dbabicwa wrote:Yes, it's broken in a straight line between the footpad steel inserts. Almost right in the middle. Interestingly, only a thin, first wood veneer cracked. Hopefully, a few glass layers would prevent this.
Unfortunately, took it for a ride in 20-25knts, for which wasn't designed for. 2-3m jump, landed dead flat. My bad.
Also, the 6mm bamboo ply is quite heavy, not sure how heavy your board will be!
If you like, I can measure my bamboo leftover and weight it to give you a clue?
Personally if my boards can't handle what ever I through at them, they fail the pass test. So if I can handle it in 20 to 25 knots then the board should be able to handle it. As for jumps and landing flat, well I think you need to make the board stronger, you can't always guarantee how you will land the board. Note your other option is to add more bulk to the board if making a new one, so some weaker (lighter) layers in the middle of the layup will make it stronger.
In simple terms your stress =
where M = bending moment. Take this as a constant.
y = distance from the middle of the board to the extreme fibre, if you have a symmetric layup, then y = half the board thickness.
I = moment of inertia = b*h^3/12
b = width of board, take this as a constant
h = thickness of board
With these two simple formulae you can easily and quickly see how much your stress drops as the thickness h is increased. For hollow sections the equation for moment of inertia is a bit different. Also if the stiffness/orientation of the layers are different, again the equations change. Hence why I said "in simple terms" to give a feeling for the changes.
What orientation did you use for the glass plies, how many plies did you use? 0 - 90 degrees or 35 - 135 degrees to the axis of the board for the top/bottom layer ? 0 - 90 would be strongest especially considering how you board broke. Often though the top and bottom layers are at 35-135 degrees so they are not the critical layer, then the next layer is 0 - 90 degrees. It's a way of protecting the critical layer.
Any way ....... how's it going Plummet, decided on your design, have you started building? Would be cool if you post some pics as you build the board.