Paddle wheel help

My father's step-father designed and built the first Aligator amphibious vehicle to help rescue hurricane victims in Florida's mangrove swamps. The only patent that he held as a result of that project was the shape of the fins on the tank treads. He found that flat treads didn't give the vehicle much speed through the water, so he designed cupped treads that increased the Alligator's headway tremendously.

In light of what I've read about cupping the tread fins, this makes sense.

 

Side wheels were covered to stop the constant and large amount of "thrown around" water from drenching the deck/cargo and passengers aboard.
They also prevented some grisly deaths from someone falling in the mechanism.
And,, the covers made a great place as a billboard for the company/ships name.
Adding efficiency? not really.
If anything, they decrease efficiency because the water being thrown around inside the covers adds drag to the rotation.

 

Rangebowdrie, sounds like you are a kindred spirit when it comes to paddle propulsion. I love the idea of the paddlewheels thumping you through the water. You are correct in your statement about props. No romance at all. Nothing about an outboard sparks people’s imaginations like the paddle wheel does. I’ve had so many people look and comment about my boat (limited as she is right now) and you can see the longing for adventure in their eye. Those paddle wheels just reek with tradition and adventure a la Mark Twain’s Tom Sawyer and Huckleberry Finn. On the practical side I do like the fact that on average a paddle wheel can have more “grunt” than a prop. That is an attractive feature. Fred Rosse, I’m a great admirer of your boat sir!! I’ve seen it before scouring the internet for information. It’s really inspiring. I loved your video where you sailed her past the USS Olympia. It’s been an inspiration to me especially since that particular place is basically in my backyard. I often wish you had more videos to watch because your boat is so neat. Any advice from you would be more than welcome!

 

Will Gilmore that is a great thought about cupping the floats. I have been thinking about that but being a non-feathering wheel I’m not sure if that cupping would decrease the efficiency on the initial down stroke of the float (pushing the water down) and the upstroke of the float (lifting the water up) it seems there is a definite balance of give and take with this whole idea and finding the perfect formula seems more an art than a science. What do you guys think about cupping the floats?

 

Messabout, those are valid concerns with the anchor system. You can’t see it in my picture but I have the line running through a metal ring on the end of the bowsprit to keep the orientation of the anchor toward the bow rather than have it swing around to the side and careen the boat in the middle of the lake lol. Good challenge though!

 

Their is an old movie from the '50s with John Wayne and Lauren Bacall, "Blood Alley". The movie can still be found online and on YouTube, (IIRC).
The featured boat is a sternwheel steamer.
The filming was done in the San Francisco Delta, and the studio bought the boat from amongst a bunch of relics and wrecks and got it operational for the movie.
Sidewheelers are more complex in their drives, but less in the steering. Sidewheelers used as tugs often had drives that would allow the wheels to rotate in opposite directions, (could turn in their own length).
With a sternwheel it's common to have 3>4 rudders behind the wheel and 3 in front of the wheel. Worked in unison they provide a very strong thrust vector, and some set-ups allowed independent operation that will "crab" the boat.
Efficiency goes up with wheel diameter, but torque requirements/loading also increase.
The "hobby" sternwheel boats of today generally use one engine, but the "real" ones used two engines, with the cranks on the wheel at 90 degrees to each other so the wheel wouldn't have a "dead spot", (get hung up at top or bottom center and unable to start).
Independent sternwheels, (split paddles,) are quite rare, requiring either a pair of dual high-pressure engines, or a pair of compound engines at large cost increases.
Keep us informed of your experiments.

 

That is really fascinating! Got the start of more floats welded up today. Going to make the floats deeper I think to get more thrust

 

If I'm understanding what is meant by covers, wouldn't they help direct the thrust aft by not allowing side spillage of water?

I just did an image search and could find no examples of paddle wheels with the sides of the blades, or floats, closed off. I misunderstood what a cover was. I was picturing something that was more like a wide rim or hub, but a cover is more like a car fender.

 

Once a retreating float clears the water, (actually shortly before, as the thrust is a function of the sine of the angle, the forward thrust approaches zero,) any water just adds drag and weight.
Here's the "Eppy"

 

Will,, I wasn't seeing what you meant. got it now.
Yeah, you mean like a disc on each side of the paddle wheel, so that the thrust of the floats just doesn't force water off to each side, the disc fastened to, and rotating with the wheel, right?
I've not seen that either, and it might be something that could be experimented with, it would seem that such a set-up would add some peripheral strength/support to the floats.

 

I would imagine that if you had "sides" to the floats you would lift water as the float exited the water and this would be a waste of energy. Before I built my paddlewheel I pushed a piece of wood by hand through my garden pond. Cutting edge experimentation, obviously. This produced beautiful eddies from each end of the timber strip. By moving the paddle to the right the nearside eddy rotated clockwise just at the tip and swirling behind the paddle. I've no idea whether this swirl of water is a waste or if it has some propulsive dimension. What I don't think was happening was that water moved "out" from the timber, that is towards me and the opposite at the other end. A video of the rear of my boat is at 13 minutes 23 seconds in this post and may reveal something....................https://mountainbiker.online/2021/10/18/a-video-of-my-boat/
I think that sides would have always been used if they were of value so I can only assume that they waste energy, though an experiment would be interesting to see. I also would expect a cupped blade to lift water so believe this would not be good either. Just my thoughts. Experimental proof needed.

 

Either, leave energy on the table, by leaving the sides open, or pick it up and throw it in the trash can, by closing the sides. One or the other might be better, or it could be a "wash", so to speak. Money and time may be the deciding factor.

 

If the paddle wheel hits the water at a, say, 95° angle, instead of slapping the water, it bites the water like a saw blade, and as it leaves the water tip first, instead of flat, it is already draining as it pierces the air. So offset the blades so the aren't radiating from the center of the axis or just make sure the axis is above the waterline.

 

I've had a dangerous thought. In a "perfect" scenario the paddle hits the water at the speed of the boat so in relation to the water it isn't moving at all. It simply enters the water and claws the boat forwards. Therefore having sides on the paddlewheel is of no significance. In reality, of course, there will be some difference between the paddle speed and the boat speed. Also, because the wheel is rotating, the rearward vector varies. As the paddle enters the water it is moving backwards at a slower speed than it is at bottom dead centre, and the same applies as it exits the water.
This is the reason for feathering paddlewheels, to try to solve the problem of the change of rearward speed of the paddles during rotation.

 

Yes, however, because of skin friction, the water against the hull is being pulled with the boat and moves past the boat faster as it gets farther away. A shallow sidewheel paddle blade or float, at the beginning of entry into the water, would enter water that is not moving at full speed opposite to the direction of the boat, while the deeper blade at the bottom of rotation would be pushing against water that was being passed by the hull at a faster rate. Depending on the stern's bottom shape, this might hold true even more with the eddy effect near the surface and less disturbed water deeper down. Thus, the slower rearward drive of the entering and exiting blade may not have the adverse effects from moving slower than the water relative to the hull.

I, of course, don't actually know what I'm talking about. I'm just trying to apply what I think I know to a logic I believe could work.