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Swiss ski core manufacturer Hess to close

AlexisLD

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So stiffness is the only property of a core?

Well, that is what he is saying in the video: "Trueblend specifically designed to optimize ski's flex. It is really the most important factor in how a ski feels...", " [...] using different densities of wood and placing them [...] in the correct position allows us to optimize flex".

You can argue with him! :)
 

Average Joe

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Re: The need for wood laminates, I would have thought that their days were done, but, they have been part of high performance laminated skis for 60 years?
Foam cores have been used, but there is still the the combination of wood, fiberglas, and alloys in high end skis.
Edit: I've laminated clear Sitka Spruce and built my own racing blades for a racing sailing dinghy. Thankfully I had an experienced boatwright to lean on for advice. I can attest to the skills needed to select, mill, arrange by grain direction, glue, and shape a laminate for strength, shape, and performance. Warpage caused by poorly selected or arranged laminates can cause the whole project to get scrapped.
The skills of the people who know how to do this type of work, which is very similar to ski cores, is difficult to replace.
 
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dan ross

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A rotary cut veneer is one that is cut off the surface of a spinning log, as opposed to sliced off a plane of the log. There are plenty of companies worldwide who do that.

The problem is glueing those veneers back up in an orientation useful for ski cores.



Hess:


Lusti:

Exactly. Unlike say a skateboard, which is essentially a molded piece of plywood with grain orientation alternating 90 degrees but always horizontal, ski cores are laminated with vertical grain orientation. Retooling of existing veneering cutters would be tricky and likely not the best approach long term.
It would take dozens of layers to achieve the necessary width required for a ski
using plywood veneer layer thicknesses and make the core nearly 30% adhesive. The torsional and flex characteristics would have to be redesigned to the degree that’s possible.
Sadly, as simple as ski core is, producing them at scale is subject to the same external forces and pressures that do not remain static. On another note, if Fischer is making their cores in Ukraine I’m assuming they’ve found another supplier.
 

James

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Well, that is what he is saying in the video: "Trueblend specifically designed to optimize ski's flex. It is really the most important factor in how a ski feels...", " [...] using different densities of wood and placing them [...] in the correct position allows us to optimize flex".

You can argue with him! :)
Well flexing something has more properties than just resistance.
Retooling of existing veneering cutters would be tricky and likely not the best approach long term.
It would take dozens of layers to achieve the necessary width required for a ski
using plywood veneer layer thicknesses and make the core nearly 30% adhesive.
The only difference is you don’t rotate the plys 90deg to each other. Not sure where the stat comes from that the glue is 30% the thickness of the wood. Seems way too much.
This isn’t that exotic a process.

Standard plywoods. They’re not always 90deg.

0BDFD1BB-12F4-4DC8-8317-D941D98E47F4.jpeg
 

dan ross

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Well flexing something has more properties than just resistance.

The only difference is you don’t rotate the plys 90deg to each other. Not sure where the stat comes from that the glue is 30% the thickness of the wood. Seems way too much.
This isn’t that exotic a process.

Standard plywoods. They’re not always 90deg.

View attachment 184764
If you are using standard ply veneers - the rotary peel type that is the industry standard -.8 to 1.4 mm in thickness, oriented vertically you would need dozens of layers to achieve the necessary width for the average ski in VERTICAL grain orientation- the standard core layout. The more layers, the greater the percentage of adhesive. The average core has between 8 and 12 vertically oriented pieces that average around 6mm thick +/-. if you are reducing the thickness to that of commercially available veneer thicknesses, you are , in effect quadrupling the number of layers and correspondingly the amount of adhesive .
B36E61F5-11C3-46E9-A2F3-28BC6CD155EB.jpeg
 

James

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If you are using standard ply veneers - the rotary peel type that is the industry standard -.8 to 1.4 mm in thickness, oriented vertically you would need dozens of layers to achieve the necessary width for the average ski in VERTICAL grain orientation- the standard core layout. The more layers, the greater the percentage of adhesive. The average core has between 8 and 12 vertically oriented pieces that average around 6mm thick +/-. if you are reducing the thickness to that of commercially available veneer thicknesses, you are , in effect quadrupling the number of layers and correspondingly the amount of adhesive . View attachment 184782
That’s exactly what they do. Build a huge thick sandwich, then slice it and flip it.

