Propeller Killer? High Efficiency Paddle Vs. Propeller 

Use code RCTESTFLIGHT50 to get 50% off your first Factor box at bit.ly/3JgFdFQ!

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

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)

I love your videos.

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.

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

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

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.

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

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.

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.

Very interesting challenge. I guess a fish inspired propeller that that creates a wavy motion would have both very high efficiency and anti clogging properties

I'd also like to see more paddle development. There are some tips from the cycling world you could try, like taking mass out of it, as well as an elliptical gear that puts a more constant amount of force on the motor throughout its path. And I second the folks that mentioned tip recurve for less drag, and that more width might also have an efficiency boost (if you can control the flex)

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.

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.

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

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.

I really want to see the long mission with the paddle. From the short test you did, it looked quite promising

If you design your rudders with a tapered skeg directly in front of the rudder's leading edge, you'll get better steering authority, better straight-line tracking, and the weeds will just slip right off. Then you can mount your propellers farther forward and maybe keep them out of the water a bit better?

on that paddle - you could probably reduce it's weight substantially by pocketing out the front side (depending on how fast you're going...) some but leave a waffle supporting set of ribs for stiffness - and on the area where it's mounted there's some excess material there - might be able to pull some crescent shapes from the next out to the sides... great video - love seeing guys experiment with things.

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.

Hi, if you reduce the distance between the paddle and the hull, you may be able to achieve even greater efficiency.

I liked the paddle the most. Please take that for a long cruise.

I love how you do your prototypes. Just slap everything together and get it working. No worries about if it tipped over or anything, lol. I wish I had that attitude I could get more done, not worrying about making everything look perfect or trying to account for any predicted failure.

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

Nice video as always! Have you ever heard of the Voith-Schneider-Propeller? Its not the most efficient propulsion system (based on a cyclorotor) but highly maneuverable and definitly a unique design. Would probably be a great fun video!

rather than moving the propellers up just move them forward, keeping the weight closer to the centre (for and aft) will reduce hobby horsing, there's a reason many catamarans put their outboards close to the centre, it prevents cavitation from hobby horsing. Also maybe look into using a youloh for a paddle (similar to a sculling oar), your paddle mechanism turned 90° would be perfect for the side to side motion and you only need to rotate the youloh oar to control forward or reverse, one on each hull still gives you deferential steering

Great video. Just some notes: (please correct me if I'm wrong) I believe to accurately measure the efficiency of the propulsion methods the speed of the boat must be constant over the different tests to exclude the effect friction has on the efficiency. The faster you go the more energy you waste. So an inefficient method might seem more efficient if it travels at a slow speed compared to a more efficient method going at a higher speed. The effect of different speeds on efficiency can be dramatic as, if I remember correctly, the drag force increases quadratically with velocity. The best way to measure the efficiency will be in a lab setting where factors such as wind, water friction and waves etc can be eliminated. An example of a lab setup would be rigging your propulsion system to a load cell in a bath, controlling it to push against the load cell at a fixed force, running it of a fixed time and the measuring the amount of power it consumed to push lets say 200 grams of force for 10 minutes or something similar. This method still is not accurate as the efficiency of a propeller increases as the speed of the craft increases and in this setup it would be standing still. On the other hand I think that the efficiency of the paddle would decrease as the speed of the craft increases. Measuring and comparing efficiency of different system types is extremely hard as you easily run the risk of comparing an inefficient method running in an efficient way with an efficient method running in an inefficient way. To eliminate this you can try to find the most efficient operating point for each method for example taking into account prop size/paddle size, rpm, vehicle velocity etc and then comparing the most efficient case of both methods. I realise that going this deep is not the intent of your video so it is just for interest's sake.😂

Next hull option: trimaran. Carry 90-95% of hull displacement in the main hull, at length to beam ratio of about 14. The longer hull should reduce the pitching problem at this small scale, ideally you’d have -6ft length or so. Single air prop near center, center of effort slightly forward of center of drag for directional stability. Steering by side hull yaw if you could do it, to eliminate the need for a rudder. Side hulls should be toward the stern, gap from side hull to main hull should be about the width of the main hull beam. Would love to see what you could do with that!

