Core Profile

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

Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp

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melvs
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Core Profile

Post by melvs »

So, basic question and I think I know the annswer, but just wanna make sure. The core is around 10-15 mm think underfoot and 3-5 at the tips/tails? How much does changing this a few millimeteres effect the ski?
-Pat
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bigKam
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Post by bigKam »

Pat:

you're right about the cores being 10-15mm underfoot. the last pair that i built, the Ahmas (click here to see them), had a max core thickness of 11mm underfoot, and the tickness tapered down to 2mm at the tail and 1.5mm at the tip.

i believe the core thickness affects the flex and performance of the ski a great deal. i would try to make the cores as precise as possible.
splat
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Post by splat »

Kam - no disrespect intended, but isn't that kind of a 'pat' answer?
I designed the Bro Model skis and did quite a few prototypes to get the flex and the sidecut where I wanted it. The core has everything to do with flex, the fiberglass giving the core flex characteristics stiffness, rigidity, elasticity, and durability. Once you have a flex pattern, stiffness of the ski can be controlled via glass. But the issues of stiff tail, soft tip, etc., etc., etc., can only be correctly finessed through trial and error.
kelvin
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Post by kelvin »

I agree with splat in the the flex (and core) of the skis is probably the most important factor in how a ski performs. If i remember correctly, the stiffness of a beam is related to the square (^2) of the cross sectional area. So small changes in core thickness can make a big difference in stiffness/flex.

Our cores are around 10-12 mm underfoot with a flat platform that is a little biased towards the tails. They then have a linear taper to the tips and tails, which are around 2.5-3mm. The skis seem to have a nice even/round flex, ala TUA :( . Compared to my atomic Teledaddies, they are all quite a bit softer. Having the tails a little stiffer, seem to give the skis 'pop' coming out of a turn.

Flex is mostly personal preference and conditions you ski in. When we designed our profiler, we pretty much made a shot in the dark and it seems to work out for us; the round soft flex seems to work for PNW conditions and how we ski. I definelty like it better than the stiff/hingy flex of the teledaddies. We haven't played around much with different profiles, but will definitely do so in the future.

-kelvin
splat
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Post by splat »

Tahoe Kam. I'm in Reno. If you're in town, let's have lunch.
You can reach me at www.pmgearusa.com
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littleKam
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Post by littleKam »

Splat, I'm actually leaving Tahoe in a week and probably won't be able to make it to Reno before I leave. But I ski Squaw everyday, so if you're going to be around within the week I'll be there.
- Kam S Leang (aka Little Kam)
splat
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Post by splat »

You guys doing anything to beef the underfoot portion of the core to hold screws better? Additional glass?
kelvin
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Post by kelvin »

We have put inserts in some of our skis and have put extra fiberglass in some as well. However, most are just a layer of fiberglass below and above the core. We haven't had any pull outs. *All our skis are mounted with tele bindings, we are fairly lightweight, and we (at least I don't) don't huck big cliffs.

I do notice a difference when drilling and screwing into maple or birch vs. poplar. The poplar is much softer and probably more likely to pull-out. Using a very hard wood underfoot may reduce some pull-outs.
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