bi-oriented wood core (burton's style)

[fa]

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hi,
in burton's website there are pictures of the cores they use in their boards.
the "dragonfly" core (seen above) has parts -around the heel and toe area, where the wood is placed with the grain crosswise, 90 deg to the length of the board.
last year i tried the 158 "Cudtom X" that uses this core concept, and i was really pleased with the board's flex pattern (great edge-hold, solid, very precice feel when loading the edge).
im thinking to try a similar lamination, propably with not that many parts, a simpler version of burtons core.
i press with vacumn, cure temp ~55 oC, and i deal with the small (10-20%) springback i get by over camber the mold.
so, my concern about using this core is a posiible uneven spring back due to the diferrent grain orientention, that will result in a concave base.
maybe a fat hard wood sidewall would smooth things up, but still i am concern about possible deformations
any opinion would be very welcome,
thanks, faidros
(sorry for my bad english, its not my native language)
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[OnDeck]

Havn;t tried it myslef, but i doubt it will be an issue. The cured epoxy is going to bring everything (wood, composites etc) into shape with it...any "springback" is probably due to varying rates of composites contraction between the top and bottom layers.

I think the vertical shape will be detemrined more by by epoxy and composites than by wood grain.

let us know how it works out!

[chrismp]

we've tried it for this year's boards and imho it isn't really worth the hustle.
the edge grip doesn't improve noticeably. maybe if you use a harder wood for the horizontal sections it would work better, but i guess that would make for a different flex pattern.
i guess their lightning bolts are what really has an impact on the edge hold...

[MontuckyMadman]

i guess their lightning bolts are what really has an impact on the edge hold...

What?

[chrismp]

scroll down on this page and have a look at the video: http://www.burton.com/mens-boards-custo ... ens-boards

it's carbon stringers that go across the core beneath the bindings.

[skidesmond]

That's a pretty complex glue up of the core. Even if you used wider strips of wood it would take quite a bit of time using traditional wood clamps.

Wonder if it would work just as well w/ a traditional wood core and then use the lightning bolt FG.

[MontuckyMadman]

yeah it has to do something. Not your average marketing spin.

My snowboard freind in wa has been telling me about the dragon fly for years but he didn't have details so I thought it was a catchy name.

[fa]

thank you all for your replies
its true, this 500 pieces puzzl looks like a big pain. but i think MM has a point. it must have quite an effect on the flex.

chrismp, what wood did you use for the cross sticks? did you glued them with epoxy? any issues with the flatness of the base caused by the different grain orientention?

I think back in the 80s elan had used a similar core concept for their "rc" skis.
before i bumped into this burtons dragonfly i had in mind to try to improve the load transfer to the edge by inserting thin carbon flat bars in chanels cross routed to the top & bottom of the woodcore.

keeping it simple only down to the L-bolts is an other option.
an easy way of having them done nice and straight, might be to wrap carbon roving around the core and sidewalls before the layup (in two spirals crossing each other, something like the paterns in the pic below).
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it would propably be more efficient to have the cf on top of the glasss, but this way simplifies the layup and plus the carrbon roving stays straight stretched, in place.

concerning the bi-oriented woodcore im still woried about distortion in the camber, so i might run some test-vacuming when i spare some time
ill post feedback when i give it a try

[EricW]

My opinion: This core looks like one of those chicken or the egg things to me. Are they using a highly engineered core because they're using horsesh!t materials or are they using said materials because they have a highly engineered core. I saw one of these on display at one of the local shops last year. It looked like finger jointed crap with knots in it. Kind of like any glued up pine block you can get at Menard's or Home Depot. I'm also pretty sure this core is all pine.

You're better off using good wood with your own recipe of species. The best boards in the world keep it simple, I'd recommend you do the same and save yourself the headache.

Physics lesson inc:

In my mind we use different species of wood to prevent chatter. Every species has a different frequency at which it will vibrate. If you mix a few together and one starts to vibrate, the others will keep it under control. Basically it's a smoother ride.

If you've ever seen Galloping Gertie the concept is the same. The wind coming down the river had the same resonant frequency as the bridge. This was accidental but it caused us to start building bridges with different frequencies every 100 feet or so. That way if one section responds to the wind or some other influence, the sections on either side keep it under control.

Burton, I think, did the same thing by changing the direction of the wood in certain areas. Don't get me wrong, I like Burton and they've done more for snowboard than anyone. However, on the scale they operate and the manufacturing equipment they have, it can make sense to use lower quality engineered materials.

Anyway, that's my 2 cents.

[EricW]

So I did some more research on the bridge, apparently the failure was in the aerodynamics of the bridge not the resonance. DAMN YOU U of W PHYSICS DEPARTMENT FOR MISLEADING ME!

Either way, my original point still stands.

[skidesmond]

Good points Eric. For the avg ski builder, that is a complex glue-up of a core. But Burton must have the R&D for stuff like that. It would be very time consuming for you're avg home builder. They obviously are putting money into R&D to come up with that design.

But if they are using inferior material (ie knots in the wood) then it would seem a waste of R&D $$$$. Seems to me that a complex core like that you'd want nice straight grain. Come to think of it, you always want to use to straight clear grain for the core, IMO. A small knot or 2 probably won't cause a problem. But knots are a weak spot. But I suppose a lot of glue/epoxy will hold most anything together.

Side note: A friend of mine makes ski chairs. Some of the skis are 10-15-20 yr old skis but never used. I've seen quite a few high end skis cut open and say, "thats it".......thin strips of wood, knots occasionally, metal or foam in some...... To me the better the materials you start the better the end product. (assuming the build goes right )