2It would be interesting to see if an "optimized" paddle shape was significantly more efficient than just a flat one. Curves, scoops to direct water inward, upward, downward, or outward, ducting, angle of attack, etc. Paddles for racing shells are usually slightly curved with interesting shapes to them.

When in 10 years or so every large ship is running paddles instead of propellers. We know who to blame. 😁👍 Merry Christmas and a happy new year. 🎅🎆

Highly enjoyable and inspiring video! I think, there are many more parameters, that might boost efficiency: First question might be, what theoretical limit or reference might apply = some car? On the other hand, transport by ship is said to be way more efficient than trucks and trains, though, on the other hand: You don't go for payload (by now). My ideas for the paddle solution are to 1.) try some shovel shaped paddle and additional vertical "walls" (what is called "fences" on airwings) to minimize vortices 2.) optimize the inner shapes catamaran body (maybe even like a jet propulsion-like tunnel and different intake/outbound diameters (maybe +/-25% ?)) 3.) add 1 or 2 paddles diving in in an interleaved pattern over the length of the hull for steady water flow And I'm really curious about the bionic/toroidal propellers, which are said to be twice as efficient.

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.

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

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

This is so awesome. As a paddler and someone from Seattle this makes me incredibly happy. Thank you

Thanks Lady! I think that just proves that you have built a very interesting machine. I'm always amazed by your clever ideas and solutions.

I recently had the pleasure of taking a river cruise on an old paddle steamer that had been converted to diesel. It was equipped with feathered paddle wheels so it would be more efficient.

Another propulsion technology you may want to look into is something some pedal powered kayaks have, which are two fins/wings that swing back and forth in alternating semicircular paths to propel kind of like how penguins swin

@rctestflight If you really want an energy-efficient ride by a watercraft, there are two possibilities: a) Nullification of water-drag and water-friction by using _supercavitation_ (pyhsical details see Wikipedia). Technology is simple and already used on big transport ships: Realease compressed air through a grid of holes in the part of the hull below the waterline. This works even for submarines and torpedoes (look up the the term «Shkval» and take a look at the achievable speeds). The second proposition sounds a bit outlandish at the first glance, but is even more effective, since water- and gas-resistance is completely taken out of the equation. It is gravitoelectromagnetism (GEM). The US-DOD uses this propulsion method since July 2011 (end of the STS-programme) in their TAV (trans-atmospheric vehicles) and AMV (all media vehicles, that can operate within the atmosphere, under water and in deep space; volgo USO). The physics behind this propulsion system is sound, the technology is simple and reliable.

Hey Partner - I was walking around Seward Park about 2-3 years ago when I got a semi-novel idea for a watercraft propulsion system that I think you might be able to realize: You know the "organic airship" design in Studio Ghibli's "Howls' Moving Castle"... with those weird 'wings' popping out of the airship recurrently to provide thrust? So... basically that, but for water. The essence of this idea is to mechanically produce a semi- (or later, fully-)parallel-to-water-surface rowing motion: This simplest version wouldn't be very Ghibli-like at all - just a mechanical row-boat, in essence: 1. Minimum two 'oars' in water, one each side of the boat. 2. Both oars would be connected to a gearbox via direct drive, which would manipulate them such that the tips move in a vaguely triangular shape: One side of the triangle would be the extension into the water, one side would be the thrust stroke, and the other side would be the retraction from the water in preparation to repeat. 3. In this simplest version, i believe the geometry would work out such that if the oar handles were above the waterline, angled into the water, this triangular path would necessarily remove them from the water in the retraction stroke, eliminating the drag that would otherwise obviate this idea. >> I can sense that steering could be gracefully accomplished by some kind or gear-box which would donate additional speed to one side if the other has brakes applies to it (a basic differential would accomplish this), but that would increase complexity. This could be done electronically if either side were driven be their own motor Given that a two-oar system may probably be pretty janky in its movements... 1. The next-most complex version of this would be the addition of two more oars.... 2. ...or ADDITIONAL oars to make a Crew / Caterpillar version. Like analysis of an animal's gait, research would have to be done to tune in the best timings for each oar to fire. However, my FAVORITE version is the following: 1. Take the entire system you develop above, and put it **under the waterline**, and parallel to the water's surface (i.e. no angle needed anymore). 2. Then, adjust the shape of the oars such that they fit in a custom rubber / silicone sleeve. This would provide a larger thrust surface, and seal the oar's interface to the hull without the usual friction of tight axle seals. >> The oar-travel geometry will need optimization, but what you'd essentially get at this point is a bunch of "fins" which scoop through the water, penetrating it at travel-speed, scooping the water backwards to generate thrust, and then retreating within its housing in the hull to repeat the stroke again... like a frog or human swimming through water. >> Naturally, there would be absolutely no way for this system to gather seaweed. The seals and the geometry feel like the most complex parts... beside that, I can't see any serious flaws in this design.

