Talk Dampness

[Core Shot]

If we could just add bluetooth capabilities, perhaps I could ditch the headphones! That would be a serious win/win. Damp skis and tunes as a bonus! The faster and crazier you ski, the louder the tunes! Sounds awesome [as long as I'm the only guy with it - some other punk would probably try to play country or somethin'.] /s

Like the piezo electric flashing lights on the k2 Merlin and four from the 1990s?
They didn’t do shit. But the theory is awesome
http://illumin.usc.edu/11/engineerin...ation-damping/

[skizix]

Vibration is motion.

And it's not wacky, it's what actually happens in certain types of rubber when they're deformed. Not saying rubber is the only thing that makes a ski damp, but the ability to convert vibration/motion into heat and dissipating it is the only way to actually get rid of energy that is put into this physical system.

Weight is essential to the feel of the ski, as it's the main variable that affects the skis' natural frequency, heavier pushing this towards a lower frequency, reducing the high frequencies in the process.

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Ok, I have to admit you must be correct. When the vibration/motion is dissipated quickly, the energy must go somewhere, and that somewhere must be heat, if a minute amount (it is not sound - inherently damp materials tend to muffle sound: dissipate vibration and you're dissipating sound).

My main point though: inherently damp materials are only a small part of ski dampness (standing on its own: rubber, mostly). Some species of wood surely are more inherently damp than others (ash, presumably, as it's the go-to wood for baseball bats - so they don't bite your hands too badly when you smash a fastball into the upper deck, etc - other considerations being strength and efficient transfer of energy, remembering that damp does not necessarily equal "dead").

But wood in general is *not* inherently damp (e.g. otherwise it'd be a shitty material for guitars). Dampness in skis is more than the sum of their parts. It is mostly due to the combination of materials with different vibrational properties, rigidly laminated together, creating a dampened structure from not-so-damp parts.

[skizix]

Like the piezo electric flashing lights on the k2 Merlin and four from the 1990s?
They didn’t do shit. But the theory is awesome
http://illumin.usc.edu/11/engineerin...ation-damping/

Yep, but you'd have to charge pretty freaking hard to keep your Bieber flowing seamlessly (personally, I'd probably head-on the nearest tree, just to make it stop).

[nickel]

Ok, I have to admit you must be correct. When the vibration/motion is dissipated quickly, the energy must go somewhere, and that somewhere must be heat, if a minute amount (it is not sound - inherently damp materials tend to muffle sound: dissipate vibration and you're dissipating sound).

My main point though: inherently damp materials are only a small part of ski dampness (standing on its own: rubber, mostly). Some species of wood surely are more inherently damp than others (ash, presumably, as it's the go-to wood for baseball bats - so they don't bite your hands too badly when you smash a fastball into the upper deck, etc - other considerations being strength and efficient transfer of energy, remembering that damp does not necessarily equal "dead").

But wood in general is *not* inherently damp (e.g. otherwise it'd be a shitty material for guitars). Dampness in skis is more than the sum of their parts. It is mostly due to the combination of materials with different vibrational properties, rigidly laminated together, creating a dampened structure from not-so-damp parts.

You continue to not know what the fuck you're talking about. First of all, whether you dissipate energy quickly or slowly, it all goes somewhere. In this case sound and heat. Period. Anything not dissipated by the ski gets sent to the binding. Anything not dissipated by the binding gets sent to you.

Dampness in a ski is precisely the sum of it's parts. I don't know what you think happens when you add wood+glue+rubber/metal/fiberglass/carbon but Gandalf doesn't pop out of the woodwork to cast a dampening spell on your shit.

Furthermore, quit lumping all genomes together as "wood". As you said, some woods are more damp than others. Just because guitars are made of certain woods, doesn't have much bearing on other woods not used for applications where preservation of vibrations is important.

[Core Shot]

The ignorance of physics in this thread reminds me of the plane on the treadmill


Or maybe it’s all semantics and assumptions
What is meant be dampening?
That is the crux of the biscuit.

The idea that damp skis work by converting motion into heat is laughable. It may happen in small quantities, but like the k2 piezo crystal skis, it ain’t much. That magic rubber or Titanal layer is not taking normal ski vibrations and converting them to kilojoules of heat.

More like the heavy damp ski is not vibrating in the first place, as it does not have a sympathetic resonant frequency like a lighter livelier ski does.

[Norseman]

The idea that damp skis work by converting motion into heat is laughable. It may happen in small quantities, but like the k2 piezo crystal skis, it ain’t much. That magic rubber or Titanal layer is not taking normal ski vibrations and converting them to kilojoules of heat.

More like the heavy damp ski is not vibrating in the first place, as it does not have a sympathetic resonant frequency like a lighter livelier ski does.

