lighter fiberglass

[uni412]

I was wondering what the differences would be between using say a single layer of 22oz fiberglass versus multiple layers of lighter 6oz or other wiegth glass. It seems like everyone uses 22oz fiberglass and I am wondering why this is. Is it just a matter of cost?

Thanks

[SCHÜSS]

haha funny you ask. i actually did a test of exactly that just recently.

here are my results

on a 1mm thick piece of bulsa, roughly measuing 200mmx40mmx1mm

i tested

-one piece with one layer of 18oz plain weave fibreglass
-one piece with 3 layers of 6oz plain weave fibreglass
-one piece with 2 layer of 6oz and one layer of 18oz

stiffness wise they were all about the same, including the third test.

'pop' or 'bounce' varied tho, with the 3x6oz having slightly more 'pop' than the single 18oz. The (1x18/2x6oz) felt about the same.

torsionally the 2x6oz/1x18oz felt alot stiffer in the torsional direction compared to the other two.

Only problem is.. i was testing over very small surface area. i dont know how it would effect a ski on a big scale?

Any way hope this helps.

schuss

[uni412]

Thanks for the help. I thought that 3 layers of 6oz would have the same stiffness as one layer of 18oz. Thats good to know about the increased pop that the lighter glass provides. However I'm still wondering why almost everyone uses single layers of 22oz glass. It seems like using more sheets of lighter glass would be preferable.

Thanks
Uni412

[mattman]

the benefit of using a single sheet of 22oz triax is that you elminate ALOT of waste. if you were to make your own triax with three layers of a lighter unidirectional glass, you would waste a good portion by creating the +45 and -45 layers (or +60 -60 depending on the fabric). also, it is faster and easier to handle and wet out one layer of fabric, than three. the only real benefit that I can see is that the three seperate layers would be slightly more formable if you have sudden compound curves.

[Idris]

I can't easily get hold of 18oz or for that matter 22oz triax. So I am using unidirectional and 45 Biax to get a similar weight.

[uni412]

Yeah, it seems like triaxial glass is hard to get a hold of but doesn't have any major advantages over lighter biaxial or plane weave glass in overlapping layers. I still want to know why everyone seems to use 22oz triaxial.

-Uni412

[mattman]

there are major advantages of triax over woven fabrics. triax fabrics are knitted, not woven. knitted triax fabrics are the three layers sitting on top of one another with a thin polyester stitch holding them together. woven fabrics have many disadvantages compared to knitted....the woven design makes them significantly weaker. First because each strand goes over and under the others, the strands act to shear one another and provide less support in the horizontal direction it is needed (for this reason 5 and 8 harness weaves are the strongest because the fibers cross less). second weaves are weaker because more resin is required to saturate woved fabrics since the strands do not lie flat. excess resin degrades your fiber:resin ratio (80% fiber is the unobtainable perfect amount).
as long as you use your uni as the lengthwise strand (0 degree), and set your woven biax at an angle (+45 -45), your stiffness will be minimally effected. if you do want to try triax eventually, check out www.raka.com, its cheap and good!

[uni412]

Thanks alot mattman. I finally have the answer I was looking for.
-Uni412