matthäus's skis

I helped a friend of mine in laminating his second pair, so I had time to get few pictures. I decided to make a little experiment, adding diolen. We will see how it works.

First, some epoxy on the base

First glass layer: UD 3150g/m2, sligthly narrower then the base, so it will fill up the gap in thichness between base and edges.

This is the new thing: diolen (polyester), 265g/m2. It is a soft, high resilience material. Maybe it will damp vibrations.

Biaxial layer, 410g/m2

Alligning the woodcores

Again a biaxial layer, 410g/m2

The last layer: UD 250g/m2

Transparent topsheet

Here I am closing the bag

Under vacuum

Out of the bag: before lamination he put some tape on the base, to keep it clean from the resin.

After pressing

nice pics. what kind of wood are you using for the core?

Man, you guys make it look so easy.... really neat and tidy. I make more of a mess when I bake an apple pie than you so when you make a pair of skis. Seeing your photos really makes me want to try a vacuum bag set-up... someday. How does the finished ski feel with the polyester cloth? They look really great. Thanks for the photos and the inspiration.

G-man

I got the cores from Hess (www.hessco.ch) a Swiss company.

These are 180cm long, 12 cm wide, 14mm thick, poplar and birch. These were samples, so I got them for free. Price should be below 15 euros per pair, I think.

They sell also machined woodcores, price is around 20/30 euros per pair, depending on how many pieces are ordered.

Regarding the polyester cloth, I like it when I try to bend them, but I should try them on the snow; anyway I am quite optimistic.

I am thinking to put up a simple system to measure the damping...

Davide,

Do you still have snow available so that you can test these lastest skis? I hope so. I've been eyeing a little patch high up on a mountain accross our little valley, wondering if it was worth the trek to get in some August turns.

This site: www.skis-lacroix.com on the 'technology' page, shows that they use a layer of 'vibrachoc' for damping. Do you think that this vibrachoc might be similar to your diolen?

Thanks,

G-man

I'll answer my own question, here. I've spent quite a lot of time over the last couple of days, trying to locate on-line info about 'vibrachoc'. It's actually been pretty difficult to find much definitive stuff on it. However, I did manage to sort out that vibrachoc is an elasomeric rubber compound, and not any kind of composite fabric. It's used for all sorts of vibration damping parts, like aircraft engine mounts and electronic component mounts. I couldn't find a source where it could be purchased in sheet form. Generally, it's bonded to other metal components, so I would guess that it would bond quite well in a sandwich ski assembly.

I haven't really noticed any vibration issues with my skis, but maybe with more time on them, I might. I don't spend much time on hard ice at high speed, and don't foresee going in that direction in the future... no plans to move to the East Coast. But, who knows, vibrachoc might come in handy for something, someday. At least now I know that's basically just fancy rubber.

G-man

I will ask to Ludovic Lacroix (his workshop is about 50 Km form my place) where he got the vibrachoc. I know it is rather expensive: about 10/20 euros per pair, if I remember well. He gave me few pieces, that I use as truck pad on the longboards.

Last winter I did few runs with one of this "vibrachoc" ski. Indeed they are less noisy that standard skis, that is the high frequency vibrations (over 1kHz) are stopped, but I am not sure it is true also for the low frequency vibrations (below 100Hz). I did not feel a striking improvement, but I did not do a serious testing.

Last week I read a technical study on the influence of kevlar on vibrations. It was done in 80's (2m long stiff narrow skis).

Indeed kevlar can dampen vibrations, but not always: it depends on how the ski is constructed (sandwich or torsion box) and on the amount of kevlar added to the ski.

It was not very clear, but the conclusion seems that the damping effect comes from the shear friction between the kevlar and the glass layers. It is clear that dissipation (friction) is needed for damping, as in car dampers http://en.wikipedia.org/wiki/Shock_absorber

That is why I put diolen between the UD glass and the wood: I hope that the UD glass layer can slide respect with the wood core, and the friction will damp vibrations.

These days I am trying to put up a test system to measure vibrations in skis, using a pick-up coil and an oscilloscope. I will keep you informed.

By the way, there are still snowfields and glaciers in the Alps (few resorts are open year round), at least for the next few years, but during the hot summer I do not feel very much going skiing, I rather go swimming in the river, walking or biking.

But it is not excluded that, once the balsa skis will be finished (I will put diolen in there as well), I can think about testing them, maybe in September or October.

Nice work! I´m sure these pictures will help us to do it better on our next pair. We have been on holidays and of course it´s possible to ski in europe in summer but not for too much time. I´ve gone skiing last 4 years and every year glaciers are in worst conditions. This year we have gone to Passo Stelvio in Italy and then to Solden in Austria. Last glacier was almost closed because of the lack of snow. The high temperatures has done a lot of damage to the glaciers in europe.

Look at this pictures:

http://www.xski.net/foro/viewtopic.php?t=1637

The warming of the planet is a reality. I was sad of seeing this but it´s true.

But in any case, people whi lives near the alps are very lucky because they can try their home made skis even in summer.

Davide, post more pictures, it´s very interesting to see your work.

Mutombo,

Really great pictures! The Alps are so beautiful. Thanks. Yes, very concerning regarding the status of the world's glaciers... and all other things related.

Davide,

Thanks for all of the great information... you seem to have a wealth of it and I'm sure that we all very much appreciate your willingness to share.

G-man

Somewhat off topic regarding ski building....but I will say something brief anyway.

Global Warming is a fact. Without a doubt, not question, global warming is occuring. The issue is what is truly causing it....whether it is our actions that are causing the temperature change or it is just a natural change in the Earth is unknown....

I'm a biology student and have been helping a professor at my school do some global warming, or climate change as we prefer to call it, reserach. From what I have seen, it does seem like we are speeding up the change occur in the carbon cycle on the Earth. Whether or not we can help slow it down or reverse it is unknown.

What must be known is that just because the Earth is undergoing a warming process....it does not mean that there will be no more snow or whatnot around the world.

As the ice caps melt, more colder water will push down from the Arctic and will eventually stop the Gulf Stream in the Atlantic. As this happens, the warm waters currently in the Mid-Atlantic will disappear and will be replaced by colder water from the North.

the result - cold ass weather in Northern Europe. It maybe warming now, but give it awhile and it will soon be snowing in London. SO.....skiing may be screwed in many parts of the world......but it doesn't mean it wont be possible. There will still be many cold and snowy spots on the Earth.

[end rant

]

Hi I just finished reading your build log and it was very well done, you managed to make the whole process a whole lot cleaner than I can make it look.

Two questions:

The first is what did you use for the clear topsheet? I've been looking around for better top sheets(I'm currently using a polyetheylene plastic). Whatever you used is alot clearer than what I am acheiving.

The second question is what type of epoxy you are using, and what the cure time on it is.

Whatever you're using it sure is working for you, keep up the good work!

The commercial name is "Duraclear": it can get even more transparent when laminated in a hot press. They sell also a varnish to improve the bonding.

I use this resin http://www.swiss-composite.ch/pdf/t-Epo ... -Typ-L.pdf , with hardener L (40 min. pot life). It should stay at least 10 h under pressure, then it harden completely in 10 more hours.

i noticed that you dont seem to use a sidewall on your skis in the layup...you press extra wide cores? this prevents having to worry about lining up the core!!! how do you seal/protect your sidewalls from abuse?