What's the deal with horizontal lamination?

[leifkj]

I've been reading through the guides, forums, and such, and there's one thing I just don't understand: why does everybody vertically laminate their cores? My understanding is that you want a ski to have longitudinal and torsional stiffness. Laminations provide this by allowing you to put together sheets with perpendicular grain orientations, which provides strength along the plane of the laminates. Vertical lamination, however, doesn't seem to provide any more strength longitudinally or torsionally than a plain piece of wood. Why not just rip a core from a clean 2x4? I guess my point is: vertically laminated plywood is a ridiculous concept, so what's different about skis? I assume there's a good reason, since it seems to be a universal practice, I just don't understand what that reason is.

Thanks,
Leif

[falls]

Finding clean pieces of wood wide enough for ski cores is more difficult/expensive, hence lamination.
Horizontal lamination leaves the adhesion between pieces of wood in the plane that sees the most force when the ski flexes. Horizontal lamination would be prone to delamination and create another layer in an already horizontally laminated product that could fail.

(not sure if your title matches your questions as you don't mention horizontal lamination in the actual post)

[skidesmond]

I have been using single piece of wood for cores most of the time because I'm lucky enough to have wood thats wide enough and a fairly consistent grain pattern. Otherwise I'd vertically laminate as well. But Like Falls said, it's not always easy to find a good single piece of wood. And I think another reason for vertical laminations is to take out the variations a single piece of wood may have, provide more uniformity. Also vertical laminations allow you to mix wood types (ash/poplar, beach/poplar, etc...) for different performance/weight characteristics.

[sammer]

My 2 cents...
cut 2 3/4 x 3/4 strips of your 2x4 about 2 feet long.
clamp one flat with half of it overhanging the end of your workbench with its grain horizontal then push down on the overhanging end and break it.
Now do the same with the next one only this time with the grain vertical.
Which one was harder to break?
The horizontal board probably showed some delam along the grain.

As falls said the layup is all horizontal and delam is probably the thing that most of us are trying to avoid. So why add more horizontal layers?

I've got probably 200 rough fir and larch 1x4s and not 1 of them has clear enough grain to make a ski core without cutting them into strips and laminating them.
(and even if one was, the grain would be horizontal due to the way the lumber is milled)
I believe that the torsional stiffness your looking for is a more a product of your triax reinforcement.

hope this makes sense.

sam

[skidesmond]

Sammer, Nicely put!

[carnold]

Hi. Light weight plywood works for me.
But.....I was thinking that if you look at the construction of a recurve bow and then apply that to a ski/snowboard core you'd be making a really flash core. It'd be a whole lot of trouble compared to vertical laminated and most likely really heavy but the horizontal laminated would really contribute to the strength/stiffness of the core.
Has anyone tried something like that?
C.

[skidesmond]

... I was thinking that if you look at the construction of a recurve bow and then apply that to a ski/snowboard core you'd be making a really flash core. It'd be a whole lot of trouble compared to vertical laminated and most likely really heavy but the horizontal laminated would really contribute to the strength/stiffness of the core.
Has anyone tried something like that?
C.

I think some are lumping in horizontal lamination with plywood. While there might be similiarities (ie the lamination part) I wouldn't call it the samething. For example if I were to do horizontal laminations I wouldn't alternate the layers 90 degrees to each oher as you get in typical plywood. I would align the the grain in the same direction, I'd use a high quality exterior rated glue and make sure there are no voids between the layers. You're not going to get that in typical plywood from a big box store.

I'm looking at a piece of 3/4 oak plywood I bought at a big box store that I used for some cabinetry. It's fine for that use but looking at it I can see small voids and random "filler" wood in the middle. Some of it looks like thin particle board pressed in between other layers. I wouldn;t use it for ski/board construction. If you are using a true furniture grade plywood it will be well contructed, no voids and very stable.

As for the DIY lamination I have a set of skis in mind that will be vertically laminated using ash/cherry so the alternating wood pattern can be seen on the sidewall, like your recurve bow.

[doughboyshredder]

Hi. Light weight plywood works for me.
But.....I was thinking that if you look at the construction of a recurve bow and then apply that to a ski/snowboard core you'd be making a really flash core. It'd be a whole lot of trouble compared to vertical laminated and most likely really heavy but the horizontal laminated would really contribute to the strength/stiffness of the core.
Has anyone tried something like that?
C.

not yet, but I want to. Or, at least something similar. You can get 2 mm veneers of vertically laminated bamboo. I keep thinking about developing a layup consisting of layers of that veneer, so yea it would be horizontally laminated, but still have the strength and uniformity benefits of vertical lamination. Also the core would have the camber profile glued in to it.

[knightsofnii]

how bout a hybrid of both? like say a 4mm at its thickest point v-lam, wrapped in a couple veneers? "dual core technology" dudes!

[knightsofnii]

we're also working on a "mono-cock chassis" core, super hybrid cybornetic organism stuff

[doughboyshredder]

how bout a hybrid of both? like say a 4mm at its thickest point v-lam, wrapped in a couple veneers? "dual core technology" dudes!

I been thinking about that, and actually removing some of the vertical lam and replacing with honeycomb. So basically a veneer sandwich with a vertical lam / honeycomb hybrid center.

[MontuckyMadman]

The way I see it you want your core to be as strong as possible. Broken core is non-fixable.
You can fix delams and edge an sidewall separation and other stuff but a broken core, the ride ends up in the landfill.

[doughboyshredder]

The way I see it you want your core to be as strong as possible. Broken core is non-fixable.
You can fix delams and edge an sidewall separation and other stuff but a broken core, the ride ends up in the landfill.

Does the strength of your core even matter though?

Look at all the foam core skis and boards that are out there. They get their strength purely from the glass and cap/sidewall.

I would think you could have a hollow core and it would be fine, except that the top would cave in.

[MontuckyMadman]

Big heavy riders that drop cliffs don't really ride that type of construction unless i t has wood in it right?
I have broken monocoque foam core skis and delammed allot of cap stuff and I am not big heavy and don't drop stuff over 15ft.

[doughboyshredder]

Big heavy riders that drop cliffs don't really ride that type of construction unless i t has wood in it right?
I have broken monocoque foam core skis and delammed allot of cap stuff and I am not big heavy and don't drop stuff over 15ft.

Yeah, but I think that is because of the lack of compressive strength of the foam. I.E. hard material could dent the core and cause a failure spot

I have delammed every cap board that I have ridden. But they were all Lib Techs so I figured that was the reason.