Sternwheeler Design and Propulsion

It's usually a v-belt-chain drive combination. The belts are the first reduction from the motor to a jack shaft. They stay dry and allow some slip and lessen damage if the wheel stops suddenly on a log or something. From the jackshaft to the wheel is another reduction and is chain because it's wet all the time and a v-belt would not work because of slippage. On a bigger wheel somewhere around 30 rpm is a working speed.

 

You're going to have to deal with the Coast Guard to haul people around as a business. The last I paid attention, below six people and a six-pack license, the boat itself was not much concern other than lifejackets, fire extinguishers, etc. Once above the six-pack level, all the whips and whistles and hoops come out. You need a different license, maybe some crew, and the construction of the boat is very important. The motor and other mechanical systems will need to conform to marine regulations, you might need approved plans and regular inspections have to be made while you build it. So before you get too involved with time and money, you should see what is required.

As far as making a boat, 12 hp is probably enough to motivate a boat that size around, and 12 hp puts it into the range of garden tractors, riding lawnmowers and things like that that are full of transmissions and drives and clutches and pulleys and all sorts of clever stuff.

This little paddlewheeler I made when I had a spare hull, a weeks wait between projects and full access to good beer has a 5hp engine and a 5 speed transmission with neutral and reverse from something. The wheel is 1" angle iron spokes, the "hoops" are indivual pieces of 1"strap iron and treated 1x6 wood deckboards. I marked it out on a piece of scrap plywood, clamped the pieces down and welded it up. Pulley and cable steering from another boat runs two rudders.

Weight becomes a nuisance hanging off the back like that, keep it in mind that 12 hp is not all that much so resist the temptation to over build. I would think the same setup I made might work for 12 hp. My "weak link" or shear pin was the bolt connecting the pulley to the wheel shaft. It was a 1/4 " bolt. After shearing off a few grade #5 bolts, a grade #8 worked forevermore.

 

Each wheel was driven by a separate Caterpillar 300hp diesel. Drive was through a reduction chain drive with small parallel chains and then to the big reduction chain to each wheel. Around locks and docks the wheels could be operated just like any dual engine boat to steer the boat about a central axis.

for Narwhal, Forward rudders would work on a pontoon boat but are ineffective on a barge hull. That was tried first on the sternwheeler I drove but was later fixed on centerline. The reason is obvious. The reverse wash runs into the flat stern of the hull and cannot steer the boat effectively.

 

Tom, the Kayot houseboats I've seen are pontoon-based, like this one: http://www.yachtworld.com/boats/1982/Kayot-Houseboat-1367522/Salt-Lake-City/UT/United-States . That's why I thought the link to the pontoon sternwheel conversion might be useful. You are certainly right that the typical flat-sterned monohull houseboats would be less likely candidates for flanking rudders.

 

600 hp is a bunch! What was the boat used for?

Sternwheelers normally have an upsweep at the stern to feed water smoothly to the wheel and to eliminate the problem you had, with the water just piling into the flat stern.

2 rudders or 4 rudders or gigantic ones like on this boat...2 independent wheels seems to be best.

 

This was a short excursion and dinner boat. Two decks and the upper deck was covered but open. I remember being passed on the Ten Tom by a power cruiser of about 35 to 40' and inquiring about relative fuel mileage. We were getting about one mpg at 10mph and he was using considerably more. The engines were pretty big and one of them needed oil on almost every watch. Ran part of the Tombigbee at night and thankful for radar, a good spotlight and a radio to talk to the barge tow captains.

Having the rudders exposed below the boat hull looks like an issue on riverboats.

 

I think most rudders didn't extend below the bottom of the boat...two of these have monkey rudders also....People say paddlewheels aren't efficient or powerful, but I have a suspicion they are both and the reason they disappeared was because they are so cumbersome and much more complicated. Also they are limited as to conditions, they don't work well in waves. And they're vulnerable to cannon fire.



[/IMG]


.

 

Paddlewheels were a practical solution for their time and place. It has been well proven that screw propellers are more efficient at generating thrust from a given amount of power than paddlewheels. They do suffer from other problems that you mention as well. Even the early propellers outperformed the paddlewheels at the end of their development period. There may be instances when these general statements are not true but, in the broad sense, props are best.

