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Triax


emteeoh
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ok, so I was at the Velocity factory a week ago, and they said that for the fast-build wings, they used triax, which, I understand, is fibreglass cloth with fibres arranged in 3 axes (axiis? however you pluralize axis). They said that, that way, they could make a lighter wing with fewer layers in the layup...

 

OK, but when I got home, I looked at the TERF CD, and the LongEZ plans call for only 2 layers of BID (if I`m not overlooking anything) as opposed to the 3 (or 6) layers of UNI I was kinda expecting, which would be more comparable to one layer of triax, I think.

 

I`m left wondering some things... Do Cozy builders ever use triax? Is there a reason why Nat wouldn`t have called for its use where appropriate? Are the wing skins on the cozy the same as on the LongEZ? Are 2 layers of UNI, appropriately oriented, comparable in strength but not weight to one layer of BID?

 

I don`t presume that velocity is selling an unsafe `fastbuild` wing, but I`m left wondering what the real tradeoffs are, beyond time and price... But thats for an email to them, not you...

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They said that, that way, they could make a lighter wing with fewer layers in the layup...

If you bag it, and you need that much glass in those orientations, then that might be true. For wet, non-bagged layups, there's way too many interstices and you get a very heavy layup.

 

OK, but when I got home, I looked at the TERF CD, and the LongEZ plans call for only 2 layers of BID....

I think you mean 2 UNI. The lower skins are 2 UNI and the top skins are 3 UNI (at least the COZY is - I believe the LE is the same, having looked at the LE plans a couple of weeks ago). The third layer of UNI on the top is spanwise, and used to prevent buckling, since the top skin is in compression, spanwise.

 

I`m left wondering some things... Do Cozy builders ever use triax?

A couple might have experimented with it, and Jeff Russell used it for a while when building AeroCad/Aerocanard wings. Heavy, difficult to orient and drape, IIRC.

 

Is there a reason why Nat wouldn`t have called for its use where appropriate?

He might have, if he had been aware of it, but there's no place where it's appropriate on a LE/COZY.

 

Are the wing skins on the cozy the same as on the LongEZ?

I believe so, in the context in which you are asking.

 

Are 2 layers of UNI, appropriately oriented, comparable in strength but not weight to one layer of BID?

No. They're heavier, thicker and stronger, and can be oriented as required, rather than within +/- 5-10 degrees of 45.

 

I don`t presume that velocity is selling an unsafe `fastbuild` wing...

Whatever it looks like, a Velocity is NOT a LE or COZY. While similar, they're not the same. Velocity is clearly not selling anything unsafe - they've had no structural failures. But they all also weigh substantially more than all but the two or three heaviest COZY's.
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I think you mean 2 UNI. The lower skins are 2 UNI and the top skins are 3 UNI (at least the COZY is - I believe the LE is the same, having looked at the LE plans a couple of weeks ago). The third layer of UNI on the top is spanwise, and used to prevent buckling, since the top skin is in compression, spanwise.

yes, now that you point it out, I realize I was (a) remembering wrong and (b) only reading about the bottom skins.

 

Thanks for the answers Marc. Helpfull as always!

 

 

 

Tyson: thanks for the link. Some good bits in there.

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It is not only the fast-build wings, but all Velo wings are built with one layer of Triax. I built my Velo wings last summer. There was no vacuum forming. Just wet out the sheet, squeegy out at much resin as possible and move on. The biggest problem was making sure the primary strand of the Triax was straight. Triax is basically a layer of Uni over a layer of Bid. But the primary strand in Triax seems thicker than the primary strand in Uni (just my opinion).

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It is not only the fast-build wings, but all Velo wings are built with one layer of Triax. I built my Velo wings last summer. There was no vacuum forming. Just wet out the sheet, squeegy out at much resin as possible and move on. The biggest problem was making sure the primary strand of the Triax was straight. Triax is basically a layer of Uni over a layer of Bid. But the primary strand in Triax seems thicker than the primary strand in Uni (just my opinion).

 

Close, but no cigar:::::::::irked:

 

 

Triax is NOT a layer of Uni over a layer of Bid.

 

Triax and biax are what is called a knitted fabric as opposed to a woven fabric as is uni and Bid.

