rule of thumb.... paddle wheel width 1/3 of hull beam...?

[anth]

To All,
           Having a conversation with roderick about paddle wheel width,I had heard of a rule of 1/3 the hull beam equals the width of a paddle wheel,
Roderick suggested it could be the combination of both paddle wheels.

As there must be some ratio that applies to both models and full size side wheel paddler's I am asking anyone to respond with an exact figure or rule of thumb that they know of..


cheers Anthony

[Brian]

Among my textbooks on Naval Architecture (which I began studying during my Shipwright Apprenticeship) I do not find many references to Paddle Ships or their Paddles. However I have found a couple of brief references and one of these references is provided below.
- - - - -
THE FOLLOWING NOTES ARE EXTRACTED FROM -
The Naval Architecture and Shipbuilder's Pocket Book* of Formulae, Rules and Tables .... , by Clement Mackrow & Lloyd Woollard, published by The Technical Press Ltd, London [UK], my copy is the Fourteenth Edition, Revised (2nd Impression) dated 1946 (but there are later editions).
* This is a 2-inch thick Pocket Book  :?

Page 192 PADDLES
Area of Floats (D.W. Taylor)

A = combined area of two floats (one on each side) in square feet.
D = mean diameter to centres of floats in feet.
I = indicated horse-power
R = revolutions in "hundreds per minute".
V = speed of ship in knots
S = slip ratio = (Vp - V) / Vp (where Vp is the peripheral speed in knots of centres of floats)  = ( (PI x R x D) - V) / (PI x R x D)

A = (212.5 - (375 x S) ) / (I / V^3)

S should not generally exceed 0.15 for feathering floats and 0.20 for fixed floats; a large slip leads to a low efficiency of the propulsion.

Number, size and position of paddles.

When fixed to the wheel, the floats are spaced about 3 feet apart, or in fast ships slightly less. The spacing of feathering paddles should be 4 to 6 feet apart. Excessive spacing is liable to cause vibration.

The width of the float is about half the beam of the vessel for smooth water, or one-third in seagoing steamers. The depth is determined from the area. Thickness of wood floats = 1/12 width;
of steel floats in inches = 0.15 + (0.16 x width in feet).

Paddles should be placed longitudinally so that they run on or near the crest of the wave, which can be determined approximately from experience in similar ships. They must also be near amidships so as not to be affected by changes of trim, except in stern-wheelers.

The upper edge of the lowest float should be immersed at mean draught about 12 to 20 inches in large sea-going vessels, and about 12 to 15 inches in smaller vessels; about 3 to 6 inches is sufficient in river steamers.

This article goes onto geometrical details of "Construction for mechanism actuating feathering paddles"

- - - - -
These notes, published in 1946 appear to be pertinent to Full-size Paddle Vessels, but are provided for information & guidance of PD members, which I hope may be useful to some. However I cannot personally guarantee the relevance to model ships.

[Roderick Smith]

Fascinating material Brian, and the first time that I have seen these guidelines.
However, I have yet to see any photos showing seagoing boats with floats which are 50% of the beam width, or even river ones at one third.  I will take a tape measure on my next Murray visit, and get to work.

The slip ratio is something which  can be calculated after construction, from water trials.  I don't see how it can be used to help design suitable floats.  Ideally Vs would equal V, but the gap will not be known until after everything is done.  I did report in a different thread that, after a few days of steaming, the floats on the replica Lady Augusta were cut back to provide better performance.

Regards,
Roderick B Smith
Rail News Victoria Editor

[Brian]

From another textbook I submit some more technical information on Paddle propulsion
- - - - -
The following notes are extracted from - "A Complete Class-book of Naval Architecture (Practical, Laying Off, Theoretical)" by W J Lovett, published by Longmans, Green & Co, London in 1905. [this was not the text book used during my education on Naval Architecture]

page 158 - PROPELLORS

The three propellors in use now are -
1. The jet propellor;
2. The paddle-wheel propellor;
3. The screw propellor.
:
:
:
Paddles. - The chief divisions of the paddle are side and stern.

They cannot be applied so readily to cargo boats or ocean liners, because where draughts vary the floats might be deep in water or hardly touching. Efficiencey of paddle is greatest at a certain constant immersion. Also, again rolling affests them, as one paddle may be out of the water and another deep in. Coal burning or going-out light alters draught. Rolling strains engines, as one paddle offers great resistance while the other is racing. They require also great breadth, but they are found very useful in excursion steamers, as they are very fast, easily started and manoeuvred.

Paddles and jets give direct sternward momentum. Speed of floats depends on diameter of wheel. If slip is known to be, say, 25 percent., and speed required, say 20 knots, then diameter of wheel would be arranged with a number of revolutions to give that speed in feet per second of a blade going through the water, allowing for the 25 percent. slip. The position of the paddles is most important. They ought to catch the top of the wave, as particles of wave then have most sternward motion, so they are put a little aft of amidship, or [the ship's] lines are designed for wave line to suit paddle wheels. Paddle are put astern where there is litle water, in order to get the big wave at the stern. Bottom of floats about one-third draught. As one paddle [float] is entering the water another should be leaving, and middle should be vertical. The churning of water in old paddle wheels is greatly done away with by feathering the floats. Upper edge of float light should should be 1 or 2 inches below water when vertical.

