Board build

[Devin Nelson]

Hmm. interesting. Now by cutting off the sides. wouldnt the glass lose some of its mystical powers?. And other than being structural is this going to dampen my Flex as much as a spine of BB?

Now what if i up the board to 34" and add the stringer would this wheelbase increase over compensate for the spine?

I could do the equation given above. But im not sure the exact number of flex BB has at that thickness.

Thanks for all the Reply's
Peace

[Eric Brammer]

Having made a few boards from cutting the edges off, and then reshaping the core to an asthetically desirable shape, using old Snowboards, I can vouch for the 'spine' concept. 1/8" Mahogany or Maple that's 3" wide will (if molded/glued in place--less effective if merely t-nut bolted) yeild a decent increase in stiffness, and even help in torsional flex a tad. However, I'd really advise that you learn about fiberglassing. Wet-wrapped, vacumn molding can do absolute wonders for strength and provide resilient bonding for materials that otherwise might not want to work together (such as foam and wood), BUT, having a good-looking finish is always a challenge with glass. I'll toss in one other 'Hhmmm" Idea to ponder; What if that 'spine; was vertically laminated wood already wrapped in glass? Find some decently beat upon OldSchool downhill skis, bandsaw off the edges (at an angle, thus keeping the sidewalls intact), and you've got a cheap, pre-pressed high strength beam to add to your deck.

Just thoughts, take from them what you will...

[Pat Chewning]

New idea. YES

What if i add a spine ..............

Would this affect the flex?

peace

Yes, a spine will certainly affect the flex.

In general, for these types of structures, the flex (deflection under load) is inversely proportional to the cube of the thickness of the material used (double the thickness and get 1/8 the flex) and inversely proportional to the width of the material used (double the width and get 1/2 the flex).

The flex is directly proportional to the cube of the wheelbase. (Double the wheelbase, flex is 8X as much).


The deflection at the center of the deck is: y= FL^^3/(48EI)

Y is the deflection at the center of the deck.
F is the force (the rider's weight, all placed at center of deck)
L is the wheelbase length.
E is the modulus of elasticity for the material being used (the stiffness of the material)
I is the 2nd moment of area for the X-section of material (width times thickness cubed, divided by 12)

You can see that you get the most effect with changing the wheelbase and the thickness of the material, much less effect when changing the width or the stiffness of the material.

Your proposed spine is a localized thickness increase which will add a LOT of stiffness and reduce the flex of the board.

[Devin Nelson]

New idea. YES

What if i add a spine on the botton, just wide enough to fit the trucks on.
It would increase its Structural integrity without making it as hea vy or as stiff as adding another ply. ?? Bonus:Wheel Clearance

Would this affect the flex?

peace

[Devin Nelson]

Yes me2, i think ive decided to go 3 lams, with a slightly smaller camber
Im still gonna keep the 30'' length and orig. wheelbase.

[Dave Gale]

I fear it will be tooooo nooodley at that wheel base!

[Devin Nelson]

Hello all. I have 5-60"x12" sheets of 3mm BB
I am looking to make PS style Camber-Flexy board
Im not looking to run cones with it, just something that pumps like madd
I was curious if 2 sheets laminated would be strong enough for a 144lb rider?
This is = to 6 ply's
I dont have the materials for doin Glass, and I know im going to get alot of posts to start out with a planker and concave. But i have no intention on wasting High quality wood on a plank.

I am well educated on board building and terminology, there is just one main question i have, IS 6mm of BB strong enough for a 144lb rider.
im looking to put around a 1" camber, no concave. and wil be around 30"
with an adjustable wheel base. 26.5-27.5

Thanks Much
peace.