REFLECTOR: Novice question

Alex Balic alex157 at pwhome.com
Tue Jul 4 11:38:37 CDT 2006


The wings are going to be plenty strong either way- squiggles, or no
squiggles, because most of the strength of the wing is provided by the spars
(which do not have any squiggles) and the fact that the triax is almost
overkill for the application. There will be some (minor) difference in
stiffness though.  I have been involved with some experiments and testing on
composite structures, and there is both a strength and stiffness issue
directly related to how the fibers are oriented and tensioned prior to
lay-up- you need to think of those roving strands as steel cables and the
wing as a bridge,  you do not want any slack in the cables or your bridge
will not be stiff and strong- the resin only is there to hold the strands of
glass in the correct position- it provides some minor compressive strength,
but that is not it/s major function. I would recommend anyone who has the
opportunity, to spend the hours it takes to pull every one of those roving
strands straight- My roll of Triax came with a ton of squiggles, and I would
guess I pulled and average of 8 inches of slack out of each strand using a
pair of pliers- you can usually get two at a time depending on how tangled
it is

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Tuesday, July 04, 2006 10:05 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Novice question

 

Steve;

 

I would suggest that it is not critical that they be laser straight.  On my
Wingco fastbuilt wings it is clear that no effort was made to straighten
them, because in every place I had occasion to sand to where I could see
them, there were definitely squiggles.  I doubt that mine are unique, and
there haven't been any failures.

 

Putting the uni side down probably results in a little smoother upper
surface requiring less additional filler.  And, of course, then no one will
ever see if there are squiggles:-).

 

Al

 

> Jack,

>  

> I would imagine, and I'm guessing here, that the factory guys are very 

> careful with rolling out the cloth.  I'm sure they have developed the 

> skills to unroll it and NOT introduce squiggles in the uni.  The 

> advantage might be in less filler on the wings with the bid layer up.

>  

 

So this brings my novice question. I'm a few weeks behind Jack so it'll be a
bit

before I do the wings. I'm wondering about how straight these fibers need to
be.

I read posts from say Andy Ellzey where I get the impression (maybe
incorrectly) that

sounds like straightness is practically checked by laser :-) and then I
watch

the video and it seems that all they were doing is getting the uni flat to
the

surface and that their hands were certainly not blistered by the operation.

 

My understanding from reading is that what seems to be important is that
there

not be slack in the fibers so that there are no load discontinuities. This
seems

to match what they appear to do in the video. Am I misinterpreting the video

and as Andy supposes above here that they are so much better at keeping the
cloth

in nice shape that they don't have much work left to do?

 

-- 

Steve

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