In that last post we talked about how the reverse camber internal springer seemed to encourage more rail twist off than anything else. Certainly not what we were looking for in that build. That got us thinking a little and we wanted to sort of think out loud here for a minute. Now, this rambling may turn out to be crapola, but it’s the process we go through, sort of observing and trying to understand the concepts then applying those to our own design. Now we are going to go back an harp of the lift vs push concept. Push would indicate that the water flow was coming from behind the board, somehow pushing the wake surf board forward. That simply doesn’t exist, and in fact the forces that we are working with are lifting coming up the wake face. It’s true in wakesurf wakes and ocean waves. So if we are driving forward down against the lifting forces, where would the force of the wake impact the wake surf board? Or maybe a better question is HOW would it impact the wake surf board?
The water flow is UP against the bottom of the board and the rail line closesest or IN the wake will have the greatest amount of those forces applied. The simple reason is that MORE of that side of the wake surf board is in the water. So in effect the rail that is in the water will have lifting forces upward and the tendency will be to flip the board up and away from the wake. We’ve all experienced that where we move our feet closer to the rail that’s in the water and typically we have to instruct newbs on just that thing. So those forces are more pronounced on the inside rail than on the outside, and in order to balance the wake surf board we have to put more counterbalancing force, via weight, on the inside rail.
So that is a huge explanation, but man is that powerful! We have all experienced that tendency for twist off and in fact it’s more evident than forces pushing against the longitudinal or length of the board. Now we instinctively know we need some longitudinal reinforcement, but the very first force that we tend to experience is with the rail twist off. We’ve experiemented enough with wake surf board design and also have surfed enough to know that an ocean wave and a wake surf wake are very different animals.
We are now reflecting on some recent design concepts that we want to think out loud about.
Remember this picture from Nationals?
What you can’t see in there is the deck side of the various wake surf boards. Now Keenan’s board has a concave deck. Pretty innovative in the surf world, and it tends to help with foot placement and providing extra leverage, but know what else it does? It creates a thick point out towards the rails. The thickest part of the board is moved away from the center and out about 2 inches or so in from the outline. As students of composite engineering you know that THICKER = STIFFER. So in effect that design element moves some of the stiffness out along the rail and that helps address that rail twist off issue, plus also, we believe, is a reflection of the designer picking up on the lifting force issue and addressing it. Or it’s just luck!
Now both Chase and Keenan have wooden center stringers, but James is basically stringerless with a healthy dose of Carbon Fiber around the rails. In previous version of the wake surf board that Chase rode, he had rail channels and a step deck and also imbedded perimeter “stringer”‘ish things. They didn’t go to the deck, but were imbedded in the bottom. The folks at Chaos, who used to shape for Chase, were most likely addressing that rail twist off issue. The curvature and also the step deck and stringer’ish things create a stiffer structure with the changes in the direction of the fiberglass and of course the wood. Another prominent shaper, Mike Walker at the Walker Project used rail channels as a means to stiffening the rail line.
So, all of these folks, including ourslves, are working with designs that in some way ahve reinforcements to help prevent rail twist off, each addressing it in a unique fashion. We’re not sure that any value judgement can be made on the manner in which it’s address, that is concave deck, rail channels, or carbon fiber wrapped rails, but each of the designs does in fact address it!
It’s interesting to see the parallels that the various shapers and designers are working with as the sprt and riding continues to develop.
So with that said, let’s go back to the drawing board and start a build that looks more closely at the rail twist off notion and working more closely with this notion of lift vs push. So we’ll start this build with our normal 1 pound density core material.
Here is a quick picture of the core of the newest wakesurf board, with the bottom rocker hot wired in. Now we don’t attempt to shape the deck at this stage for a few reasons. First is that one pound foam is really floppy and it’s hard to shape without creating damage until something is attached to the bottom or rails. So we leave the deck side full and “thick” because it offers additional stiffness.
We’re going to give some additional thought to our rail material and are leaning towards a full perimeter framework for this wake surf board build. We’ll keep you posted as we progress and hopefully have some lucid thoughts to pass along!