a steel gunwale surrounding the stern like I've seen on some boats, you have to cut out an area to allow for the front of the S shape where it connects to the rudder stock. This would be far more complex to have to make an inset pocket, to match the outer curve of the gunwale steel (like the initial post photo). Simply doing a C shaped tiller would have meant they would not have needed to make the pocket co clear the lower end of the S curve tiller.

 

While there may be other reasons, I think the primary reasons are to build in a "stop" to keep the tiller from being pushed hard over far enough to hit the prop, plus a little bit of "that's the way we do it" thrown in for good measure. Why change if there is no clear advantage.

I'm not sure what you base your assertion that a cut out is needed to accommodate the steering assembly, i've never seen any normal boat with that set up.

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On 21/04/2019 at 00:19, Chris Williams said:

I think the Safety 'elf has had a hand in this, nasty dangerous things.

Agree about people dressing up to go boating, but life has changed.  The price of a genuine working boat is ridiculous, who can afford one except yuppies.

My pontoon hull cost Forty-five quid.  No hope for hard-up real enthusiasts today.

I think the last thing we could  be described as are yuppies... however working boats have made us broke ,childless , and old before our time. But 40 years of fun..

if id spent all i have on houses rather than boats i might now be wealthy, but im now old retired and downwardly mobile..

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On ‎21‎/‎04‎/‎2019 at 07:26, Ray T said:

Grantham’s Bridge means nothing to him, it has to be “‘morton,” or Hillmorton.

Never heard of it, and I left the canals in 1975.  I understand that the lift bridge at Thrupp is now called 'Aubrey's Bridge'.

They were both really nice people to know.

The Z-shape tiller on my pontoon was made from Kee Klamps - fittings designed for cattle fencing.  They had 45 degree angle bits.

keekl.JPG

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I always assumed that the shape evolved to allow an even balance of the tiller above the bearing or bush while allowing a long handle pointing forwards for leverage, most other designs would put extra weight on one side of the bearing and increase wear

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Since the normal bearing was steel on iron/steel with sufficient allowance to be a "rattling good fit" and  with minimal lubrication I doubt that any considerations of wear or balanced load drifted across the designers mind.

 

N

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