hey everyone , im building first board with a center channel, the channel starts at 5" wide and fans out to 9" out a diamond tail, length is 20" and board is 4.8" long (WAKESURF BOARD). My question is on the depth of the channel at end of tail, right now i have it at .250 depth out the back, would this be effective depth for lift for 10 to 13mph speed . the board starts at single .250 concave from nose tip to channel then flat out the back.
That sounds like a safe “middle of the road” depth for starters. A couple of more important questions are… How steep are the sides of the channel going to be? And how hard or sharp are the edges and corners of the channel going to be? These will likely have a greater effect on how it feels then the exact depth.
Also, do you realize that a primary effect of channels is how they stiffen up the board? Not unlike folding a dollar bill, you are essentially doing the same to the fiberglass skin, substantially changing the form stiffness, reducing flex and also where it bends. All of which, may require adjustments in the amount of rocker, its placement and your glassing schedule. It isn’t just about the water flow or potential lift from the depth of the channel. Additionally, since this is a wakeboard, these issues may also effect your ability to slide the board sideways across the water.
Some fun stuff to consider before you get too deep into the shaping.
i plan to bevel the edge so it wont have a super locked in feel , the customer likes quad fins so doing 360's is not big on his list , he just wants speed and the ability to get air wakesurfing. My boards are made with 3# eps with no stringers thickness is 1.375 and tail thickness is 1". i have been useing 4/6 cloth on deck and bottom so boards last a long time even though they may weigh .5to 1# more then a lighter build. i also use a low rocker of .5" out the back.
Depending on the lift effect you want to get, trapping the water and forcing it out the back rather then letting it leak out the sides is important. If you angle “bevel” the sides you might want a harder edge. If you “bevel” the edge, you might want to have steeper sides to the channel.
At the same time you don’t want to create a negative tracking effect that messes up the overall function of the board
Sounds like you understand the basics of this. I would start with a bit softer edges and then build them up as you test till you get the water directing out the tail and no negative tracking effects.