The physics of prone foil paddling vs surfboard paddling

When I paddle a prone foil board, I feel like the foil underneath is giving efficiency to the prone paddling. Ever notice when there is a current or wind, and you let go of your foil board and it drifts downwind at a really fast pace. On a normal surfboard, it doesn’t seem to drift at that fast of a pace. So my initial thoughts are saying the foil helps you when there is a current as the foil is engaging. Vice versa, if you are paddling against a current, I wonder if the foil makes it worse than paddling with a surfboard. Another scenario, no wind, no current. Flat water paddling the prone foil, does the foil increase paddle efficiency or does it hurt efficiency compared to normal surfboard. What about current caused by a wave? I’ve noticed that when duckdiving a prone foil it really absorbs the wave power alot easier than a normal surfboard where if you don’t get under the rolling wave you will get dragged back quite a bit. It’s amazing how the foil changes all the variables when paddling around compared to a normal surfboard

it is the foil engaging. happens more on bigger foils and tails as the stall speed is lower, which is about the speed your paddling at when going for a wave. it is noticibly harder to paddle a smaller foil with high stall speed onto a small wave without the assistance of the foil engaging. in bigger waves with plenty of power it is less noticible. current does effect, but not as much as rips running out through gutters. if you are pumping into a rip in a way that has the water moving in the same direction as the foil, your relative speed drops and you will be way closer to stall speed. alot easier to stall out, and the opposite if you go into current or rip that is flowing against the way you are going. hitting currents and rips side on is a pain in the arse as we all know.

hope this helped mate

So flat water prone arm paddling no rip, no wind. Will you be more efficient (distance per calorie) on the same volume surfboard or foil board (either big or small foil).

Have you foiled a break where the current is pulling you away from the takeoff zone? It’s awful. Non-stop paddling to stay in place while the surfers zip past you with a few strokes.

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i dont know about that. before foil engages i cant see how it would be more efficient especially with a foil dangling underneath it.

but remember what happens when u let go of a foilboard and there is wind and/or current, it seems to travel faster than a normal surfboard right, this is when its in the water, not while your pumping it. So maybe the foil helps when ur going with the current and wind? but worse going against?

I feel like it’s slower till it isn’t. But one thing I’ve noticed is when paddling out over a wave, the foil gets pulled down by the back of the wave which has made me in the habit of holding onto the nose at that moment.

are you sure its slower? think about it, if ur on a huge foil, and u start paddling and generating speed, and youre halfway speed from starting to foil, the foil would definitely help you more than slowing you down? but maybe from dead zero, its a bit slower b/c the drag outweights the lift generated? Im just trying to figure out the physics on how the foil will influence paddling.

Foil can only “help you more that slowing you down” if its able to reduce drag. And it can only do that by lifting some or all of your body and then board, therefore removing the drag caused by body/board. And you are not going to reach that speed prone paddling a sinker board on flat water. Knee paddling a semi-sinker with hand paddles while also rocking (pumping) maybe. Otherwise, defintely slower with foil attached.

Then how come when you let go of your foilboard and there is wind/current, you can barely swim fast enough to catch up to it. Whereas if it was a surfboard, it would be not going away from you as fast. Do you think that the current or wind going will help a foilboard more than a surfboard if going with the current, and also say the opposite is true if the current/wind is going against you?

Not sure if this helps, but one thing I’ve noticed is my board/foil setup is easier to paddle fast (either just paddling around or for a wave) when I’m sitting a little further back on it. This makes the foil pitch up slightly. I believe the relatively high AOA of the wing does help generate a little lift, even at paddling speed, to help lift me and the board up so the total drag is reduced. This creates a problem when paddling for a wave, though, because if I’m further back on the board, it makes it harder to keep the board down when popping up. When paddling with the board pretty flat, it feels more draggy. Yes, this is setup dependent but I think, in general, the foil is generating a little lift even when paddling and regardless of board angle.

i still think any instance where you notice a board with foil on it going faster than ‘normal’, letting go of it and floating downwind, getting onto waves easier, paddling at back of board etc, is all as a result of the foil starting to come into play at lowest stall speed. try putting on a tiny foil and tail and go try paddle onto small gutless waves. its wayyyy harder.

I thought we were still talking about “flat water prone arm paddling no rip, no wind”.

Another thing that happens when I’m a little far back, I think, is that little bit of extra AOA becomes a problem when the wave catches up to you. The foil brakes when the water starts moving up into it, and you miss the wave.

I usually lie a little further back on the board when the waves are really small and hard to catch. I want to say it makes it easier to catch, but am not completely sure. Will try and pay more attention and see what it does.