Propeller Killer? High Efficiency Paddle Vs. Propeller

[mnswamp]

Check the tide tables - a slight breeze and an opposing tide can set up a nasty chop on the Salish Sea. Also, paddle efficiency tip - once the paddle passes vertical, you are pulling the bow down. To reduce that effect, offset the tip of the blade 15-20 degrees forward relative to the shaft. (almost every marathon racing canoe paddle and most SUP paddles are set this way)

[chrislivengood]

You should try a paddle that tightly hugs the hulls, almost like a ducted fan. The efficiency on that that would be interesting.

[AlBundy]

two ideas come to mind:
- use the rudder (extra long) as a drive like fish movements
- use sails

[stevenworthington]

Have you considered moving the air props closer to the middle of the hull to minimise them hitting the water? It would move them closer to the pivot point and reduce the amount of up/down swing.

[DanielinLaTuna]

Oars is a great propulsion option. And not so outside reason. It is reminiscent of a the Adventure Galley, Captain Kidd’s hybrid ship that combined square rigged sails with oars to give her manoeuvrability in both windy and calm conditions. It gave her advantage when enemy ships were dead in the water.
Oars also mimick human swimming, as I was taught: arms into the water ahead of the body perpendicular to the surface, arms push straight back, and then out of the water and begin the cycle. Very efficient

[davidglenn]

Before watching the whole video, the efficiency seems like it would be low with the single paddle. Half of the cycle time there is no propulsion at all while the paddle is out of the water. Adding a second paddle on the opposite part of the cycle seems like it would drastically improve the efficiency in my simple brain. That’s why props are efficient is because there is no wasted motion. All movement is providing thrust.

Also, a flat paddle is pretty inefficient. Designing a more efficient paddle shape would help to even the playing field a bit more.

[pietlopsa]

Your response to:
„Ohh and its remote controlled“ killed me completely! 😂😂

[JH-lout]

Some ideas:
-Sails. (Sorry couldn't resist it)
-Scullying oar. This is an ancient propulsion technique where you use a single oar from the stern of the boat, wich is moved from side to side with a special technique.
Modern engineers and amaterur tinkerers have developed this concept quite a bit, and modern scullying oars are surprisingly effective.

When I see the dual paddle mechanism, it reminds me of how ducks and other swimming birds paddle with their feet.
The big difference is that they fold their toes on the forestroke, to reduce drag, then they spread their toes again on the backstroke.
There was a model of scuba diving fins developed by Mares, that tried to mimic this. They were sold back in the early 00's if I remember right.
Extreme free-divers otherwise tend to use very long and floppy fins, apparantly those are the most effective for the human body.

For human-powered crafts, rowing with oars is far more effective than using a paddle, and the double-sided kayak paddle is way more effective than the one-sided canoe paddle.
I think the key is getting as long a stroke as possible. The effort you spend with the oar or paddle out of the water is minimized by having it counter-weighed. An oar is balanced so that if you let go of it, the blade will sink just enough to where it dips in the water and floats there. You don't need to use much energy to lift it out of the water. The double-sided kayak paddle is held so that it balances in between your hands. But again, these are techniques based on the human physiology. Muscles and bio-mechanics are not as effective as rotary motion, or we would have running cars.

When you steer a boat, you either utilize the hull speed, and the rudder will create a difference in pressure by altering the waterflow around the hull.
With a propeller craft, you can use a much smaller, and simpler rudder, because you are only re-directing the waterflow from the propeller. Single-hull, displacement-crafts have the rudder as an extension of the hull, so they won't catch seaweed.
Catamarans and dingy's are non-displacement hulls, (ride on top of the water) and they need to extend the rudder down below the hull, so they will inevitably catch weeds. I don't see a way around it with a traditional rudder design.

A longer hull is more course-stable, and you need to excert less energy to make course-corrections.

Just looking at your prototype boat, I think it struggles in the waves because it is too short, too top-heavy😢 and it is a bucket-shaped catamaran. It's deplacement isn't very progressive, so the pitching makes it dive in each wave. If your hulls had been more V-shaped, they would carry over the waves instead of dipping into them.

Another propulsion type that would be cool to explore is a bellows based water jet.
I have no idea of how to build it, but maybe start with a gusher-type bilge pump.

[manhorse]

Just a thought, but instead of moving them mid hull as many have suggested… maybe move them up front with props angles slightly downward. This does 3 things,

1: it pulls the front end up slightly, countering it’s own weight, thereby reducing drag.

2: Air pushes partially against the water itself, which may help it to gain a little speed.

3: Makes steering even more efficient, slightly increasing the overall efficiency of the vessel over the duration of the mission, due to less energy being required to execute each turn.

I hope you try this, I’m sure it’ll be much better.

[theworkshopwhisperer.]

I would like to see you try the paddle again with another catamaran design. If the dimensions of the paddle are as close as possible to the distance between the port and the starboard hull very little water can escape around the edge of the paddle increasing efficiency. Alternatively putting a single big paddle wheel in the middle of a catamaran would also be an interesting idea.

[Splode_]

Absolutely love that quirky paddle mechanism - I'd love to see that do the mission. Even if it's not as efficient as the air propellers it seems like it'll be a lot more reliable.

[jeremyschumacher]

Do you think mounting the props on the centerline would make any difference? I feel like the front and the back go up and down a lot with the waves but the center kinda stays the same.

[daveffs]

This is why I love youtube, for the creators actually creating things and exploring the world around them. There are still efficiency gains to be had on the paddle I feel. As it tilts and pulls out it's lifting the water rather than pushing. If you look at rowers they have a really efficient paddle stroke (as efficient as a human can make them). they put in vertically and pull out vertically. I doubt it would make anywhere near enough difference to beat the out of water prop though.

[derandiheissst]

7:50 I think a chain with several paddles mounted at a reasonable distance could provide a more consistent advance and more efficiency

[DingesKarel]

Do you take into consideration the weight changes, and the center of gravity? Both could influence the drag significantly.

[cschrislsmit]

Props to the lady giving you footage, that you actually used in the video!

[SteamCrane]

The feathering paddle wheel was patented in 1841.
It does what you are trying to do, make a paddle wheel more efficient by keeping each blade perpendicular to the water. It uses a rather simple mechanical linkage on the wheel to accomplish this.
Example, many videos of SS Waverley, a very fast sidewheel steamboat.
Both my mother and mother in law traveled on fast paddle wheel steamboats with feathering paddles.

[Johnschaffter]

I canoe and I suggest that you take a lesson from marathon canoeing. A classic straight-shaft paddle is inefficient because the paddle is pushing down in the first third of the stroke and lifting water in the last third. It is only efficient in forward motion in the middle third where the blade is vertical. Efficient modern paddles are called "bent-shaft paddle". google it to see what I mean. I think with a bent shaft you will see less bobbing up and down. In your video you can see the big paddle lifting the water at the end of the stroke. 
A bent shaft with a smaller blade but a higher stroke rate would have several advantages. A smaller blade with have less air resistance in recovery. Love your videos. Thanks for sharing your journey

[ronnieshirilla]

Two possible ideas.

I know you said you made the paddle as wide as possible, but it really seems that there are a few inches on each side of the paddle left.

Second, high end canoe and kayak paddles are made with a buoyant material to lessen the amount of force needed to pull it back up from the water. Making the paddle thinner and lighter would be great as well, and I’m sure a higher quality/more hydrophobic coating will help.

[ariadnavontardium]

This is what people in 1870s thought electric boats would be like