Ripstick + Depleted Uranium

[tomahawkins]

I love my new Ripstick 88s (179): very playful, light weight, soft flex, but can still somehow hold an edge and arc turns.

I had an interesting day at Baker last time up. Conditions were a thin layer of refrozen melt on top of 4 inches of new snow on top of hard chalk. I started the day on my Ripsticks, but the upper layer was causing my skis to bounce all over the place. After two runs I switched to my heavier Fischer Ranger FR 102s and had a much better time of it.

This got me wondering: How would a lightweight ski perform like the Ripstick in chunkular conditions by adding weight to the tips and tails? Say you carried around a few pucks of depleted uranium in your pocket and if the conditions called for it, you would clip the DU on the ends to increase the moment of inertia -- ok, maybe tungsten. By concentrating the medal at the ends, you could get the same inertia of a burlier ski, but with lighter weight. Has any manufacturer or enthusiast played with the idea of on-the-hill adjustable moment of inertia?

 

[Ron]

post deleted.

 

[Andy Mink]

Back in the 70s Fritzmeier did just that. It never caught on.

 

[Ron]

you could just build a ski with more torsional rigidity and a stronger core. Elan is improving the RS for 2021.

 

[cantunamunch]

By concentrating the medal at the ends, you could get the same inertia of a burlier ski, but with lighter weight. Has any manufacturer or enthusiast played with the idea of on-the-hill adjustable moment of inertia?

Yes. Both as a static mass and as a moving damping mass.

The Fritzmeier duo was one design to popularize the concept - several other manufacturers have chased the idea. Both Volant and Salomon had a perimeter weighting system in the late 80s- early 90s on their lighter skis.

Now, if you allow the perimeter mass to be a damping mass, things get a lot more interesting. Volkl's UVO, Dynastar chicken hearts, Floski's oil-loaded bearings all both do weighting and energy absorption. This allows the net mass to be smaller and more noticeable in damping effect.

Now, there is such a thing as over-damping a ski (as well as making a ski too plain heavy). Especially a relatively soft ski like the Ripstick 88. If you want a well-thought-out discourse on this, check Sandwich Tech's page.

Mass damper: http://sandwichtechskis.com/technology/md-ski-damper.htm

Overall opinion: http://blog.sandwichtechskis.com/2013/06/vibration-damping-and-skis.html



So, takeaways:

- Adding rigid mass doesn't damp, it just changes (lowers) the amplitude and frequency.
- Adding stiffness raises oscillation frequency
- Moveable mass lets you couple to a highly lossy material - which material may well already be part of the ski itself.


Back to your question - specifically the 'on the hill' part. The biggest problem with that (aside from carrying the mass in your pocket) is that you are limited in how tightly you can bond the mass to the ski. You cannot use adhesive, so you immediately lose the ability to alter shear wave modes. Really tight but really light screw-downs have to be precisely manufactured - which means expensive. Probably the best you're going to be able to do is something similar to an inline skate wheel through-bolt axle - cheap enough, tight enough, light enough. The next question is - is it as effective for the money as a lighter, tuned but non removeable system?

 

[James]

Get some Flo packs and attach to tips.

FloShocks System

RIDE FASTER & SMOOTHER WITH MORE CONTROLAdd On for any Skis or BoardsLiquid FloShocks provide vibration absorption and stabilization. This results in the smoothest and most stable performance. Skiing and boarding is much easier and safer from knee injuries by allowing much shorter ski lengths...

floskis.com

 

[cantunamunch]

Don't use the Flo on anything other than relatively short (170cm or less) groomer skis until you are accustomed to it. Especially not in crowded conditions or tight terrain.

Expect to be skiing just the sidecut for the first (several) days, after which your steering inputs will adapt. Not to 'normal' tho.

you could just build a ski with more torsional rigidity and a stronger core. Elan is improving the RS for 2021.

Yeh, if removable masses improved the downhill part enough to justify pocketing the weight, every skimo racer in Yurp would be using them, right at the skin slot. OP's skis are already miles better at downhill than the average skimo ski - because internal structure.

 

[AngryAnalyst]

There's a guy on another forum who does stuff like this. I find him entertaining.

My experience is that some of damping is mass and some is actual material dependent (i.e. just a thicker heavier core isn't as good as adding a metal laminate and a rubber layer).

