Science of pumping

Real good post here.

 

+1 SiSurfdogg dropping knowledge!

 

I feel that with skateboards, the pump is driven by angular momentum.

With a surfboard (without wheels) you are looking to the fins to creat your thrust. This thrust is created by driving with your back foot forcing more water between the fins. While driving with your back foot you force the board to a higher point on the face of the wave increasing your potential energy which is immediately converted into kinetic energy (due to gravity) as you move down the face of the wave. Drive with your back foot again and now your a pumping fool.

 

LOL. Rollerblading. Yes, that.

 

[video=youtube;saj542nSgwU]https://www.youtube.com/watch?v=saj542nSgwU[/video]

 

that's a pretty juicy-looking teet.

 

With a boogie board, you are looking to the rails to allow you to harness the energy of the wave. Same with skimboards like this guy...

[video=youtube;2Cu0VnsWNTI]https://www.youtube.com/watch?v=2Cu0VnsWNTI[/video]

 

WWWWWWWWHHHHHHHHHHAAAAAAAAAAAATTTTTTTTTTTTTTT!!!!!!!!!!!!!!!!!!!!!
That is insane. Guys needs a wheelbarrow to carry his huge brass balls in. Crazy.

 

ha! i think about surfing

 

You just saw this now? Look back to about June/July and we have a whole tread or two discussing this and Domke's other exploits. You'll enjoy it.

 

exactly.

 

The influence of pumping in terms of propulsion is limited to around half a horsepower or less, it's a small percentage of the propulsion equation, and gets less as the wave increases in power.

Most people want it to be more mysterious but it isn't.

 

This is something we continue to disagree on, but still... sometimes all you need is that half a horsepower to make that section. So in that sense, it's still significant.

 

Quite so, an extra 5 to 10 percent ( for example) is definitely significant... even one percent is significant.

I wonder what the efficiency is in terms of energy transferred into thrust? I seem to recall that marine propellers operate at about 30% efficiency. It might be higher with surfboards if dome right, but it's still using a foil section for drive just like a propeller so should be similar. If so then the gain would be more like 2 to 3 percent.

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The thread isn't about me, but I'll amswer your question anywway.. even though you appear to be taking the tack that if i don't currently ride a 'thruster ( and I don't) then I don't know what I'm talking about.. that's where you are going with this, right? If so it's a BS argument for several reasons.

I rode shortboards for 20+ years, including many years surfing full time at NZ's most consistent and well known point breaks... and yes I 'pumped' my boards. It's a myth that only thrusters respond to pumping. I rode singles and twins mainly, and they both respond well to pumping. My more flexible longboards are also designed to accelerate via pumping action, though the movements used are not as rapid in frequency.

Any well designed board will deliver gains of this nature during turns or weighting and unweighting.

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You're the man I'm sure.

Are you able ride a 70 pound board of 14 feet in length on overhead waves?

Not intellectually or physically capable, I mean is this a skill that you currently have in your surfing arsenal?

Lol you walked into that one.

By the way I ride two coasts.. east and west and beachbreaks are my main diet... where your shortboard types barely get a look in, just saying.

You seem to be offended by the fact that there is a known range to the amount of power which humans can produce via muscular effort... scattered your 'pixie dust' did I?


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Those Coils are tight. What are the dims on the MM