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Effects of weight gain on ski performance

post #1 of 21
Thread Starter 
It is said in many places that the perfect choice of a ski includes the skier's weight. What is the effect of too much (or too little) weight on a particular ski's performance characteristics? In my case I am 5' 10" and last year got 165 RX8's (Fischer.) They were fantastic. I now weigh 200lbs. What would the 10-15lbs I've gained since then do to the way they respond to me? In the more hypothetical area, what would an additional 25 lbs of skier weight do? What disadvantages would a 170lb male on the same skis have over a heavier skier, or advantages?
post #2 of 21
I cannot tell you what gaining weight will do, but can tell you that losing weight definitely made a differnce. I am 5'5" between 110 -115 lbs. Used to be 130-ish. Used to ski Atomic R:10-20s in a 170 (unisex, not womens) found that after losing weight I had to really work at making anything but very long, wide, fast turns. They became too long, too stiff, too hard. I was at first worried that I'd forgotten how to ski! Then I realized it was that the skis had outgrown me.

In order to make short turns or navigate trees and crowded slopes, I had to stomp on them so hard, it just became a chore, so i had to finally give them away and bought Dynastar (my 1st non-Atomic skis!) Skicross 9s in 165 which are just wonderful.

My guess is that in gaining weight, skis that were OK may become squirrelly or soft feeling. Or, you may find you like 'em better!
post #3 of 21
SMJ, a couple of hard days skiing and that weight gain will gone.
post #4 of 21
Thread Starter 
Quote:
Originally Posted by Taxman
SMJ, a couple of hard days skiing and that weight gain will gone.
If only that were so I bet I'll lose a lot over the season though. I think that the obvious effect is putting the ski into reverse camber too easily, thus very possibly making short turns easy. Question is will they lose stability at speed in longer turns?
post #5 of 21

Leave your backpack off.

To me, aside from even formerly dubious float, the obvious effect is to exceed the torsional stiffness of the ski, so that it lets out from under you when set on edge*.

Of course, a 10% increase in weight only corresponds to a (sqrt(1.1)-1)*100 or 4.8% increase in speed. So, ski 5% slower this year.








*You're on your own at low edge angles and on surfaces weaker than your skis.
post #6 of 21
Quote:
Originally Posted by SkiMangoJazz
If only that were so I bet I'll lose a lot over the season though. I think that the obvious effect is putting the ski into reverse camber too easily, thus very possibly making short turns easy. Question is will they lose stability at speed in longer turns?
I think the RX8s will be fine in that length at your new (temporary!) weight. The guy who convinced me to try the RX8s in a 165 last year weighs well over 250.

The issues with weight are related to the performance characteristics of the ski: what happens to the flex and tortion of the ski? Stiffer skis see less impact from a 5% change in weight than do soft ones. You will be decambering the ski a bit more this season, but they are are strong enough to hold the edge, anyway.

Just be aware; they may rocket around a turn while you keep going down the fall line.
post #7 of 21
SMJ,

The RX8 has a pretty wide performance range. I don't expect that you'll notice much difference from your weight gain.

Jim
post #8 of 21
I am 255lbs and pretty decent skier. I have been skiing for 30 of my 33yrs. I can ski almost anything well. I am guessing that Bode Miller at 205lbs can flex any ski I can...better.

As much as I love gear, reading about it, talking about it, and trying it....at some point it becomes the Indian and not the arrow, don't you think?
post #9 of 21
Quote:
Originally Posted by 12CSki
....at some point it becomes the Indian and not the arrow, don't you think?
Yeah, man, but it's SkiMangoJazz we're talking about here!
post #10 of 21
Thread Starter 
I'm glad to take my Indian responsibility! I look forward to doing what I did in my lighter days (of March 2005.)

It is an interesting topic though, and I was hoping to hear from you Comprex. Is that accurate?


One thing I'm thinking is that your dead weight isn't a major component of the pressure put on the ski, which is a function of the forces of motion, and the edge angle.

Torsional flex, also linear flex are put to more of a limit. But to what effect? Will they "slip at speed" as said? Or will they bite more and just not turn as easily?


Seems like too heavy is better than too light.
post #11 of 21
Quote:
Originally Posted by ssh
Yeah, man, but it's SkiMangoJazz we're talking about here!
Sorry, I am kind of new. Haven't had the chance to meet everyone yet!
post #12 of 21
Quote:
Originally Posted by SkiMangoJazz
It is an interesting topic though, and I was hoping to hear from you Comprex.
Yeah, OK, you caught me at 16lbs over. But I'm on 170cm

Quote:
Is that accurate?
It's just mv^2/R applied to a simplistic center-weighted ski

Quote:
Torsional flex, also linear flex are put to more of a limit. But to what effect?
Not sure there is just one answer.

The syndrome I've noticed most is that the tips hook up easily, then wash out when you commit to the turn. ssh saw me cursing at them too.

I think the significant point in the posts above is that you would have noticed problems last season as well, at high speeds and on steep terrain for example.
post #13 of 21
Quote:
Originally Posted by comprex
The syndrome I've noticed most is that the tips hook up easily, then wash out when you commit to the turn. ssh saw me cursing at them too.
It was the PACK! That's been bugging me all summer!
post #14 of 21
Extra weight would be a benefit on stiffer skis. The extra wieght should allow you to flex the ski into tighter corners at lower speed. It should also make it easier to keep the tails pressed onto the snow and keep them railing without drifting out, due to a larger gravity component keeping them down. With less weight you have to be very sensitive and frugal about where to put your weight to keep the ski down, especially when forcing it to flex tighter than it wants to.

However, if you have a less stiff ski, you may find it becomes overpowered sooner than you would like it to be.
post #15 of 21
Thread Starter 
Quote:
Originally Posted by Ghost

However, if you have a less stiff ski, you may find it becomes overpowered sooner than you would like it to be.
And my query thus is, what does that mean, a ski to be overpowered? What control and stability issues arise from it?
post #16 of 21

heavy

It's simple for me, extra weight hurts my athletic performance. I went to 216Lb and I could bend the ski but I couldn't perform. There are way more reasons to stay on top of your weight than bending the freakin ski. My friends calling me a load is one.
post #17 of 21
Thread Starter 
Quote:
Originally Posted by freeskinow
It's simple for me, extra weight hurts my athletic performance. I went to 216Lb and I could bend the ski but I couldn't perform. There are way more reasons to stay on top of your weight than bending the freakin ski. My friends calling me a load is one.
True dat.
post #18 of 21
Quote:
Originally Posted by SkiMangoJazz
And my query thus is, what does that mean, a ski to be overpowered? What control and stability issues arise from it?
Tip and tail breaking loose. Tip flapping. Difficulty tracking. In general, stability issues.
post #19 of 21
Quote:
Originally Posted by SkiMangoJazz
And my query thus is, what does that mean, a ski to be overpowered? What control and stability issues arise from it?
It means that if you are on a good hard solid surface and you tell the ski to make a sharp turn, it might just deflect instead of digging in and you won't be able to turn as hard as you would like to. F=ma, you now need more force to get the same acceleration, or make the same turn. No problem if the ski can give you that force, but if the ski bends instead of pushing you you might want a stiffer ski. I don't think you would find much of a difference in stability per se.

Edit: what steve said, when the tip and tail deflect because the force is too great for their torsional stiffness they let go of the snow.
post #20 of 21
Don't get back on 'em, either. I remember just decambering the heck out of a pair of ST Comps, once...
post #21 of 21
I know last year i got so used to carrying a pack with rescue gear, med supplies and some personal items that when i tried to ski without it i could tell a difference. I liked with the pack alot better.
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