If Ya re-read this post of --plummet--
You will note that :
Land-boards take WAY more punishment than a Kite board; so he probably has
a Good understanding of "Strength"
I'll start off by saying I haven't build a kiteboard yet. But i have build nemerous skateboards and a landbaord that flexes 130mm and bottoms out on the ground without breaking. Infact i have had no failures in all my builds. the techniques are very simalar. infact the landboard is quite abit more difficult than a kiteboard.
I say use Uni-direction mainly with a couple of layers of Double bias on the 45. Matt in either glass or carbon is the weakest form of layup. All the fibres need to go in the direction you want. 90\0 as handy states is pretty pointless. 50% of 90/0 matt fibres are doing nothing. So..l Uni directional will give you the strength lengthways. double bias on the 45 will get your torsional strength.
Get rid of the pvc core and use a more flexible/durable core. Bamboo is the shiz.
Strength is Different than stiffness.
Strength mostly refers to durability while stiffness is more associated with ability to flex.
A Kevlar board would be Strong, but stiff as a noodle.
A Carbon board would be Stiff,(resistant to bending) but carbon is like
an egg-shell, it will crack and and chip when point loaded.
A carbon board that is reinforced with Kevlar, will be Stiff, + it will have ample
ability to resist a point-load, (ie rock ding).
The core material used will determine the balance needed between stiffness and strength
A Thick board will need Less skins because the stiffness increases by the cube of the height ,(thickness).
The further apart your skins are, the stiffer the beam will be.
So a thick core needs less skins to keep it rigid so a lighter --Lb /cubic ft-- core will be needed
The heal of your foot can now crush the core because Ya need less skins to protect it.
& just How much Flex do Ya want or need to turn the board ?
So here is the start of Over-all Balance in the Matrix !
Torsional stiffness must be considered.
Imagine a 2 X 4 stud was attached to each end of your board at 90 degrees & sticking
Lift the end of one stud & press down on the other, ( This is Torsional stiffness).
Placing your Fiber orientation down the length of the board,on a + - 45 will Increase Torsional stiffness.
Placing your fibers on a + - 90 will decrease the Torsional stiffness.
Nether Fiber orientation will help with the resistance to crushing your core, (point load), unless
there is a shear-webb like ply or carbon keeping the skins from separating or getting closer
together. Then the + - 45 works better because there are More fibers crossing the sheer-web; but
then your Increasing the torsional strength as well IF their placed both Top and bottom of the board.
placing the + - 45 fibers just on the top deck will Not increase torsional stiffness.
So now were back to Just how strong does the core Need to be ?
If Ya use a Bamboo core, (on end-grain) Ya got resistance to crushing over 100% of the surface aria
but it's heavier.
If ya use 3 Lb / cubic ft foam, then it's Light but will crush after a bunch of jumps.
For me-- i prefer using a lighter 3 Lb ; then strategically place the bamboo or carbon or ply
sheer-web only in the aeries that are Most at risk for crushing. ie-- the center where the tie-down bolts are located, and under the heal of your foot, & ((don't forget about the front of your foot if ya ride tow side a lot)), especially if you land jumps on tow-side !!
The Carbon Uni is the BEST bang for the buck when looking at Stiffness. It should be placed directly on top of your shear-web. When purchased on the roll by the Lb, it's kinda cheap.
The moment they add cross fibers to bind the Tows of carbon, the price increases Drastically!
E-glass is a Good material for row-boats in a flat lake, I won't waist my money on this product
when we got :
***S-Glass which is near 30% stronger and 15% stiffer than e-glass ,--(( "for the Same weight" ))--.
Kevlar is a Good product when combined with Carbon. But a lot of people don't realize that
Kevlar fibers Don't wet-out like F-glass or carbon.Resin will ,(Encapsulate) the fibers of Kevlar, but Not saturate them. For this reason i prefer S-Glass.
& -- OH Yea : Don't even Think about adding MATT to your skins ; all it does is add weight and is fairly Useless .
Hopefully some knowledgeable people will be willing to argue with me
so we ALL can find that "Perfect" compromise in the matrix for our
next board ?