 

[Eleeski]

If your skis bounce enough to affect your line, adding weight might cause more problems than it solves. The energy imparted to the ski from your speed hitting the bump is the same regardless of the weight of the ski. A light ski will displace more. Either ski will need to be turned back on line. But getting the light ski to start a recovery turn will take less force - important for a weaker old guy like me. Note that the energy required to offset the bump displacement will be the same but my light ski will not require as much muscle if I'm patient about the recovery. Also, the mechanics of larger changes seem to require less energy from me - those smooth subtle movements really tire me out. Skills and conditioning could change that. Some people prefer heavy skis???

Bottom line, skiing is a pretty mature sport. Weights have been tried and marketed for a long time. I've never seen even one on the hill. But I have seen monoskis, snollerblades, ridiculously fat skis, backcountry skis, hybrid backcountry/resort skis, telemark skis, snowboards, splitboards, Anton gliders, sit skis, short skis, long skis, ballet skis - you get the point. There's a lot of innovation making it on the snow. Weights haven't made the cut.

Disclaimer, I'm a weight fanatic. I love my light skis!

Eric

 

[cantunamunch]

Bump. Some of you may remember the guys that did the ski flex data for friflyt.no Some of some of you may remember that that lab grew into a ski company.

Well, check out one of their design concepts.

 

[tomahawkins]

There's a guy on another forum who does stuff like this. I find him entertaining.

Can you point me to this guy? I'd be interested to see his work.

 

[AngryAnalyst]

You want swissiphic on TGR. Some examples:

New and hopefully improved heel riser xtendr...make 'em go to 11

With the covid thing going on, personal ski touring goals of big line first descents all around nw bc have been put on the back burner. Hopefully, the social mores change before the snow melts and attempts can be made later in the spring/summer. In lieu of big line first descents, the new...

www.tetongravity.com

https://www.tetongravity.com/forums/showthread.php/326948-No-tip-dive-touring-skis (post #130)

He also had a post somewhere (I can't find it) where he used lead tape or something like that to add mass.

 

[Wendy]

Bump. Some of you may remember the guys that did the ski flex data for friflyt.no Some of some of you may remember that that lab grew into a ski company.

Well, check out one of their design concepts.

What’s the mass/area (g/cm2) represent?

 

[Bill Miles]

Use highly enriched Uranium and really end your day with a bang.

 

[François Pugh]

Use highly enriched Uranium and really end your day with a bang.

You would have to bang those tips together pretty hard.

 

[cantunamunch]

What’s the mass/area (g/cm2) represent?

I expect they're trying to tell us how much surface area the ski makes available for each gram of ski mass you have attached to your feet going uphill.

And yes, I did notice that 1300g/1800cm^2 is about .72 - close but not on the money so

 

[James]

Bump. Some of you may remember the guys that did the ski flex data for friflyt.no Some of some of you may remember that that lab grew into a ski company.

Well, check out one of their design concepts.

I’ll be disappointed if you don’t get a pair.
Surely @Eric Edelstein will try them? EVI Ski is the brand?

 

[Eric Edelstein]

I’ll be disappointed if you don’t get a pair.
Surely @Eric Edelstein will try them? EVI Ski is the brand?

Dang it... missed those Evis with weights way back when.....They are now making a nice collection of customizable ski shapes and constructions...

I HAVE tried the Flo Skis..... lived to tell the tale.... "interesting" to say the least! Gotta step outside your comfort zones every now and then!

 

[James]

Ha, I tried the Flo Skis too at Abasin. We ran into the guy on trail and started talking to him. Doesn’t take much to get him going. I wanted to try the packs too but he was taping them on with packing tape. I would’ve lost them, so didn’t bother.

 

[tomahawkins]

As an experiment I got some carbon skis (Fischer Hannibal 106, 186, ~1740 g per ski) with lightweight bindings (Shift) and mounted a 280 g mass on each tip: hockey training pucks, heavier than normal pucks. I've had them out in three heavy Baker powder days so far. They are a total blast. Light underfoot, easy to pivot and bang out turns, yet still very stable through chop, much more so than my Ranger 102FRs. The only weird thing is picking them up in the parking lot. With the center of mass shifted forward, it makes them a little awkward to carry.

I've tried it with a 2-puck setup (~500 g per ski), but that was clearly too much. No, I didn't drill holes in my skis. The Hannibals come with holes to mount skins!