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Grip physics?



 
 
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  #21  
Old March 27th 06, 09:14 PM
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Hi J,
Glide and grip is all about having the proper ski for the proper
person.

Say you weigh 100lbs. Your ski be it wider or not is flat under your
foot(grip zone)
at 120lbs the skis are no good for you as it would take 120% of your
total weight yust to get grip.The ideal ski for a person with 100lbs
weight is one that is flat at 75lbs. This is because on every step you
have to flatten the ski to get grip.
Sure a lightweight person could get more skibase in the snow if they
get a wider ski.
This has nothing to do with glide or grip. A wider ski does not glide
faster or grip better if the skis have not been selected properly.
The optimum is to have your skis selected by a competent ski shop.
RW

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  #22  
Old March 27th 06, 09:47 PM
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RW,
Thanks for that info! I had figured out that part already, although I didn't
know those percentages yet.
I meant to wonder, how a significantly wider ski with the same (correct)
flex properties for the athlete's weight would compare for grip and glide.
All the same dimensions, just 10-20% wider, and as said perhaps a bit
thinner if that works out that way to accomplish the correct pre-tension.
The fact that the answer is not readily available gives me the impression
that perhaps this is not investigated often, at least in recent times.
Would two athletes, each 60kg and 100kg, both 1m85, be recommended the same
ski length, shape and width, just different tension? Joseph already
expressed that he notices he has a definate edges over lightweights when it
comes to gliding downhills, easily explained by weight/frontal surface ratio
as air resistance is a big factor there. I'd love to know if he could
benefit from wider or even narrower ski's for grip, and if it would cost him
(fast and slow) glide or actually improve that further.

J

"rw" schreef in bericht
oups.com...
Hi J,
Glide and grip is all about having the proper ski for the proper
person.

Say you weigh 100lbs. Your ski be it wider or not is flat under your
foot(grip zone)
at 120lbs the skis are no good for you as it would take 120% of your
total weight yust to get grip.The ideal ski for a person with 100lbs
weight is one that is flat at 75lbs. This is because on every step you
have to flatten the ski to get grip.
Sure a lightweight person could get more skibase in the snow if they
get a wider ski.
This has nothing to do with glide or grip. A wider ski does not glide
faster or grip better if the skis have not been selected properly.
The optimum is to have your skis selected by a competent ski shop.
RW



  #23  
Old March 28th 06, 06:50 AM
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wrote:
rw wrote:


The place I bought the skis did a thorough job of fitting and marking
them. They used a digital deflection micrometer to measure the
deflection for my weight. They also marked the skis individually at the
various deflection depths (0.0, 0.15, 0.1, 0.2, 0.3) fore and aft. And
recommended which one is right and left based on leg measurements. Also
very specific written instructions for which markings to use with what
type of wax, etc. There was a reason I drove 2 hours each way to go to
that store! ;-)


The markings 0.1, 0.2, 0.3 (millimetres, weight on both feet) and 0
(for 0.1 mm, weight on one foot) are used in Sweden, too (for hard wax,
soft wax, klister and special heavyduty multilayer wax areas,
respectively) - what purpose do the Norwegians have for the 0.15 areas
?


Question number two: I was under the impression that today's skis are
completely interchangeable between right and left leg (and that leaving
it to random choice merely results in a more even wear, not that uneven
wear would be a real issue).
Is there really such a difference between a normal pait of upper grade
skis? (I know that sometimes one ski can have a strong tendency to veer
to one direction, but that's usually considered a manufacturing defect
or the result of some kind of collapse due to long use or damage.)


Anders (who is never afraid to reveal his ignorance)

  #24  
Old March 28th 06, 06:54 AM
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It is important to note that Jan is talking about wider or narrow skis
outside of the range of what is commercially available for normal
fitting. He's talking about what is optimal in a theoretical sense, not
what one should actually be looking for to buy today.

Do I understand you correctly, Jan?

