Youd be miles ahead by learning from a pragmatic shaper like Dick Brewer. Surf history is full of foolish designers and their theories whove ultimately failed to “make the drop”. Literally and figuratively! To those who know, properly configured concave is a potent, proven accelerator.
different drag does different jobs …viscous drag = surface area in contact with the water ,turbulent drag = a contour or any thing that creates turbulence in the form of vortices that then get draged with the board because of the cohesive propertys of water ,pressure drag = changes in curve which cause water to move from regions of high pressure to low or low to high or low to high and back again ( change takes energy) induced drag =where a change is made to either the speed or weight or shape of the board to cause drag to start to happen,high and low turbulent drag = moving from stable low speed laminar flow to unstable high speed turbulent flow and onto stable high speed turbulent flow…all of these effects are present in the bottom of your board understand each one of them and what part of your board is dealing with each of the different drags and there is no need for this discussion… regards BERT
Bert, Many of my boards have been built so that once the initial shape has been evaluated for a while, a single design element (such as concave) can be added, modified or completely removed. Reasonable evaluations proceed logically, one change at a time. At every level, the addition of concave to my equipment, i.e. width and length, has resulted in significant gains of lift and velocity, with a corresponding loss of control. But inclusion of convex bottom contours can counter-balance the effect of the concaves, improving a boards handling at higher speeds. For me, its all about the feel, an intuitive, pragmatic process. ‘Scientific’ theories and opinions (while fun to discuss) offer little relevance in respect to that which I can personally create and experience. Bottom line: “Nothing ventured, nothing gained.”
Bret & Losos, I’m sure you’ll agree that understanding variables is really what discussions like these are about. Fact is they go on and on and on, the variables that is. Pinning down what we’re talking about, though not easy, is essential and makes solution and epiphany possible. We have to consider that the entire bottom of a board is never submerged unless it’s being duck dived. When riding a wave air is constantly entiring the area between the board and surface of the water in different areas. The more convex the board bottom is the less air is entertained and the more concave the more air is entertained. Obviously water is more viscous than air so if the mix under the board has more air in it one can postulate that there is less resistance. One thing seems a sure bet and that is as laminar flow is encouraged and less wetted surface is entertain drag is lessened and speed easier to accomplish. We can’t really expect there ever to be the kind of money it would take to make an objective scientific study to tell us what an ultimate configuration is. And frankly I don’t think there is one. So what we do is share our work and learn from each other. The more secrets we share the more we learn. Off to work, Rich
yes i agree but an under standing of the principles means you are less likely to venture without gaining ,amd more likely to venture further and gain more because you can evaluate the variables and weigh them up before ever building the board…but i suppose you have to build those boards to get the knowledge to know there not worth building???thats just part of being a progressive shaper is going on trips …thats probably why young shapers do radical stuff and older shapers who have been on all those trips have found that happy balance with out extremes and can deliver consistence peformance…they have found the edges ,the limits and worked there way back to simple reliable shapes… does anyone ever graduate from the school of surfboard design??? i dont want to anyway i have to much fun going to class every day regards BERT
hey rich did ya get the email on the air thing???by the way your work is up there and so are your concepts… regards bert
Bert, Thanks for your explanation on the different types of drag. I had lost sight of the principles and had fallen back on examples (mainly because I still don’t understand all of the principles at hand). Time to hit the whiteboard and see how these things all interact.
It is the high pressure of the concave which makes it faster.
Bump. can someone explain the theory in depth behind the 2 concepts.