Sorry bud, you're not correct here.

Denition of Hysteretic Damping

Vibrational damping is associated with the dissipation of energy during mechanical vibrations/deformations
of an elastic body, usually via the conversion of mechanical energy to thermal
energy producing heat in the body which is readily dissipated. Damping is most properly embodied
in constitutive laws that relate a body's deformation (strain) or displacement to the stress or
force associated with this deformation. These are most often given in terms of stress/strain laws,
the most elementary of which is Hooke's law
where E is the material dependent Young's modulus or modulus of elasticity.

https://pdfs.semanticscholar.org/333...63262427df.pdf

The materials within the complex composite structure of a ski all have some inherent ability to dissipate mechanical vibration.

Damping, in physics, restraining of vibratory motion, such as mechanical oscillations, noise, and alternating electric currents, by dissipation of energy. Unless a child keeps pumping a swing, its motion dies down because of damping. Shock absorbers in automobiles and carpet pads are examples of damping devices.

A system may be so damped that it cannot vibrate. Critical damping just prevents vibration or is just sufficient to allow the object to return to its rest position in the shortest period of time. The automobile shock absorber is an example of a critically damped device. Additional damping causes the system to be overdamped, which may be desirable, as in some door closers. The vibrations of an underdamped system gradually taper off to zero.

There are many types of mechanical damping. Friction, also called in this context dry, or Coulomb, damping, arises chiefly from the electrostatic forces of attraction between the sliding surfaces and converts mechanical energy of motion, or kinetic energy, into heat.

Viscous damping is caused by such energy losses as occur in liquid lubrication between moving parts or in a fluid forced through a small opening by a piston, as in automobile shock absorbers. The viscous-damping force is directly proportional to the relative velocity between the two ends of the damping device.

The motion of a vibrating body is also checked by its friction with the gas or liquid through which it moves. The damping force of the fluid in this case is directly proportional to a quantity slightly less than the square of the body’s velocity and, hence, is referred to as velocity-squared damping.

Besides these external kinds of damping, there is energy loss within the moving structure itself that is called hysteresis damping or, sometimes, structural damping. In hysteresis damping, some of the energy involved in the repetitive internal deformation and restoration to original shape is dissipated in the form of random vibrations of the crystal lattice in solids and random kinetic energy of the molecules in a fluid.

There are other types of damping. Resonant electric circuits, in which an alternating current is surging back and forth, as in a radio or television receiver, are damped by electric resistance. The signal to which the receiver is tuned supplies energy synchronously to maintain resonance.

In radiation damping, vibrating energy of moving charges, such as electrons, is converted to electromagnetic energy and is emitted in the form of radio waves or infrared or visible light.

In magnetic damping, energy of motion is converted to heat by way of electric eddy currents induced in either a coil or an aluminum plate (attached to the oscillating object) that passes between the poles of a magnet.

https://engineering.purdue.edu/~dead...ecture2010.pdf

[tuco]

The ignorance of physics in this thread reminds me of the plane on the treadmill


Or maybe it’s all semantics and assumptions
What is meant be dampening?
That is the crux of the biscuit.

The idea that damp skis work by converting motion into heat is laughable. It may happen in small quantities, but like the k2 piezo crystal skis, it ain’t much. That magic rubber or Titanal layer is not taking normal ski vibrations and converting them to kilojoules of heat.

More like the heavy damp ski is not vibrating in the first place, as it does not have a sympathetic resonant frequency like a lighter livelier ski does.

To damp and to dampen are 2 different things.
You tryin' to tell me these weren't magical?
All skis create heat. It's called friction. The layers of a laminate are all following a different arc at any given moment within that arc. This creates friction. Each layer would also build its own heat as the bottom/ top sides of each layer are following a different arc at any given point. Rubber helps dissipate heat because it acts like a shear layer.

[Gepeto]

The ignorance of physics in this thread reminds me of the plane on the treadmill

Yes, but the 747 on a rubber band has been recently bumped with a summation that should meet everyone's inspection

*

Good thing the norse is around to clip wings

I prefer the more terse versions before the edits

[Core Shot]

To damp and to dampen are 2 different things.
.

That was my only point. Not that the physics definition of dampening does not mean converting motion to heat.

Rather, that this thread was really about what we perceive as dampness in a ski feel. Piezo crystals did not make the k2 Merlin damp

[Core Shot]

My dream ski is just ptex and rubber.
And metal edges.

Maybe a dozen piezo crystals.
That would be dank damp




Sorry for typing “ignorance” of physics. I was thinking more the over application of physics on a micro scale, and the issue of semantics and definitions in the initial question.

[swissiphic]

My dream ski is just ptex and rubber.
And metal edges.