 

In Uni and Bid, (woven) there are strands perpendicular to each other (used to be called the whoop and wharf) which, like most cloth are woven, meaning a specific strand will go under one (or two) of the perpendicular strands, and then over the next one or two etc. think of when you were a kid-- alright much younger and you made square constructions out of Popsicle sticks with the over under technique. The only difference between Bid and Uni is the weight and possibly number of one strand vs the perpendicular. Obviously with Uni, the strands perpendicular to the major fibers are rather light in weight.

 

The Tri or Biax is different in that it is made of fabrics that are all truely unidirectional. Each of the three (or two) fabrics are laid out of strands which are then sewn together, not woven.

 

What's the diff?????

 

 

Well, sir and madam, (he says rolling up his fiberglass sleeves)

 

In he uni and BID, since the individual strand must go over and under other strands, because it is not a straight shot, they suffer in tensile/compressive strength.

 

The Biax or triax because the fibers are straight enjoy a significant strength premium, I believe it is about 20% for equal weighted fabrics.\

 

I have used a lot of biax and find it a pleasure to work with.

 

Triax is difficult because the unidirectional fibers (actually those that are orientated along the long axis of the cloth,) tend to get out of place easily and are difficult to get back into their proper orientation. A great deal of care must be exercised in using it.

 

I think the ideal would be to use Biax with a standard Uni over it.

 

Try not to be clothsminded

I Canardly contain myself!

Rich :D

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Triax is basically a layer of Uni over a layer of Bid

^^^^^^

 

So BASICALLY, for the uninitiated, you can think of it as a layer of UNI over a layer of BID...

Sort of yes for application-- knowing that it will be stronger and as Marc said the surface will be rougher needing more filler ---unless you vacuum bag

 

but Noooooooo not exactly

 

Think of a fabric made strictly of unidirectional fibers (not unidirectional fabric)

 

Take one sheet of these fibers (remember they have no cross fibers much like what you end up with in the spar once you remove the cross fibers)

 

Take one of these sheets, orientate the fibers at 45 degrees.

Take another one of these sheets lay it on top of the other so that the fibers are orientated 45 degrees the other way, thus making the fibers of the first sheet and the second sheet with fibers oriented at 90 degrees to eachother.

 

These fibers have no relationship to each other other than being laid on top of one another.

 

If you take these two sets of fibers and sew them together, you now have Biax

 

Now, before you sew the above sheets together, if you take another layer of unidirectional fibers (as before) and put it on top of the two others and orientate the fibers of this one toward the long axis of the sandwich, this which would yield it's relation to the two prior sheets, at 45 degrees to each.

 

Now with this sandwich, (thought of as looking down the long way), you will see the bottom layer at 45 degrees to one side, then next layer at 45 degrees to the other side and the top layer straight the long way.

 

Take these three layers and stitch them together and you have Triax.

 

With the Bi and the Triax the intersecting fibers never cross over and under each other as they do in the woven fabric,that we know as BID and Uni (they just lay on top of each other. The stitching just holds the sandwich together and yields no strength) . Because the fibers are straight and not woven to each other (wavy), we get the increase in strength.

 

With either bi or Triax, if you eliminate the stitching, you will have only a handful of separate individual glass fibers.

 

Hows that for clarifying mud and making it murkey.

I Canardly contain myself!

Rich :D

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So BASICALLY, for the uninitiated, you can think of it as a layer of UNI over a layer of BID...

 

You don't get it!! I KNOW what Triax is. I've used it. I have some in my garage right now. I tried to give a simple explaination for those that have never seen or used it.

 

Now you can re-write the same in-depth explaination that you have written twice. We all acknowledge you know the details of what triax is.

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So BASICALLY, for the uninitiated, you can think of it as a layer of UNI over a layer of BID...

 

You don't get it!! I KNOW what Triax is. I've used it. I have some in my garage right now. I tried to give a simple explaination for those that have never seen or used it.

 

Now you can re-write the same in-depth explaination that you have written twice. We all acknowledge you know the details of what triax is.

 

Greetings Jp,

 

I was in error,

 

I assumed that the implication in your statement was that apples and oranges were basically similar because they were both round, and that it was you who didn't get it.

 

I also assumed that there were probably more people in the state of confusion, which you were obviously not, although seemed to be by your statement, who might benefit from my spending my time in review. Just trying to help.

 

I guess the statement that no good deed ever goes unpunished still stands.

 

I was wrong in my assumption about your knowledge, and I apologize.:o

I Canardly contain myself!

Rich :D

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