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Ski Cores

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ReturnToMonkey
Posts: 6172 - Karma: 66,434
As much as I'm really into composites and materials, and also ski gear, I know pretty much nothing about wood especially as it pertains to cores.

What are the different common (and maybe not so common) layups as far as cores go? What materials exhibit certain desired properties and what do most designs have to compromise on to succed in other ways?
Nov 10 2021 12:02AM
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BradFiAusNzCoCa
Posts: 6637 - Karma: 57,172
The more I pay attention to core and sidewall, the more I am noticing certain characteristics. Fun topic to explore
Nov 10 2021 12:33AM
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dkels
Posts: 137 - Karma: 648
My thoughts:

Ultra-light = karuba (I.e. white walkers) More companies are starting to put a few layers of karuba around some other core to lighten their skis (icelantic)

light and poppy = poplar (I.e. bent Chetlers, icelantics, fat-ypus)

Stable, ultra-durable = bamboo (ON3P)

Light-weight, energetic, but I find to lose snap faster than poplar = maple (many LINE skis)

stiffness mostly depends on core thickness throughout the ski so the material list above is all assuming you have skis with similar thickness. I personally think that having a full wood core is super important in creating a lively/responsive ski. While those carbon fiber touring skis are ultra-light, they lack life IMO. Hope that serves as useful info! All of it was off the top of my head so I apologize if there is an obvious mistake.
Nov 10 2021 6:49AM
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Lazylightning
Posts: 1221 - Karma: 6,438
You might enjoy this:
https://www.folsomskis.com/recommend-construction-combinations-explained
Nov 10 2021 12:18PM
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BallHooter
Posts: 121 - Karma: 742
Talking ab ski cores is core
Nov 10 2021 1:06PM
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FaunaSkis
Posts: 592 - Karma: 6,490
Some more woods, maybe more commonly used in skis from the EU

white/European ash - similar density to hard maple and harder types of bamboo. Good strength to weight, good rebound.

european beech - more dense than ash and maple, stiffer, strong rebound, usually only used as a couple of bars in the ski.

paulownia - super light, second to balsa as lightest wood but far better strength to weight ratio. Super sustainable as the fastest growing wood species.

And then there are the fancy Swiss b-comp balsa/flax cores that went through a bit of a trend but seems to have dropped off as companies struggled for durability using it (a lot of the super lightweight skis that were delaminating a few years ago we’re using this core) https://www.bcomp.ch/products/bcores/
Nov 10 2021 1:54PM
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ReturnToMonkey
Posts: 6172 - Karma: 66,434
LazylightningYou might enjoy this:
https://www.folsomskis.com/recommend-construction-combinations-explained

I had a feeling that was slightly misleading and when they started talking about the composites, they are straight up wrong. Maybe it's just them dumbing it down, but they were talking primarily about strength and weight which are extrensic properties meaning it depends on the geometry of the construction. What really matter are stiffness and density. At one point, they mentioned how fiberglass is stronger than carbon fiber but fiberglass will yield a softer flex. Both of these are actually opposite. CF when used in skis is usually used in smaller quanitities, which is why they might appear less strong and stiff, but the intrensic properties of it (geometry does not matter) show that it has a higher stiffness and much lower density than fiberglass. If the same mass (amount) of CF was used as glass, it would be an extremely stiff ski and probably not be as fun or easy to ski. Also much more expensive. So they use less.

This makes me take what they have to say about wood cores with more than a grain of salt. Smh @folsomskis
Nov 10 2021 2:38PM
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ReturnToMonkey
Posts: 6172 - Karma: 66,434
What specifically makes different woods more "stable" (more damping and mass to resist movement), or "poppy" (more energy retention when deformed), or "strong" (less likely to fracture under deformation/load)? I get what the behaviors mean, but not what makes them happen, at least in organic materials.
Nov 10 2021 2:46PM
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folsomskis
Posts: 6 - Karma: 95
ReturnToMonkeyI had a feeling that was slightly misleading and when they started talking about the composites, they are straight up wrong. Maybe it's just them dumbing it down, but they were talking primarily about strength and weight which are extrensic properties meaning it depends on the geometry of the construction. What really matter are stiffness and density. At one point, they mentioned how fiberglass is stronger than carbon fiber but fiberglass will yield a softer flex. Both of these are actually opposite. CF when used in skis is usually used in smaller quanitities, which is why they might appear less strong and stiff, but the intrensic properties of it (geometry does not matter) show that it has a higher stiffness and much lower density than fiberglass. If the same mass (amount) of CF was used as glass, it would be an extremely stiff ski and probably not be as fun or easy to ski. Also much more expensive. So they use less.