30% glue of a 150mm thick panel would be 45 mm . That would be 1 3/4” of glue. That’s just crazy.
The more layers, the greater the percentage of adhesive.
This is the issue. It’s only a little true. Maybe someone can explain the math function.

glue layers are (n-1), n is the plys.

Let’s say plys are 1mm, glue is .1mm. 10% glue

So 10 layers is 10mm wood, .9mm glue.
9% glue
100 layers is 100mm wood, 9.9mm glue.
10% glue (.099)
150 layers 150mm wood, 14.9mm glue
10% glue (.0993)
200mm wood, 19.9mm glue
10% (.0995)
250mm, 24.9mm glue
10% (.0996)
It’s never going to get greater than 10%, the original glue to ply thickness ratio.
 

dan ross

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That’s exactly what they do. Build a huge thick sandwich, then slice it and flip it.

30% glue of a 150mm thick panel would be 45 mm . That would be 1 3/4” of glue. That’s just crazy.

This is the issue. It’s only a little true. Maybe someone can explain the math function.

glue layers are (n-1), n is the plys.

Let’s say plys are 1mm, glue is .1mm. 10% glue

So 10 layers is 10mm wood, .9mm glue.
9% glue
100 layers is 100mm wood, 9.9mm glue.
10% glue (.099)
150 layers 150mm wood, 14.9mm glue
10% glue (.0993)
200mm wood, 19.9mm glue
10% (.0995)
250mm, 24.9mm glue
10% (.0996)
It’s never going to get greater than 10%, the original glue to ply thickness ratio.
Having laminated dozens of things , glue is never .1 millimeter in thickness -more like .3 mm -that’s generally the manufacturers recommended thickness for pva , phenolic or epoxy laminations. That said I may have done my top of the head math wrong. However a hundred millimeter ski made out of 1mm veneer layers laid on edge is going to have a crazy amount of adhesive. The substrate absorbs .1 mm faster than you can say .1mm thus creating a glue starved joint. We can agree to disagree on this , and you may be correct- my point is super thin ply veneers on edge defeats the purpose of super thin veneers - they are designed for and best applied
horizontally, with alternating layers and a balance veneer to prevent warping. This is the theory of plywood- the glue and alternating layers are
75B868EE-1DCC-4535-BACA-5EB5135293F1.jpeg
what gives it rigidity. But I digress. Here’s a detail of a piece of furniture I designed and made . This is urea formaldehyde glue ( extremely rigid)
on European Beech . If I had done this properly-tinted the glue a lighter color -the glue lines would barely be noticeable . I’m not claiming this is 30 % glue but there is more glue in those laminations than is visible. If this was something that was subjected to dynamic loads -a ski for instance- I would have used a different adhesive likely requiring a thicker layer to prevent shear failure at the glue line.
 
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Swiss Toni

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The veneers used in RCV ski cores are much thicker than the veneers used in plywood. I’m not absolutely sure but I think they are usually 3.8mm thick.

RCV_Core.jpg

The veneers in Lusti’s laminated veneer lumber (LVL) cores are probably about the same thickness as the veneers normally used in plywood.

Lusti.jpg
 
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Swiss Toni

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I don't understand why they go through such a complicated process to make their core when the stiffness can be adjusted with the thickness of the core and the fibers used in the laminate. Especially if they really adjust the blend of wood for different ski lengths...

