Side note on vocabulary: I've always used "damp" to describe the variable Bruno is calling "suspension". But some folks apparently use "damp" to mean "lacking in pop". Personally, I have found a fair number of skis that are damp but still have pop, and I have sometimes resorted to calling these skis "strong".
Perhaps "suspension" is a better word -- although how would one rank "suspension"? It's a category, not a descriptor.
Relevant to this discussion only in the sense that words only mean something if everyone understands/agrees on the meaning. I'd love more finely-tuned adjectives.
I think defining words is really important. I see at least three different things:
1. Damping... the capacity to reduce vibrations over time.
2. Pop... how much it pushes back on you.
3. Suspension.
Blister ranks some skis in their Gear Guide according to their suspension. They have a good podcast about it too. They spend a lot of time saying similar things to what has been said here: suspension is related to stiffness and mass. But the more interesting question to me would be "why is that"?
People talk about a ski being push around or a lot of the terrain being transmitted to your leg. This can give us insight about how a ski behaves. Imagine that the ski is moving flat on snow. Imagine that the ski tip is a mass and that the rest of the ski is a vertical spring that connects the tip mass to your foot. If the tip hits a bump, it will be pushed up. Your feet will feel the tip being pushed up through the stiffness of the ski (displacement x stiffness = force). You will also feel a lack of control when the tip is up in the air.
You can make a few hypothesis about exactly how the ski is being pushed up. One of them is to assume that a constant
impulse will be transmitted to the ski. This might not be the case depending on the snow and the ski, but let assume that it is true and let's see where that brings up. If you have a constant impulse, this means that a heavier tip will be pushed up at lower speed compared to a light tip. This means that the lighter tip will have more kinetic energy (because the squared velocity term in E = 1/2*m*v^2). For the same ski stiffness, the lighter tip will be pushed higher due to its higher energy and will transmit more force to your foot (Force = stiffness x displacement). This is why light and stiff skis create harsh rides.
The problem is that if you lower the stiffness of the light ski to feel less of the terrain, the tip will go higher up in the air and spend less time with the snow. This lowers the speed at which you feel you are loosing control of the ski, i.e., this is the speed limit of the ski.
The heavy tip might also "destroy" the snow instead of being pushed back by it, thus reducing the impulse created. This is fun when charging around.
Heavy and soft thus create a nice suspension, but it is heavy and soft! Heavy is not good for touring, and a heavy tip at the end of a soft ski will be harder to control as it flaps around without you being able to drive it. It won't feel like a race car. You need some stiffness.
An important thing to remember also is that all of that is happening within half a cycle (goes up and comes back onto the snow). Damping, as defined by engineers, won't do much during that little bit of time. This is specially true at the damping level that is present in skis (i.e., very little... on the order of 2-3% per cycle). Damping should not be called suspension. They are different things.
The description given by
@Bruno Schull is spot on for what has been referred to on this forum as "digital" carbon feel - and we've had several dozen skis tarred with
that brush.
The challenge with carbon is it
specific modulus (i.e., stiffness divided by mass). It is 4 times higher than fiberglass. If you replace the fiberglass in a ski with carbon with a 1:1 weight ratio, you will get ski that is 4x stiffer. This is no good. If you try to keep the same stiffness, you will have a ski that is much lighter. It is pretty hard to get the same suspension with such different material. But done properly, with some understanding of the physics, it is possible...