Pumping a Foil Board Explained . . . with Skateboard

[Beasho]

Light Bulb Moment:

"Pumping a Board Left to Right should produce Lift and Forward motion similar to Pumping the Board up and Down."
- Beasho

You heard it here first.

Like a skateboard generating forward thrust from pumping left to right the foil board should be able to achieve the same forward thrust from pumping left to right.  The harmonics, or resonant frequency, favors up and down motion but should work left to right if you can turn fast enough.

A Few Quick Searches Later and OMG!     This guy figured it out.  He explains Pumping on a Skateboard and unknowingly explains Pumping on a Surfboard, "Accelerating" down the line, and explains Pumping on a Foil board. 

Its all about reducing the Radius of Curvature by standing up.

Ahhhhhhhhhh!  Creek and all those Crazy wiggle-waggle pumpers have been vindicated by some Khan Academy YouTube guy with fluorescent chalk. 

Summarized Here --> https://youtu.be/YgUmAwq1WG4?t=299

[Beasho]

Full Video Here:

[jondrums]

The skateboard ramp description translates exactly to riding a bike on a pump track. I think it also explains part of how pumping a shortboard on a wave works too. But with pumping a board on the wave I think there is another effect at play of letting the water flow bring the board up the wave, then using that gravity gain to accelerate down the face again.  In between, the legs are compressing or extending without any gravity potential being used or gained.

I never thought about it before, but the effect described in the video can also be used to generate speed through a bottom turn and big sweeping cutbacks.  I had always thought the speed came from gravity accelerating the surfer down the face of the wave and everything after that is losses, but now I realize that's not the case at all.

Very cool.

I wonder when we'll start seeing people try to pump side to side rather than vertically...

[PonoBill]

Remarkable. Sal Kahn will no doubt be thrilled to know that his chalk talk approach has replaced Powerpoint as a way to convince people no matter how many silly things you say while drawing. Cars move because they accelerate the planet? So obviously if I put two of them back to back and step on the gas they will go nowhere. Centrifugal force pushes him off the skateboard? Someone should have told him about inertia, Issac Newton, and, gee, I don't know, all that stuff from the ninth grade.

I'm assuming you're just kidding with this?

 

[jondrums]

huh?  PB - are you questioning the explanation of how pumping works in the video?  Did you watch it?

[PonoBill]

Yup. And yup.

I don't know how pumping works. It's a more complicated question than one might think. I could take a cut at it, for surfing, skateboards or pump tracks. I'd have to choose one or two because surfing doesn't really relate well to bicycles or skateboards. But I really don't care enough. I have some fundamental ideas but it would take a lot of time, some experiments, and a fair amount of math--more math than using a differential equation for display and nothing else.  But it's very clear to me that the author of this video doesn't know either. Anyone who confuses the fact that an automobile accelerating on the surface of the earth imparts a force and resultant acceleration on the earth (true) with the notion that it's the reason why the car moves (not) doesn't understand enough physics to prove much of anything.

Here's the underlying issue. If you're going to claim to understand the physics of something involving motion, the easiest way to check on the idea is to sum the forces with reasonable numbers and see if they work out. If you don't do that you're just waving your arms. I could do a very convincing chalk talk on how epicyclic motion demonstrates that the earth is the center of the universe--until I tried to reconcile the forces required and what the source of the forces are. If we're not going with angels pushing the planets around the numbers need to make sense. No numbers, no proof.

[TallDude]

From my purely conceptional physics understanding, all parts of our body store kinetic energy (more or less depending on age), right? We are in a sense, a spring. As our body is propelled into motion via a push / pull or incline on a directional vector. Any tangential change in direction creates friction or resistance. We use that friction or resistance to load up (store) kinetic energy in our bodies. We then release that spring (kinetic energy) on a new tangent. A which point we will more than likely become unweighted (overcome gravity to a certain degree). If this all happens as intended and velocity of our body increases, we will have fun    Obviously, this can work against us as well 

[PonoBill]

Well okay then.

[TallDude]

Works for me

[clay]

Sounds like it's being suggested that one of these will work on a foil:


That would be crazy impressive! 

I'm still working on up and down pumping.  This video gave me a light bulb aha moment, and practicing it a couple days later I was like WOAH it works!

[TallDude]

Vlad!!!!!!!!!! He is the International Skateboard Slalom King. That was fun Clay. Thanks'.

[Beasho]

Take it from the Pros:  Kai referenced the Huntington Hop
 
"And you gotta keep that board speed up some people hop some people go side to side"

Exact Quote here -->   https://youtu.be/ok7FDYCQjIs?t=27

[surfinJ]

The hop is a shortboard trick. Unweighting and weighting with the front foot to generate or conserve speed through flat spots. While it might be a viable foiling tool, with surfing it can be overdone and look bad, kind of like us continuing to use too many paddle strokes after we catch the wave.

In a skatepark or bike pump track (foilboard I guess), rising and dropping transitions a ridden by compressing your stance coming up, and pressing to extension coming down. This generates a lot of energy.

The pump is a series of small s turns, left rail, right rail...... to generate speed down the line to make a section or launch an air. This is very handy and is duplicated from the skateboard to a surfboard very easily.

[supthecreek]

interesting..... very interesting!
I for one am glad that what doesn't work, works.

ps
beasho.... remove the "s" from https when posting a link and the vid will appear instead of the link.

[Beasho]

Here's Khan Academy explaining the same thing:

L = M x V x R

If you can introduce a Radius of Curvature.  Then stand up to REDUCE the radius of curvature you will increase Tangential speed. 

Exact Quote Here -->  https://youtu.be/nFSMu3bxXVA?t=445

Full Video: