Reversing

[alan_fincher]

The usual recommendation is 1.5 x the shaft diameter.

So with a typical 1.5" shaft, only about 2.25" then.

 

That would seem to go against adding 3" to what was already there, unless the shaft was already in excess of 2", which sounds unlikely.

 

Here's what ours was like, and not appreciated by our surveyor. (I don't seem to have an "after" picture.)

 

[down the north]

So was the butty still strapped to the back or did you bring it round and tie the rudder to Anne's T-stud?

SteveE

Hmmmm its half retirement away, but I think we took both forward, then a short 20 ft line between boats with a tiller strings on, on the butty Phoebe, ( or was Mrs J on it in charge) and the boss on the butty foredeck with the shaft ,,,, either way Anne was on tick over, but still pulled back at about 1 mph!

Must try to work out how to post a piccy in a reply, although some kind gent has given the detail, I jus aint got there yet !! oh well,

martin

[mykaskin]

Alan,

 

Our prop was right next to the swim, you couldn't even get your fingers in between the blade and the end of the swim.

 

Your original setup seems a little close to the rudder, and I think I would have taken 1, maybe at most 2 inches off the length. However the main thing is how it performs. I don't think even at that length there would be any problems with bending the shaft (unless you did something really silly!).

 

Cheers,

 

Mike

Edited September 21, 2008 by mykaskin

[alan_fincher]

My enduring thought when I see it out of water, or look at th pics, is what a puny little egg whisk that prop actually looks!

 

However it seems to deliver the goods, and be pretty well matched to the engine.

 

As it was in the pictures you got an unpleasant pulsing through the tiller when underway. Moving the prop away from the rudder has improved, though not totally alleviated that.

 

Alan

[churchward]

So with a typical 1.5" shaft, only about 2.25" then.

 

That would seem to go against adding 3" to what was already there, unless the shaft was already in excess of 2", which sounds unlikely.

 

Here's what ours was like, and not appreciated by our surveyor. (I don't seem to have an "after" picture.)

 

I don't know from a prop hydro-dynamics point of view but from an engineering perspective I believe it best to have as short a length of shaft unsupported as possible. The pressure (thus potential wear) on the shaft bearing and an increased chance of vibration will increase significantly the longer the shaft sticks out from the bearing and making the sunsupported mass ( i.e. the prop) less controllable.

Edited September 22, 2008 by churchward

[Timleech]

I don't know from a prop hydro-dynamics point of view but from an engineering perspective I believe it best to have as short a length of shaft unsupported as possible. The pressure (thus potential wear) on the shaft bearing and an increased chance of vibration will increase significantly the longer the shaft sticks out from the bearing and making the sunsupported mass ( i.e. the prop) less controllable.

 

It's common on larger vessels to have little or no unsupported length, such as here (I'm working on this vessel at the moment, though inside {gearbox} rather than outside):-

 

 

Inside the ring behind the stern post is a 'Newark gland'

 

http://www.ocean-venture-seals.com/prod02.htm

 

which keeps the lubricant within the stern tube. Apart from that, there is nothing between prop and stern post.

 

Tim

Edited September 22, 2008 by Timleech

[mykaskin]

It's common on larger vessels to have little or no unsupported length, such as here (I'm working on this vessel at the moment, though inside {gearbox} rather than outside):-

 

 

Inside the ring behind the stern post is a 'Newark gland'

 

http://www.ocean-venture-seals.com/prod02.htm

 

which keeps the lubricant within the stern tube. Apart from that, there is nothing between prop and stern post.

 

Tim

 

It does have a (hmm, stern post is that was it is called?) so the water can freely get to the prop.

 

It looks a little like a TID tug from this angle, or perhaps at least a Dunston's tug? What boat is it?

 

Cheers,

 

Mike

[Timleech]

It does have a (hmm, stern post is that was it is called?) so the water can freely get to the prop.

 

It looks a little like a TID tug from this angle, or perhaps at least a Dunston's tug? What boat is it?

 

Cheers,

 

Mike

 

 

Well you can call it a skeg if you like, but to me the vertical-ish bit the prop shaft emerges from will (almost) always be the stern post. A similar arrangement of very little (maybe a sand seal or Newark or other gland) between prop and stern post is common even where the stern is more comparable to what we see on the canals.

 

Yes it's a TID, and it was built or at least 'assembled' by Dunstons. I've no idea what the TID number was, but it's been known as the Seaport Alpha for a good few years.

