bigKam's latest core material

For discussions related to ski/snowboard construction/design methods and techniques.

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mark
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Joined: Sat Mar 24, 2007 5:37 am
Location: Western Mass

Post by mark »

MDF? :D Have you looked up the weight on that stuff?

A 4'x8' sheet of 19mm is something like 90lbs!

...and it has a tendancy to peel apart right down its middle when flexed, so be sure to use cap construction. ;)

There are wheat boards being made now that are very similar to MDF. They use urathane adhesives (formaldehyde(sp?) free) to bind them together. From working with them, I'd say they are lighter, and hold together better than MDF, but couldn't say for sure.
East_Coast_Style
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Post by East_Coast_Style »

CARDBOARD BOXES!

i have a background in downhill skateboard construction, and the site Silverfishlongboarding.com has a very large community of builders who post thier work and share ideas. one of the members used vertically laminated strips of recycled cardboard Coragate to create a natural, affordable honeycomb core. the results were very impressive, ultra light, very stiff, and next to free. he used stringers under areas along the rails and under the truck mounts to increase crush strength and provide durability. i personally have done some work with coragate laminate construction, and let me tell you, that stuff is INCREDIBLY strong when you use it right.
dbtahoe
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Location: Lake Tahoe

Post by dbtahoe »

I have yet to build a pair of skis but how about...

Bamboo.

Did you ever make a fishing pole when you were a kid. Bamboo has snap like nothing else. In addition, I think you could just buy 2 pieces of premade flooring to make the cores.

Maybe too much snap. It might not want to retain the camber.
BigG
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Post by BigG »

Bamboo has been used for years by Indigo.

It's a german skibuilder.

http://indigosnow.de

Geoff
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wildschnee
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xxxx

Post by wildschnee »

- indigo a german builder :|

a cleever marketig office

it s only show and a poser company.....


the work with cabon -

every child - nows . 100 % carbon in a board a big mistake is .....


look at pur ski . the work real with wood



burton
ride on .
plywood
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Re: xxxx

Post by plywood »

i somehow have to agree with wildschnee. the whole bamboo thing with indigo is not that great.

some time ago they wrote that they`re using bamboo cores. actually these were normal poplar cores with 10 stripes of 2mm thick bamboo between the poplar stripes - this could easily be seen in a short video of indigo and the guy who built the board also told so.
in my eyes it`s a fake to call this a bamboo core.

they may look pretty - but check who they work with: bogner
an other company that just sells their shit ten times too expensive.products for all the dorks driving a porsche cayenne around in st.moritz, skiing on blue pistes - to give them a so called "designed" gadget they can carry around and get the attention of all the other folks in the golf club ;)
plywood freeride industries - go ply, ride wood!
BigG
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Post by BigG »

I didn't know that.

Thank for clearing out this wrong idea

Geoff
collin
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Post by collin »

While I agree that Indigo looks like stuff for poseurs...

Kingswood uses a bamboo core and I've heard nothing but good stuff about their skis. Do a search on TGR for some opinions.

http://www.kingswoodskis.com/html/materials.html
------------------Take nothing I say as expert advice------------------
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wildschnee
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xxx

Post by wildschnee »

@ plywod - RIGHT ....


your wourds right and real 8)




bamo has long fibra in his groundbody . its for some thing good and other things not.
a new idea is a mixed wood like a dubbel T piner. becaues the glue is havyer than the wood , too much stringer in a core is not the finish line ;)
i think a mix in the middel of a board ore ski in head cuting bals and esche is a good way to save wight. littel balsa blocks in a chane with steps in palonia wood .a littel problem is bonding head cuting balsa... because a way we can make it at home.

burton
ride on .
dbtahoe
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Post by dbtahoe »

Popsicle sticks
Three31
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Post by Three31 »

Ive built with bamboo and it has given me good results. I got some left over flooring from a friend (9/19 x 6 x 72") Had to run it through a planer first to get the manufactured finish off though, but it was real easy to work with. When it comes to core material though, initially the thickness of a core should have a greater affect on a skis flex than the core material itself

I wrote this to Chaka earlier....

"How thick are the cores on your first pair? That should have a greater affect on the stiffness than the core material because it moves the strongest part of the ski, the fiberglass, further away from the centroid of the ski in the bending plane. Causing there to be a greater "I" Value (Second moment of inertia) which causes there to be less deflection under equivalent loads. Dont get me wrong, the core material will have an affect on the flex of a ski (and how its vibration is dampened and how much "energy" the ski has) But the thickness of the core and what materials you use on the outermost layers, i.e. metal and how many layers of fiberglass you layup, will have a much greater affect on the stiffness of a ski than the core material. Think of it as an steel I-beam If you have a taller I beam it will be stiffer than a shorter beam."

I would like to make some changes to that though...