This makes me take what they have to say about wood cores with more than a grain of salt. Smh @folsomskis


Sup nerds... the reality is, every manufacturer has different ways of measuring these material properties and how they stack up against each other. Of course Icey claims bamboo is the GOAT of organics. ON3P will argue maple is the king. But as you've pointed out, the thickness or stack height of any core is the dominant factor in how stiff a ski will feel. You can take Balsa - the shittiest wood in the world (sorry DPS) - and mill out a tall enough core to have it feel stiff.

The balance to achieve here, and our philosophy, is in strength to weight ratios. And on the custom level, which are the right organic balances for the right skiers.

Monkey returner - you're spot on in saying that in the same weave of carbon vs. fiberglass, carbon would win the stiffness battle. But a megastiff touring ski don't make no sense. So we (and most manufacturers) use different weaves of carbon and fiberglass to accomplish similar flexing skis. This allows us to easily swap composites for our customers to make a ski much lighter, but not have it flex drastically different.

Anyway, no need to shake your head, we love this shit 🤘
Nov 10 2021 4:13PM
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folsomskis
Posts: 6 - Karma: 95
ReturnToMonkeyWhat specifically makes different woods more "stable" (more damping and mass to resist movement), or "poppy" (more energy retention when deformed), or "strong" (less likely to fracture under deformation/load)? I get what the behaviors mean, but not what makes them happen, at least in organic materials.


Stable is typically used interchangeably with "damp". Which by definition, is the ability for a material to absorb oscillation. (Think quiet, not chattery.) You can run a slap test on how fast or slow different materials take to reduce oscillation to a certain percentage. Grain structure and density are the dominant factors for "stability", but it's important to have a balance of damp materials and lively / energetic organics to have a good versatile ski.

Poppy is rather subjective, but we'd classify it with lively and energetic. Some might even say poppy is the opposite of stable...

Strong is another word for "built in the USA". Most organics are "strong", but need to be assembled and used in the right ways for the right skiers. Another kinda subjective one...
Nov 10 2021 4:28PM
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Jems
Posts: 7248 - Karma: 93,066
FaunaSkisSome more woods, maybe more commonly used in skis from the EU

white/European ash - similar density to hard maple and harder types of bamboo. Good strength to weight, good rebound.

european beech - more dense than ash and maple, stiffer, strong rebound, usually only used as a couple of bars in the ski.

paulownia - super light, second to balsa as lightest wood but far better strength to weight ratio. Super sustainable as the fastest growing wood species.

And then there are the fancy Swiss b-comp balsa/flax cores that went through a bit of a trend but seems to have dropped off as companies struggled for durability using it (a lot of the super lightweight skis that were delaminating a few years ago we’re using this core) https://www.bcomp.ch/products/bcores/


are there any downsides of paulownia? everyone in the musical instrument world despises that wood with a passion
Nov 10 2021 5:07PM
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Session
Posts: 5318 - Karma: 21,393
folsomskisSup nerds... the reality is, every manufacturer has different ways of measuring these material properties and how they stack up against each other. Of course Icey claims bamboo is the GOAT of organics. ON3P will argue maple is the king. But as you've pointed out, the thickness or stack height of any core is the dominant factor in how stiff a ski will feel. You can take Balsa - the shittiest wood in the world (sorry DPS) - and mill out a tall enough core to have it feel stiff.

The balance to achieve here, and our philosophy, is in strength to weight ratios. And on the custom level, which are the right organic balances for the right skiers.

