Hello Garagedweller,
Ummm, just let me go and ask my wife. . . 
OK here goes:
- If there is more fore and aft grain orientation overall then the board will be stiffer (particularly if those fore and aft members are close to the bottom and deck, thus further from the Neutral Plane).
Regarding flex across the board, theoretically there will be more if the grain all runs fore and aft, I haven’t noticed any across the board flex at all, although no doubt there is some. A cross section of a very wide thin board is still quite thick proportionally compared with the fore and aft proportion of the board so there is going to be a lot more fore and aft flex.
- Lateral ribs are easier to bend to a tight rocker curve than fore and aft ribs, and they give the board a softer flex (all else being equal).
With the sandwich sytems which we use (4 &5 layer usually), there are always at least two internal layers, and they run at ninety degrees to each other . . . so if one layer is fore and aft, the next will be across the board, and if one is at 45 degres, the next will be at 45 degrees the other way.
With the Three layer system, you could run the grain in the tapered inside layer either fore and aft, across the board, or a combination of both ( fore and aft on the rail with acrossways internal frames) , but I wouldn’t suggest having a single layer running at 45 degrees because the board would be likely to twist.
- Regarding diagonal ribs and flex, double diagonal ribs give a softer flex than all fore and aft ribs, but the stiffness or softness of the flex depends more upon the overall thickness of the board in relation to its length, and also upon other factors like deck and bottom thickness, and the density of the materials used on the deck and botomm.
My experience has been that a dose of flex comes naturally in this kind of board, and it’s really easy to get a handle on how much flex you like . . . it really isn’t all that critical (at least with longboards). . . because gaining more flex via going thinner is kind of self tending. . . I have a 13’9" which is only 1 and 5/8ths of an inch thick, and although very flexy, it is really nice to ride. By going thinner you lose buoyancy, so it just naturally balances itself out.
I wouldn’t sweat it regarding flex if I were you, it’s not as mysterioso as it seems, and a bit more or less flex isn’t all that critical. . . a stiffer board still works fine, and making a board that is too flexy is unlikely with these systems because to do that you would have to go extremely thin.
-
Don’t put one diagonal layer on the inside without the opposing layer unless you want a twisted board
-
About the maximum/minimum number of layers:
Firstly, there is no maximum.
Secondly there is a minimum. For a wooden laminate to hold a curve there is a minimum of four layer needed. The three layer system is a little different, because it is like a truss, it has a flat deck with a bent bottom. . . and the curve comes from the tapered inside layer. You can’t do a spooned bent board like I do with 4 and 5 layer systems using the 3 layer system. The three layer system is ok for making a low rockered flat decked traditional longboard.
- No, you are not way off. . … as far as I know !
Regards,
Tom