I think you could squeeze some more out of the paddle idea. Your first attempt went pretty well, compared to the highly engineered air propellers. I'm thinking two paddle linkages mounted on the a centrally located drive gear 180 degrees apart, with the vertical shafts on the outside of this assembly right up next to the hulls. Each paddle and shaft would have to be L shaped like a flag, so they could pass one another. The circumference of the drive wheel might have to increase too (bigger gear is probably better for the forces at the teeth anyway). Then there's the idea of curved paddles rather than flat ones. Real kayaking paddles are not flat.

Paddle with closer tolerance between the paddle and the hulls. Propellers mount them further forward, say 3/4 aft. Love your projects.

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.

While back i encountered a popular science article about a steam powered marine thruster. It seemed to be somewhat based on quite old tech of steam ejectors, "air movers" and a more recent equivilent might be a dyson bladeless fan. Basically a set of cones which are arranged so there's a tiny gap between them towards the downstream end. Steam exits through that gap supersonical(or faster if nozzle shape adjusted careful) so has huge KE. The steam slams into water and condenses which shares the KE with the water. And results in thrust per rocket equation. Supposed to be fairly resistant to weed.

Very inspiring and I must ask about the paddle. Would giving it a scoop shape make a difference? It make quite a difference in a water wheel when it is a Pelton wheel.

Another great video. I’d be happy to watch another one with the same catamaran and the propellers up and more centered instead of on the back. I like scientific method in these videos. Thanks! 🙏🏻

That album y'all put up comes up while I' driving. in the shuflfle and it's really a nice set of jams. Thanks for that. Sick paddle.

Very very cool. I do like the dual propeller design I think if you Where to lengthen your hulls to about double the length and move the propeller closer to the center of the Craft length you would get away from hitting them on the water

yeet the beet so it beet to the yeet

What about a corkscrew propeller? Make the propeller blades continuous with shallow angles so there aren't any corners for sea grass to catch onto. Edit: if you want to be fancy, you could try a golden ratio turbine. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BxNHOMJGcj0.htmlfeature=shared

Fantastic stuff - thanks. I was wondering about putting the propellers halfway along longer hulls - always clear of the water and hull length is related to max speed.

Great project. You seem to have covered all the bases. My observation for what it is worth is regarding the position of the airscrews. Maybe consider, positioning the pylons at the longitudinal centre of flotation (LCF) - I feel this may reduce the effect of the thrust on the hull which at the current location (aft) may be inducing longitudinal oscillations on the vessel. PS: The LCF is at the centroid of the water plane area (at the working draught).

I love your paddle design. The angles entering and leaving the water are almost perfect. Feathering the paddle parallel to the direction of travel would be most efficient on the return stroke, that is what you do with a canoe paddle. But the mechanism to do that would probably not be worth the small mechanical advantage. The main problem with paddle wheels is that half the wheel does nothing, the front quarter tries to push the boat up and the back quarter tries to push the boat down. Only the blade at the bottom is pushing in the desired direction. But, what if you made a tank tread instead of a wheel. A larger percentage of the paddle would be pushing the boat forward and half the paddle would always be in the water instead of a regular paddle which is out of the water half the time. Just a thought.