Monkey returner - you're spot on in saying that in the same weave of carbon vs. fiberglass, carbon would win the stiffness battle. But a megastiff touring ski don't make no sense. So we (and most manufacturers) use different weaves of carbon and fiberglass to accomplish similar flexing skis. This allows us to easily swap composites for our customers to make a ski much lighter, but not have it flex drastically different.

Anyway, no need to shake your head, we love this shit 🤘


ON3P is full Bamboo. I think they only use Paulownia stringers in their tour layup. I'm sure outside of maybe some prototyping that maple has never graced the factory.
Nov 10 2021 5:12PM
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FaunaSkis
Posts: 592 - Karma: 6,490
Jemsare there any downsides of paulownia? everyone in the musical instrument world despises that wood with a passion


Gardeners don’t like it either because it grows so quickly.


there’s not any that I’ve come across. Because of its lightness it can brittle on its own, but paired with stiffer, heavier wood like ash and reinforced with glass and carbon it makes for a great weight saver in skis.
Nov 10 2021 5:38PM
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PacificRimJob
Posts: 24704 - Karma: 29,687
Jemsare there any downsides of paulownia? everyone in the musical instrument world despises that wood with a passion


Paulownia is disliked because it doesn't work with acoustics as well as other woods. The most common 'tonewoods' are like, Spruce, Maple, and Rosewood. Like, a stradivarious is made out of spruce and maple, and then has some other wood thats more flexible for the ribbing if I'm not mistaken. Most good acoustic guitars are made out of Spruce and Rosewood.

You might also hear Walnut or Mahogany in there too, but they tend to be a bit heavy I think. (like, My Fender Mustang is a Mahogany build, and it weighs like a fuckin brick)


I think its kinda rare for instruments to be made out of super dense and heavy hardwoods like that... so something like oak or whatever is rarely used because then they just get too heavy, and theyre also a lot more difficult to work with.

Still.. Paulownia is completely fine for cheaper beginner instruments when people don't always have the ear for the intricacies of an instrument and are more just focused on learning to play, and don't care how bright or tinny their guitar ultimately sounds.
Nov 10 2021 6:22PM
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folsomskis
Posts: 6 - Karma: 95
SessionON3P is full Bamboo. I think they only use Paulownia stringers in their tour layup. I'm sure outside of maybe some prototyping that maple has never graced the factory.


Yeah I got 'em twisted. Full bamboo for ON3P, J does a lot of full maple. It's a heavier one but supremely damp. Probably the top dog in torsional rigidity for organics.
Nov 10 2021 6:22PM
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PacificRimJob
Posts: 24704 - Karma: 29,687
DingoSeanMy Fender Mustang is a Mahogany build


Correction: It's definitely ash, but its still a brick.

My Telecaster is Mahogany with a maple top and Mahogany neck and that thing is absolutely not light either.
Nov 10 2021 6:29PM
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ReturnToMonkey
Posts: 6172 - Karma: 66,434
ReturnToMonkeyAt one point, they mentioned how fiberglass is stronger than carbon fiber but CF will yield a softer flex. Both of these are actually opposite.
@folsomskis

Meant to say carbon fiber instead of fiberglass here... Kinda contridicted myself there.
folsomskisSup nerds...
...the thickness or stack height of any core is the dominant factor in how stiff a ski will feel. You can take Balsa - the shittiest wood in the world (sorry DPS) - and mill out a tall enough core to have it feel stiff.

Monkey returner - you're spot on in saying that in the same weave of carbon vs. fiberglass, carbon would win the stiffness battle. But a megastiff touring ski don't make no sense. So we (and most manufacturers) use different weaves of carbon and fiberglass to accomplish similar flexing skis. This allows us to easily swap composites for our customers to make a ski much lighter, but not have it flex drastically different.

How do you feel about making weaves of both carbon and glass, such as ON3P's new hybrid of carbon in the 0 direction and glass in the 45s? As skis usually flex upward, is it very noticable if there is more/different composite below the core instead of above (tension vs compression)? Another thing I heard scott say was part of the deal with their new hybrid weave is it bonds better with the core, but isn't that a matrix issue, not a fiber layup one? On that note, do you only use epoxies for matrix materials and how do different ones behave regarding bond strengths, especially with the cold weather and heavy impacts many skis endure?
DingoSeanPaulownia is disliked because it doesn't work with acoustics as well as other woods. The most common 'tonewoods' are like, Spruce, Maple, and Rosewood.

