In the press today - as Swiss as it gets :)

[pmg]

Hi satch,

my plan for future builds is: Take the normal 10mm thick sidewall material, cut it in half with the bandsaw. That way I will have sidewall material a bit thicker than 4mm.

I think Akiwi might be right that the shift in the middle section can be created by the vacuum pulling towards the middle, thats exactly what happened here. So the issue was not the core positioning itself, but the press... Will figure a solution.

[satch]

How would the vacuum shift the core towards the middle? The film or Membrane presses the skis onto the mold. Even if you have a little bridging that won't push the core to one side.
I'm pretty sure it's your effort to push out air or you somehow misaligned base and core.

[pmg]

I am pretty sure the alignment itself can't be the reason, used this method: http://www.skibuilders.com/phpBB2/viewtopic.php?t=5218

And I think vacuum can pull sideways: the peel ply is very static, and I just laid it down over both skis. If the vacuum foil gets sucked down it might cause the peel ply to pull on the cores.
For the next build, I will cut peel ply and "bleeding cloth" for each ski indididually.

[pmg]

Daha Daha Daha ;)

Tested them today, they really ski great! definitely the best ski I built and also one of the best skis I skied in general - haven't skied many allrounders before. Lets say the best allrounder I skied :)

Ok, so the skis are great but won't last forever. So my summer project will be to build this ski again without the small flaws it has. What I want to change is:

- Sidewalls a bit thicker to have more room for error
- Further improve core positioning to avoid core shift
- paint the backside of the topsheet white to get shiny colors
- alter fibre setup a bit to save weight
- change the tipspacer: more tipspacer in general: the transition from wood core to tip spacer is in the area where the tip is bent the most, leaving a visible mark. I will taper the tipspacer then (3mm where it joins the wood core, about 1,5mm at the very tip) and of course make it hollow again.
- adapt the design to perfectly fit the binding at its position.

One question:
My fibre setup was:
320g/m² glass biax
120g/m² flax unix
300g/m² carbon triax
--- wood core ----
300g/m² carbon triax
120g/m² flax unix

Do you think taking away the 320g/m² glass below the topsheet (was mainly there for the white color) will change the way the ski rides a lot? I would like to tale it away saving maybe 50g per ski.

Cheers
Philipp

[SleepingAwake]

woah that is a very thin layup. The biax glass layer doesn't do much when its not balanced above and below the core. So it won't make a huge difference, especially as you combined it with carbon that is so much stiffer than the glass.

[pmg]

woah that is a very thin layup.

Thin? u mean not so much fibres?
The skis are pretty stiff, the wood core is 2.5 - 14 - 2.5

[SleepingAwake]

Yes with a thicker core the skis might have the stiffness, but with very thin composite face sheets the strength might be critical. Strength and stiffness are not related. Or not necessarily at least.

But if you had good results with similar layups in the past then is all good! If it ain't broke don't fix it! It's just that I use way heavier face sheets.

Cheers, Reto

[mammuth]

... and especially with thin fibres the type of wood has more impact on strength. Thin glas with thick woodcore (thick means thickness necessary to have the desired stiffness) out of ash may work, same with balsa, paulownia,... probably will not last long

[pmg]

2/3rd of the core are poplar, 1/3rd ash. Lets see how it keeps up.
The torsional stiffness of the 300g/m² carbon triax is definitely enough, other skis I built have a bit too much imo (built with 450g/m² triax or 300g/m² biax),

The flax really dampens, didn't believe it but these skis definitely are more damp than the pure carbon skis I used to build - damper in a very positive way!

[SleepingAwake]

I built my last couple of skis with biax flax and unidirectional glass or carbon and this makes for a really nice calm ski. Probably not what you want in a race ski, but wonderful in a freeride ski.

[Hannes]

Your ski looks great!

Why didn´t you put the flax next to the core? Like

Topsheet
Carbon triax
Flax uni
Core
Flax uni
Carbon triax
Base

I think it would give you even stronger damping.

[pmg]

I did this to get a whiter color below the topsheet. That won't be neccessary in the future as I either pait the back of the topsheet white or switch to wood veneer tops - really like those.

[pmg]

That ski is great! The only thing I don't like: Its not immune to rocks, (As any other ski). Have a look yourself:




Caught a rock when riding Firn in the Arlberg region (Wow, this area is paradise!). You can already see my repair approach in this picture: I cut out the damaged base (its 98x20mm) and glue in a new piece.

[Akiwi]

Ouch, Sympathies!

[sami]

Daha Daha Daha

Tested them today, they really ski great! definitely the best ski I built and also one of the best skis I skied in general - haven't skied many allrounders before. Lets say the best allrounder I skied

Ok, so the skis are great but won't last forever. So my summer project will be to build this ski again without the small flaws it has. What I want to change is:

- Sidewalls a bit thicker to have more room for error
- Further improve core positioning to avoid core shift
- paint the backside of the topsheet white to get shiny colors
- alter fibre setup a bit to save weight
- change the tipspacer: more tipspacer in general: the transition from wood core to tip spacer is in the area where the tip is bent the most, leaving a visible mark. I will taper the tipspacer then (3mm where it joins the wood core, about 1,5mm at the very tip) and of course make it hollow again.
- adapt the design to perfectly fit the binding at its position.

One question:
My fibre setup was:
320g/m² glass biax
120g/m² flax unix
300g/m² carbon triax
--- wood core ----
300g/m² carbon triax
120g/m² flax unix

Do you think taking away the 320g/m² glass below the topsheet (was mainly there for the white color) will change the way the ski rides a lot? I would like to tale it away saving maybe 50g per ski.

Cheers
Philipp

Hi,

I was considering a very similar layup (but without the 320 g/m2 glass), and saw your post. As this was a few years back, I wonder if you have done any further experiments on these materials / this layup? I have now made six pairs of skis, all using 750 g/m2 glass, and wanted to try something potentially lighter - Most of my skis have been 104-112 mm wide, 184-186 cm long, and the weight between 2100-2250 g per ski. With the carbon-flax layup, I believe I could get it down to something like 1900 g.

- I assume you have used a glass-based layup earlier, how does this layup compare in stiffness? It should be somewhat more stiff, 300 g/m2 carbon is probably close to 750 g/m2 glass, and then there is the extra flax uni.
- BComp data sheet shows flax uni only on the top of the core (i.e. non-symmetrical layup), did you consider that option too? I assume the top flax in the data sheet is mainly to get the desired damping properties, it has less effect on stiffness.
- Did you try altering the carbon/flax order in the layup? May not have that big effect with stiffness, but could affect e.g. durability.

Best,
Sami