 

Tim

[mykaskin]

Well you can call it a skeg if you like, but to me the vertical-ish bit the prop shaft emerges from will (almost) always be the stern post. A similar arrangement of very little (maybe a sand seal or Newark or other gland) between prop and stern post is common even where the stern is more comparable to what we see on the canals.

 

Yes it's a TID, and it was built or at least 'assembled' by Dunstons. I've no idea what the TID number was, but it's been known as the Seaport Alpha for a good few years.

 

Tim

 

Cool - I found some more info:

 

http://irishseashipping.co.uk/photofeature...alpha200608.htm

 

Built as TID 43 by Richard Dunston in 1943 and weighing in at 54grt SEAPORT ALPHA is seen on the Mersey on June 20, 2008. Between 1949 and 1986 she carried the name TIDEALL.

She has recently joined the Viaduct Shipping fleet for barge towing work on Merseyside having been based in Fleetwood, Lancashire for several years.

 

My ancestors were the Dunstons so have a bit of an interest in them.

 

Cheers,

 

Mike

 

ps. I'd probably call it a skeg...

[Timleech]

Cool - I found some more info:

 

http://irishseashipping.co.uk/photofeature...alpha200608.htm

 

Built as TID 43 by Richard Dunston in 1943 and weighing in at 54grt SEAPORT ALPHA is seen on the Mersey on June 20, 2008. Between 1949 and 1986 she carried the name TIDEALL.

She has recently joined the Viaduct Shipping fleet for barge towing work on Merseyside having been based in Fleetwood, Lancashire for several years.

 

My ancestors were the Dunstons so have a bit of an interest in them.

 

Cheers,

 

Mike

 

I'm not party to the precise legalities of who owns what, but AFAIK that piece isn't strictly accurate & the current owners are Mersey Tanker Lighterage.

 

I part-owned the Dunstons-built Humber Keel 'Beecliffe' for quite a number of years, travelled thousands of miles on continental waterways with her.

Also worked for four years as engineer on the Dunstons-built VIC 32.

 

Tim

[good7saint]

Rather proud of my first attempt at reversing, when I took Warwick back to Sowerby Bridge last week.

Reversed straight into the place I wanted to get the boat at the first attempt without any problems, even got a comment of good job from one of the people working for Shire Cruisers

[Athy]

Is there any way (except the obvious but undesirable one of putting one's hand down to have a feel ) of knowing which way the propellor is spinning when the boat is in reverse, and therefore which way it is likely to send the boat? I have heard that not all engins are standard, that some drive the prop clockwise and some drive it anti - clockwise.

[alan_fincher]

You don't need to feel the prop.

 

It's very obvious if you observe the propshaft, or, even better, the couplings on the prop shaft.

 

Watch as you are just putting it into, or out of, gear, and you can't mistake which way it's turning.

[Athy]

Ah yes, but as our shaft is under the floor I was hoping to find out without unscrewing a portion of engine room floor to have a look. So there is no "standard" direction?

I'll get me screwdriver...

[Mac of Cygnet]

You don't need to feel the prop.

 

It's very obvious if you observe the propshaft, or, even better, the couplings on the prop shaft.

 

Watch as you are just putting it into, or out of, gear, and you can't mistake which way it's turning.

 

Sorry if this obvious to everyone, but can I just ask, which way RH and LH props rotate? That is, which way does a prop described as RH rotate when viewed from the engine end - clockwise or anticlockwise? Just so I know when getting a replacement.

 

Mac

[alan_fincher]

Ah yes, but as our shaft is under the floor I was hoping to find out without unscrewing a portion of engine room floor to have a look. So there is no "standard" direction?

I'll get me screwdriver...

Is even the coupling on the rear of your gearbox covered over ?

 

You unfortunately can't tell from engine rotation, (e.g. flywheel or crankshaft pulley), as depending on gearbox type some will make the rotation of the propshaft the opposite of the engine, whereas others will have engine and propshaft turning the same way.

 

Sorry if this obvious to everyone, but can I just ask, which way RH and LH props rotate? That is, which way does a prop described as RH rotate when viewed from the engine end - clockwise or anticlockwise? Just so I know when getting a replacement.

 

Mac

Hi Mac,

 

If you are viewing the prop from behind the boat, then a right handed one turns clockwise for forward drive, whereas a left handed one turns anti-clockwise to move forwards.

 

I believe, but may be wrong, that RH is by far the more common on modern engines, but seem to recall that thinks like the Lister SL/SR/ST series were generally LH.

 

I'm sure someone will correct me if that's wrong.

