Hydroplaning Rowboat

Hi, Skip--I wanted to get back to you on this. It looks like you may have been involved with Animal Dynamics/Malolo? Didn't mean to harsh out on your work, if so. What you're describing--vertically oscillating horizontal fin, mechanism above water--looks like the opening photo on the BBC article you mentioned.

Things I like:
Oscillating propulsion (big "actuator disk" of the "linear propeller")
hinged foil
mechanism above water
means of controlling vertical oscillation of rider
no hull
general minimalism and lightness

Things I'm not as enthused about:
Any up-and down motion (central stabilizing fin has drag)
Hard to control pitch (?)
Pedal only, no arms or trunk
Rotary cranks give no mechanical advantage at top and bottom of pedal stroke
Craft sinks if it's not moving (I'd assume)
I don't see any mechanism for variable pitch (maybe not needed?)

The article is pretty fluffy, without a lot of specifics. What I can't see is the mechanism that turns rotary input to oscillating output. Are there any videos? I'd like to see it in motion.

I have read that the real limiting factor to efficiency/speed is the cardiovascular fitness of the "engine," as you state. It's why sea kayaks, which don't use as many muscles as rowing shells, or canoes, which have a comparatively short power stroke (jab) are competitive with shells, which to my earlier way of thinking they "shouldn't" be. Certainly over distance, it's not as important exactly how low-drag you are or what your peak power is, or stroke length, or whatever--it's whether your pilot has the aerobic capacity to keep up the motions required to activate whatever powertrain layout is chosen over the long haul. So I see why you went with a displacement hull.

I'm not sure a planing boat has staying power either. Certainly, hydrofoils seem to be a short-duration application--most seem to be able to sustain being on foil for maybe a minute? Or I guess some stayed on foil over 2000m? But not 24 hours, for sure.

I'd be willing to bet that, even if one could get an HPV to plane, one couldn't keep it up for long. 100m flying start, for ten seconds? Oh, for sure. Might even get some aerodynamic lift there. 2000m, ~6 minutes? Um, I doubt flying. Maybe you could plane for that long. Longer than that, though, and yup, I'd agree with you that displacement is the way to go.

DaggerRo has such a wide stance because he needs a stable platform for his foils shuttling back and forth. I like flat-bottom quad floats for shorter L/B for planing, but they could also possibly be useful for negotiating big waves (articulated), even at lower speeds.

But both flat bottoms and short L/B are not an ideal configuration for displacement travel. Don't know if there would be variations that would couple the opposed, balanced, dual vertical foils idea with a goal of challenging the 24-hour record (or R2AK, or ocean crossing), but if so, I'd say go for it! Or encourage some ambitious and perhaps young person(s) to go for it. Make it a mechanical engineering semester(s) project. Mix and match whatever might suggest itself. (Just again--don't take credit for ideas that aren't yours. A simple "credit to Paul," when you're talking or writing about it, does just fine, for me.)

 

Hi, wet feet--thanks for the input. Not ignoring. I think rowing actually CAN provide non-intermittent power delivery, and have thrown out some ideas (I guess this gets appended below, so, "above?").
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What I personally don't like about pedaling is that you can't "coast." You have no "flywheel," like, say, a bicycle does, when it has a lot of momentum rolling down the road. You're always working against a lot of drag, maybe like riding up a very steep hill while seated, in too big a gear. The only experience I can draw on is pedaling a paddlewheel boat on a pond, and I absolutely HATE that feeling. It's like molasses. I get exhausted after a few strokes, but I have to keep up some reasonable cadence or I get stuck at the top of the pedal stroke. I have no leverage at all when the crank's in that position, so if I don't have some momentum built up to carry me through the "apex" and get me going down so the cranks get more perpendicular, I'm out of luck. Maybe it's better with a rotary propeller instead of a paddlewheel, or if one used gearing, or if I weren't such a wimp. But I do not like it, Sam-I-Am. Love bikes, hate paddlewheel boats, expect I'd hate pedal-powered, rotary-propeller boats, but it's not fair to judge without trying one out. (I'm not actually a rower, by the way. Have a rowing machine I barely use, have rowed Dad's dinghy--a Phil Bolger-designed Nymph) around. Fun, and I like the sensation, just not enough to do it every day. When I retire, maybe I'll go live by a lake.)

As an inventor, I HATE hearing and saying things like "if it were such a good idea, then why don't we see pedal-powered, rotary-propeller boats everywhere?" But it's tempting, here. We do see them, but extremely rarely. They're maybe like recumbent bicycles--a good idea, lots of theoretical advantages, but almost the only ones I see on my rides are pedaled by lovable cranks, usually fit old guys, usually retired engineers. I can't say why this is. Hard to control, maybe? Subject to tipping over? Heavy? They hold no speed records, but maybe because they haven't been given an honest try. Give my man Tadej Pogačar one. Maybe he'll excel at it. He seems to excel at every other discipline, so might welcome the challenge.

(Actually, come to think of it, what I just said above is baloney--ALL HPV speed records on land are held by recumbents, aren't they? Faired recumbents, on the flat, usually. Huh. Well, let's just load Mr. Pogačar into one of those, shall we? He needs to polish up his time trial skills, though, based on yesterday's results in the Dauphine. He's probably just using the whole stupid race just as week of training. That punk.)