Tiller & prop

[bottle]

I do not know all the right names hope you can follow.

 

The tiller blade is behind the prop, there is a small blade to the front of the vertical fixing

and a large blade to the rear.

 

How close can the small blade be to the prop and does size matter, ie would a larger blade to the front or rear have any effect on manouverability or steering.

[Gary Peacock]

I do not know all the right names hope you can follow.

 

The tiller blade is behind the prop, there is a small blade to the front of the vertical fixing

and a large blade to the rear.

 

How close can the small blade be to the prop and does size matter, ie would a larger blade to the front or rear have any effect on manouverability or steering.

<{POST_SNAPBACK}>

 

I once waisted a day doing calculations for a hydraulic steering system on this subject. To find out on a slow moving boat it made little difference.

This site describes some principles of rudder design.

http://www.glen-l.com/weblettr/webletters-...38-rudders.html

 

Gary

[bottle]

Thank you Gary

 

From that link information, I think a balanced aerofoil shape would be best being careful not to have "too much in front" as the tiller would be a constantly moving, making for a tiring day at the tiller.

 

I have read in reports about heavy or light steering on narrow boats perhaps it is the design of the rudder that has some bearing.

 

Hears a little something for your trouble. I have heard that it can used in our pub.

[Alastair]

A balanced rudder is a very good thing. However, not felt very heavy steering on any narrowboat.

 

Unlike my orange pig, where the tiller is scaffold pole, and even that bends with the force required to turn her.

[John Orentas]

Bottle.

 

Most of the data with with Gary's link concerned rudders which operate in clear water as on a sailing boat or a high speed type of motor boat.

 

The principle of the rudder operation on a narrowboat is rather different, being located in the water stream from the propeller, the rudder directs that very strong stream to give the steering, narrowboats are one of only a few craft which have some manoeuvring capability (but not much) without forward way. The effect can be judged by comparing the steering effect when the drive is removed, (in neutral) or compare the size of your rudder with the massive dimensions of one fitted to a horse boat or butty.

 

When your boat is on dry land, and with the tiller hard left or right, when sighted from the rear all the propeller should be obscured.

 

Imagine if the balance blade was not fitted, not only would the steering action be very heavy but the rudder would only be directing half of the water stream, the other half would continue directly astern.

 

As I described on an earlier thread, my boat originally suffered from heavy steering and lack of steering force when manoeuvring. Adding 2 inches to the balance blade cured both problems at a stroke.

[stuart]

John, havent seen a horse boat, what do they look like?

Edited March 8, 2005 by stuart

[NB Willawaw]

Rudders (non narrowboat ones anyway) are a black art in themselves.

If you have interest, "google" Schilling rudders and Becker flap rudders.

The former have a fishtail rudder application used on dutch barges which use aerofoil sections.

 

I supply autopilot systems in my job and these have to work with a wide variety of different and quite sophisticated rudder designs. The forces that come into play when you apply 35 degrees of rudder on a VLCC going ahead, on emergency turns can be head-swimming.

 

Best Regards

 

Mark

 

NB Willawaw

Oxford

[John Orentas]

"John, havent seen a horse boat, what do they look like?"

 

Stuart.

 

Look for a horse with a rope trailing behind it. If the rope is tied to a boat that is probably a horse boat.

[David Schweizer]

John, havent seen a horse boat,  what do they look like?     

<{POST_SNAPBACK}>

A horse boat is identical in design to a Butty Boat which is an unpwered boat that accompanies a motor Boat. It is pointed at both ends and has a huge wooden Rudder with a curved (removeable) RTiller.

[John Orentas]

David.

 

"Identical", We could say a horse boat can double as a butty, but all butty's could not really work as a horse boat.

[bottle]

Thanks to you all

 

 

Even if some went a little

 

 

From all thats been written, A balanced tiller in the shape of an aerofoil would be best.

 

As John extended his forwards it made the steering lighter but if he had gone to far I think steering a straight line would have been more difficult.

Edited March 8, 2005 by bottle

[Amicus]

The part in the water is the Rudder (blade), it is usually "balanced", i.e. some of the rudder blade is forward of (in front of) the rudder stock (the vertical shaft) this increases the effectivness of the rudder on a slow vessel (boat) The "balancing" also reduces the effort needed to move the Rudder

The Tiller is the curved (swan-neck) shaft attached to the top of the stock, ending on it's upper part with a hand-hold which the helmsman (steerer, coxson, driver holds, thereby steering the vessel.

