Hull design-side paddlewheeler-need help

[russ@riverland.]

I have almost finished the design of a small timber side paddle wheeler, 43ft x 11'6" x 11", flat bottom,raked frwd to stem and aft to rudder post. The bow is the usual pointed shape and the stern rounded.The paddles will be each 2ft wide. The vessel is to be used solely on river and her approx finished weight will be 13 tonne including fluids, people, etc. My concern is the shape of the hull aft the paddles, of which are to be fitted 5/8's the length of the hull from the stem. Do I taper the stern aft the paddles to the rudder post and do away with the round backside, thus allowing more water to reach the rudder ? or, could I leave the round rear at the gunwale and taper the hull from the paddles down to meet the skeg, virtually forming a flared affect. or am I concerned about nothing? It seems that the rudder at present will have very little use unless it is submerged lower than the bottom. Hope someone can put me straight.

[tom28571]

I have driven a paddlewheeler but with twin independent wheels. It had rudders both in front of and behind the wheels. The rudders in front (not lower than the draft) were completely useless. The aft rudders worked but only when the wheels were turning. Low speed and docking steering was best left to the wheels although, as said above, aft rudders gave response when the wheel in front of it was turning forward. I would expect similar results with your boat.

If your wheels are located midships, I don't think aft rudders will be very effective unless they are deeper than the hull. That is my experience but it is only with one boat which was about 100' long, 35' wide and a 3' draft increasing toward the stern.

[SamSam]

These seem to show the stern below the waterline tapered to the rudders. The pictures came from
http://modelplans.steamboats.org/index.html

[russ@riverland.]

Forum Team, Thanks guys, please understand that this is my first attempt at design, so I am keeping relatively simple. I am a Marine Engineer,built 4 boats from stock plans, but want my own design to enjoy in retirement. The most important criteria is shoal draft due to increasing water problems on the River Murray. I have all the timber, Toyota drive train and all aux equip to do the job. Your help in the correct hull shape will be invaluable. Cheers for now, Russ.

[alan white]

Originally Posted by russ@riverland.

I have almost finished the design of a small timber side paddle wheeler, 43ft x 11'6" x 11", flat bottom,raked frwd to stem and aft to rudder post. The bow is the usual pointed shape and the stern rounded.The paddles will be each 2ft wide. The vessel is to be used solely on river and her approx finished weight will be 13 tonne including fluids, people, etc. My concern is the shape of the hull aft the paddles, of which are to be fitted 5/8's the length of the hull from the stem. Do I taper the stern aft the paddles to the rudder post and do away with the round backside, thus allowing more water to reach the rudder ? or, could I leave the round rear at the gunwale and taper the hull from the paddles down to meet the skeg, virtually forming a flared affect. or am I concerned about nothing? It seems that the rudder at present will have very little use unless it is submerged lower than the bottom. Hope someone can put me straight.

With the paddles at 5/8 back, the deadrise you mention as taper to the skeg will require you to carry more depth than a flatter bottom. Twin paddlewheels introduce a fantastic potential for manuevering, obviously, and it would seem you could carry a mere vestigal rudder at the rear.
By the way, I would like to ask what is the efficiency of paddlewheels relative to props. Also, the gearing is very tall. How do you plan to reduce RPM, and did you consider steam as a power plant, and if so, how did it compare with gas/diesel?
Terrific project, I should add.

Alan

[artemis]

From what I've seen in steamboats (and I've seen a lot), sidewheelers used a fairly traditional hull design (many were nothing more that "knock offs" of traditional sailing vessels). There is a lot of sidewheel design info on the internet (google "sidewheel boat"). And a lot of info via libraries or online libraries (like unviersity of rochester stuff).

Independent wheels for maneuvering were used extensively on tugboats - usually two engines each of which could independently move a wheel or be coupled together for longer hauls.

As to efficiency - extensive tests have been made starting in the 1850s. Sidewheels come in at only a little better than 50% with feathering paddles, very poor in comparison to propellers.

[alan white]

Thanks Artemis.

Alan

[Pericles]

Russ,

There is a large amount of information on Wikipedia. You could try getting data from the links.


http://en.wikipedia.org/wiki/Steamboat

http://myweb.tiscali.co.uk/tramways/...teamernews.htm

This for fun.

http://www.swallowboats.co.uk/content/view/94/104/

Home grown.

http://www.murrayriver.com.au/boatin...rs/default.htm

Regards,

Pericles

[Guest625101138]

There are some calculations here on efficiency.
http://home.clara.net/gmatkin/pwheel.rtf
You will see 71.4% given for a river steamer. This is probably better than an outboard prop doing the same job.

