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CNN's French inventor makes 'beautiful' flight across Channel on hoverboard reports that:

"French inventor Franky Zapata has successfully crossed the Channel on a jet-powered hoverboard for the first time, after a failed attempt last month.

Later in the article it says:

The inventor said that he tried to "take pleasure in not thinking about the pain," even though "his thighs were burning."

What is it exactly about flying a Flyboard across the English channel that made Zapata's thighs burn? 20 minutes of standing shouldn't be that stressing, what is it exactly about flying this board that requires so much muscle activity that it would be painful?

Franky Zapata has successfully crossed the Channel

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    $\begingroup$ Looks like you have never skied :) $\endgroup$
    – Martin Argerami
    Commented Aug 6, 2019 at 15:54
  • $\begingroup$ What was his airspeed again? That's a lot of energy hitting your body. $\endgroup$
    – Mast
    Commented Aug 7, 2019 at 6:58
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    $\begingroup$ @Mast Is Zapata European or African? $\endgroup$
    – dotancohen
    Commented Aug 7, 2019 at 12:13

4 Answers 4

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He's using the angle of his legs to control the attitude of the platform (and as a result, the direction he's flying in). So he can't take a relaxed pose, he's standing with his knees slightly bent the whole time.

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    $\begingroup$ I see, thanks! Hmm... I don't yet understand why it's necessary to have knees bent though. Most two-wheeled electric vehicles (e.g. Segway) let you move/drive forward and backward just by leaning a big, you don't need to bend your legs. I wonder what he's doing exactly that requires bent legs. Possibly because there is no road in this case, so no encoder... $\endgroup$
    – uhoh
    Commented Aug 4, 2019 at 13:32
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    $\begingroup$ @uhoh -- maybe because it lacks a vertical pole to hold on to, like the Segway has? $\endgroup$
    – quiet flyer
    Commented Aug 4, 2019 at 13:56
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    $\begingroup$ @quietflyer Since it's the inventor doing the flying, if it needed a vertical pole I'm sure he would have added it. I think it's more related to there being no contact with a fixed surface like the ground. Although... the pole wouldn't look cool, and Zapata does want to look cool, so maybe the burning thighs are the price one pays to fly without a handle. $\endgroup$
    – uhoh
    Commented Aug 4, 2019 at 13:58
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    $\begingroup$ @uhoh In an interview he mentioned that he's traveling at 160-170 km/h so simply resisting the wind takes a lot of effort. $\endgroup$
    – Sanchises
    Commented Aug 4, 2019 at 14:08
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    $\begingroup$ Even riding a Segway for an hour makes your legs start to ache, and that's much slower and more stable than this. $\endgroup$
    – Dan Hulme
    Commented Aug 5, 2019 at 12:23
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This is what he said after the 1st attempt

"When you fly with your body, even your hands affect the direction you want to go in. You feel the turbulence and the air through your fingers," Zapata told CNN. "It's like becoming a bird. But it's also very hard. I have to fight against the wind with my legs so there's pain too. It's not as peaceful as it looks."

https://www.cnn.com/travel/article/franky-zapata-flyboard-channel-gbr-intl/index.html

I imagine it's like a long ski run, where you're compressed down with every bump & turn. Do a mile long run at high speeds and you really feel it in the thighs.

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    $\begingroup$ It sounds like he's both the pilot and the aircraft, facing dynamic structural loading $\endgroup$
    – uhoh
    Commented Aug 4, 2019 at 19:50
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    $\begingroup$ Indeed it does. Like a parachutist and wingsuit glider. $\endgroup$
    – CrossRoads
    Commented Aug 4, 2019 at 21:03
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There is another bit of information worth mentioning in the CNN link in CrossRoads' answer

The flyboard looks like a chunky skateboard and is powered by five small engines. It is fueled by kerosene, which Zapata carried 104 pounds [47 kg] of in his backpack.

I believe that carrying a 50 kg backpack and balancing on a jet powered air skateboard combined delivers some serious strain on the pilot's legs.

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    $\begingroup$ And you really don't want to "hit the wall" $\endgroup$
    – amI
    Commented Aug 5, 2019 at 17:34
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There is no ground; he is responsible for balance during the whole high-speed flight. Imagine putting a large ball on a freight car of a speeding train and standing on top of it.

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    $\begingroup$ Image the train bumping up and down, and accelerating/decelerating continuously. You'd have to counteract a lot of forces to keep stable on top of the ball. This is more or less the effect that wind turbulence has on the 'pilot'. $\endgroup$
    – florisla
    Commented Aug 5, 2019 at 12:31
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    $\begingroup$ Oh, and the train and ball are going 100+mph $\endgroup$
    – Bill K
    Commented Aug 5, 2019 at 22:05
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    $\begingroup$ Aaaaand you have a fifty kilo bag on your back. Really, as much as I admire the machine, the real feat in this case is the guy who engineered the whole thing did all this hardcore athletics himself. For a minute there I felt like we all were back at the 1910's and it fest just awesome! $\endgroup$
    – Pavel
    Commented Aug 7, 2019 at 7:50

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