At canal speeds the Rudder blade does not need to be an airofoil, it usually consists of a lump of steel plate.

Edited March 8, 2005 by Amicus

[Paul Evans]

Here's an image of a fairly standard narrowboat rudder:

Anything more sophisticated than this would be unlikely to add to steering performance. John added a couple of inches to the short part of the plate on his boat and you might try the same but getting a builder to fabricate an aerofoil section is likely to cost you a lot of money for very little improvement.

 

In my experience, if your boat is built like a pig it will steer like one. Avoid square sterns and look for long and finely shaped swims to ease the flow of water over the propellor and rudder. Make sure that the tiller arm is as long as possible to give you extra leverage. Finally, take it easy and think ahead!

[Guest st170dw]

Thanks to you all

Even if some went a little

From all thats been written, A balanced tiller in the shape of an aerofoil would be best.

 

As John extended his forwards it made the steering lighter but if he had gone to far I think steering a straight line would have been more difficult.

<{POST_SNAPBACK}>

 

From my (limited) understanding of aerodynamics an over balanced rudder could also lock in the fully deflected position I suspect a boat rudder could do the same.

[howardang]

From my (limited) understanding of aerodynamics an over balanced rudder could also lock in the fully deflected position I suspect a boat rudder could do the same.

<{POST_SNAPBACK}>

 

You can overdo the balance of a narrow boat rudder. I have recently carried out handling trials on two new boats, one of which had more balance plate than the other . This boat steered perfectly well with very little force needed on the tiller, but if you let go of the tiller even for a split second - to take a cup of tea etc - the rudder flipped hard over and the boat headed for the bank. The other boat had a rudder whose balace plate was only a very small amount smaller in area and was mounted maybe an inch ot two further from the propeller. This boat was perfectly balanced and if you let go of the tiller it stayed exactly where you left it making for a boat which was much easier to handle in confined spaces.

 

I agree with the earlier comment that an aerofoil section is not needed in a canal situation where speeds are very slow.

 

Regards

 

Howard Anguish

[David Schweizer]

David.

 

"Identical", We could say a horse boat can double as a butty, but all butty's could not really work as a horse boat.

<{POST_SNAPBACK}>

I would be interested to hear your arguement defending that statement John.

[Alastair]

In my experience, if your boat is built like a pig it will steer like one. Avoid square

 

Try a completely unbalanced rudder, 4 ft long. The boat handles beautifully, is just very very heavy on the tiller at high speeds and fast turns.

 

I once managed to turn her 180 in a space about 2 ft longer than her hull (the rudder hangs off the stern and makes her 4ft longer). Although it was a very cold night I was drenched in sweat when I finally got her round.

 

Would have given a credit card for a bowthruster that night.

[bottle]

Looks like suck it and see, if you can not get a test.

 

It can be adjusted though.

Edited March 9, 2005 by bottle

[John Orentas]

Hi David.

 

How about the "Blue Top" boats, there were a great many motors and butty's built in the sixties, I once knew a chap who lived on 'AXE' they were built to be as light weight as possible and with very bluff lines to maximise their cargo potential. Although quite satisfactory when being towed by a motor boat, their very un-streamlined shape would make them very tough going for a horse.

 

They were also I think, the first all welded mild steel working boats on the system. There rudders, though very much larger than those on the motors, were not anything like the dimensions of those on a horse boat and were of course a steel blade.

Edited March 9, 2005 by John Orentas

[David Schweizer]

Hi David.

 

How about the "Blue Top" boats, there were a great many motors and butty's built in the sixties, I once knew a chap who lived on 'AXE' they were built to be as light weight as possible and with very bluff lines to maximise their cargo potential.  Although quite satisfactory when being towed by a motor boat, their very un-streamlined shape would make them very tough going for a horse.

 

They were also I think, the first all welded mild steel working boats on the system.  There rudders, though very much larger than those on the motors, were not anything like the dimensions of those on a horse boat and were of course a steel blade.

<{POST_SNAPBACK}>

Several historical points here so please forgive me for being a bit of an anorak. I believe that the first welded steel boats were the Admiral Class built between 1957 and 1960 comprising six Motors and six Butties, they all seem to vary slightly in style and did not have blue tops, instead they had hoops over the hold area over which tarpaulins were fixed. All the butties had conventional Timber Rudders. Between 1959 and 1961 twenty five River Class (Blue Tops) butties were built, using the same welded steel construction. They were originally built with small rudders to maximize cargo space and as a consequence did not handle well, they were quickly re-fitted with conventional timber rudders which improved their handling but made them difficult to manouver in locks because of the increased overall length. One other Steel Butty (Beryl) was also built in 1960 to partner the experimental Motor Anne.