I have seen figures for slip less than 10% but obviously these need big blades relative to the boat size.

Efficiency was not a big factor in props overtaking paddlewheels. Props are little affected by sea conditions; not so for paddlewheels.

Modern engines also rev higher than the old steam engines so gearboxes get heavier to drive paddlewheels compared with spinning a prop.

Paddle wheels have not undergone the same level of development as props so there is a lot of catching up that provides opportunity for development.

Rick W.

[alan white]

An unexplored science. And no doubt the paddle is best in low speed craft that rarely deal with rough seas-------- river boats and the like. A river boat nowadays could anchor in the stream and generate power for batteries while you sleep. What with all the people looking for independance from real estate and high rent, look for this type of boat catching on. An electric power plant might be the ideal prime mover for low speed paddle wheels and river travel.

[SamSam]

This guy was trying for speed. As for effeciency of paddlewheels, like Rick says,I think they are very effecient with around 20% slip, but they are real inconvenient for a number of good reasons.

[russ@riverland.]

Thanks gents for the interest. Efficiency, although a consideration is down the list in favour of tradition. Steam power is out, I am a steam enthusiast, but govt regulations, OH & S, etc make it far too hard. I am employing two options. I have in the shed a Toyota 3ltr diesel, gearbox and locked up diff. Controls of Gear change, only one fwd and reverse gear,and the clutch will be by electric solenoids.Drive shafts from the diff already at reduced revs will have the facility to reduce further if required by sprockets and chain drive to the paddles. the only draw back being that the paddles cannot be operated independently. The other choice is diesel electric, 3 phase power thru variable speed controllers. Each wheel can drive seperately giving more control, but it will mean the purchase of a diesel alt. Although I have managed diesel electric ships, putting it all together looks rather expensive at this juncture. Having served as Engineer on a 1500 ton sternwheeler, driven by hydraulics, that is also an option. As for paddle speed, the sternwheeler ran at 6 knots at 21rpm. This I believe is an important issue due to the hole made as each paddle exits the water. If the speed of the wheel verses the number of paddles is not correct,each paddle will virtually work in space and the vessel will go nowhere. Any one with any formulae on this issue,will join the commissioning crew. Cheers Russ.

[Guest625101138]

Russ
My view is that you will be limited on the Murray if you are solely reliant on a rudder for steering. If you have experience that indicates otherwise I am interested.

I have reasonably intimite knowledge of the stretch of the river that the Murray Marathon covers and find it challenging to navigate in a small boat at 6kts. I have measured current of 4kph over some sand bars. You get some interesting reverse eddies as well.

The diesel electric would be a complex beast but very nice for steering if done well. Hydraulic would seem OK for mechanically minded but can be very messy.

You could do independent steering through a diff if you had brakes. Not the best solution though. However no different in principle to traction control on a modern 4WD.

The wheels and hulls would also need to be able to take a hit from a decent log.

Do you know how others operate sidewheels independently?

Rick W.

[alan white]

A differential is cheap to find. I would consider, if I were you, using a pair of generators to have different paddle speeds. The generators could draw power from the slower side by differential action. All you'd need would be a drive from each axle-end. Since very little power is required for steerage speeds, relatively small (10 kw) generators could be used. They would, of course, contribute to a battery bank. with 10 kw to each paddle from the engine, a draw of 5 kw from one side would reduce the speed by half that of the opposite side (which would speed up). Easy, cheap, and efficient.

[russ@riverland.]

This feedback is great. I failed to mention the steering on the sternwheeler. The designers, no names no courtmarshalls, had a few goes at getting it right, ending up with three rudders aft the paddlewheel,mongrels to set up when they went out of sinc,plus thrusters for and aft. This particular vessel, had many problems as well with the paddlewheel set up in diameter,depth in the water and speed. Of the few small sidewheelers that I have heard of, it appears the most common set up is a tractor diff with the facility to brake each wheel independently. Maybe I ditch the toyota diff and fit one in place, plus a small thruster up fwd. The diesel electric is quite appealing but such a shame to do away with what I have acquired so far. Cheers Russ.