EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › Ski Gear Discussion › Customizing skis with weights, elastomers?
New Posts  All Forums:Forum Nav:

Customizing skis with weights, elastomers? - Page 2

post #31 of 46

Beyond: Well, our feet may be boney but they're pretty well connected to our skeletal system running throughout our bodies which contain something like 60% water, so for relative scale something like 100 pounds of water is a hard to ignore viscous fluid mass. Yes, a large "squishy mass" is already pretty well connected to the rough center of our skis from a system view (well, maybe a bit further back from center for some folks).

 

As respects adding some small "squishy mass" to ski tips, Sorbothane is one of the better if not the ultimate viscoelastic polymer. I recall it has less than 50 percent efficiency at "damping" vibration (converting vibrational energy to heat and/or affecting the time constant of the vibrational energy temporarily stored in it and ultimately returned to the original vibrating structure/environment) when used in its best case application in compression. However, just stuck on something that's vibrating and not in actual compression within the vibration transmission path it would be quite less efficient. For your application of sticking some of it on a ski tip I would suggest it would be quite less than 20 percent efficient at "damping" vibration. Accordingly, I am suggesting that quite more than 80 percent of the vibrational energy would merely travel down the length of the ski (a fairly rigid structure) completely unaffected by some Sorbothane on a ski tip. IMO, there are many other things in this system that will make vastly larger differences, including the skier and the snow surface.

 

Well since Bob already mentioned them in this one thread, and Rossi is always allowed to talk about them, then I'll just add that Spademans do actually suck and leave it at that - unless I'm invited to add more...

post #32 of 46

 

Quote:
Originally Posted by Bob Lee View Post

I've never done that myself, but the skis that Bill Briggs used to ski the Grand Teton for the first time are on display at the park service building at the entrance to GTNP and...they have strips glued down the length of the tops of the skis.  I thought I had a pic but I can't find it.  The skis had Spademan bindings on them - pretty awesome and worth checking out if you're in Jackson Hole.


I came across some pictures of those skis, not mine:

http://www.tetongravity.com/forums/showthread.php/190339-Bill-Briggs-skis

 

post #33 of 46
Thread Starter 

Chris, you clearly know of what you speak here, but having some trouble reconciling it with experiential data. Specifically: Rubber dampers, most obviously on Kastles, but as foil along the edges of many other skis, appear to make a difference in feel. Now either companies just stick rubber in there for marketing hype, kinda the luddite stance on all modern ski tech, or it achieves something. If it achieves the smooth feel a Kastle has (much more pronounced, for instance, than a Blizzard with an oil piston, incidentally), what percentage of the vibration is it absorbing/turning into heat? Is an elastomer far more efficient under compression inside a ski? And along those lines, everybody who ever skied an old Rossi with VAS would probably remark on how weirdly smooth they were for skis with foam cores, compared to say early Salomons. So I have trouble saying that OK, it's all in my mind. Now maybe sticking something on the outside for tuning is all in my mind...

 

But on a related topic, here's my real issue: If our bodies are so massive a vibration sink, why do ski makers even bother with vibration control, whether weight or rubbery stuff? Why not just let all that water do it for them? I keep thinking about the jolts traveling up my leg bones, and wondering why I feel them at all, if my bones aren't that well connected to forces at the ski except as part of this watery meat bag. And then I recall that the calcaneous doesn't actually have fat under it unless you're way obese, it's just a fibrous pad invested in the bone, and calloused skin. (PITA to dissect cleanly, I might add.) And I recall that 60% figure is mainly contributed by muscle, which is very watery, brain, and blood. Bone is only about 15-17% water. So shock at the heel goes up the leg more efficiently than you assume, I think. Moreover, it starts doing its work, in terms of proprioception and muscle fatigue and all the other aspects of vibration and shock, long before it's reached most of that massive sink you assume, cuz that reservoir lives mostly above the knees. This is why the new thing in running is forefoot strike, thin soles, keep your heels off the ground as much as you can. But in a boot, can't do that. I dunno, just think that the meat puppet model doesn't reflect the particulars of anatomical reality. But don't know enough physics (and zilch engineering) to take it any further. th_dunno-1[1].gif

 

 

 

post #34 of 46

Our bodies are wonderful vibration sinks. From the footpad to the dynamic motion of all those lower body joints, we are naturally good at dampening vibration. That's why our boots have relatively hard foam liners and footbeds - we want the responsiveness more than dampening. A gel pad under the binding would likely make a ski "feel" dead. At the foot to the snow connection there is enough dampening naturally.

