Pedal Powered Boats

Thanks Jeremy.

The RPM would be the same, I'm 1:1...

Again, I'd like to try the increased cadence (RPM) as I know from experience this smooths the torque peaks out in a big way. Otherwise, it's added weight waaaay up high where the pedals are...

Once on foil, the energy demand drops as does the cadence and general level of effort therefore, loading.

A possible flex drive attached. No aft stabilizer shown... That's a K-1 shown. I've just bought four of them for $100 used! The bulb is ~60 litres which floods and purges according to velocity. The canard is servo controlled by a micro processor stabilizer from the R/C world which keeps the whole thing upright at speed. At low speeds, it relys on a kayak paddle to remain upright.

 

What about using a large and massive prop itself for the flywheel? Maybe the blade positions could be configured to coordinate to smooth the cadence power strokes. There was mention of such things way back with the wave bike. Pedals would continue to turn for a time without being powered, to the point of being a hazard if your feet slipped and got tangled in the cranks... Also, elliptical sprockets were used for a while to smooth the power stroke, but have largely disappeared....

Porta

 

Porta,

The prop is quite large at 50cm but it is downstream of the UJ's so wouldn't have the damping effect sought.

My pedals are LOOK clip-ins so there shouldn't be any tangling in the cranks.

Higher cadence and technique has a huge influence on smoothing out peak torque loads associated with leg power.

I had a set of those eliptical chain wheels years ago. I never did really ever warm up to them. But I'm not using chain wheels or chain anyway.

A flex drive may provide some peak torque reduction but I'm not sure I like the idea of a "mushy" drive train.

 

Porta,

I didn't follow your blade position vs pedal position idea.

Would you dumb it down a little for me?

Thanks, and thanks for your input.

 

Just my imagination, thinking out loud and being put to writing..

Maybe with a very large surface piercing prop. Jake Free offered 5'+ and single blade? at one time: http://www.freeenterprises.net/HPBoats.specs.html His printed catalog has interesting pics of some contraptions.

P.

 

I have finished my prop studies now and have come to the conclusion, that my custom 7.8 inch prop can do the same as a 14 inch RC prop, while having better characteristics.

You see in the diagram, that for 0-5 knots my prop outperforms the 14 inch prop, while having nearly the same efficiency at 10 knots.

When you experiment with Javaprop, you will see that the RC props outperform my props by more than 10% in efficiency for every point. But if you compare the props using a fixed power-setting (e.g. 150W or 650W) and rpm's, you can see the real difference like in the picture.

The bad thing is, that weed shedding takes more penalty than thought, so I am still experimenting with that. 3D simulations have shown a decrease in efficiency of about 6%.

For a 10 inch custom prop, the values would be better in all speed regimes, but with 7.8 inch the prop is small enough that is doesn't have to be retracted in shallow water and it can be 3D-printed for about 10$.

So the best boat prop for 10$, that's quite a deal, isn't it? The only drawback is, that it needs a gearing of 1:12, but with chain and gears it should still be possible.

PS.: The prop is optimized for a boat like the V15. For other (slower) boats like coach Dave's it can be designed even better!

 

Mikhail Puchkov should be mentioned in this thread.
Thanks to rwatson for bringing this video to our attention.

http://www.boatdesign.net/forums/powerboats/home-buuilt-pedal-powered-submarine-45157.html

 

Scheny,
I am glad you are looking at propeller design and sharing your findings. I currently use a 20” diameter prop on my heavy boat so I need over 2’ of water for cruising. It would be nice to have a smaller diameter efficient prop so that I can navigate in shallower water. I looked at your thrust vs. speed plot @ 650 Watts and your design point for sprinting:
650 Watts @5 m/s (11.185 MPH, 18.0 KPH, 9.719 knot) 104 Newton drag
@5 m/s I read 115 Newton for the 14” prop (115 * 5 = 575 Watts of effective propulsion for 650 Watts input, 88.5% efficiency). For the 7.8” prop I read 105 Newton (105 * 5 = 525 Watts, 80.8% efficiency). So the 14” prop has 7.7% better efficiency if I am interpreting your plot correctly.
On the other hand @ 2 m/s your 7.8” prop can deliver more thrust: 166 Newton vs. 139 for the 14” prop and more efficiency: 51.1% vs. 42.8%. The 19.4% higher thrust @ 2 m/s (in comparison with the 14” prop) means quicker acceleration. In a sprint getting up to speed quickly (after a start, after a sharp turn, etc.) is very significant.
I am interested in a thrust vs. speed plot at your 150 Watt cruise design point also.
Thanks, Dave

