Very interesting design ideas:
http://www.dpskis.com/
Innovation in Powder Skiing
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For the story about DB -> DP look here: http://www.telemarktalk.com/phpBB/viewt ... sc&start=0
Well, I wonder why the price is not going down. They are now making classical wood core - carbon skis, rather then AirexC70 - carbon. And apparently they moved the production from US to China. You can get few hundreds pair of high quality skis at 80$ each (shipping included).
But as long as people is happy to pay a lot...
About the Lotus 130, I like the fact that the widest part is about 40/60cm from the tip.
Well, I wonder why the price is not going down. They are now making classical wood core - carbon skis, rather then AirexC70 - carbon. And apparently they moved the production from US to China. You can get few hundreds pair of high quality skis at 80$ each (shipping included).
But as long as people is happy to pay a lot...
About the Lotus 130, I like the fact that the widest part is about 40/60cm from the tip.
Yes - prices are just crazy - but people seem to pay it. Here in Munich there are some dealers selling ski for more than 800,-EUR and they have much more than one pair in stock!!!!
But that wasn't the thing i wanted to make you know. I've been watching the company (former db) for some time and what's realy interesting for me is the transition in shape and construction:
Last season they were absolutely convinced that traditonal sidecut still is optimal for powder skiing. This season it goes towards water ski like design - the way Shane McConkey went with his Spatula - but they try to improve things for harder conditions by combining a tranditional center with reverse sidecut tip and tail! Is this the way to go? Something that should be tried!!!!
The new construction with the wood core confuses me a bit. The former design with a carbon fiber structure (the foam just giving the shape) adapted from aviation design principles was just awesome. I spent some time thinking about using it myself for my own ski - too complex for the first try - but i want to return to it some time.
This might be the reason why they gave it up - just to complex for a comercial ski.
But that wasn't the thing i wanted to make you know. I've been watching the company (former db) for some time and what's realy interesting for me is the transition in shape and construction:
Last season they were absolutely convinced that traditonal sidecut still is optimal for powder skiing. This season it goes towards water ski like design - the way Shane McConkey went with his Spatula - but they try to improve things for harder conditions by combining a tranditional center with reverse sidecut tip and tail! Is this the way to go? Something that should be tried!!!!
The new construction with the wood core confuses me a bit. The former design with a carbon fiber structure (the foam just giving the shape) adapted from aviation design principles was just awesome. I spent some time thinking about using it myself for my own ski - too complex for the first try - but i want to return to it some time.
This might be the reason why they gave it up - just to complex for a comercial ski.
I talked to CB about it 2 yrs ago and he told me they had tryed woodcores but could not avoid delamination with them. that's the reason for the vertical stringers in the foam. CF skis with wooden cores was what they were aiming for all the time. Will be exiting to see if the cinese managed, (and not Goode)
Hmm - that's interesting - the only reason i see for moving back too wood is the dampening (absorbing vibrations). Do you know more details?
Delamination? Was this because of the enormous difference in stiffness between wood and carbon just making it pop off? The bonding with the epoxy should be absolutely the same!?
Delamination? Was this because of the enormous difference in stiffness between wood and carbon just making it pop off? The bonding with the epoxy should be absolutely the same!?
I suppose that it should be like this: the foam is quite stiff in compression, but it has poor mechanical properties in tension (I bought some Airex C70.75 to make a carbon seat for a paraglider). When the ski is bent, in the tip and tail the top and bottom carbon layer tend to squeeze together, so the foam can sustain the stress, but in the biding area the two layers tend to pull apart, and the foam just breaks. The vertical carbon walls help to keep together the top and bottom layer.
I think it can be tricky in a factory to optimise this construction for mass production. But if you build ski in the house, it is not such a big problem. Airex C70 is easier to machine than wood, I think.
Probably, in the case of wood core, the situation is like the one proposed by Alex. I should try to do some simulations (FEM).
They said they add some kevlar to add dampering
I think it can be tricky in a factory to optimise this construction for mass production. But if you build ski in the house, it is not such a big problem. Airex C70 is easier to machine than wood, I think.
Probably, in the case of wood core, the situation is like the one proposed by Alex. I should try to do some simulations (FEM).
They said they add some kevlar to add dampering
Bending a ski means tension on the lower laminate (maximum close to the base) and pressure on the top layer. These forces will shift both layers against each other. To compensate the forces you need a connection between both layers taking the shearing forces. This can be implemented by a complete core or by just joining both sides with a small but strong "wall" (think of an airplane wing construction). If you use carbon fiber for this it almost prevents the shift - foam or wood is not that stiff so it will allow a certain amount of movement. Consequently you gain a lot of stiffness with minmal weight.
What davide mentions is the buckling of the shell due to the pressure in the laminate. This can be well compensated by a foam. Airex or Rohacell are ideal for this.
What davide mentions is the buckling of the shell due to the pressure in the laminate. This can be well compensated by a foam. Airex or Rohacell are ideal for this.
Thats an interesting point Davide. My consideration simplified the ski to a structure were forces will affect from the center (like the mentioned wing of an airplane). The center part of a ski is almost rigid and forces from the binding will directly go into the top layer.
You mentioned doing some simulations with FEM? This would be a very interesting thing that may lead us to engineering a much better mechanical structure!
You mentioned doing some simulations with FEM? This would be a very interesting thing that may lead us to engineering a much better mechanical structure!