Pedal Powered Boats

I can understand it, it's like some of my videos, it's not meant to be a documentary, just a quick visual aid. I do wish he was still here though to explain ........

 

But I thought he had a web-site, no?

-Tom

 

His blog is kinda like the youtube video, visual only.

http://www.rickwill.bigpondhosting.com/V15_58.htm

http://www.rickwill.bigpondhosting.com/V15_58.htm

 

Okidokie.

Thanks.

-Tom

 

Rick has answered a couple of questions about his CF prop on the hpv-boats forum. You can access the archives through this page but it is a couple of months behind.

http://hupi.org/cgi-bin/mailman/listinfo/hpv-boats

You can sign up to get his latest messages (yesterday's posting).

Porta

 

I have been checking on the prop from Torqeedo. They say, that it takes 180W at 10kph (5.5kt) and 1200rpm. The rpm are a bit high, but this might be the perfect prop, if you plan to build a boat using a toothed belt.

At 1200rpm the torque is so low, that a belt with a small pitch and therefore low losses can be used. I think, that I will give it a try.

The prop has a diameter of 200mm, which makes it perfect for shallow water. I have calculated the losses of a 200mm compared to 405mm of a 16x16 prop and I found out, that efficiency is about the same, if you do not request too much thrust.

So in my opinion, a stabilized monohull or catamaran would have the same efficiency, if you are willing to limit speed to cadence. If you are going for thrust, like coach Dave, the "Texas sized" prop surely will be the better choice.

 

I don't know how you compared the Torqeedo prop to a larger diameter, higher aspect ratio prop, but can say with certainty that the latter will be more efficient. The Torqeedo props are reasonably good, but still poor when compared to the sort of high performance props we're using. Like all commercial manufacturers, Torqeedo have made compromises in the design, which reduce efficiency.

Firstly, propellers need to be accurately matched to the hull resistance, something that Torqeedo cannot do, because they are marketing a general purpose drive unit that will be used on a wide range of hull types. They therefore pick a prop design that will work reasonably well over a wide range of conditions, which inevitably means that it works less well than an optimised propeller.

Secondly, Torqeedo designed their propeller to shed weed, because weed and plastic bag fouling is an important characteristic when marketing a commercial product. Unfortunately, as we've found out from experiment, making a fixed prop that has high efficiency makes it more susceptible to weed fouling. If the blades are swept to reduce fouling risk then the efficiency reduces, both because of the change in blade shape and also because of the reduced torsional stiffness of the blade, which tends to make it de-pitch under load.

The most accurate modelling programme that I've used (and which people like Rick Willoughby and others have confirmed as being accurate) is Javaprop. If you put the Torqeedo propeller parameters into Javaprop and then compare them with those for something like a model aircraft propeller of a larger diameter (obviously at a lower RPM) then you will see that the Torqeedo prop compromises impact on performance quite significantly. The Torqeedo propellers are also quite expensive, IIRC.

 

Thanks Porta, I got signed up!

 

Ya, I got signed up too but didn't get anywhere...

-Tom

Scheny,

I've used JavaProp and can second Jeremy's post.

-Tom

 

I signed up and already got my first digest, found rick's email and sent him off a few questions.

 

I'll try again.

Thanks.

-Tom

 

Here is an example of a heavy boat (Peccadillo 8 tons), low speed, high thrust using a pair of 30x20E props. When the wind died down they put a crew member on the pedals at the back of each hull to get a 1 knot advantage over their competition.

http://www.sail-world.com/photo.cfm?NID=82737&Pid=136037&flash=&width=1200

Here is a link for the prop

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=8293

The Peccadillo won the Australian Three Peaks Race in 2011. Here are Rick Willoughby's comments:

"The win was due primarily to sailing ability. They managed a
slightly faster trip using the thrusters when the wind died in the
Derwent River on the final sailing leg.

The drive legs are folded up with the big prop on the back of the
seat. The thrusters were secured in this place for the whole race.

Charles said that during the pre race testing and up the Derwent two
pedalers could hold 2.4 to to 2.5kts working on 30 minute rotation.
The other boats could hold about 1.5 knots using oars."

 

Hi 157,

Ian, are you using the outriggers from your previous boat on the new one as well , or building new ones?

Thanks, Glen

 

heres a bit more info.

i did post about this systems few months ago here a few picts off it in a kayak fishing site tread.

http://www.boatdesign.net/forums/boat-design/what-you-guys-think-about-new-pedal-boat-41791.html

here more picts.




http://www.yakfisher.net/smffiles/index.php?topic=6064.msg49147;topicseen#new

joco

 

The flexible drive shaft will soak up a lot of power, reducing efficiency a fair bit. I experimented with a drill flex drive and found it used around 10% of the available power. Add in that the unit linked to has two right angle gearboxes plus a toothed belt drive and I'd suggest it's losing around 20% of the available power in the drive system.

It does have the advantage of being fairly simple to install and use, though, and could be fitted to a fairly wide range of boats pretty easily, and without making holes in the hull.

Overall I suspect it's probably on a par with the Hobie Mirage in terms of efficiency, maybe a bit less.