Pedal Powered Boats

http://youtu.be/uBP4xwt5p28

http://youtu.be/uBP4xwt5p28

 

Wow, she's very nice.

I like the boat too.

Thanks Spidy

 

Jeremy,

I came across this today.

Check out the red boat about half way through the video. The seat is stationary but the foot mounts slide in conjunction with the oars!

I thought of you when I saw the vid.

http://www.youtube.com/watch?v=9BXxL9gztO8&feature=youtube_gdata_player

 

Thanks, Tom, I'd not seen that one. It doesn't look like it needs a lot of power to remain up on the foils, either, unlike the Flyak that seems to need a near-Olympic standard paddler to remain foil-borne from the videos I've seen.

My guess is that the main problem with rowing a foil-borne boat is the need to maintain way between strokes, and keep the thing stable - I can imagine it tending to want to pitch and heave a fair bit from the intermittent power input. They've done an impressive job on that boat, it seems remarkably stable to me.

A pedal powered hydrofoil like this has to be possible, and would have the advantage of not having to cope with the power pulses and varying C of G from rowing.

I might sit and do some calcs in a quiet moment and see how the total drag compares. It'll depend a fair bit on the level of induced drag from the foils, so will be more weight sensitive than for a displacement hull, but on the plus side wave making drag will be very low when foil-borne, so the rate of increase of total resistance with velocity will be a lot lower than for a displacement boat.

 

Tom,

This is the often discussed slidding rigger which was outlawed for racing about 80 to 100 years ago. There are commercial variants avalable. Note that there is a reduced amount of pitch of the boat due to less movement of the body weight. I suspect this is the only way they could keep the angle of attack of the foils constant enough to make this work.That guy is really working to get the boat up.

 

Jeremy,

Almost missed your reply.

Quite the bow dive at 1:23 min!

I didn't even notice it's the same seating configuration throughout the video. Blows me away.

I think the amount of power being transfered is deceiving. They make it look easy compared to a kayaker. I make this comment having done both (rowing competitivey).

A few considerations: the mechanical advantage of the oars, the length of time the blades are in the water, the full body/longer range of motion.

I'd guess 20 - 30% more power transfer available compared to a kayak. Of course the power has to be there in the first place i.e. a strong, fit engine.

I was always surprised Rick W didn't persue the foil idea. I know he considered HYSWAS but couldn't overcome the stability issues when getting underway and was also under the impression the gains were not worth it as he didn't use sufficient depth for his submerged pod (more than three diameters).

 

In case this hasn't been seen before, I've seen similar but not this one.

http://youtu.be/3PdOIXvfB3g

 

Tom:

I think foils are essentially beyond the reasonable extended power limits of human engines. They only seem to work for short distances with HP source. Also, what happens when the foil strikes something hard like rocks in shallow water, floating logs/branches or even clingy sea weed/algae in open water? Lots of things to drop you out of warp speed and keep you below maximum displacement speed with the added resistance of damaged/clogged foils. Even props become impractical with minor hits/clogging under human power. Witness the development of Ricks folding CF props that don't have be banged back into shape.

As I understand it, water resistance on completely submerged stable pods was a bigger than on comparable displacement designs....

Hope this helps.

Porta

 

The best man powered boat (ride on)that i've seen is the Hobie"s "Mirage" system.simplicity itself.

 

It's been discussed on this thread a few times, but it isn't a particularly efficient system, probably less efficient overall than rowing and certainly far less efficient than a good propeller. It does have the advantage of being relatively free from weed entanglement problems, though, plus the way that the flippers fold up flush with the bottom of the hull is useful when beaching. Apart from the poor efficiency the other main disadvantage with the Mirage drive is that it won't go astern.

 

Hi,

I have a couple questions about positioning of the center of mass vs center of bouyancy (fore and aft). Would you expect the relative position to be the same for cat and a mono? Is there an advantage to having the bow a little lighter in rougher conditions if the hulls are the same on both ends? And I imagine the outriggers need to be included in this calculation for the mono.....
Thanks, Glen

 

I respect and accept your opinion but I think you are wrong.

 

ahhhh, seems we might have a little competition going on? Pass over the popcorn!

 

One of the things that could make hydrofoils more useful is adjustability. You need lots of lift at a low speed to lift off. Once you are up and going faster you quickly need to reduce the lift and mostly the drag to keep going faster. When you are faster, you just don't need the area required to get lift off. I'm thinking about T foils. Or you could sweep the foil which effectively reduces the camber, or you could reduce the camber. You could even reduce the area but I don't know a practical method.

 

sounds like an F 111 ?