 

However the edges of the ski do extend well past the area underfoot. In soft snow, powder or slush the snow itself naturally dampens vibrations. A ski used primarily in these conditions needs no consideration to dampening - I love soft snow! On hard snow or racing conditions, the ski ends will vibrate unchecked by anything other than the ski's dampening characteristics. This vibration could interfere with the edge holding and make the ski "feel bad". Strips of carefully engineered elastomeric foam glued to the tips and tails might really improve the feel of the skis in these conditions. Peel them off (velcro?) for soft snow for custom tuning for the day's conditions. At least it would be a good marketing gimmick.

 

Eric

post #35 of 46

Our bodies are increasingly less effective at absorbing vibration as we get older, and put ski days on our body. The meniscus, cartilage, elasticity of ligaments, all are on the decline.

 

Damp skis (incorporating dampening material in form of a rubber layer in the sandwich), are very effective. Back in the day, I remember the Rossi vs. Volkl (or other Austrian or German skis) debate. One used dampening for edge hold, one used stiffness and liveliness for edge hold.

 

 

post #36 of 46

I just did a quick read through the thread. The Flo Ski's (http://www.floskis.com/id28.html) Patented Hydrodynamic Dampening and Stabilization System was available as an add-on. I saw them being used by Franz Fuchsberger a few years back. He doesn't have them on his skis anymore.

 

I thought the holes in the SL and GS skis these days (by Fischer at least) were to reduce swing weight. Back in the day, they were to reduce wind resistance in DH skis.

post #37 of 46



 

Quote:
Originally Posted by CHRISfromRI View Post

Quite a few good skis that have holes in the tip to make them lighter, rather than heavier, in the quest for lower vibration. 

 

Higher mass should store/sink energy over a longer time constant, rather than allowing it to dissipate/drain more quickly as with lower mass. Maybe strategic mass reduction is better? 


I found this article , while doing other research. About adding lead wieght to ski tips. Interesting read.

 

http://books.google.ca/books?id=aOQDAAAAMBAJ&lpg=PA80&dq=ski%20tech&pg=PA131#v=onepage&q=ski%20tech&f=false

 

 

read right under the B&D add, the article starts earlier in the issue, from 1984

 


 

 

post #38 of 46

MR is correct about the large cut outs at the tip or tip and tail, reducing weight in those areas (where weight is not useful) for performance gains in quickness and finesse.

 

Anti vibration has been focused on two things for a while: a material in the sandwich to dampen (absorb resonance). something to interrupt the resonance (vibration) traveling along the length of the ski.

 

Bicycles are also concerned with reducing vibration for comfort primarily, using (aluminum) tubes which are not symmetrical and therefore carry vibration along their length less. The early aluminum frames were brutal, to see what the new tech has accomplished since then. Not a bad analogy as both sports use a lot of the same materials, and both involve a lot of speed on a variable surface.

post #39 of 46

bplatt and MR: The solutions you have highlighted are really about moving a "piston" with vibration, and then damping the piston's movement once there is energy in it. That's a little different approach than we've been discussing, and I would think it may also produce a small positive desired effect and maybe it would even be a bit more effective than just sticking some viscoelastic polymer to a ski tip.

 

My hunch is that the tricky thing with all of these damping methods will be managing undesired effects due to added mass and lengthened time constants.