 

Alan

Edited October 18, 2008 by alan_fincher

[John Orentas]

One way to remember all this; Think of using a starting handle on a car, it engages directly with the 'front' of the cranksaft, i.e. the opposite end to the gearbox, the handle would always be rotated clockwise or right handed looking at the top of the handle..

 

Without a gearbox in the way this rotation would be transmitted straight through to the propeller so it would turn clockwise when observed from the front of the engine.. Now the slightly complicated bit 1 a props rotation is described when looking from the rear (that makes it inti-clock) , 2 gearboxes nearly always reverse the direction, that makes it clockwise as are the vast majority of propellers).

 

Seemed a very simple explanation before I wrote it down.

[Timleech]

Hi Mac,

 

If you are viewing the prop from behind the boat, then a right handed one turns clockwise for forward drive, whereas a left handed one turns anti-clockwise to move forwards.

 

I believe, but may be wrong, that RH is by far the more common on modern engines, but seem to recall that thinks like the Lister SL/SR/ST series were generally LH.

 

I'm sure someone will correct me if that's wrong.

 

Alan

 

That's right, also the Lister 'H' series, along with quite a number of 'real' marine engines from the past (as opposed to marinised base engines) including the National/RN.

 

Some hydraulic gearboxes, including some PRM boxes, allow continuous operation in either direction so a LH prop is theoretically an option even with a modern engine/gearbox combination but you just don't see it in normal canal boat installations

 

Tim

[Mac of Cygnet]

Some hydraulic gearboxes, including some PRM boxes, allow continuous operation in either direction so a LH prop is theoretically an option even with a modern engine/gearbox combination but you just don't see it in normal canal boat installations

 

Tim

 

Are you saying that most gearboxes do not allow continuous operation in reverse? What happens if you reverse for too long, and how long is too long?

 

Mac

[alan_fincher]

Are you saying that most gearboxes do not allow continuous operation in reverse? What happens if you reverse for too long, and how long is too long?

 

Mac

Mac,

 

There is a world of difference between a hefty spell of reversing down several hundred yards of canal, and driving the gearbox in it's designed "reverse" setting for continuous 8 hour days, day in, day out.

 

If you have a gearbox of the type where all the internals are locked to give a straight through drive when going forwards, but where all the gearing comes in to play when it's reversed, then you are unlikely to knacker it with any reasonable amount of reversing, but if you installed it with a wrong handed propeller, it would not last long, I suspect.

 

When I had a box of this type fail catastrophically many years ago, forward drive was still possible, but not a chance of any reverse to actually stop.

 

Alan

[tidal]

Is there any way (except the obvious but undesirable one of putting one's hand down to have a feel ) of knowing which way the propellor is spinning when the boat is in reverse, and therefore which way it is likely to send the boat? I have heard that not all engins are standard, that some drive the prop clockwise and some drive it anti - clockwise.

 

There are actually two ways..............one is to put it into reverse and find out which way it kicks your stern (I know)

 

The other is also deeply technical. Tie up somewhere where the you can see over both sides of the stern of the boat

Put engine into reverse with tiller LOCKED dead centre

look over each side of the stern in turn. You will normally see a bigger "boil" or disturbed flow of water on one side or the other.

On whichever side it is smaller is the direction it will be the direction it will move towards.

 

It has always worked for me........so far

[Liam]

Or, you could get even more technical, and go to the length of lifting up either your stern deck board, or your engine covering, and physically see which way the shaft is spinning in both gears

[Athy]

Good thinking, Tidal. In fact, when we started the boat up yesterday, I noticed that there was a tiny gap in the engine room floor through which I was just able to see about a half-inch of prop shaft. It's a right-hander, which rather surprised me as the engine is very old.

Now, this reversing thing ( I am relieved to read that I'm not the only one who finds it a bit of a mystery). Given that my propellor will be turning anti-clockwise, or to the left, when I am in reverse, will anything I do with the tiller influence where the boat goes, and if so, what? Up till now I have rather relied on lining the boat up in forward gear and hoping that, in reverse, she'll go in exactly the opposite direction. It, er, often works.

[bottle]

Athy

 

Whatever works for you and the boat is the way to do it.

 

They are all different, the rudder, I have found, makes little difference in reverse.

 

Some say point the rudder the way you want the boat to go but it has little effect, there are others that say 'flapping' the rudder, a bit like using as an oar works.

 

Some say go fast, others slow.

 

Another method when in reverse if the boat goes off line a little forward straightens it up then reverse again.

 

Practice will make perfect, until there are a lot of 'gongoozlers' about.

 

Oh!!!!! the joys of boating.

[Athy]

Thanks Keith, the little-blast-of-forward is about the only technique which i have come close to mastering!