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That looks absolutely amazing. Super cool that you can maintain elevation at less than 6 MPH — I was expecting it to be closer to 10 or 15 MPH.
by gnicholas 2y ago
That looks absolutely amazing. Super cool that you can maintain elevation at less than 6 MPH — I was expecting it to be closer to 10 or 15 MPH.
- RajT88 2y ago6mph is nothing to sneeze at on the water, in terms of the power it takes to sustain that kind of speed. A person paddling can't sustain 6mph for very long, if they get there at all.
- Retric 2y agoWorld record for a human powered hydrofoil is 21.3 mph. https://en.wikipedia.org/wiki/Decavitator https://en.wikipedia.org/wiki/Decavitator 6mph looks a lot more reasonable in that context.
- gnicholas 2y agoSure, but a person paddling isn't hydrofoiling, right? They're using their arms instead of legs and contending with tons of additional friction/drag. I see this as being akin to bicycling, since it uses the same muscles.
- RajT88 2y agoHere's what I am getting at... https://youtu.be/SDX3Hz2gsas https://youtu.be/SDX3Hz2gsas A guy on one of these doing the minimum speed. He doesn't look like he's casually pedaling, no? It's probably harder to maintain 6mph than you might think.
- malfist 2y agoEh, it's hard to tell power output from pedaling cadence unless it's a fixed gear ratio. Most people pedal between 70-100 rpm regardless of the watts they're producing.
- diydsp 2y agoThere are some clues in their body language. they appear to be straining. And the pedal movement looks a little jerky, as if the load is changing dynamically in relation to the effective flywheel/inertia of the system. Spinning a higher speeds with less torque is supposedly less tiring. So they might want to gear this down a bit and include a larger flywheel/inertia. Very impressive device tho. Maybe a hybrid approach with a solar panel for charging on the beach...
- newaccount74 2y agoTo me it doesn't look like it they were struggling with the physical exertion, but it does seem like they are struggling to properly hold on to the boat. It looks like the boat suffers from poor ergonomics, and needs some proper handles for holding on and steering.
- schiffern 2y ago>A guy on one of these doing the minimum speed. Counterintuitively, that probably makes it harder. With any wing, the faster you go in level flight the less drag is caused by lift. This strange fact is because moving a large amount of fluid slowly is more efficient than moving a small amount of fluid fast, and a faster wing can interact with more fluid mass per second ("m dot"). https://en.wikipedia.org/wiki/Lift-induced_drag#Calculation_of_induced_drag https://en.wikipedia.org/wiki/Lift-induced_drag#Calculation_... Since skin drag increases with speed, adding these two drag curves together forms a 'valley' in the overall speed-vs-drag curve. Going slower or faster than this ideal speed will result in increased energy per mile. The math is better explained in David MacKay's brilliant ebook, 'Sustainable Energy Without the Hot Air.' https://www.withouthotair.com/cC/page_269.shtml https://www.withouthotair.com/cC/page_269.shtml
- cfn 2y agoThey seem to be struggling a bit and the there's no wind or waves. Maybe coupled with a battery like an ebike it might be sustainable for longer than a few minutes.
- kitd 2y ago6 mph is a gentle paddle in a rowing shell, albeit using an additional set of muscles.
- viraptor 2y agoIt depends what they're paddling in. Long, slim racing kayak - easy. Short whitewater kayak - impossible.