Joseph

Jan Gerrit Klok wrote:
RW,
Thanks for that info! I had figured out that part already, although I didn't
know those percentages yet.
I meant to wonder, how a significantly wider ski with the same (correct)
flex properties for the athlete's weight would compare for grip and glide.
All the same dimensions, just 10-20% wider, and as said perhaps a bit
thinner if that works out that way to accomplish the correct pre-tension.
The fact that the answer is not readily available gives me the impression
that perhaps this is not investigated often, at least in recent times.
Would two athletes, each 60kg and 100kg, both 1m85, be recommended the same
ski length, shape and width, just different tension? Joseph already
expressed that he notices he has a definate edges over lightweights when it
comes to gliding downhills, easily explained by weight/frontal surface ratio
as air resistance is a big factor there. I'd love to know if he could
benefit from wider or even narrower ski's for grip, and if it would cost him
(fast and slow) glide or actually improve that further.

J

"rw" schreef in bericht
oups.com...
Hi J,
Glide and grip is all about having the proper ski for the proper
person.

Say you weigh 100lbs. Your ski be it wider or not is flat under your
foot(grip zone)
at 120lbs the skis are no good for you as it would take 120% of your
total weight yust to get grip.The ideal ski for a person with 100lbs
weight is one that is flat at 75lbs. This is because on every step you
have to flatten the ski to get grip.
Sure a lightweight person could get more skibase in the snow if they
get a wider ski.
This has nothing to do with glide or grip. A wider ski does not glide
faster or grip better if the skis have not been selected properly.
The optimum is to have your skis selected by a competent ski shop.
RW


  #27  
Old March 28th 06, 10:05 AM
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Thanks for helping me clarify Joseph, indeed.

As you must have encountered buying your 195mm cycling cranks, you didn't
have much choice, while they suit you fine, better than any of the 99.9% of
crank offerings, yet your build is nothing out of the ordinary.
Height/Weight, you're actually super close to average, had you not been an
athlete.
My experience from cycling is that the best thing to ride, is sometimes not
even for sale, while relatively easy to craft.
My own passion in MTB'ing is 29" wheels. Only came into existence in '99,
while the MTB was invested in the mid-70's. They used kid's bike tires as
those happened to exist with a wide casing, while before that all adults
rode 28" for all performance disciplines. Just no wider 28" tires existed.
MTB caught on (world-wide sports revolution, really), and 26" is what
everyone rode for cross-country cycling ever since. "No-one" ever questioned
the 26" standard, and who did, was silenced. The initial cost of making a
new tire (mold) of $5-10k was never coughed up, in a quarter century of
almost unlimited sales success with sporting goods costing $600+ average.
Now, 7 years after the introduction of 29" wheels, nearly everyone that has
tried them, is an instant convert. I won't bore you with the advantages they
bring, but the forum I moderate on mtbr.com is stuffed with testimonials.

I wonder whether ski width, especially for clydesdale athletes, could take
some of their disadvantages away.
As not all cyclists ranging from 1m40 to 2m10 can't find their optimum in
175mm cranks, or 26" tires, even tire width, I wonder how that translates to
skiing.

-is there an optimal width for classic skiing grip?
-is there an optimal width for gliding, be it classical or skating?
Are the above weight-unrelated, and coming down to the same width?

Not meaning to bash on centuries of skiing technology per se, just trying to
understand why things are the way they are. At least in cycling I know for a
fact that the business were more into keeping up a hype than to offer
customers the best cranks or wheelsize they could.

Do two top-fit skiers, one 1m80/60kg, and one 1m80/100kg get the same width
skis? If so, why? What width should I look for with my 1m94/82kg, or really
just focus on length and tension?


schreef in bericht
ups.com...
It is important to note that Jan is talking about wider or narrow skis
outside of the range of what is commercially available for normal
fitting. He's talking about what is optimal in a theoretical sense, not
what one should actually be looking for to buy today.

Do I understand you correctly, Jan?

Joseph

Jan Gerrit Klok wrote:
RW,
Thanks for that info! I had figured out that part already, although I

didn't
know those percentages yet.
I meant to wonder, how a significantly wider ski with the same (correct)
flex properties for the athlete's weight would compare for grip and

glide.
All the same dimensions, just 10-20% wider, and as said perhaps a bit
thinner if that works out that way to accomplish the correct

pre-tension.
The fact that the answer is not readily available gives me the

impression
that perhaps this is not investigated often, at least in recent times.
Would two athletes, each 60kg and 100kg, both 1m85, be recommended the

same
ski length, shape and width, just different tension? Joseph already
expressed that he notices he has a definate edges over lightweights when

it
comes to gliding downhills, easily explained by weight/frontal surface

ratio
as air resistance is a big factor there. I'd love to know if he could
benefit from wider or even narrower ski's for grip, and if it would cost

him
(fast and slow) glide or actually improve that further.