The outside layers, fiberglass and epoxy, are under tensile and compressive stresses when flexed, but the inside layers, the core, is under shear stress when bent. This is caused bey the top layers being in compression and the bottom layers being in tension. Think about it like this, say you have a phone book and "roll" it or 20 pieces of paper (like a set of plans) and they are stapled on one end and you roll them up. once they are rolled upo thepaper on the ouside seems to be shorter and the inner layers longer. When actually what happened is that the the paper slid along itself when rolled up. When a ski is flexed, instead of the outer layer looking shorter than the inner layer from the two layers wanting to slide relative to each other (as an affect of the radius of curviture and arc length) the outer layer is put into tension, the inner layer in compression, and the middle layers, the core, is in shear (and minor tension and compression for the middle layers). So the core material will have an affect on the ski but not so much from its tensile strength, but more from its shear shterngth in the fiber direction. becuse most of the tension and compression and tension are in the fiberglass layers.

If you go to buy bamboo flooring for cores, buy vertical laminated and not the horizontal laminated. In horizontal laminated flooring there are glue layers in the shear plane. Although sometimes the glue layer can be stronger than the wood layer, you may get inconstancies or material breakdown where the glue is.

Another thing to consider (further research req'd) is material breakdown.... in this, how multiple loads can cause the bonds between the fibers to breakdown.

I was not able to find much good information on what woods hafe better shear values, but that would be a good place to start.

As For using trex or composite decking, I think that material is very dense and has a good impact and weather resistance (great for decking) but the structural characteristics of it seem to be horrible. Which is why you would never see a trex deck joist. Just try picking up a 20' long board, its like picking up a noodle, it weighs a crap ton and flops all over the place.
Brian
plywood
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Post by plywood »

may be a little off-topic. but here is what my wood supplier told me about bamboo:

every bamboo plank has to be build out of small bamboo pieces which get pressed together and glueged together. so it`s a lot of work to get such a bamboo veneer or whatever.
first thing: bamboo pieces glued together?! i don`t know, but when something gets glued together, the glue is always the weakest spot. and somehow i feel unconfortable with using small glued togheter pieces.
second thing: bamboo is really workintensive to produce. that`s why they get assembled in china. but who does assemble them? my supplier told me that he has no idea about this, that there are no certificates and it seemed like nobody knows where and who works for such bamboo things. as we know the labour conditions in china happen to be not always on our "western humanistic standard". and i personally don`t want to use wood that may get`s assembled by children or other working slaves...

this is one of the reason i avoid using bamboo. there are so many other woods out there!
plywood freeride industries - go ply, ride wood!
Easy
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Joined: Mon Mar 26, 2007 12:31 pm
Location: Enschede, The Netherlands

Post by Easy »

plywood wrote:may be a little off-topic. but here is what my wood supplier told me about bamboo:

every bamboo plank has to be build out of small bamboo pieces which get pressed together and glueged together. so it`s a lot of work to get such a bamboo veneer or whatever.
first thing: bamboo pieces glued together?! i don`t know, but when something gets glued together, the glue is always the weakest spot. and somehow i feel unconfortable with using small glued togheter pieces.
second thing: bamboo is really workintensive to produce. that`s why they get assembled in china. but who does assemble them? my supplier told me that he has no idea about this, that there are no certificates and it seemed like nobody knows where and who works for such bamboo things. as we know the labour conditions in china happen to be not always on our "western humanistic standard". and i personally don`t want to use wood that may get`s assembled by children or other working slaves...

this is one of the reason i avoid using bamboo. there are so many other woods out there!
Bamboo is laminated, but that's exactly the same thing as you do with the regular wood for your core. So it saves you the laminating process. The composites that surround your ski core will make sure that your ski stays in one piece, no matter how crapy the glue which is used for the core is.

The inhumane labour is a viable point, but logging in (other) 3rd world countries can also incorporate inhumane labour. Bamboo is better for the environment than normal wood, because it grows faster and needs less natural resources. So bamboo has is disadvantages, but the labour problem also arrises for tropical hard woods. It also has it's advantages, like it's material properties and the fact that it is more ecological.
alexisg1
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Location: Grenoble, FRA

Post by alexisg1 »

I did not take part in this conversation, but from what i've heard, the bamboo is probable the worst wood from an environmental point of view...

Of course it grows faster, but it needs a lot of water, and so it totally empty the water resource from the soil. In the country where the baboo industry is growing excessively fast, the rain forest (and all the species) is destroyed to be changed into huge baboo forest. Moreover, it produces a lot of leaves which poison the soils when they decomposite and prevent the same species to live.

I am no environmental expert so everyhting I write here has to be taken carefully, but I really think bamboo if far from being environmentally friendly...
I'll try to find some more scientific infos...
davide
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Post by davide »

I suppose that every tree, if grown in an intense way, will have negative effect on the enviroment.
In any Country it is possible to find local woods with great properties for ski-building, without looking for exotic woods. Balsa is the only one that has no equivalent in the Northern emisphere. Am I right?
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