:: View topic - Another carbon thread

Would carbon stringers laminated in the core (as shown in this crude diagram) cause the same "issues" with the fiberglass as carbon sheets?

I don't really think that core setup would have the same bad issues. I would think that it would make the core tend to behave as if it were the average of the two materials and their cross-sections in the core. I know with the Bremallows, I used maple and mahogony in a similar fashion, and had a much softer core than when I used a solid maple core in my second pair of skis.

I'm just looking to gain a little pop/ stiffness over my first skis. I used maple/ poplar in them. Is the best way to gain stiffness without a lot of extra weight switching to all maple? trying to find wood with really tight grain? using a thicker core? extra layers of glass? some sort of carbon stringers?

In my opinion you gain nothing with placing the carbon on the core. All issues of combining materials with different Young modulus remain. You might even experience delamination issues (as far as i rember dbskis had this problem with carbon/wood skis).

I would suggest to use a wood with higher Young modulus (ash e.g.) for more pop and a thicker core for stiffness and stay with simple glass.

So you mean stick with just 2 layers of glass?

Just a little tip!

Remember that the, do not know the word for this, modulus for two layers increase with the sqare of the distance between them. So if you increase thicknes from 10 to 11 mm the flex increases with 20 %. Small changes makes big differences!

Henrik

A while back I was looking into what titanal actually is since lots of companies seem to use it. Though I don't have the info in front of me, I can find it if people want the specifics. I was mistaken in thinking that it's a titanium alloy when it's an aluminum alloy, which is only made by one company in europe.

I tried to find a US alloy which is similar [and maybe cheaper] but since the european alloy numbering scheme is different than the US one it was kind of difficult. There was one 7000 series alloy that was close, but it didn't have quite the same fatigue resistance as titanal, which is what makes it great for skis, and it seemed equaly rare and expensive.

The reason I'm writing this fairly uninformative post is that I was looking at a pair of Volkl Sumos at an online shop and it said that they had spring steel in them. It doesn't say anything about metal in the Sumos on volkl's site, but then it doesn't say anything about the Mantras having any metal which obviously do. I've never heard of anybody using spring steel, stainless or titanium yes. But both of those are very expensive like titanal, where as spring steel is really cheap.

Besides the weight penalty can anybody think of a reason that spring steel would be worse than titanal? And K's, some of the ski's you guys have made have some titanal. Does it make a big difference?

And happy new year everybody. Try not to get into trouble.

as to spring steel in Voelkls; I would think that it might possibly refer to the edges--speaking to a factory rep last summer-- they were pretty interested in designing/making ski's with less warranty issues------less/no metal and abs sidewalls instead of wood--------leather topsheats on the otherhand dont fit this M.O. I too am interested in hearing more about incorporating the use of metal/titanel into your designs-------of the ones I've seen here; it seams sort of odd to only use one layer of metal(titanel) (in a non-binding plate fashion) as this (I) would create a structural imbalance---Atomic did this once in the 80's: and I do not think one pair exists that was'nt bent in short order (and no I did not spell Voelkl wrong-------I do not have an umlaut on this machine)

Another option for a less exotic aluminum for skis might be the 6069 alloy. That's what's used for the chainstays on the Castellano Fango mnt bike, which is a pivotless soft-tail. Which means it has to have good fatigue resistance. And this is the guy that designed the Ibis BowTi, so I imagine he knows what he's doing.

http://www.castellanodesigns.com/fango.html

Most of the skis are reinforced with glass, because it is cheaper and easy to find. Some people could maybe be interested in playing with other reinforcement fibers.

Here are some data for the fibers alone (no epoxy around):

I found basalt fiber (it is a igneous rock) on swiss-composite.ch. The fiber is ligheter and stiffer than glass, and a little bit cheaper.

Zylon (regular and Hign Modulus) is a new polymer made by Toyobo (Japan). It is the best reinforcement material around today. It is lighter and stiffer than carbon, and more shock-resistant than kevlar. It is now used for armoured vest.

I like the sound of that! Especially the cheaper part. Any specific info about the prices?

At swiss-composite the glass (UD/biax/triax) costs about 3/4 CHF per square meter and 100g/m2. Basalt fibers (only UD) costs 2CHF/m2/100g.

Usually glass it is cheaper than that, but they sell also small quantity, so they charge more.

Actually basalt is an effusive rock, if I remeber well.

It should be nice to found some zylon. I have no idea about the price, probably high.

R&G in Germany offers some - looks quit interesting if combined with a +/-45 biax Glass layer:

http://shop.ezentrum.de/1609097/mh5tfxXJEMaMCHBS3RA74CXPqhQo1H/4DCGI/ezshop?action=artmehr&artid=50352

Hi Davide!

I think some of the values are for laminates and some for single fibers!

Here is a link to values for single fiber values!

http://www.nilsmalmgren.se/produkter/industriprodukter/industriindex.html

In swedish only but I think you can figure things out!

All the best!

Henrik

Don't forget about the "melting" of the glassfibers for example when they are curing in the epoxy. It brings the extra strength. Therefore I think such a table should be with epoxy or something similar.

Geoff

If I remeber well the properties listed above are for the fibers only.

But maybe I made some mistakes. I will check it. Anyway the trend is pretty much the same.

I had also some data for the fiber impregnated, and the E modulus was lower: the epoxy is less stiff than the fibers, so the tensile stiffness is lowered.