 

But for the nostagia minded, a splashing big red sternwheel is worth $$: http://www.generaljackson.com/site/

 

Feathering blades (floats) will increase efficiency, and also reduce the "slapping" noise.
--------------------------------------------------------------------------
The Mechanical Engineers Pocket-Book
Seventh Edition

by William Kent, A.M., M.E.

New York: John Wiley & Sons
London: Chapman and Hall

1909



The Paddle Wheel

Paddle-wheels with Radial Floats. (Seaton’s Marine Engineering.)-- The effective diameter of a radial wheel is usually taken from the centres of the opposite floats; but it is difficult to say what is absolutely that diameter, as much depends on the form of the float, the amount of dip, and the waves set in motion by the wheel. The slip of a radial wheel is from 15 to 30 per cent, depending on the size of the float.

Area of one float =
* C.

D is the effective diameter in feet, and C is a multiplier, varying from 0.25 in tugs to 0.175 in fast-running light steamers.
The breadth of the float is usually about 1/4 its length, and its thickness about 1/8 its breadth. The number of floats varies directly with the diameter, and there should be one float for every foot of diameter.
(For a discussion of the action of the radial wheel, see Thurston, Manual of the
Steam-engine, part ii, p. 182.)
Feathering Paddle-wheels. (Seaton.) – The diameter of a feathering-wheel is found as follows: The amount of slip varies from 12 to 20 per cent, although when the floats are small or the resistance great it is as high as 25 per cent; a well-designed wheel on well-formed ship should not exceed 15 per cent under ordinary circumstances.
If K is the speed of the ship in knots, S the percentage of slip, and R the revolutions per minute,
Diameter of the wheel at centres =


The diameter, however, must be such as will suit the structure of the ship, so that a modification may be necessary on this account, and the revolutions altered to suit it.
The diameter will also depend on the amount of “dip” or immersion of the float.
When a ship is working always in smooth water the immersion of the top edge should not exceed 1/8 the breadth of the float; and for general service at sea an immersion of ½ the breadth of the float is sufficient. If the ship is intended to carry cargo, the immersion need not be more than 2 or 3 inches, and should not be more than the breadth of the float when at the deepest draught; indeed, the efficiency of the wheel falls off rapidly with the immersion of the wheel.

Area of one float =
* C.

C is a multiplier, varying from 0.3 to 0.35; D is the diameter of the wheel float centres, in feet.
The number of floats = ½ (D+2)
The breadth of the float = 0.35 * the length
The thickness of the float = ½ the breadth
Diameter of the gudgeons =thickness of the float
Seaton and Rounthwaite’s Pocket-book gives:

Number of floats =
,

where R is the number of revolutions per minute.

Area of one float (in square feet) =
,

where N = number of floats in one wheel.
For steamers plying always in smooth waters K = 1200. For sea-going steamers K = 1400. For tugs and such craft as require to stop start frequenlty in a tide-way K = 1600.
It will be quite accurate enough if the last four figures of the cube (D*R)
be taken as ciphers.
For illustrated description of the feathering paddle-wheel see Seaton’s Marine Engineering, or Seaton and Rounthwaite’s Pocket-book The diameter of a feathering-wheel is about one half that of a radial wheel for equal efficiency. (Thurston.)
Efficiency of Paddle-wheels. –Computations by Prof. Thurston of the efficiency of propulsion by paddle-wheels give for light river steamers with ratio of velocity of the vessel, v, to the velocity of the paddle-float centre of pressure, V, or
, =
, with a dip = 3/20 radius of the wheel, and a slip of 25 per cent, and efficiency of .714; and for ocean steamers with the same slip and a ratio of
, and a dip = 1/8 radius, an efficiency of .685.


Pages 1013, 1014

 

Thanks, Tad. That's the best technicals I've seen on paddlewheels. I wonder how the slip of a regular paddlewheel, at 15-30%, compares to propellers.

 

Check out Karl Stambaugh design, He may be able to help with the propulsion details,

http://www.cmdboats.com/smlboat.htm?cart_id=d73683718b8b4474a02d673dbb667888