Neither do I; I presume it’s because they can, and for marketing reasons. As things stand, they will have to change the core and the marketing blurb for next year.
 

justplanesteve

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But I digress. Here’s a detail of a piece of furniture I designed and made . This is urea formaldehyde glue ( extremely rigid)

The furniture is probably beautiful and functional, photos are notoriously poor evidence for accurate analysis. Nontheless my first impression of your lay-up was "Yeesh, those are bad, thick & variable gluelines, possibly improper viscosity, certainly low pressure/poorly distributed pressure, and possibly too long open before pressing"

Literature suggests "good" gluelines are in the range: "The glue line thicknesses for wood joints are generally from 0.13-0.18 mm (0.005-0.007 in.) thick for glued assemblies"

More importantly: "There is a strong relationship between glue line thickness and loss of joint strength. The strength of all the glued joints decreases when thick glue lines present. The thickness of a glue line introduces one of the more fractious factors in bond formation because it directly affects how the glue line functions"

"Thick glue lines frequently occur in the manufacturing processes due to thickness variation in adherents, poor preparation of gluing surfaces, inaccurate machining, warping or moisture induced dimensional changes (Marra 1992), lack of adequate pressure methods, non-uniform adhesive spreading and the use of adhesive mixes approaching the end of their pot life."

The paper addresses gap-filling glue specifically for engineered products where a thick glueline may occur for multiple reasons. Even this glue, tailored for gap filling, develops ever decreasing bond strength as the glueline thickness increases past 0.18mm:
"The effect of gap-filling phenol resorcinol formaldehyde (GPRF) adhesive on the shear strength of wood joints when thick glue lines present was studied. A number of wood-to-wood joints were manufactured using the press-gluing fastening method with various thicknesses of GPRF adhesive. Th e results showed that the shear strength was signifi cantly aff ected by the glue line thickness, so the strength decreased as the glue line thickness increased. Th e strength decreases by 10.52 % at a glue line thickness of 0.25 mm and by 39.48 % at a glue line thickness of 0.48 mm. Th e adhesive may be used for bonding up to 0.25 mm glue line thickness that is 43 % more than the normal glue line thickness (0.18 mm)."

Although published in Turkey, I found this paper through links starting at the NFPL & have read many others over the years.
http://www.woodresearch.sk/wr/200601/07.pdf Also, do keep in mind that the subject is gap-filling urea. Standard urea performs even worse as the glue line increases only minimally. A real problem with many straight urea glues is that they have a half-life and gradually self destruct.

smt
 

James

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Having laminated dozens of things , glue is never .1 millimeter in thickness -more like .3 mm -that’s generally the manufacturers recommended thickness for pva , phenolic or epoxy laminations. That said I may have done my top of the head math wrong. However a hundred millimeter ski made out of 1mm veneer layers laid on edge is going to have a crazy amount of adhesive. The substrate absorbs .1 mm faster than you can say .1mm thus creating a glue starved joint. We can agree to disagree on this , and you may be correct- my point is super thin ply veneers on edge defeats the purpose of super thin veneers - they are designed for and best applied
horizontally, with alternating layers and a balance veneer to prevent warping. This is the theory of plywood- the glue and alternating layers are View attachment 184799 what gives it rigidity. But I digress. Here’s a detail of a piece of furniture I designed and made . This is urea formaldehyde glue ( extremely rigid)
on European Beech . If I had done this properly-tinted the glue a lighter color -the glue lines would barely be noticeable . I’m not claiming this is 30 % glue but there is more glue in those laminations than is visible. If this was something that was subjected to dynamic loads -a ski for instance- I would have used a different adhesive likely requiring a thicker layer to prevent shear failure at the glue line.
Cool stuff.
The .1mm was just an example to make the math trivial. I’m also talking about finished size glue layer, not what gets absorbed into the plys. If you look at your example, perhaps all the glue lines, 8, add up to one ply thickness. Doesn’t look it, but looks are deceiving. That would be 1/8 or 12.5% glue.

The important part of the example above is whatever the ratio of glue layer to ply, for one layer, that’s the maximum in a lamination. You will never exceed that percentage, and the fewer layers you have the farther away you are from it.
So if your glue line thickness is 20% of the ply, it’ll never be more than that even with a million layers. It doesn’t continue to increase
In terms of optimal glue line thickness, I’m sure this has been studied to death over the last nearly 100 years.

