ok men. I'm about to embarke on my first twin tip build. been building longboard skateboards and landboards for years. so..... building skills are sweet.
I want to build a lightish wind board for chop swell and wave. Been thinking for a while and this is my idea. I want to stay upwind around 10 knots, really main wind this baord would be used in is 12-15 knots (using my 15m speed 3) but still be able to hold a line when the wind/chop builds to 20 knots.
So i've decided i need a wide, not super long board. but the tips need to be flexible to so they can bend when the wind is up sort of auto rocker. So hopefully it will hold a good like in light wind but not be too harsh through the chop.
138x47 rocker 1.5" with 5-6mm concave flatening out at the edges to have the last 50mm of so with no concave.
I intend to use 2.6mm bamboo as the base layer. then adding a couple more shorter layers tapering in to reach a max thickness of 8mm at the center and 2.6mm at the tips.
I'm still contemplating the glass lay up. at this stage i'm thinking 300gm double bias on the bottom with a stringer uni directional of carbon about 300mm wide. On the top i'm considering a layer of triaxle glass.
You might want to go a little narrower unless you are big. Otherwise it sounds ok if the bamboo you use is good stuff. Not sure you need any carbon on it though, especially on the bottom. I'd try something like what you said without carbon. Ride it and if it is too wiggly maybe add some carbon strips (narrower than 300mm) to the top, rather than the bottom, capped by a light glass layer just a few cm wider than the strips -that would stiffen it right up.
yeah not sure if carbon is required or not?.... It works best under extension. so the most efficient use of the carbon is on the bottom.
I would slap a layer of triaxial glass on the bottom. but i don't want the uni full width. thus the idea of the thinner carbon stringer. My theory goes that it will stiffen it up with but leave the tips and edges to flex under power and chop.
Note this will primarily be used sub 16 knots. So it needs to get up and plane really well.
Normally carbon goes on top to stiffen the board and increase reflex. Sounds weird but it works. On the bottom it can make a board too stiff and vulnerable to point loading unless there is a lot of it and the core is rather thin (a la brokite.com for example) Leaving the carbon on the deck still lets the board flex, avoids the carbon hitting rocks, and still increases reflex. I'm your weight and would stick to 45 or less width, especially at 135+ length. Really wide and you might need to offset the straps to heelside, which might not suit the riding you want to do -but that is up to your preference of course.... In fact it's all what your preference is, so good luck and enjoy. And show some pictures!
max 42 wide or toeside riding and general trickery = less control also board slap landings with super wide boards are uncomfortable
32 mm rocker - lightwind twintip works off flat rocker most effectively - raceboards publish volume so comparing twiptip and raceboard widths is not a good idea
bamboo sound interesting - not sure about your tip and centre thickness - sounds on the low side a little bit not 100% sure - i don't know bamboo
(i have shaped and layed up and riden about 40 -50 completely different board designs and hundreds of similar ones, i am always up for learning something new tho..)
"Normally carbon goes on top to stiffen the board and increase reflex. " Carbon is a lot better under tension than compression (ie more effective for strength on base, I would keep top and base layers exactly the same tho and both the top and base can come into contact with similar stresses at some stage. Putting carbon strips between the footstraps to stiffen up this area is asking for a world of trouble as this end point is exaclty where it will snap.
I just chucked out a van load of board making stuff - this made me feel inspired for the first time is years - mind you even the thought of epoxy make me feel sick lol