Great video as always! I think the boat is still usable .. What if you raise each mast and move them to the middle?? From the middle of the boat it would be almost impossible for the props to hit the water! Give yourself about an inch of clearance from the deck. I think your next boat should be a larger scale autonomous sail boat! Saw the ones that now go around the ocean mapping and can stay out for a year.

I like your videos. On this I would like to give you some of my thoughts. 1) in dragonboat racing teams are starting to rotating their paddles 90° to reduce drag on the forward stroke. 2) when comparing efficiency. There is a great influence of hull drag in regard of the achieved speed. Unfortunately I don't know what it is called in English. In German it's called "Rumpfgeschwindigkeit" that describes the effectiveness of hull length to desirable speed. It has to do with the produced wave ... Sorry I'm no pro in that area. But I suggest it could have an impact on the way you test efficiency. 3) the best solution is not always the most practical one. There is a reason why traditional Propeller underwater are so commonly widespread used. But I do like your creative approach to discover new possibilities. Keep it up.

I would create a waterproof sheet on the bottom half of the hulls with the same texture and aerofoils as shark skin. Idk how small of details a 3D printer can print but maybe you could research the shape of the individual shark skin foils and make some thing similar you can wrap on the bottom. Anyways if it’s possible to get a similar scale “scale” pattern (I think they are called placoid scales) to cover the parts you want the direction of water to flow your efficiency would increase dramatically.

Fantastic! I would love to see you try a 'whale tail' propulsion system where the whole paddle stays underwater and pivots up and down.

I don't think you have milked this subject dry yet. I'm wondering if a surface penetrating propellor might reduce underwater drag enough to be an efficient option. Thanks for the videos !

Love the test, fail, test, fail, test, success! This is so cool to watch the constant striving for efficiency. Thanks for sharing!

Very cool! For the paddles to avoid needing a rudder, could you have paddles on the sides of the boat (they could all be synchronized via the same drive shaft), and create differential thrust using another mechanism to control the depth of the stroke? Alternatively, maybe you could rotate the paddle head.

I think that Mabe using 2 paddles that alternate when they are in the water could help with the slowdown between strokes and making them a little more snug against the hulls

Would be interesting to try a caterpillar track system for the paddles. Would be similar to having multiple paddles

1) Wind direction is a more important variable in wave height as is wind speed. The longer distance the wind gets to work the bigger the wave for the same wind speed. 2) For the paddle design, try experimenting with elliptical drives to max efficiency. Also if you want to test a folding paddle design use a coordinated solenoid hinge mechanism. 3) On an unmanned vessel, it shouldn't matter where you put your propellers. I would put them amidship offset (èasier turning)from the hull to accomodate larger propellers higher off the water at the mean stable point of the boat.

If you observe Olympic rowers, their oars are above water for quite a while before next stroke. It helps synchronising of course but also reduce the amount of turbulent water the rowers are pushing around, because their boats keeps gliding in between. Of course I don't know if the same would work with your 2 hull paddle setup... their boats are very long and narrow, which is a clear advantage in fluid dynamics (like comparing an arrow with a ball).

You can get more efficiency by mounting the propellers more to the front of the vessel. Bow waves increase in height with the speed of your vessel and cause the boat to dip at the back. This increases drag and messes up the thrust vector of the prop. Edit: This would probably also help with your water hitting problem.. The would be raised higher above the waterline...

I studied and tested a concept a while ago that basically used two rudders or flaps moving like the tail of a fish, but with their movements mirrored across the center so they would move inward or outward at the same time to not steer the boat like a single flap would. It would be interesting to see that tested again

you could center the props more, near the center mass of the hull. That would eliminate front to back water contact you could also make an outrigger that contacts the water and arrest the pitching and oscillations although some wave peaks could still affect it in extreme situations. I would also try to keep any items from the upstream side of the props as to not block airflow. Even a slight mast in the way, slows the flow of air, this is a factor in wind generation and could be impactful in an efficiency situation like yours. Another thought, would A vertical stabilizer work in place of the rudder, may reduce drag in the water but would wind conditions have to many variables? would a vertical stabilizer be effective enough to even work or would it need to be to large for slow speed? Too bad you dont have a wind tunnel to test all of this, could be helpful.