 

So in all thirty two steel butties built in the late fiftys/early sixties which differed significantly in design from the thousands, based upon the traditional lines of the old horse drawn boats, that preceeded them. The principal difference was the very bluff bows and the absence of almost any swim, this certainly made them unattractive to look at and unpopular with the boatmen because of their poor handling qualities. However they were not disimilar in shape to the Birmingham Joeys which were designed to be horse drawn, and I can remember some still being drawn by horses ofr mules in the 1960's. The earlier Town and Star Class butties built in the late 1930's were of much bluffer appearance than the more gracefull lines of Joshers and Nursers however they function perfectly well as Horse Boats, indeed several commercial horse drawn Trip boats that ply the canals today are actually ex GUCC butties.

 

A interesting aside is that the Blue tops were apparently designed to enable a single man to cover the cargo hold on a pair of boats in ten minutes, unfortunately the experiments to acheive this were clearly carried out on a calm day, as they were a disaster on a windy day. I once witnessed two men struggle to get one section secured in five minutes on a blustery day as the wind caught in them and turned them into something akin to a kite.

[Alan Saunders]

The forces that come into play when you apply 35 degrees of rudder on a VLCC going ahead, on emergency turns can be head-swimming.

<{POST_SNAPBACK}>

It is interesting that you chose 35 degrees as this is considered to produce the greatest effect, except in some exceptional circumstances. 45 degrees maximum rudder, except when moored, makes sense to me but I have failed to find out what those exceptional circumstances are.

 

From my (limited) understanding of aerodynamics an over balanced rudder could also lock in the fully deflected position I suspect a boat rudder could do the same.

<{POST_SNAPBACK}>

I think 'lock' is a bit strong but I know of a narrowboat from a reputable builder that had the forward, balance, section reduced to prevent the rudder 'overbalancing' at 45 degrees or so.

--------------------------

 

I think if you set the rudder too close to the prop' it will vibrate from side to side in the turbulent vortex, a vice that I have noticed in some boats, very tiring!

 

I assume that a 'fishtail' refers to the steering operating a small 'tab' on the rear of the rudder which acts as a servo and deflects the rudder in the opposite direction.

 

At low speeds a flat plate effectively becomes an 'aerofoil' due to surface drag and Bernoulli effect. At higher speeds the flow around a flat plate would become turbulent and an *aerofoil would be preferable, especiallly if drag was a significant factor.

 

*Surely it should be a 'hydrofoil' but that word has already been assigned!

 

Alan

[bottle]

We have two discussions going on at the same time.

 

See: Boat building and maintenance. Schilling rudder

[bottle]

I assume that a 'fishtail' refers to the steering operating a small 'tab' on the rear of the rudder which acts as a servo and deflects the rudder in the opposite direction.

 

Alan

<{POST_SNAPBACK}>

 

Fish tail applys to the shape of the rudder, when veiwed in plan section and is very like a fish in shape, the way children tend to draw them.

 

Put "schilling rudder" in google.

 

The rudder is used mainly by barges, tugs and big ships for extra manouverability at SLOW speeds.

 

Pictures on the other discussion.

[John Orentas]

Quote. "It is interesting that you chose 35 degrees as this is considered to produce the greatest effect, except in some exceptional circumstances. 45 degrees maximum rudder, except when moored, makes sense to me but I have failed to find out what those exceptional circumstances are".

 

I don't think there is an ideal calculable angle. On a ship these angles are set during the commissioning trials, even then there isn't an optimum or maximum angle. On a supertanker I was on (I have only been on one) there was a maximum rudder angle set by the engineers beyond which the helmsman could not go.

 

Interestingly there was also a 'break-glass' emergency control whereby the helmsman, to avoid a collision could break the glass and apply more rudder even at the risk of damage to it or it's control mechanisms. "Exceptional circumstances".

Edited March 10, 2005 by John Orentas

[Liam]

finely shaped swims to ease the flow of water over the propellor and rudder. Make sure that the tiller arm is as long as possible to give you extra leverage.

<{POST_SNAPBACK}>

But short enough so when you put the tiller hard over, you don't knock someone off the towpath into the cut.

When entering locks, you sometimes have to put the tiller hard over, make sure it stays within the profile of the boat to avoid any damage being caused.