Hull design-side paddlewheeler-need help

[Guest625101138]

Jan
This is the full scale boat. It has a diplacement of 3.2 tonne. Looks about right. If my modelling is accurate it would take 40kW to do 10kts. Wheel efficiency is showing as 62% for 2.4m diameter wheels each having 1m wide blades.

10kts is on the verge of semi-planing for a beamy 9m hull and there is likely to be squat that Michlet does not take into account. At 8kts (1400rpm) the Michlet data should be accurate and this requires 22kW at 61% efficiency. From my experience with 3 tonne boats around 9m this looks reasonable. Will be very interesting to see if a wheel can achieve this efficiency. From what I have read it looks in the ball park. An outboard prop on a boat like this would not do much better.

I will have a look at a 1/10th scale model tomorrow.

Rick W.

[Guest625101138]

Jan
I scaled by 10 to 1. I have set the speed at 3.16kts as this is roughly on the same part of the hull resistance curve as the full scale boat at 10kts.

The calculated power seems low for a 3kg boat but the speed is not that fast. I was thinking you might have a little electric motor that would do the job so set RPM at 5000 and adjusted gearing to suit.

I also found an error in the previous file that set the blade width at 1m. Changing the value in the input page did not alter the value in the thrust page. Hence the corrected full scale file is also attached.

I will be very interested in any results you get from model testing. You would not need an elaborate set up to do some ballpark testing. I am almost tempted to dig up one of my old battery srew drivers and set up a paddle wheel drive. Would take about 1 hour to carve out a piece of blue foam to the right shape. Epoxy coating would give surface toughness.

Let me know how you progress.

Rick W.

[Sternwheel Rat]

O.K., I've got to jump in here.
Tom28571 wrote, "The rudders in front (not lower than the draft) were completely useless." Sir, I respectfully submit, you know not what you speak of! ALL sternwheelers have the rudders in front of the wheel, and I have to wonder, if your statement is true, then why did they build them that way for over a hundred years? I'm not a Navel Engineer, or an expert on anything, but I have to have faith in the experience of the men who were, and my own experience owning and operating this type of vessel. The rudders behind the wheel are called "Monkey Rudders", {Monkey see, Monkey do}. Not all sternwheelers had these, as they are only useful WHEN BACKING! Many of the larger boats didn't back up that often. Rudders on a sternwheeler only react when water is being PULLED ACROSS them, not pushed. My current boat has monkey rudders, because it did a lot of turning while backing, as an auto Ferry on the Ohio river.
Russ, since this a NEW build, I very strongly suggest bow thrusters, and maybe stern thrusters, be built in.
Jan, I like your drawing, but again, I have a problem with your design. You wrote, "My hull is steamboat/wedgeshaped in the stem and has a flat stern" and your drawing reflects this. This won't work. The wheel needs a lot of water to pull from under the hull, and a flat transom will create an eddy in front of the wheel. It's hard to find drawings of old hulls below the waterline, but I would describe it as a stern rake, with a sharp curvature. This is where you mount the rudders, so that water can be pulled accross them for steering. And the wheel is mounted at, or above the bottom of the hull so it does'nt hit the bottom first. Remember, sternwheelers were designed to be shallow draft boats.Your chevron wheel design is not new, just tried and abandoned. Don't go drilling holes in the buckets, you'll just lose power. But you will still need rudders, and I would install thrusters. Your aversion to electric is unfounded, unless you intend to mount all your power and drive outdoors.
Hope I don't hurt anyone's feelings, but there is usually a large gap between design and reality. Looking at what worked for so long versus the dreamers, I can't help but recall the old saying, "If it ain't broke, don't fix it!"

[SamSam]

Originally Posted by Sternwheel Rat

The wheel needs a lot of water to pull from under the hull, and a flat transom will create an eddy in front of the wheel. It's hard to find drawings of old hulls below the waterline, but I would describe it as a stern rake, with a sharp curvature. This is where you mount the rudders, so that water can be pulled accross them for steering. And the wheel is mounted at, or above the bottom of the hull so it does'nt hit the bottom first.

This site sells old plans for modelers, and has some sideviews of hulls below the waterline.
http://modelplans.steamboats.org/paddlewheelers.html

The plans below are from Harry Suchers book "Flatbottom Boats" or something like that.

[ongolo]

Actually, any car axle can be used to brake one wheel or the other. That is what the purpose of the diff is.However, you would need a difflock engaghed when you are not maneuvering.

Car gear boxes are actually not made to run extensiveley in 1st gear only. They will wear a lot faster than the engine.

Using a tractor assembly, engine (tractors are usually derated) would turn the paddle wheels slowly.

One engine you could consider would be an aircooled Deutz 912. They come as a building block system from 1 to 6 cyl. No cooling problems. Incredibley durable, they are used in SA goldmines at a dept of 4000m in dust and dirt and heat.

While Deutz engines in genreal are a bit noisy, they are verey low on vibrations. The Tractor engine have W extention, That means they have a counter balance shaft and no vibrations at all.

A 4 cyl 3.8 litre has only 80HP, weighs only 260kg, A 6 cyl has 120 HP and any air cooled engine would not have clogged intakes and overheating problems.

I have designed my gaff schooner around the deutz and I am very happy.

I can also heat the boat by redirecting the air or dry washing.

These are maybe just some ideas to help you.

Regards WAH

[volkswagen50]

I agree with the idea of the Chevron design, some experimenting will tell what the degree of "V" will need to be. I disagree with the idea of making each wheel one half of the "V". Unless the paddle is very close to the side of the boat, it would only be a varying degree of pushing water sideways. Think of it this way, push a blade flat against the water, it's tough, because you are moving lots of water. Now turn it 90 degrees, it slices through the water very easy. Anything in between these two extremes is just less effiecent than a flat blade. Thoughts?

[wnash]

Hi, I just successfully completed test-run the barge with stern paddlewheel propulsion system. The system is still under development . Anyone interested to know more please visit the project site at http://selftaughtengineer.googlepages.com/

See the paddlewheel barge in action...