Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Wed, 31 Mar 2004 17:16:41 -0500 Message-ID: X-Original-Return-Path: Received: from rwcrmhc13.comcast.net ([204.127.198.39] verified) by logan.com (CommuniGate Pro SMTP 4.2b1) with ESMTP id 3139212 for lml@lancaironline.net; Wed, 31 Mar 2004 16:19:35 -0500 Received: from MJR (h000094c615c2.ne.client2.attbi.com[65.96.140.242]) by comcast.net (rwcrmhc13) with SMTP id <20040331211934015007p5b5e>; Wed, 31 Mar 2004 21:19:34 +0000 X-Original-Message-ID: <002901c41766$c7128800$f28c6041@ne2.client2.attbi.com> From: "Mark Ravinski" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: mixing carbon and e-glass X-Original-Date: Wed, 31 Mar 2004 16:26:05 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0026_01C4173C.DDBF60C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_0026_01C4173C.DDBF60C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Scott, I'm not sure of your point. In the cases you describe, the graphite is designed to cary the whole = load and the glass is only the supporting structure. That's good = engineering. The L2 spar and legacy skin are perfect examples. The = carbon sections are thick and strong enough to carry the whole load. = (Webs of beams, ribs and bulkheads only support the load bearing parts). If you were to make a spar cap by substituting glass for half the = graphite, you would have precisely the two rope scenario and 25% less = ultimate strength. =20 Mark, Speed Demon Ravinski From: Sky2high@aol.com=20 To: Lancair Mailing List=20 Sent: Wednesday, March 31, 2004 12:59 PM Subject: [LML] Re: mixing carbon and e-glass In a message dated 3/31/2004 7:22:53 AM Central Standard Time, = mjrav@comcast.net writes: If the graphite rope were smaller than the glass rope, like using a = smaller percentage in the layup, then the failure of the graphite would = occur much earlier in the loading, (like under normal flight conditions.) This is a simple analogy and nothing in the aircraft is so simple. Mark, Think on this. With a composite glass/carbon construction, the more = flexible material (glass) does provide some structural support along = with the stiffer one(carbon). In both compression and tension the glass = has no problem because it is not stressed to the same amount as the = carbon. The bond (shear) between the two is less stressed than if both = materials were of the same stiffness because the distance (arc) over = which the compression or tension has a different radius. It's no wonder = those aluminum spar caps have so many rivets. =20 Once again, consider our 320/360 main spar. It was designed to have a = certain strength and stiffness at the various BL stations - more demand = inboard than outboard. Built entirely of glass it may have been too = heavy and not stiff enough. Built entirely of carbon, it may have been = too stiff. The distance of separation (web) of the caps also contributes = to the stiffness. So, we have generally a "[" spar where the caps (top = and bottom) are encapsulated by molding it within the web glass that is = continuous from the aft edge of the bottom cap to the aft edge of the = top cap. Where the wing spars are bolted to the main spar, both spars = have an aluminum plate embedded in the web glass, a bushing bonded thru = each spar to tie everything together and a few countersunk bolts taking = some of the load between the plate and the web glass in addition to the = giant bolts that keep the wing attached. Futhermore, certain parts of = the wing and main spar are double webbed i.e. "[]", and this leads to = further stiffness, strength and resistance to twist. Consider the Legacy. Monocoque construction contains a skin solely of = carbon - sort of. Just like spars, the "web" between the outer and = inner skin is either paper (honeycomb) or foam. Orthogonally organized = paper (or foam) is certainly no match for the carbon, but this is what = holds the Legacy together. The total thickness of such skins is much = thinner than that if it were made of glass because the greater stiffness = of the carbon allows for a smaller web. Of even greater interest is = that the Legacey skins are all held in place by glass ribs and = bulkheads. Also, our wee glass Lancairs use foam in the top stub wing because the = glass/nomex honeycomb combination is not very resistant to puncture = wounds, those easily caused by a high-heeled wench or a dropped wrench. = I don't remember the core composition of the Legacy stub wing skin. Scott Krueger AKA Grayhawk Sky2high@aol.com II-P N92EX IO320 Aurora, IL (KARR) LML, where ideas collide and you decide! ------=_NextPart_000_0026_01C4173C.DDBF60C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Scott,
I'm not sure of your point.
In the cases you describe, the graphite is designed to cary the = whole load=20 and the glass is only the supporting structure. That's good = engineering. =20 The L2 spar and legacy skin are perfect examples. The carbon = sections are=20 thick and strong enough to carry the whole load.    (Webs of = beams,=20 ribs and bulkheads only support the load bearing parts).
If you were to make a spar cap by substituting glass for half the = graphite,=20 you would have precisely the two rope scenario and 25% less ultimate=20 strength.
  