Maybe a dozen piezo crystals.
That would be dank damp

I've got a few dozen meters of thick conveyor belt rubber if yer lookin'. Multidensity layered laminate. I'd say eschew the ptex..just wax the shit out of it. And metal edges? Nah, just adds weight...gotta gram shave...and take the 'V' out of 'slarve'...

[old goat]

In the short run everything turns to heat (1st law of thermodynamics)
In the long run everything gets cooler and cooler until they universe dies. (2nd law of thermodynamics)
If you want to mess up your GPA, take physical chemistry (old goat's 3rd law of education)

(This is grossly oversimplified of course; P Chem for poets)

Now can we get back to the plane on the conveyor belt?

[Core Shot]

Lol. Pchem was my favorite class ever.

Taught by an old fossil in socks and sandals.

[Mudfoot]

You want to see a ski dampener click on the blue HDT and go to 30 sec on the video:

https://renoun.com/pages/hdt

[SiSt]

You want to see a ski dampener click on the blue HDT and go to 30 sec on the video:

https://renoun.com/pages/hdt

That's not dampening. That's a material that becomes harder during fast deformation, than during slow. It's a rheopectic material. The main thing happening in a Renoun ski is therefore that it changes its flex, and the dampening properties change as a result of changes in how the ski flexes. Not having skied a pair, I can't comment more on that specific ski, or its performance.

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[old goat]

My nice light undamp skis certainly behaved differently today with 4 inches of sun-warmed powder stuck to the top sheets.

[GeezerSteve]

Where does K2 Four piezoelectric damping fit in here? Profound game changer before its time? Mere gimmick? Cure for common cold? Some combination of the above?

[SiSt]

Where does K2 Four piezoelectric damping fit in here? Profound game changer before its time? Mere gimmick? Cure for common cold? Some combination of the above?

Piezoelectric dampening is legit. It can be tuned for specific frequencies and turned on off in milliseconds. However, getting to that point requires an external power source and an embedded chip to control everything. I don't really know enough to be specific, but I guess a passive device won't be quite so impressive...

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[abraham]

This thread inspired me to apply some 3m 434 damping tape to the front of one ski this weekend.

My conclusion: I'm not sensitive enough to notice the difference.
Or it does nothing.
Or tracked out heavy schmoo and grooming down avy debris doesn't make for the best test conditions.

I'll leave it on and see if I find anything

The tape is pretty cool stuff and it works decently well. https://www.3m.com/3M/en_US/company-...3242555&rt=rud

[SiSt]

This thread inspired me to apply some 3m 434 damping tape to the front of one ski this weekend.

My conclusion: I'm not sensitive enough to notice the difference.
Or it does nothing.
Or tracked out heavy schmoo and grooming down avy debris doesn't make for the best test conditions.

I'll leave it on and see if I find anything

The tape is pretty cool stuff and it works decently well. https://www.3m.com/3M/en_US/company-...3242555&rt=rud

@MnO should have details on a tape used for developing the Swedish "Project Opinion" ski... They may just have glued strips normally used in the layup to the topsheet though.

Just adding weight also leads to interesting results.

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[abraham]

@MnO should have details on a tape used for developing the Swedish "Project Opinion" ski... They may just have glued strips normally used in the layup to the topsheet though.

Just adding weight also leads to interesting results.

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This tape is pretty heavy stuff too. It's bonded to aluminum to dissipate heat. I don't know if I should have put it on something other than GPOs.

[Talisman]

Where does K2 Four piezoelectric damping fit in here? Profound game changer before its time? Mere gimmick? Cure for common cold? Some combination of the above?

I owned a pair of K2 Fours and decided the piezoelectric damping was a gimmick, but the red LEDs on the top sheet were fun to look at in low light conditions.

[swissiphic]

This thread inspired me to apply some 3m 434 damping tape to the front of one ski this weekend.

My conclusion: I'm not sensitive enough to notice the difference.
Or it does nothing.
Or tracked out heavy schmoo and grooming down avy debris doesn't make for the best test conditions.

I'll leave it on and see if I find anything

The tape is pretty cool stuff and it works decently well. https://www.3m.com/3M/en_US/company-...3242555&rt=rud

Looks very interesting....

What about adding more layers?

We've got perfect testing conditions atm...bullet proof chattery crust, breakable crust and refrozen avy debris.

I'll give er a go.

[Core Shot]

What about dynamat. The shit they put in the trunk of boom boom car stereos?
If you covered a DPS topsheet with that, you would be fly. Or dope. Or some such shittasticness

[abraham]

Looks very interesting....

What about adding more layers?

We've got perfect testing conditions atm...bullet proof chattery crust, breakable crust and refrozen avy debris.

I'll give er a go.

It's kinda spendy. But I could mail you some if you don't need a whole roll