It was my understanding that one was always better to have a layer of uni and a layer of double bias, over one layer of triax.

As I understand it, and I am often wrong, the straightness or 'inlineness' of fibers greatly contribute to the composites abilities. This becomes even more important as one gets better resin ratios. Which we seem to be able to do in II.

So, ideally, all fibers would align in one direction, and different directions would be different layers stacked of uni, according to the properties desired in the composite. Given some of these uni layers would be very fine (small strength needed), double bias is considered a very good compromise, as the right angle strength is generally always needed.

The compliant with triax is the different bias are inherently compromised by the weave of the fabric, as three different strands plus the binder are all interfering with each other, so they can never align and perform like they should.

Secondly, it is a more expensive cloth per gram. So you pay a premium for a poorer performing composite.

Thirdly, as rob mentions, the thicker triax creates a problem in overlaps. So more weight/work faring. Thinner layers can stagger these, which reduce the bulge, and work and weight.

The advantage to triax is the labour savings of one layer over two, and the relative guaranteed direction of strength.

But I am not a composites engineer, and my understanding comes from years ago. These are the things I remember being told by them.

On July 8, 2018 6:50:47 PM UTC, "Björn bjornmail@gmail.com [harryproa]" <harryproa@yahoogroups.com.au> wrote:
|Depends on what kind of loads I suspect. I've read that in a multihull
|the
|main loads are in line with the hull. Then double biax 45 can't be
|optimal.
|Neither can uni, since there are other types of loads as well. So triax
|with 50% along the hull seems like a very good compromise to me.
|
|On Sun, Jul 8, 2018, 15:18 '.' eruttan@yahoo.com [harryproa] <
|harryproa@yahoogroups.com.au> wrote:
|
|>
|>
|>
|>
|> | How about combining the two best then: 400g uni and 400g double
|bias
|> 45°. Voila, what did you get? =)
|>
|> As i understand it, a more expensive, less performing version of two
|> layers?
|>
|>