Neither do I; I presume it’s because they can, and for marketing reasons. As things stand, they will have to change the core and the marketing blurb for next year.
Well bizarrely, it may be far more efficient and cheaper to manufacture a high quality clear, straight grain core with the rotary cut veneer method. If you have access to veneer quality logs and they’re not outrageously expensive. What you end up with is clear straight grain for the plys, and making the rough core stock is just slicing a very thick sheet of plywood.

So to get that in solid lumber you’d essentially need clear quarter sawn lumber which is then ripped and milled into strips. Wasting a lot of an expensive material. It would seem the layup is more difficult too, but industrially maybe it’s a wash between the two methods.

It would be interesting to get some details.

edit- I see justplanesteve answered the issue while I was writing
 
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dan ross

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I think part of the confusion stems from the nomenclature. In this In this case, ply vs. veneer. Most European/Baltic “ plywood “ suggested in the OP, is veneer core . Veneer as I have always understood and purchased it , is around .8 to 1.2 mm in thickness- about the thickness of a heavy business card. To use this material to construct a core would take a great many layers and thus a greater percentage of the core is actually glue. The more layers, the more glue and when we are talking about laminating a 100 mm wide core with 1mm veneers that’s a lot of glue layers. These glue layers themselves would be roughly 1/64” each in thickness -and they have to be applied to each face so capillary action doesn’t suck the joint dry.
Interesting, I sometimes get ahead of myself.Anyway, my point was that vertically oriented veneer is not a good substitute for the precision cut, vertically oriented strips currently used.
( SEE quote above -it belongs here - no idea how it jumped up there)

Core making is essentially custom made plywood, just vertically oriented so your idea is on track. The blanks are now CNC cut and profiled to exact tolerances and surprisingly thin at tip and tail. The vertical orientation and grain orientation allows this thinness ( and the resultant flex) without being overly weak. Horizontal layers would have to be thicker -and thus stiffer -to be strong enough for the stresses encountered.

Your point about waste is well founded- after it is culled for knots, grain run out, etc, the milling process also wastes a great deal.
Bamboo ,on its face , would seem to be a sustainable replacement candidate since it’s technically a grass but I suspect it’s properties would require a re-design in terms of flex, torsion, dampening, etc. ( hasn’t some one done this already?) of any existing model - essentially a complete ground up re-design. Naturally, the “ if it ain’t broke, don’t fix it” mentality prevails until it is no longer feasible. We may be reaching that point if for no other reason than the sole supplier of cores at scale can’t make the numbers work.
I doubt Olin would still be using west African Okume for their cores if they still made skis- too many unpredictable factors and regulations.

I suspect we agree on this more than we disagree, but as I said earlier, I sometimes get ahead of myself.
 

cantunamunch

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A slightly different product than that in OP - this time flat sliced:


notice the slice thicknesses though (yes I know it's pine and not beech) range from 0.6 to 3.0mm

The final product does have 2 cross-grain veneers, the rest are long-axis oriented.
 
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Swiss Toni

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I think part of the confusion stems from the nomenclature.

There might well be differences be differences in the terminology used in the US and Europe. In German speaking countries Furnier (veneer) is the term used to describe 0.3 to 6 mm thick sheets of wood that are separated from the log by various sawing and cutting processes.

Rotary cut and sliced veneers are available in thicknesses of 0.5 – 4 mm. Sawn veneers are available in thicknesses from 1 mm.

Well bizarrely, it may be far more efficient and cheaper to manufacture a high quality clear, straight grain core with the rotary cut veneer method. If you have access to veneer quality logs and they’re not outrageously expensive. What you end up with is clear straight grain for the plys, and making the rough core stock is just slicing a very thick sheet of plywood.

So to get that in solid lumber you’d essentially need clear quarter sawn lumber which is then ripped and milled into strips. Wasting a lot of an expensive material. It would seem the layup is more difficult too, but industrially maybe it’s a wash between the two methods.

It would be interesting to get some details.

The manufacture of rotary cut and sliced veneers is pretty energy intensive. The logs first have to be boiled / steamed for quite a while to make them soft enough to be peeled /sliced. As phenolic adhesive is used to glue the veneers up into sheets a heated press is also required.