I think its kinda rare for instruments to be made out of super dense and heavy hardwoods like that... so something like oak or whatever is rarely used because then they just get too heavy, and theyre also a lot more difficult to work with.

As opposed to skis, I'd imagine instruments want far less damping in order to resonate better, correct?
Nov 10 2021 7:34PM
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BradFiAusNzCoCa
Posts: 6637 - Karma: 57,172
Did you ever see that thread where someone, I think @Caveman. , was discussing the properties of bamboo vs paulownia for ON3P and getting very technical?

Also heard about the new ON3P layup on blister podcast briefly too but haven’t really deepdived. Something like 200g savings I think it was?
ReturnToMonkeyMeant to say carbon fiber instead of fiberglass here... Kinda contridicted myself there.

How do you feel about making weaves of both carbon and glass, such as ON3P's new hybrid of carbon in the 0 direction and glass in the 45s? As skis usually flex upward, is it very noticable if there is more/different composite below the core instead of above (tension vs compression)? Another thing I heard scott say was part of the deal with their new hybrid weave is it bonds better with the core, but isn't that a matrix issue, not a fiber layup one? On that note, do you only use epoxies for matrix materials and how do different ones behave regarding bond strengths, especially with the cold weather and heavy impacts many skis endure?

As opposed to skis, I'd imagine instruments want far less damping in order to resonate better, correct?
Nov 11 2021 12:43AM
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HypeBeast
Posts: 9774 - Karma: 72,202
ReturnToMonkeyI had a feeling that was slightly misleading and when they started talking about the composites, they are straight up wrong. Maybe it's just them dumbing it down, but they were talking primarily about strength and weight which are extrensic properties meaning it depends on the geometry of the construction. What really matter are stiffness and density. At one point, they mentioned how fiberglass is stronger than carbon fiber but fiberglass will yield a softer flex. Both of these are actually opposite. CF when used in skis is usually used in smaller quanitities, which is why they might appear less strong and stiff, but the intrensic properties of it (geometry does not matter) show that it has a higher stiffness and much lower density than fiberglass. If the same mass (amount) of CF was used as glass, it would be an extremely stiff ski and probably not be as fun or easy to ski. Also much more expensive. So they use less.

This makes me take what they have to say about wood cores with more than a grain of salt. Smh @folsomskis


folsomskisYeah I got 'em twisted. Full bamboo for ON3P, J does a lot of full maple. It's a heavier one but supremely damp. Probably the top dog in torsional rigidity for organics.


I'm just gonna drop this here. Should probably update your website. Also you have a typo "quite" not "quiet". That will be $50 for my editing time 😁.



Ummmmmmmmmmmmmmmmmm no lololololol
Nov 11 2021 4:17AM
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folsomskis
Posts: 6 - Karma: 95
HypeBeastI'm just gonna drop this here. Should probably update your website. Also you have a typo "quite" not "quiet". That will be $50 for my editing time 😁.



Ummmmmmmmmmmmmmmmmm no lololololol


Yeah... we're better at building skis than spelling. But thanks for reading!
Nov 11 2021 9:55AM
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PacificRimJob
Posts: 24704 - Karma: 29,687
ReturnToMonkeyAs opposed to skis, I'd imagine instruments want far less damping in order to resonate better, correct?

Its less about how damp and flexible the wood is and more about its ability to refract sound well. Something denser is generally going to refract better, such as Oak or Alder. Additionally, you probably want a wood that refracts sound across a wide spectrum of tone... whether that be higher or longer wavelengths. Some woods/cuts of wood probably don't work as well for bass tones, for example, and others dont work so well for high pitched tones.

The real key to it however is to just get rid of all/most parallel surfaces because that's what creates that disturbing echo that ruins the acoustics. A well built instrument or auditorium is going to try to bounce sound around the whole interior very evenly, rather than having any specific area receive too much refracted sound.
Nov 13 2021 11:00PM
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