Can this be wakesurfed?

[NICKYPOO]

That's an interesting concept. The surface area thing makes perfect sense to me. The more surface area you have, the more it distributes the constant weight (rider). More, for argument's sake, square inches for a given constant force (weight of rider), the more it will distribute that weight making each square inch work less to stay above the water. Displacement. This equals less resistance or more speed due to a reduction of friction between the two surfaces. Fairly basic.

Flexible surface. I can also see how this can work. As you "weight" the front of the board, it flexes downward, effectively giving you more surface area. At the same time, this weight shift would "release" the back section up and allow the water release out the back even faster.

Now the $64k question; Is it worth it? Obviously the Hydroepic was not. I'm not sure what those things cost but, I'm betting they weren't cheap. Can you find a way to build enough of this effect into a board to make it viable while keeping costs down to a sub-orbital level?

[Surfdad]

Nick, help me understand how a wing works at semi-slow speeds. I've watched out the window of an airplane and seen ailerons and flaps moving and creating different curved surfaces, but I'm not sure I "get it". I would there there is some similarity to our little surfboards, save that we are ON the surface of the fluid and not ripping through it.

When you have a moment, I'd appreciate it!

I used to have a working relationship with Kendall who was the production manager for Hydroepic. He explained that there biggest problem was these boards had the seams along the rails and would break in heavy surf. They moved the seam to the bottom of the board, which resolved the problem, but the cash was already gone.

The folks at Aviso use a bladder molding system that eliminates the seams, but they can't put any of the internal framework in because of alingment issues and puncturing of the bladder under pressure.

Below sub-orbital. I'd bet not, some of those boards RETAILED at $1,500. That's like 5 price point boards! That dynamic hull is really interesting though. I know on that super thin board, it was just as you described, less and less friction and more and more goooooooooo.

I wonder if only a certain portion of the bottom of the board needs to have any of that morphing capability?

Wait a minute. I remember Nev Hyman and Josh Dowling creating super thin boards now. They flexed and morphed the bottom shape based upon the deck shape. So if they wanted a double concave on the bottom they shaped a double concave on the deck and then it flexed and flattenedd on the deck surface, the bottom took on the double concave shape. Then it would return to a flat shape when unweighted.

So maybe THAT would be the way to keep it sub-orbital. Do it in foam and wood and not molded hollow carbon. Those boards were crazy thin also, like 1/2" through the middle.

[NICKYPOO]

To save time- http://www.allstar.fiu.edu/aero/flight41.htm

The same laws aren't going to apply for surfboard shape because is surfboard is between two vastly different viscosity fluids, air and water, obviously. There are however some interesting principles that we might want to look at.

The allerons are just for rolling the aircraft side to side. The flaps that you see extend during landing and takeoff basically create more lift at slower speeds by extending the leading and trailing edges. The low speeds don't create enough lift for a wing that is shaped for optimum efficiency at cruising speed. Bigger wing = more lift.

$1500 for a surfboard? That's like buying a $50 towel. It had better be one badazz towel.

[Ewok]

To save time- http://www.allstar.fiu.edu/aero/flight41.htm

The same laws aren't going to apply for surfboard shape because is surfboard is between two vastly different viscosity fluids, air and water, obviously. There are however some interesting principles that we might want to look at.

The allerons are just for rolling the aircraft side to side. The flaps that you see extend during landing and takeoff basically create more lift at slower speeds by extending the leading and trailing edges. The low speeds don't create enough lift for a wing that is shaped for optimum efficiency at cruising speed. Bigger wing = more lift.

The flaps do create more surface area but they also change the camber of the wing, which is the relative distance for air to travel above and below the wing. The greater the camber, the greater the distance the air going over the top of the wing must travel relative to the air going under the wing. The difference in travel of the air means that air going over the top of the wing must speed up in order to meet the air at the back of the wing, and that is how lift is developed. The difference in relative speed of the air over the top vs air under the bottom creates a low pressure area on top of the wing which creates lift, literally sucking the wing and the aircraft up into the sky.

[NICKYPOO]

The flaps do create more surface area but they also change the camber of the wing, which is the relative distance for air to travel above and below the wing. The greater the camber, the greater the distance the air going over the top of the wing must travel relative to the air going under the wing. The difference in travel of the air means that air going over the top of the wing must speed up in order to meet the air at the back of the wing, and that is how lift is developed. The difference in relative speed of the air over the top vs air under the bottom creates a low pressure area on top of the wing which creates lift, literally sucking the wing and the aircraft up into the sky.

100% That's perfectly stated. I have no such gift. If we're talking about fins, then we're talking foils. Bottom shape, as it relates to the face of the wave, is more of a running surface. I think the tree were barking up is altering the angle of attack at the rails and trailing edge, in an effort to get the water to release as fast as possible.

...I think.(?)

[Ewok]

That checks. When you put more weight on your back foot you are increasing the angle of attack of the bottom of the board relative to the waters surface creating induced drag which slows the board down. The inverse is true when you put more weight on the front of the board, you are smoothing out the flow of water, reducing the AOA, reducing drag and allowing the board to accelerate "down hill" relative to the surface of the wave.

