Pedal powered catamaran
Posted 15 November 2007 - 10:02 AM
Posted 15 November 2007 - 10:27 AM
Paddling or rowing is much more efficient and there are a lot more designs for very efficient pulling boats.
Have your friend go down to the local lake or river, where you can rent one of those peddle boats and have him peddle around for an hour. Then cover the same distance under oars or paddles. He'll quickly see he can get there faster with less fatigue using an oar.
Posted 15 November 2007 - 11:07 AM
Most of the pedal boats I've seen have been the paddlewheel type and there has been no apparent effort at making them efficient.
I was thinking that the main obstacle to building a pedal powered boat is the prop design. I don't know of any props out there that have been designed to make the most of fractional horsepower for a lightweight boat. The props on trolling motors seem to be optimized for pushing a heavy boat slowly. I'm half tempted to make a prop from scratch that has proper pitch, diameter and foil section but that way lies madness My friend has Dave Gerr's Propellor Handbook, though...
It seems like once the correct prop has been designed and built the transmission wouldn't have to create any more drag than a bicycle transmission.
Posted 15 November 2007 - 08:39 PM
Coffee break/Change flies
Maligne lake Jasper National park
My own design 21' tip to tip and a little over 6' wide. She is far from perfect (weighs a ton, gel coat is a mess, still no gunnels) on the up side I can stay on the lake long after the wind pushes the 14' aluminums to shore. And for fly fishing in comfort, its like sitting on the dock with your favorite lawn chair and as stable as well. To make her pedal power would be awesome.
Posted 15 November 2007 - 08:55 PM
You can jump up and down to power a small hydrofoil, for instance. But you get tired after about 10 feet. We think that legs are more powerful than arms, so there should be some way to make your legs do the work ... but if you really think about it, a rowing scull actually uses the arms and legs to good advantage.
Still, there are some human powered contests ... see http://www.ihpva.org/ for some pictures of past events.
Posted 15 November 2007 - 09:38 PM
It looks like you live in a very pretty neighborhood too
Good point about oars and paddles using legs as well as arms. I think the problem with most leg-powered propulsion, though, is that people who don't know enough to use oars end up hijacking a prop design from a higher powered boat which means they use a little prop that accelerates a little water a lot instead of using a big prop that accelerates a lot of water just a little bit. Think of the difference between a jellyfish and a squid. Jellies make pretty good progress with almost no power whatsoever because they push a lot of water gently. Squids move really fast using little tiny jets but they can't sustain the pace. A paddle blade is typically bigger than a prop for a small boat so it's more of a jellyfish than a squid.
Tugboats and tankers have big, slow-turning props and ski boats have little, fast props but need greater power per pound than tugboats or tankers (okay, that's not fair because ski boat plane and the others I mentioned don't).
I guess it's obvious that I think the prop is the key to a pedal powered boat. I've seen some of the race boats with athletes sprinting along on foils (including that jumpy-foil boat you mentioned) but I'm looking for a way to efficiently push a light boat at a kayakish pace. My friend's rationale for the boat is that typically a catamaran is more easily driven at less than planing speeds than a monohull (see Boatnut's boat) and pedal power allows for providing power with legs while fishing and steering with arms.
I was hoping somebody would chime in with "My Michalak such and such is a dream" or "My Bolger blah-blah works great" because I know somebody has worked this challenge out before me but I like the propulsion twist this thread has taken.
It seems like I've heard of a commercially available pedal power unit that could be retrofitted to something like Graham's new Moccasin...
Posted 16 November 2007 - 08:18 PM
Posted 24 February 2011 - 07:09 PM
Note that when fishing, the value of having your hands free while you move about is enormous. You can cast and catch fish! Can't do that with a paddle in your hand, so it's likely worth the trade-off in efficiency.