I would like to preface this post by saying that I am not an engineer of any sort nor am I very experienced at foiling.

After watching all these videos of people pumping like mad i thought to myself what about a foil built with a certain amount of flex that would facilitate the pumping action?

I know the foil needs to be completely rigid in the mast and leading edge of the wing to maintain stability and turning. but what if there was some flexibility in the trailing edge of the wing and lengthwise along the fuselage to create a whipping effect similar to the tail and fins of a fish that would increase propulsion?

Obviously the flex would need to be properly dialed in so that it aids the pumping motion not takes away from it. Also I don't really know how or what to use to build the foil.

It would be part foil part flipper and with the added propulsion maybe you could pump and coast like a bike rider instead of just mad pumping all the time.

What are people's thoughts.

I know of an experiment where the rear part of a monofin has been glued to the rear of the main wing. Didn't hear anymore about it, so I guess it didn't work, or at least wasn't improving things globally.

Maybe some rotational range on the stab may help, like these swimming fins:
www.ultimateswimfin.com/
or www.tecreationdev.com/articles.php

Or this new FYN surfboard fin www.fynsurf.com/ that rotates following the water flow. A simple experiment could be to make a stab stump with 2 fin boxes on the side, and add 2 Fyn fins.

But I guess the main issue is that differences in rider technique and physique now are much more important than the gear, it will surely chnage.

It would probably work to absorb the energy you put into pumping

Interesting idea. I feel like there's a few more as as-yet-unimagined design breakthroughs that will revolutionize surf foiling. Considering that what people are doing now was unimaginable only a few years ago ... who knows what the next changes may be.

That first video of Kai Lenny pumping back and catching 4 waves in a set was mind-boggling. And then ones following with people linking rides for 3-4 minutes in a row. Imaginative minds saw the potential for unlimited surfing without having to paddle. But the average surfer or non-surfer saw the inelegant monkey hopping and declared it an abomination in the wave world.

If the design catches up to the athleticism, and finds a way to make this work with half the energy expended, double the efficiency, and eliminates the style violations, then we'll really be onto something!

(disclaimer: I can't do this yet, but hope to eventually....and I fully recognize that the hopping and surf foiling in general is one of those things that feels a lot better than it looks....highly functional and satisfying, even if it looks a little goofy at times)

Select to expand quote

RAL INN said..
It would probably work to absorb the energy you put into pumping

It is worth it, if it allows the flow to stay laminar. The goal would be to avoid (partially) stalling the wing/stab during pumping.

A flexible stab could be helpful in turns, not just for pumping. A bit like the flex tails in surfing or windsurfing, and as our design wizard Kami here with his SUPs:
www.seabreeze.com.au/forums/Stand-Up-Paddle/Review/FLEXTAIL

Thanks for the reply's and interest. As I had said I am no expert in the matter it was more just an idea. It will be interesting to see how far the efficiency and propulsion can go as designs progress and evolve.