Cool idea! I would like to see the way-point mission’s data. Maybe just put horizontal flat or curved hull extensions under the props so the water always stays below them. They could be above the normal water line and only touch the water when a wave comes.

Being that airprops have the highest efficiency rating so far: Perhaps having them mounted closer to center for whatever boat you do next would help. Also, there's another comment that mention caterpillar track paddles. That would be interesting to at least see, maybe with the paddles in a crescent shape too.

I think for these longer waypoint missions with the larger props, you might just be better scaling up your hulls. More room for batteries while potentially resisting larger waves better?

Very well presented and interesting. Your timing and presentation style is a refreshing change from most "technical" videos on RU-vid. It is nice not to be talked down to. On a technical note, I'd love to have seen a comparison to a big slow turning prop, like that on a nuclear submarine. However, you would also have to sink most of the hull under the water, ie, teardrop style. Cutting the surface is just so wasteful, but that really changes the parameters of your investigation rather too much maybe?

the paddle wheels in our old german steam driven ships on the river Elbe in the town Dresden do constantly adjust the angle of the blades, so the keep beeing amost vertical all the time they are in the water.....with an very easy linkage system

Great videos! It was super cool to see the efficiency of the fans over the paddles and props. But one thing: those aren't puffins; they're some kind of duck.

I really like the idea of supersized air propellers and electric motors. On real boats they could be used to extract some power from winds, maybe enough to meaningful on recreational boats that are only used occasionally. Maybe you should explore wave propulsion.

The wave issues out on the sound could be examined as a function of hull length vs. wavelength. On a different sized hull the lever action of the waves would just pass under the hull unnoticed or perhaos you could tune a short hull to cause destructive interference with the 2-knot wind speed wavelengths.

Always entertaining and educational. A bonus for PBW views for this PNW Expat. Thanks!

your paddle boad might work on land, if it is mounted a little lower. Would be a cool amphibious vehicle.

If you added a flywheel to the motor it would even out the current spikes mechanically as well. This is awesome btw!

Put the props at the longitudinal center of the hulls. You could put rudders behind the props like airboats use to alter thrust vector and steer the boat. Also, put as much weight as you can towards the center rather than the ends to help with the hobby horsing when you encounter waves. The paddle mechanism was pretty cool.

Check out how the implement prop/s into the hull of the newer fishing kayaks. Basically they are recessed into the bottom of the hull. Although to repletely negate prop fowling you could also incorporate a mesh, cage as encapsulating the prop. However this ideally is flush with the bottom of the hell. Just a thought. Watch the videos they have made on these fishing kayaks. I know a fowl proof prop can be employed.

Nice video ! I hope one day you can test out contra-rotating props !

Wouldn’t it be better to mount the props in the middle of the boat (lengthwise) to a) minimise the height difference they experience when the boat is rocking front to back and b) for more effective differential thrust cause the center of rotation would be in line with the props?

I love it! You're right that you can't really call the paddle area "disk area", but there is a definite relationship. The reason bigger propellers are more efficient than smaller ones is that Mass x Delta_V gives you thrust. But 1/2 Mass x delta_V^2 is the energy used to do it. So you can easily see that you want to accelerate as much mass as possible over the smallest possible delta_V. The bigger your paddle, the more you're just pushing off the water rather than accelerating the water. Basically, stirring up the water is lost energy.

Closer to the pontoons and scooped ? Like have the edges of the blade curved up in the direction of travel slightly to cup the fluid for highed efficiency maybe. Love the content heaps !!! Can’t wait for the next part !!!