J

"rw" schreef in bericht
oups.com...
Hi J,
Glide and grip is all about having the proper ski for the proper
person.

Say you weigh 100lbs. Your ski be it wider or not is flat under your
foot(grip zone)
at 120lbs the skis are no good for you as it would take 120% of your
total weight yust to get grip.The ideal ski for a person with 100lbs
weight is one that is flat at 75lbs. This is because on every step

you
have to flatten the ski to get grip.
Sure a lightweight person could get more skibase in the snow if they
get a wider ski.
This has nothing to do with glide or grip. A wider ski does not glide
faster or grip better if the skis have not been selected properly.
The optimum is to have your skis selected by a competent ski shop.
RW




  #28  
Old March 28th 06, 05:53 PM
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J
A skier of 60kg should never ski on a ski which is closed at 100kg and
visa versa.
The skier of 60kg: And here is the kicker::::::: if is a super athlete
and a excellent classic skier.( see now we have to factor in the
persons skiing ability!!!!!) Should buy a ski that closes at 100% of
his body weight. A skier like Joseph who admitted he is not an expert
in classic technique. Should buy a ski that closes at 50kg or even
less. So when Joseph climbs or when he gets tiered he will still be
able to close the ski and have excellent grip.

Now to answer your question (Which is not real world)
For Joseph of course at 100kg he will be faster on the downhills then
any body else because he has more weight behind him.
Yes he could get a wider ski and have more surface for glide and grip
with the same length ski.
The wisdom is more base more glide more grip. Now this is if the skis
have excactly the flex for him. (His WEIGHT his SKIING ABILITY = SKI
FLEX 100kg - 25%= 75kg for a intermediate skier)
I hope this was helpful

rw

  #29  
Old March 28th 06, 06:13 PM
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Anders,
I do not work with a deflection micrometer so I can only guess.
But it looks like
1. The thing with left and right ski is probably just a guide not to be
too concerned about. There is no left and right ski in today's world.

2. of course he will have a short grip zone for klisters. No rocket
science there either.
One applies Klister wax just under the foot. (heel to toe) no more or
the ski will have no glide.

3. the numbers. 0mm = 100% of bodyweight on ski closed
1.5mm = ? 80% of body weight on uphills
2.0mm = ? 70% of body weight grip when he is
tiered
ask him about the numbers I have no clue
rw

  #30  
Old March 28th 06, 06:46 PM
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Hey guys - Here's a link to a flex sheet from my website which may
clarify some of those mysterious numbers that get put on the side of a
ski:
http://www.engineeredtuning.net/ClassicFlex.pdf

As for a the possibilities of better grip from a wider ski - I would
suggest that the overwhelming factor determining grip is the amount of
dowforce the skier can apply through the wax. Nobody - not even the
best in the world ski on classic ski that closes at 100% of body
weight. I just brought all of Kris and Justin Freeman's skis home from
Spring Series. There are a few pairs I haven't seen before and I'll
take a look at them. But the stiffest pairs those guys carry close (to
0.2mm residual camber under the load - "closed" is not an absolute as
the error in measurement would go sky-high) at something like 67% or
68% of body weight. Anyway - I don't think that a wider ski would help
grip in the least - at least not before it completely killed the
handling characteristics and running speed of the ski.

A while back in the thread I think somebody mentioned that it's almost
impossible to find skis stiff enough for a 100kg guy. That's not true.
There are plenty of very stiff skis out there. I've got half a dozen
pairs of used sis in my shop which are too stiff for most guys so
they're just sitting here collecting dust. The big problem with skis
for a guy that size is finding a pair that is supple - something that
can keep the wax clear of the snow, but then flattens easily and loads
the wax pocket well.

Just my two cents...

Zach

 




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