The manufacture of glued board cores is much easier and requires much less energy, to make a simple core all you need are some floor boards, some glue, some clamps and a band saw.

Core.jpg

Even on a commercial scale you don’t need much in the way of equipment, a roller glue spreader, a press and a multi blade frame saw is pretty much all you need.

TDS-Isosport_Core Production.jpg

As well as full length boards, boards made up of short pieces of wood that are either finger jointed or just plain butt joined into a strip and then edge glued into boards are also used. Some cores are made of one type of wood, usually either balsa, poplar or paulownia. Others are made of 2 woods, usually beech and poplar and others have a strip of foam down the middle. Some skis have cores that are made from 2 short core blanks, these are finger jointed together by the ski manufactured under binding heel piece mounting point.
 

James

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Good point- when laid up like that, radial sawn works like quarter sawn.
Yeah fingerjointed… bleh. Seen too many boards fall apart. I’m sure done right, offset, blah blah it’s “fine”.
 

justplanesteve

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random notes:

First, wood is the original carbon fiber. Literally. Cellulose bonded with lignin, which is not a bad analog of phenolic or vice-versa.

So the efforts to use wood as highly tailored engineered material tend to be whatever is the most economical method at the time to make a "uniform" product. IOW the blanks. When forests were limitless, lots of skilled people worked for pennies, and the market for the product was limited in a way that precluded capital investment, that tended to mean QS (vertical grain) blanks, perhaps even split blanks to get the optimum grain run out, highly selected, from selected "perfect" trees or cuts from same. They did not have glues good enough back in the day, but the only modification i can see to the above would be book-matched blanks for uniform response across the ski. Either that, or a 2 ply flat lam using wider but thinner book matched vertical grain pieces with the grain reversed between layers.

As all the costs go the other direction, the market is relatively huge and perfect trees either no longer exist or are prohibitively expensive, milling the starting wood product ever closer to a small fiber which can be re-constructed into the ideal blank with all the blanks in a lot having essentially uniform macro characteristics, has become both economical and possible.

Apparently, however, there is some anomaly in the market currently that makes the process un-ecomomical for this season? At least one major player could not pass on costs and had to go bust?
Ski makers with a market are not going to stop making skis - so what are they using instead, for cores?

I have been (anecdotally, not rigorously researched) seeing what some others report above all across woodworking markets. It was big. People made money. Now they are getting our while the getting is good. Some seems to be generational/age related.
This coming winter looks like a good time to buy equipment, or bet it will get worse and wait another 6 - 12 month. I'm too old and never was a good enough business person to hit it very big. But being in it, the industry always interested me.

smt
 

David Chaus

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Bamboo ,on its face , would seem to be a sustainable replacement candidate since it’s technically a grass but I suspect it’s properties would require a re-design in terms of flex, torsion, dampening, etc. ( hasn’t some one done this already?) of any existing model - essentially a complete ground up re-design. Naturally, the “ if it ain’t broke, don’t fix it” mentality prevails until it is no longer feasible. We may be reaching that point if for no other reason than the sole supplier of cores at scale can’t make the numbers work.
A couple of ski makers use bamboo; all ON3P cores are bamboo, and Liberty uses a bamboo poplar and pawlonia core. Don't know who supplies the cores.
 
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Swiss Toni

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Apparently, however, there is some anomaly in the market currently that makes the process un-ecomomical for this season? At least one major player could not pass on costs and had to go bust?
Ski makers with a market are not going to stop making skis - so what are they using instead, for cores?
Several factors have made their business non-viable; the Euro Swiss franc exchange rate, a 62% increase in the cost of electricity and a 15% increase in the cost of logs. They are currently the only supplier of RCV cores. Fischer also makes them but does not currently supply other ski manufacturers and as their facility is located in the Ukraine it’s not known whether they are able to produce any at the moment. They haven’t gone bust, they are closing to avoid bankruptcy. The ski manufacturers are obviously not going to stop manufacturing skis but will have to replace the Hess cores with something else. Will these cores be as good as the Hess cores they will replace and will they be able to obtain them in time for next years production?
 

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