Sometime in the 80's or 90's I remember some F1 powerboat competitor experimenting with a very high speed paddle wheel instead of the regular propeller used on the competition boats. I have no idea what the results were, but at least it shows that people has experimented with paddles relatively recently. I'm also uncertain if this was before surface cutting propellers were developed or not. Surface cutting propellers can be run at much higher revolution than ordinary propellers without suffering from cavitation causing performance problems or propeller damage.

The flipper-style 'mirage' drive some kayaks use would probably cut down on weeds with added speed. it's a pair of side to side paddling flippers that are opposed, to mostly balance out the lateral movement.

good for you!! 1% inspiration 99 perspiration!! with the resources you have, now Id like you to try tyhe efficiency of an hidrofoil moving into a sinusoidal wave pattern like the propulsion of an "aqua skiper or pogofoilor or water bird" depending who copied it, I've tried it in real dimensions and it works!! but what I think it would be the best efficiency setup would be the whale like tail propeller, no doubt, I´m into it

Interesting video. It reminded me of the story of Isambard Kingdom Brunel. I don't know if you have heard of him. I live in Bristol UK and he is very famous here. I think he was responsible for designing the first iron ocean-going steamship. He is known for an experiment to decide which was more efficient a paddle steamer or a propeller-driven craft so he staged a tug-of-war between the two, The propeller craft won and that is what he used for the SS Great Britain. The hulk was towed back from The Falklands and somewhat restored rests here in Bristol.

I love the lady who sent the video she's so enthusiastic! Anyways, I hope I'll see you around Seattle while working on these sorts of projects (I'm at UW lol)

I like the use of herringbone gears, usually when being used in situations where liquids are involved, to reduce fluid lock, we cut a gap the center of the V.

In human propulsion, one of the recurring footnotes is that the Chinese yuloh oar allows someone to propel a very large boat or even a barge with tens of tons displacement at several knots for well under a hundred watts (one woman, one hand, not breathing hard). It's a similar oar motion to how animals swim using their tails. I am curious if you could replicate it in a motorized dual yuloh design for your cat.

I love the boat videos. Really interesting variables to design around.

Maybe you could try three or four paddles on that power wheel. Also perhaps longer hulls would greatly improve efficiency. Very interesting experiments.

Awesome! Some friends and i were toying with the idea of sending an autonomous boat across the ocean (a big loop of the Pacific, passing by Hawaii). I imagine the chances of survival would be low.

You should use a cam style shaft and have 2 paddles so one is constantly in the water. Similar to the guya bicycle set up in the canoe 🛶. But still in the center. But even if you don't. The paddle still need to be cupped or concaved like a snow shovel. You're losing thrust efficiency with water going around the outside of the paddle while it pulls the boat forward. And on the return stroke water would move smoothly off of the blade as well. You could also try thinner hinged blades around the entire diameter of the paddle (in the water) that flip back during the return stroke to eliminate drag. Just some recommendations\ideas.

My solutions for weeds jamming up underwater props, is either using fans like a swampboat, or long, flowing bio-mimicry tail fins, from like a fish or whale. Swimming tail fins are also my solution for noise, if the back & forth mechanism is well sealed up & lubricated. Inside a shin maybe. It would be fun trying to mimic fast fish, like marlins/swordfish or mako-sharks.

Have you heard of the experiment the British Navy conducted in 1845? They built two virtually identical ships with the same displacement, engine size, and hull geometry. HMS Rattler had a screw prop, and HMS Alecto had paddle wheels. They tied the boats together stern to stern and had a tug-o-war battle. The screw prop won the battle. You could do a similar experiment!

This is awesome! Just an observation (which you probably already saw) I noticed the props hitting the water was due to too much pitching forward and back. Longer, skinnier hulls might be the way to go to improve stability!

When I was young in the 60s we had a hand powered paddle that worked pretty well. It was about the size of yours but turned parallel to the water with an L shaped handle and a v shaped pivot that would let it go back and forth like a fish tail. You pushed the handle back and forth or left and right and if I remember right it pushed our aluminum john boat without a lot of effort. Of course we we were just fishing along the bank and lilly pads so speed wasn't a factor.