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Why does a canal boat have a S shaped tiller?


Stubones99

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5 hours ago, alan_fincher said:

Don't forget that there have been exceptions.

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

 

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I am pretty sure the cabin chimney (none of this 'chimbley' nonsense from me I'm afraid) is also hinged on these boats, and I think the counter weight is just visible :captain:

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5 minutes ago, pete harrison said:

I am pretty sure the cabin chimney (none of this 'chimbley' nonsense from me I'm afraid) is also hinged on these boats, and I think the counter weight is just visible :captain:

 

I wondered about that, and thought for it to work the nonsense chimbley would need to hinge forwards, which seems counter-intuitive. 

 

But then if it hinged backward the S-shaped tiller would prolly foul it whilst down....

 

 

 

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5 hours ago, carlt said:

The narrowboat swan neck is the exception.

 

48 minutes ago, Tom Morgan said:

The swan-neck form allows the tiller bar to start "further back" 

Back in my day a 'swan neck' was a piece of decorative ropework attached to a butty's helm / elum.

 

The 'Z' shaped bar used to steer a motor, along with the main stock of a butty's helm / elum were both 'rams head's' - but like everything there are probably regional variations :captain:

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51 minutes ago, Tom Morgan said:

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.

 

No, not so.......

 

Consider this.....

 

1) Weld a bar from the top of the rudder stock to join up with the horizontal part.
2) Now cut away all the other bits.

The leverage and movement of the tiller will remain identical.

 

(OK, I do know you couldn't actually do those 2 steps in that order because part of the Z bit you would cut away in step 2 would obstruct you doing step 1, but that doesn't change the theoretical outcome.....)

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1 minute ago, Mike the Boilerman said:

 

I wondered about that, and thought for it to work the nonsense chimbley would need to hinge forwards, which seems counter-intuitive. 

 

But then if it hinged backward the S-shaped tiller would prolly foul it whilst down....

 

 

 

I do not know how this worked, and I suspect it did not last long as it is quite un-necessary :captain: 

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1 minute ago, pete harrison said:

I do not know how this worked, and I suspect it did not last long as it is quite un-necessary :captain: 

 

Yes just lift the nonsense chimbley off as it is right 'there' for the steerer. A complicated hinge for the tall pipe is arguably only 'needed' because the pipe is out of reach from the steering position.

 

 

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As noted above the mechanical advantage is defined by the horizontal distance between the fore end of the tiller bar and the vertical axis going through the rudder post.

 

Here's another theory: when the tiller is removed it is still quite easy to move the rudder back and forth, should you wish to do so, by putting one hand on the joint (ie where the bar goes) and the other on the S bit.

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6 minutes ago, Scholar Gypsy said:

As noted above the mechanical advantage is defined by the horizontal distance between the fore end of the tiller bar and the vertical axis going through the rudder post.

 

Here's another theory: when the tiller is removed it is still quite easy to move the rudder back and forth, should you wish to do so, by putting one hand on the joint (ie where the bar goes) and the other on the S bit.

 

Quite. 

 

I think Peggers has it in Post 20. Its all about how to have a dismantling joint at the top end of the rudder stock. A taper collar goes on the rudder stock and the obvious way to connect a tiller arm to the collar is to weld a tube horizontally to it, then shape the tube so a tiller can be joined at the right height. This can be done using a C shape as per the pics Alan posted, or a Z shape as most boats have. The Z shape looks nicer and is no more difficult to form than a C shape, possibly easier, so a Z shape is the way it is normally done.

 

 

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1 hour ago, Tom Morgan said:

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.

 

There is no mechanical advantage since the mechanical advantage is from the imaginary line directly above the rudder stock to the tip of the handle. Anything aft of the rudder stock is of no advantage.

 

I see some value for the S curve being a "rudder angle indicator" and it should act to a degree like a balanced rudder would, since some of the rudder will project forward of the rudder stock, and most of the blade will be aft of the rudder stock, would act as a indicator of where it is and what angle the rudder is currently. Still, the bottom of the S could be a J, exiting from the aft edge of the rudder collar and simplify the aft railing manufacture.

 

I think it is the way it is primarily since it has been the way it is for a while, and they know how to make it that way, and if they changed, people would say "That looks funny, why did you do it that way, and not the S curve way?"

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51 minutes ago, Stubones99 said:

There is no mechanical advantage since the mechanical advantage is from the imaginary line directly above the rudder stock to the tip of the handle. Anything aft of the rudder stock is of no advantage.

 

I'm not suggesting that there is any mechanical advantage - just that a lever (say) 5 feet long is only going to take up 4 feet of the deck, if it starts one foot behind the boat.  But what do I know?  My boat's a yogurt pot with a steering-wheel! :)

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It allows unfettered access to the bolt or other fixture that holds the tiller boss to the rudder bar (along with any tools used).  As the tiller then leans back it passes through an imaginary line, an extension of the rudder bar, this then "sets" the correct leverage.