Number of floats = number of feet in diameter of wheel. Breadth of float about 1 inch per foot of diameter. In feathering floats only half the number are used, but they are twice as large. Breadth of paddles about half-breadth of boat.
- - - - -
As with my earlier contribution of a technical nature, they are both provide to give an insight to the thoughts about Paddle Propulsion (of full-size ships) by the writers/editors of text books on Naval Architecture.
- - - - - -
Furthermore - I not yet ascertained whether there have been any relevant Technical Papers about Paddle Vessels etc., published by The Royal Institution of Naval Architectures (RINA), which was originally established in 1860. In view that this professional institution has a long historical heritage from Queen Victoria's reign, and there was a professional interest in Paddle propulsion (e.g. I K Brunel's "Great Western" & "Great Eastern"), although the Royal Navy ceased with paddle propulsion after the British Admiralty's trials in 1845 between HMS Rattler (screw-propelled) and HMS Alecto (paddle propelled). However Paddle vessels were still used in the Merchant Maritime service until the 1960's. Nevertheless the RN did use paddle ships (from the Merchant Navy) during WW1 & WW2  because of their shallow draught.
.

[mjt60a]

....I have yet to see any photos showing seagoing boats with floats which are 50% of the beam width....

I realise that the width of floats will be somewhat less than the width of the paddlebox, but....
One of the 'information notices' (for want of a better term) onboard Tattershall Castle gives the Hull width as 33 feet but width over the paddleboxes as  sixty-seven feet! - so it can't be too far off....

[Roderick Smith]

Thanks for the latest additions to this thread.  It is nice to have a technical understanding to add to the admiration of the lines and the history.
My suspicion had been that the rule of thumb was for port & starboard floats combined, and Mick's post reinforces this view.
I have just looked at my frontal shot of PS Uri (in the Swiss thread in Preserved): I could believe that each float is 1/6 of the hull width, hence the two paddles add to 1/3 of the hull width, which is the guideline mentioned in this thread for calm-water vessels.

Regards,
Roderick B Smith
Rail News Victoria Editor

[anth]

Thankyou All,
                     So I guess it's not an old wives tale,1/3 of beam will equal the combined width of both paddles for calm water.
this would also depend upon the work required....eg tugs wider than passenger..?
 

cheers anthony

[mjt60a]

Here are some specs from the book 'Famous Paddle Steamers' by F.C.Hambleton, from the chapter L.B.S.C.R Cross-Channel Steamers...
Paris and Rouen...
Length 250 ft
Beam 29 ft
Width over sponsons 55 ft
Paddle floats, nine, 10 ft by 3 ft 8 ins...........etc
so...beam 29 ft,  floats 10 ft wide....approx 1/3 of the hulls beam....each side!
When I mentioned the Tattershall Castle being 67 ft across paddleboxes, I was suggesting that, as the hull is 33ft at its widest point, the paddleboxes must each be 17 ft wide - more than half the beam so each paddle could, allowing some clearance, be up to half the width of the hull! (I should get out the plan and see how it looks...or if it has details written  )

[AlistairD]

Well, Tattershall Castle needed to be  beamy, and had extra large sponsons because she was a car ferry. Her shape  wasn't a typical paddle steamer shape
 Â 
 Alistair
 

 
Here are some specs from the book 'Famous Paddle    Steamers' by F.C.Hambleton, from the chapter L.B.S.C.R Cross-Channel    Steamers...
Paris and Rouen...
Length 250 ft
Beam 29 ft
Width over    sponsons 55 ft
Paddle floats, nine, 10 ft by 3 ft 8    ins...........etc
so...beam 29 ft, floats 10 ft wide....approx 1/3 of the    hulls beam....each side!
When I    mentioned the Tattershall Castle being 67 ft across paddleboxes, I was    suggesting that, as the hull is 33ft at its widest point, the paddleboxes must    each be 17 ft wide - more than half the beam so each paddle could, allowing    some clearance, be up to half the width of the hull! (I should get out the    plan and see how it looks...or if it has details written )


     
Posted by Mick.
(.....gonna need a bigger boat.....)


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[anth]

ok  before making a verdict I think we need a few more post's
or some consistent spec's  to prove or disprove the theory
 so we still have two rule of thoughts.
combined and non-combined

I have been looking at the plans we have here for the p.s royal falcon
she has very narrow paddle wheels which suggest's the combination of the two wheels equal a 1/3 of beam.

what have I done I am so confused the falcon is sea going with narrow side wheels,it must come down to application
passenger
tug
freight
who knows....!

anthony

[mjt60a]

Well, Tattershall Castle needed to be  beamy, and had extra large sponsons because she was a car ferry. Her shape  wasn't a typical paddle steamer shape....

A valid point, those humber ferries do seem to have unusually wide decks...
let me have a look at some of these plans..
Caledonia - no paddle wheel details but, measuring straight from the (1:96) plan, hull beam is 95mm, width across sponsons is 190mm.
So combined width of both paddleboxes is also 95mm, so each one is half the width of the hull, 47.5 each. If the wheels 'fill' the available space, with some room for the feathering mechanisms and clearance between the wheel and hull, they could easily be one third the beam, yes?

Bilsdale (1:48 ) - beam 135mm, max width 238mm, floats 42mm.
Paddlewheels are shown 'in place' on the diagram but may not be accurate. Whatever, they're slightly less than 1/3 but certainly bigger than 'both wheels together being 1/3 the beam'

Albion (1:48 ) - beam 157mm, max width 320mm, no paddle details but space inside paddlebox is 75mm...
As with Caledonia, each paddlebox is almost half the beam so floats being 1/3 doesn't seem unreasonable, and both wheels together being 1/3 the beam would leave a lot of space inside there.....

Waverley (1:96) - beam 95mm, max width 178mm, again no wheel details but space in paddlebox is 40mm....
Someone here must know/have access to the actual measurements of the Waverley, but even looking at this small plan 30mm floats (just under 1/3 the beam) would look about right....