GS Race ski

[dorabito]

Hey everyone!
During my summer vacations I am thinking of building a pair of skis.
This is what I want:
- A GS (Giant Slalom) ski according to men´s FIS rules for Giant Slalom
- Max stability on long radius turns
- Max grib on hard, iced and transformed snow
- High speed

Here is my project:

Tip: 103mm.
Waist: 69mm.
Tail: 88mm.
Camber:15 mm.
Lenght 185cm.
Tail to Waist: 67cm.
Estimated Radius: 28m.

UPDATE: NEW LAYUP (probably the final one)

CLEAR TOPSHEET
750g/m2 FIBERGLASS
OBECHE/OAK CORE, ABS SIDEWALLS and TIP/TAIL SPACERS
750g/m2 FIBERGLASS
340 g/m2CARBON UD-TAPE 25mm. (twice)
VDS RUBBER FOIL
STELL EDGES and P-TEX BASE



This is the core lamination:

sidewall(or tip and tail spacers) /obeche/oak/oak/obeche/obeche/obeche/oak/oak/obeche/sidewall
(or tip and tail spacers)


The heights of the core:

Tip: 2mm.
Waist: 12mm.
Tail: 3mm.





This was the firts layup. It was changed due to advices from people from this forum (thank you guys) and experiments.

I´m (was) thinking on building it as this:

TOP SHEET
TRIAXIAL FIBERGLASS
BI-DENSITY WOOD CORE, ABS SIDEWALLS and TIP/TAIL SPACERS
TRIAXIAL FIBERGLASS
TRIAXIAL FIBERGLASS
CARBON FIBER
RUBBER (anti vibration and edges bonding)
P-TEX BASE and STELL EDGES



Tip Height: 2mm.
Waist Height: 10mm.
Tail Height: 3mm.


So guys, what do you think about it? Should I change carbon fiber to fiberglass, kevlar or whatever? Is it a good idea to put rubber there?
Will it be stiff and resistant?
I am open to any suggestions, so if you have one please tell me

[OAC]

What I understand is that the carbon fiber should be under the core.

[OnDeck]

Never tried it perosnally, but i understand that dfferent weight glasses (or even a total lack of glass on one side) will affect the camber, because of different rates of contraction during curing.

[dorabito]

What I understand is that the carbon fiber should be under the core.

Skis should have at least one layer of fiber under the core and one above. This is what I read:
http://www.skibuilders.com/howto/skicon ... ites.shtml

[OAC]

I meant if you are using carbon fiber you should have it under core. Of course there should be fiber above the core but should be regular triax or biax glass. But if you want a stiff race ski you can have carbon fiber above aswell.
The theory is about tension(under) and contraction(above). There are differences between carbon and glass in this matter. But how much, I'm not able to tell you. That's up to you to experiment with!...

Cheers
Good luck

[leifkj]

I've been thinking of doing a race ski at some point, and one thing I've noticed is that most commercial race skis have two layers of aluminum, one above, one below the core.

[dorabito]

I've been thinking of doing a race ski at some point, and one thing I've noticed is that most commercial race skis have two layers of aluminum, one above, one below the core.

It should be aluminum paper or hard aluminum?

[MontuckyMadman]

your user name makes me think of doritos

[chrismp]

your user name makes me think of doritos

you should put some of those in your cores and give it super space-techy name sth like dorito-ultra-lightning-bolt-special-weapon-makesyouridiculouslyfast-tech

[skidesmond]

What's bi-density wood core? Are you using 2 types of wood? Rubber is a good idea. It will be a stiff ski alright. But it also depends on the thickness of your wood core and the type of wood(s) being used.

Are you building them to actually race? Is it beer-league racing, NASTAR, ....?

The tail sounds pretty narrow as does the waist. Check out what the big manufactures are using for designs/shapes to get a good idea (Fischer, Atomic, Volkl, ....). You can give the ski a little more shape but still keep a high turning radius if you want.

There's some good info in the forum on the uses of Kevlar and CF. Check it out.

[OAC]

I was loitering in one of the bike/ski store in my neighbourhood and they had some Atomic GS race skis there. And I was surprised to see how narrow they were! And stiff as h**l! Looked like my old ones from the 70's...

[skidesmond]

I was loitering in one of the bike/ski store in my neighbourhood and they had some Atomic GS race skis there. And I was surprised to see how narrow they were! And stiff as h**l! Looked like my old ones from the 70's...

Yeah I was at the ATOMIC website last night looking at one of the GS skis, 99.5/67.5/85.5. That's a skinny ski by todays standards.

[jono]

Why did FIS go from 21m to 27m for men's GS skis?

Dorabito,
I made a pair of skis last year that had 34oz triaxial glass on the bottom of the core and 20oz triaxial glass on top. These skis have a thick core profile that makes them stiff. The asymmetrical distribution of fiberglass (greater weight of the bottom glass) has given these skis less tip height and greater camber. They ski like SG skis and the extra glass makes them damp. There was no need for rubber to damp vibration in these skis.
Unless you are talking about VDS rubber foil (on top of your edges), I would skip rubber on your first pair and focus on keeping the skis simple. Get a racing plate with rubber in it for vibration absorption.
I would also say that if you want damp skis you'll have more luck with fiberglass than you would with carbon fiber + rubber.

Also check out: viewtopic.php?t=835

Good luck!!

[chaka]

I have already built a pair of GS skis using 3 layers of 720gr triax glass under core and three above. I also added two carbon ud tapes under and other two above. I used a very hard oak core, not too thick. I think that using a hard wood makes the difference in this kind of skis.
They were room temperature cured but the symmetrical layup has kept the camber after 2 seasons.

One more advice... if you are only going 182 long I would keep the radius about 21 meters. If you want more radius I would build something a little longer... maybe 190 cms.

[dorabito]

What's bi-density wood core? Are you using 2 types of wood? Rubber is a good idea. It will be a stiff ski alright. But it also depends on the thickness of your wood core and the type of wood(s) being used.

Are you building them to actually race? Is it beer-league racing, NASTAR, ....?

The tail sounds pretty narrow as does the waist. Check out what the big manufactures are using for designs/shapes to get a good idea (Fischer, Atomic, Volkl, ....). You can give the ski a little more shape but still keep a high turning radius if you want.

There's some good info in the forum on the uses of Kevlar and CF. Check it out.

My bi-density wood core is made of poplar (flexible and light) and maple (stiff and resistant) in this construction:
Sidewall, poplar, 2 maple, 3 poplar, 2 maple, poplar, Sidewall

These skis will be for beer-league racing, and the shape was adapted from an Atomic Race GS D2 WC/EC from the season 2010-11