 

Coach:
If you don't need full power and have a short distance to navigate shallows, you might consider running the 20" in surface piercing mode. You would need a way to pull up on your flex shaft, so only part of the prop is in the water. That is what I do to go in under 5" of water with a motorized version and 10" prop. There will be more side thrust because less of the prop is submerged. You could get back some of the power when running in surface piercing mode by increasing rpm with a gear shifter....

Porta

 

"Fat Bike" catamaran

I got a bicycle trip in the planning stages and it's a fairly good distance but I have a series of obstacles, water features.

I've been looking around for something off the shelf and I like the bike powered catamaran type but not if I have to take off the wheels. The shuttlebike is pretty much what I'm looking for but I can't seem to have anyone there answer my inquires. Maybe they don't speak any english? could be? Anyway it's getting to the point where I might start designing and building my own.

Here's the catch though, I'm making this for the new "fat" bikes that use a wide tire, and I might use a cargo bike that has a longer wheelbase.

I don't have a terribly big distance so the cable drive would be ok. the parts must be able to breakdown and fit on the bike along with all my camping gear, other gear, food, and water (lots of it).

Ideas, suggestions, comments? I'm digging for ideas ......

http://www.shuttlebike.com/
just a note, I've just sent another email via the website, and I've asked on their facebook page.

 

Hi Coach!

Looks nearly the same for 150 Watt (if rpm is reduced in a linear way).

I would like to test 3D-printed prop design (made out of PA-6 Nylon). If you are interested we could make a custom prop designed for your boat and it would cost you only the printing fee (well below 50$ I guess).

Just send me your cruise speed in m/s and rpm, the diameter you would like and how the hub should look like (rod diameter in mm and how it should be connected to it). Also state if it should weed-shed and if other gearing (higher rpm) is possible.

Greetings, Andreas

 

Now this is a very interesting idea! Hopefully this type of nylon can hold up to testing for the prop? But it could be used for lots of other parts as well? Especially if I want to make my own cable drive system with prop mounted in it's own lower leg. This nylon should work out fine for that fairing? (or whatever drive method I want to employ). yeah, 3D printing!

 

Yes. Unluckily it is no fiber reinforced PA66-GF, but for my design with low disc load it should work with that material too.

Who would join me in my project to make a crowd-sourced high-end boat for the price of a normal bike? You guys have the year-long experience to make that possible.

I currently design a steerable (+/- 45°) and protected driveleg with 25cm total draft which can take 650W (7Nm @ 1080 rpm). I would gladly take the advice of all the others in this forum. I will post my design as soon as it is ready. The key point is a Nylon bevel gear mounted on a standard bike crank with module 2 gears at 1:4 and a 1:3 toothed belt (HTD 5M) inside the driveleg. Between the two gears, an 8mm aluminium flex (only 10°-15° over 2m length) rod should do the trick.

The prototype could be 3D printed, while the production could be fibre reinforced injection moulded. This would be strong enough to also work for rental purposes and everyday use. Ball bearing would be acetal/ceramic to be non-corrosive and except for the rods everything out of Nylon to make it cheap. Hull can be roto-moulded, as it is already possible to make that ultralight too (low density core with hardened outside). This works like sandwich laminate but only costs a part of it.

@Rick
@Porta
@CoachDave
@SpiDennis
@SubmarineTom
What do you all think about that idea?

 

Shuttle-Bike has finally contacted me and answered some of my questions. It appears this is what I'll be getting for my trip. They will have to make special attachment brackets for the fat bike tires though.

I've attached a few pics that they provided for me.
It's 998,00 euros and they take paypal.
shipping is included in the price.

 

Scheny,

I'm all over looking at your design ideas and collaborating to a fruitful end (i.e.brainstorming)!