 

 

post #40 of 46
Quote:
Originally Posted by CHRISfromRI View Post

bplatt and MR: The solutions you have highlighted are really about moving a "piston" with vibration, and then damping the piston's movement once there is energy in it. That's a little different approach than we've been discussing, and I would think it may also produce a small positive desired effect and maybe it would even be a bit more effective than just sticking some viscoelastic polymer to a ski tip.

 

My hunch is that the tricky thing with all of these damping methods will be managing undesired effects due to added mass and lengthened time constants.

 

 


Yep , everything is a compromise... as they say there is no free lunch!
 

 

post #41 of 46
Thread Starter 
Quote:
Originally Posted by CHRISfromRI View Post

My hunch is that the tricky thing with all of these damping methods will be managing undesired effects due to added mass and lengthened time constants.


Agree, but consider that Dynastar made their red bubble tip models for a while, quite successful. I had some friends who owned them. They said the design seemed to work; biggest problem was the plastic housing ripping. Which did allow a view of the gizmo inside at least; I'd have done it in clear plastic. Would be interesting to know why they phased it out, suspect too expensive compared to inlays in the core. But the general idea would appear to allow for customizing; make the bubble removable, you could buy the ski with two or three different weight "pistons," put in the one you wanted. Or at least have it doable at the shop. 

 

bplatt, great article. Didn't know exactly what VAS was until now. Seems the little rubber/alu plates on the topsheet had nothing to do with the actual system. Ah well, so much for that idea...redface.gif

 

post #42 of 46

John Howe, a former designer for Head, designed the Claw which has an external elastomer and metal 'plate' that is designed to reduce vibration. I have a pair of 'the arcing rockets' http://www.epicski.com/products/the-claw-185-arcing-rockets/reviews/880.

 

post #43 of 46

Feasibly the piston could be a magnetic slug moving back and forth inside a coil to generate electricity to be used in a KERS (Kinetic Energy Recovery System), where the generated power from the kinetic energy in the slug could be used for a positive effect on say the flex of the ski rather than only being converted to heat as in the systems already discussed. This type of KERS has the potential of generating substantially more power than current Chip systems based on flex power generation used to in turn to affect flex.

post #44 of 46

Well someone has been making a ski with dampening material.

http://www.floskis.com/id28.html

 

I tried them for one run.

Pros: The dampening does work. If you're looking to make your current skis feel light, this is the ticket. They're short with a short tail. Chris you'd be interested in the acl  injury reduction of the short tail. I think the plate is good.

Cons: Heavy. Hope for a foot rest on the chair. Going from carving to steering is uh...not fun. Can I stop? You probably could get used to it.

post #45 of 46


Interesting, My son has a pair of addidas soccer cleats that have small lead shot in them that move to the toe on a kick to deliver more power, He fount he liked the shoe better when the pocket holding the shot boke and lightened up the shoe.

 

Also I wonder if PSIA knnows that flow is using their logo to sell skis? I dont think they are a sponsor
 

Quote:
Originally Posted by Tog View Post

Well someone has been making a ski with dampening material.

http://www.floskis.com/id28.html

 

I tried them for one run.

Pros: The dampening does work. If you're looking to make your current skis feel light, this is the ticket. They're short with a short tail. Chris you'd be interested in the acl  injury reduction of the short tail. I think the plate is good.

Cons: Heavy. Hope for a foot rest on the chair. Going from carving to steering is uh...not fun. Can I stop? You probably could get used to it.



 

post #46 of 46
Quote:
Originally Posted by bplatt03443 View Post


Interesting, My son has a pair of addidas soccer cleats that have small lead shot in them that move to the toe on a kick to deliver more power, He fount he liked the shoe better when the pocket holding the shot boke and lightened up the shoe.

 

Also I wonder if PSIA knnows that flow is using their logo to sell skis? I dont think they are a sponsor
 

 

That's Psi man, created by Bob Barnes. I'm not sure he's aware that he created a justification for ...I don't know.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Ski Gear Discussion
EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › Ski Gear Discussion › Customizing skis with weights, elastomers?