Glassing wing center section

[jim ivey]

Guys
Are we missing something in all these posts about center wing sections?
When a wing bends under load the top sheeting is under compression, the 
bottom sheeting is under tension. The center wing joint is the weak point 
here.The center glassings job, is to connect the top and bottom sheeting so 
that this is not a weak point.In other words give continuity to the sheeting 
across the wing. One layer of fiber cloth is all that is necessary to tie 
the wing panel sheeting together.However, it is necessary to use a  a spar 
between the two wing halves for strength for the bending moments. Also it is 
my experience that epoxy resin is better to use than glass resin because the 
fiberglass resin dries out and gets brittle over time. I have good results 
with Zpoxy in this respect.I'm not a chemist and don't know why, but it 
seems to stay plyable.(sp)
Since the center wing fibers  sole job is to connect the top and bottom 
sheeting together the joint would be stronger if the dominent fibers are 
orientated spanwise of the wing.
My opinion is that a wing either needs a tube or a spar and one layer of 
fiber glass cloth and thinned epoxy.
Another can of worms.

Jim Ivey



jivey61 at msn.com





>From: "Edward Skorepa" <edsko at xmission.com>
>Reply-To: discussion at nsrca.org
>To: <discussion at nsrca.org>
>Subject: Re: Glassing wing center section
>Date: Wed, 26 Nov 2003 10:40:42 -0700
>
>Amir,
>
>I usually don't say something without having proof. When my first and only
>one wing broke in 1974 on my Mach 1, I've performed several tests. If I
>remember well, the wing sample glassed with 4oz  0-90  was the weakest, 6oz
>0-45 strongest and 4oz  0-45 and 6oz  0-90 failed at exactly the same load.
>Ed
>----- Original Message -----
>From: "Amir Neshati" <amirneshati at earthlink.net>
>To: <discussion at nsrca.org>
>Sent: Wednesday, November 26, 2003 2:30 AM
>Subject: Re: Glassing wing center section
>
>
> > Ed,
> >
> > Even when using a balanced bi-directional cloth, it is still strongest 
>in
> > the
> > 0-90 direction. This way, either the warp or fill will be perfectly 
>lined
>up
> > with the span, which is still stronger than both warp and fill in a 45
>bias.
> >
> > The one yarn of cloth in the correct orientation (span wise) will be
> > stronger
> > than both yarns in the wrong direction (0-45)....
> >
> > by the way, I accept PayPal...could have saved ya a stamp ;-)..You did
> > put the stamp on 0-90, right?
> >
> > Happy holidays,
> > Amir
> >
> >
> >
> >
> >
> >
> >
> > > You're right! The strongest lay up would be with unidirectional cloth
> > > running span wise. But that wasn't my point! If somebody wants to use
> > > bi-directional cloth (most people do, it's widely available unlike 
>uni)
> > then
> > > cloth needs to lay down on bias. Otherwise,  filaments laying cord 
>wise
> > > don't contribute to strength at all and are just waste and extra 
>weight.
> > As
> > > I said before, TWO yarns on 45 are stronger (not optimal)  but much
>better
> > > then ONE running span wise.
> > > As for 60/40 ratio, it's achievable. I seal the wood first with 
>sanding
> > > sealer before glassing.
> > >
> > > Enjoy your turkey.
> > > Ed
> > > P.S. thanks for nice comment about my pipes (check's in the mail)
> > > ----- Original Message -----
> > > From: "Amir Neshati" <amirneshati at earthlink.net>
> > > To: <discussion at nsrca.org>
> > > Sent: Tuesday, November 25, 2003 2:29 PM
> > > Subject: Re: Glassing wing center section
> > >
> > >
> > > > Will all due respect to your fantastic quality pipes, I humbly 
>submit
> > the
> > > > following:
> > > >
> > > > The strongest lay-up in the case of the wing center section is to 
>run
>as
> > > > much of
> > > > the glass fibers in the same direction as the balsa fibers, which is
> > span
> > > > wise....
> > > > 45 bias to the span/balsa grain is great for torsional strength, but
> > > that's
> > > > not what
> > > > we're after. The strongest will be to go to an 80/20 style fabric 
>with
> > 80%
> > > > of the
> > > > fibers running span wise and 20% cord....The  little 20% cloth cord
>wise
> > > > will be good
> > > > since no balsa or foam grain runs that way, but an all out uni will
>work
> > > > too...
> > > >
> > > > The weakest direction of loading the bi-directional cloth in the
>center
> > > > section is the 45 bias.
> > > >
> > > > Since there is balsa under our glass here, 60/40 may be hard to
>achieve
> > > for
> > > > most
> > > > with a bi-directional cloth, but with a uni, perhaps better can be
> > > achieved.
> > > >
> > > > Have fun,
> > > > Amir
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > > It's quite important to cut glass on bias (0-45) then both warp 
>and
> > fill
> > > > > yarns will work. Strength wise, one layer of bias cut 4oz equals 
>one
> > > layer
> > > > > of 0-90 cut 6oz. You will save weight and you will have smaller
>step.
> > > Also
> > > > > if you can, chose what's called balance weave cloth (warp and fill
> > yarns
> > > > > have equal number of filaments). Do NOT use any kind of fast 
>curing
>5
> > or
> > > > 30
> > > > > min epoxies. Use thin laminating resin preferably West System by
> > Gougeon
> > > > > bros. It has been designed for laminating over the  wood in boat
> > > industry
> > > > > and it's user friendly. I'm glassing center section with only two
> > layers
> > > > of
> > > > > bias cut 4oz cloth applied separately. First 2 inch wide over the
> > joint.
> > > > Let
> > > > > it cure completely then lightly sand and make smooth transition on
> > both
> > > > > sides to balsa. Apply 2nd layer over which will be wider than fuse
>by
> > 1
> > > > inch
> > > > > on both sides and do the same. Ideally, your glassing job should
> > > consists
> > > > of
> > > > > 60% of glass cloth and 40% of resin by weight. You should see the
> > weave,
> > > > if
> > > > > you can't you have way too much resin which will do nothing to
> > strength.
> > > > > Laminate must be flexible otherwise when resin breaks so glass
>fibers
> > > > > inside. Paint small amount of resin on balsa first, then lay down
> > cloth.
> > > > > Press it down with brush, wait till resin soak in then add some
>more.
> > Be
> > > > > patient, don't rush.
> > > > >
> > > > > Ed Skorepa/EScomposites
> > > > > ----- Original Message -----
> > > > > From: "Jerry Wilson" <JWilsonJr at houston.rr.com>
> > > > > To: <discussion at nsrca.org>
> > > > > Sent: Monday, November 24, 2003 6:07 PM
> > > > > Subject: Glassing wing center section
> > > > >
> > > > >
> > > > > > I'm glassing the center section of my Elan.  Using 6 oz/yard K&B
> > cloth
> > > > > > and 30 minute epoxy warmed with a heat gun on application.  The
> > epoxy
> > > > > > brushes on well and when dry the weave of the cloth is 
>noticeable.
> > In
> > > > > > other words the surface is not a smooth glasslike finish.  Is 
>this
> > OK
> > > or
> > > > > > do I need more epoxy applied for strength?
> > > > > >
> > > > > > Thanks,
> > > > > > Jerry Wilson
> > > > > > Katy,TX
> > > > > > NSRCA#3107
> > > > > > AMA#119585
> > > > > >
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