I don't think a flexible bottom of the surfboard would make it faster. I'm not sure about this but is rocker what helps the board pop and release off the wake or is it the lack of rocker that boots the board. If the rocker helps it to release I would think a stiff and flat board with a little tail rocker would be ideal.

[Surfdad]

Talking only my experience here. On that super thin board, when it was bent over in a negative rocker shape was FASTTTTTT. If I were concluding anything from that, it would be that wetted surface area is MOSTLY the key for down-the-line speed. I think this is consistent with other observations. A bigger/longer board of the same shape tends to go faster everything else being the same. So, I think, we can say that increasing wetted surface area makes a board go faster, so long as it doesn't increase drag like by burying the nose or some such thing.

I think also, like you guys are pointing out, the bottom shape or contour would have different optimum shapes depending upon where the board was in the water, or maybe it's in relationship to the wake and what the rider wants to do. So if he wants to turn hard to the right, perhaps the best bottom shape is a heavier concave over on the right side of the bottom of the board. Like you guys say, helping to smooth out or flatten the water flow on that side of the board. The opposite or left side of the board might even be out of the water, so it could be flat or even convex for all we care.

I think the deck side of the board and the rails need to be ridiculously stiff so that the rider can actually intiate turns, but the bottom, maybe what we want is for it to change shapes such that water flow is optimized? Did I state that last question correctly? I mean, we want the water flow that passes under the board to be optimized, so that there is the least drag or turbulance, but that would be a different shape depending upon any number of factors including wake shape, placement of the rider/board on the wake, direction of travel, etc.

Am I all wet?

[Ewok]

If we go much deeper into fluid dynamics I'm going to have to phone a friend. The greater wetted surface is sliding across the water as opposed to digging in the back end of the board. It's creating less turbulence at the end of the board which is the result of induced drag. Less drag means you go faster. I'm not sure if you'll feel the effects of a flexible board vs a very stiff board and just moving your foot position up and down the board to adjust the center of gravity of the board in relation to the waters surface.

I have an idea for a test mule board for you. Is it possible to build a board with a hinge in it or some sort of channel that initiates a point of flex? Then you could attach a strap or adjustable bolt to the top of the deck in between where you feet stand on the board which would limit travel of the flex. Then you could adjust the amount of flex the board gives you to find the optimum amount of flex or the perfect fixed angle and location for the shape of the bottom of the board if a flexible board is indeed faster.

The only true way to test this idea is to build two identical and very stiff boards. One board would have a hinge and the other board would not. Then ride the hinge board vs the straight board and play with the angle of hinge and see if there is any benefit. Here is a rough sketch of my adjustable hinge idea:

[Surfdad]

I think that can be done, but I'm not sure I am explaining the situation clearly. The super thin board that flexed like a mofo, wasn't at a right angle. The curvature of board was actually like an inverted rocker. So instead of the bottom curving up, it curved downward. The apex of that curve was between my feet. It was like taking a board and turning it backwards AND upside down.

I have made a TON of super stiff boards with the same basic outline, rocker, etc and none of them is as fast as this one. Now, I was able to shift my weight etc on that super thin flexy board and it would allow it...what is the term I'm searching for. Rebound, maybe? It returned to it's original shape when I unweighted it.

Having said that, would that change your test mule thoughts?

[Ewok]

I understand the flex you are talking about. I proposed the test mule to attempt to measure and test different levels of flex and angle to test the speed effects of flex vs no flex in a board. It might have been the super thin sidewall or flex or a combo of both, but a testing board with measurable angle or movement might help nail down a new board design.

On the test mule sketch above one side of the locking plate has a slot for the screws to slide through, by changing out plates and the length of the slots you can control the amount of travel and "flex" the board gives on the wake. In order to do a proper experiment you need a control, a perfectly stiff board made the same way, thickness and stiffness, as the test mule board so the only variable in the testing is the amount of flex you allow the mule to have. Then you can experiment with different angles or "flex" to see what is optimal for a board. Then you can attempt to build boards with the optimum "flex" to allow speed as well as maneuverability and air time. You might even be able to work with slingshot boards, I would think they might have a jig that stresses their flex boards to measure maximum angle and overall strength. This is assuming that a flexible board is the key to speed. You might find that a stiffer board will offer the same speed if it is as thin as your current prototype, with straight sidewalls. There is no way to be sure unless you build identical boards, one with the hinge, and one perfectly straight, in my head anyway. I have never built a surfboard and I've only ridden a few different boards, so I may be off on all my ideas, but it sounds like a scientific method to me.

[Surfdad]

Thanks for your input! It might be easier to test the rail component separately before movng on to the hinged board. That would isolate that component real quick and then the hinged concept could be built. I'm struggling with how to afix the plates and "hinge" component on the bottom such that the thru bolts won't just rip through the foam core when getting up, or creating a delam on the bottom.

Intereting concept!