Ski Builders Forum

I currently use 220gsm Uni and 430gsm 45 Biax wich is about the same as 650gsm triax

I am wanting to switch to 750gsm triax (I can't find 650gsm triax)

If I normally have a core that is say 3mm tip 12mm underfoot 3mm tail

What would I reduce this to in order to have the same flex as before? Surely someone has an empirical method for calculating this as opposed top my experimentation methods.

I am wanting to do this to reduce messing about in layups when using glass. With my hemp skis I'm stuck with 2 layers each side until someone starts weaving triax hemp (I use canvas which is really crude biax)

Thanks Tom

would 19 oz be closer to 350 gsm?

doh I meant 650.
so im right and your problem is solved.

750 gsm = 22.11 oz/yd

650 gsm = 19.16 oz/yd

Calculations based on figures from Vectorply

PM Bambi perhaps?

I wrote up a program for flex matching longboards and skis with various layups/core materials. Its pretty involved, but if you tell me your ski dimensions, I can tell you what your core thickness should become for the 22oz glass. There are some easy ways to convert your core thickness if you are just changing lengths or widths...but once you change fabrics a good mechE background is useful.

mattman wrote:I wrote up a program for flex matching longboards and skis with various layups/core materials. Its pretty involved, but if you tell me your ski dimensions, I can tell you what your core thickness should become for the 22oz glass. There are some easy ways to convert your core thickness if you are just changing lengths or widths...but once you change fabrics a good mechE background is useful.

Length 180cm

Core length 1550 (20cm tip 5cm tail)

Core thickness 3mm,12mm,3mm - smoothed pyramid in shape.

Tip width 130, 100 underfoot, 119 tail

Many thanks Tom

Luc @ www.bmb-ski.nl/ has 600gr/m2 fg
(127cm wide roll)

check GAVAZZI: http://www.gavazzispa.it/?page=home_page&lingua=eng
they have ~400gr biax

i tried them both

I ve used Luc's 600gr fg by it self, and along with some cf roving
the glass is quite tide stitched -no gaps

a lighter -230gr biax from gavazzi' s i had, was not so tide

good luck

I ran those numbers for you and here are the results:

-Assuming the core length is the contact length when carving:
-Assuming 60% glass volume fraction
-Assuming poplar core (Aspen works out to the same thickness)
-Assuming Vectorply fabrics
Current Flexural Rigidity underfoot w/19oz: 1.02*10^5 in^2-lbs
Current Flexural Rigidity tip/tail w/19oz: 7.29*10^3 in^2-lbs
Equivalent thickness underfoot w/22oz: 11.5mm
Equivalent thickness tip/tail w/22oz: 2.5mm

Hope this helps,
Matt

mattman wrote:I ran those numbers for you and here are the results:

-Assuming the core length is the contact length when carving:
-Assuming 60% glass volume fraction
-Assuming poplar core (Aspen works out to the same thickness)
-Assuming Vectorply fabrics
Current Flexural Rigidity underfoot w/19oz: 1.02*10^5 in^2-lbs
Current Flexural Rigidity tip/tail w/19oz: 7.29*10^3 in^2-lbs
Equivalent thickness underfoot w/22oz: 11.5mm
Equivalent thickness tip/tail w/22oz: 2.5mm

Hope this helps,
Matt

Many thanks Matt - yes it does help - loads actually