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3 minutes ago, Tom Morgan said:

I'm not suggesting that there is any mechanical advantage - just that a lever (say) 5 feet long is only going to take up 4 feet of the deck, if it starts one foot behind the boat.  But what do I know?  

 

Not a lot about levers, it appears!

 

 

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3 minutes ago, Tom Morgan said:

I'm not suggesting that there is any mechanical advantage - just that a lever (say) 5 feet long is only going to take up 4 feet of the deck, if it starts one foot behind the boat.  But what do I know?  My boat's a yogurt pot with a steering-wheel! :)

 

Is this the new "Which uses less water in a lock...wide or narrow beam?" debate? 

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1 hour ago, Rob-M said:

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.

When 'Tadworth' rammed me as I slowed for a bridge 'ole she did hit it and bent it.  I used the old forge at Castle Mill, Oxford, to bend it back.  Probably the last time the forge was used. All gone now.

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1 minute ago, Chris Williams said:

When 'Tadworth' rammed me as I slowed for a bridge 'ole she did hit it and bent it.  I used the old forge at Castle Mill, Oxford, to bend it back.  Probably the last time the forge was used. All gone now.

 

Was the "Tadworth" a butty back in the day then? 

 

 

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2 minutes ago, Mike the Boilerman said:

Was the "Tadworth" a butty back in the day then? 

No, we were on a camping run, but the post would only apply to an empty butty, surely.  A loaded boat would just hit the tipcat, which is what it is for.  I can't see a loaded butty 'running up'.

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Making the bar between rudder stock and steerer's hand longer will alter the vibration frequency transmitted to the steerer's hand. Probably making it less damaging to the hand over long hours. 

 

I know someone who thought it would be clever to use a non conventional tiller ie an upright part and a horizontal "tiller bar" and the boat is horrible to steer due to the vibration frequency at the end of the tiller bar. 

 

 

Just a theory. 

 

 

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19 minutes ago, magnetman said:

Making the bar between rudder stock and steerer's hand longer will alter the vibration frequency transmitted to the steerer's hand. Probably making it less damaging to the hand over long hours. 

 

I know someone who thought it would be clever to use a non conventional tiller ie an upright part and a horizontal "tiller bar" and the boat is horrible to steer due to the vibration frequency at the end of the tiller bar. 

 

 

Just a theory. 

 

 

That adds to the theory of the ease of connection. In the system you describe your friend having what dampens the vibration of the upright arm? Presumably just the bearing. It sounds like a very lightweight system.

 

Whether the tiller is a C shape or a an S shape both have a big heavy annulus formed on the end to connect it to the rudder stock which is probably effective in damping vibration. A nice big brass tube on the other end probably helps too and in that context maybe the additional length does help.

 

JP

Edited by Captain Pegg
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Dunno why it's like it is, but it does allow the incident hat happened to me one on the Upper Peak Forest. Two boats passing very close, and turning hard to get  the backs inline as soon as they passed, managed to hook the top bends of the Zs together. causing both boats to stop very suddenly. To be honest I'm still amazed it's possible and I'm sure I couldn't repeat it if I tried, but it did happen, and was a hell of a job to untangle. My tiller bar still bears the scars in the form of a large dent.

 

MP.

 

Edited by MoominPapa
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1 hour ago, Captain Pegg said:

That adds to the theory of the ease of connection. In the system you describe your friend having what dampens the vibration of the upright arm? Presumably just the bearing. It sounds like a very lightweight system.

 

Whether the tiller is a C shape or a an S shape both have a big heavy annulus formed on the end to connect it to the rudder stock which is probably effective in damping vibration. A nice big brass tube on the other end probably helps too and in that context maybe the additional length does help.

 

JP

The boat I was referring to was a diy narrow boat. The tiller is heavy as the upright is rolled channel section. Plenty of weight but overall length of material from stock to hand is much less than you get on a "Z bar"

1 hour ago, Captain Pegg said:

That adds to the theory of the ease of connection. In the system you describe your friend having what dampens the vibration of the upright arm? Presumably just the bearing. It sounds like a very lightweight system.

 

Whether the tiller is a C shape or a an S shape both have a big heavy annulus formed on the end to connect it to the rudder stock which is probably effective in damping vibration. A nice big brass tube on the other end probably helps too and in that context maybe the additional length does help.

 

JP

It is heavy as the upright is a thick rolled channel section. Its just too rigid and transmits vibration badly. 

 

The extra length of bar you get using a "z bar" is going to be helpful not just because of the weight but also the actual change in vibration along the solid bar. 

 

 

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