 
Mark, Speed Demon Ravinski
From:=20 Sky2high@aol.com=20
Sent: Wednesday, March 31, 2004 = 12:59=20 PM
Subject: [LML] Re: mixing = carbon and=20 e-glass

In a message dated 3/31/2004 7:22:53 AM Central Standard Time, mjrav@comcast.net writes:
If the=20 graphite rope were smaller than the glass rope, like using a=20 smaller
percentage in the layup, then the failure of the graphite = would=20 occur much
earlier in the loading,  (like under normal = flight=20 conditions.)

This is a simple analogy and nothing in the = aircraft is=20 so simple.
Mark,
 
Think on this.  With a composite glass/carbon construction, = the more=20 flexible material (glass) does provide some structural support along = with the=20 stiffer one(carbon).  In both compression and tension the glass = has no=20 problem because it is not stressed to the same amount as the = carbon.  The=20 bond (shear) between the two is less stressed than if both materials = were of=20 the same stiffness because the distance (arc) over which the = compression or=20 tension has a different radius.  It's no wonder those aluminum = spar caps=20 have so many rivets.  
 
Once again, consider our 320/360 main spar.  It was designed = to have=20 a certain strength and stiffness at the various BL stations - more = demand=20 inboard than outboard.  Built entirely of glass it may have been = too=20 heavy and not stiff enough.  Built entirely of carbon, it may = have been=20 too stiff. The distance of separation (web) of the caps also = contributes=20 to the stiffness.  So, we have generally a "[" spar where the = caps (top=20 and bottom) are encapsulated by molding it within the web glass that = is=20 continuous from the aft edge of the bottom cap to the aft edge of the = top=20 cap.  Where the wing spars are bolted to the main spar, both = spars have=20 an aluminum plate embedded in the web glass, a bushing bonded thru = each spar=20 to tie everything together and a few countersunk bolts taking some of = the load=20 between the plate and the web glass in addition to the giant bolts = that keep=20 the wing attached.  Futhermore, certain parts of the wing and = main spar=20 are double webbed  i.e. "[]", and this leads to further = stiffness,=20 strength and resistance to twist.
 
Consider the Legacy.  Monocoque construction contains a skin = solely=20 of carbon - sort of.  Just like spars, the "web" between the = outer and=20 inner skin is either paper (honeycomb) or foam. Orthogonally organized = paper=20 (or foam) is certainly no match for the carbon, but this is what = holds=20 the Legacy together.  The total thickness of such skins is much = thinner=20 than that if it were made of glass because the greater stiffness of = the carbon=20 allows for a smaller web.  Of even greater interest is that the = Legacey=20 skins are all held in place by glass ribs and bulkheads.
 
Also, our wee glass Lancairs use foam in the top stub wing = because the=20 glass/nomex honeycomb combination is not very resistant to puncture=20 wounds, those easily caused by a high-heeled wench or a = dropped=20 wrench.  I don't remember the core composition of the Legacy stub = wing=20 skin.
 
Scott=20 Krueger AKA Grayhawk
Sky2high@aol.com
II-P N92EX IO320 Aurora, = IL=20 (KARR)

LML, where ideas collide and you decide!
 
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