Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Tue, 11 Jan 2005 22:31:15 -0500 Message-ID: X-Original-Return-Path: Received: from mail-relay-1.tiscali.it ([213.205.33.41] verified) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP id 603680 for lml@lancaironline.net; Tue, 11 Jan 2005 13:46:56 -0500 Received-SPF: pass receiver=logan.com; client-ip=213.205.33.41; envelope-from=robert.overmars@tiscali.it Received: from trottolino (62.11.1.163) by mail-relay-1.tiscali.it (7.1.021.3) id 416A80380112273E for lml@lancaironline.net; Tue, 11 Jan 2005 19:46:26 +0100 X-Original-Message-ID: <008d01c4f80e$eea77900$a3010b3e@interbusiness.it> From: "Robert Overmars" X-Original-To: "Lancair Mailing List" Subject: Lead Sleds... X-Original-Date: Tue, 11 Jan 2005 19:54:06 +0100 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_008A_01C4F817.4EFA9DC0" 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_008A_01C4F817.4EFA9DC0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Salutti tutti, Time for some myth busting: ...data data Data! where to start? How about with tonight's LML Digest = and and Brent R's assertion that "you could load a IVp to 28,500lbs and = it would still fly" Well, sorry Brent, it won't. (Brent, if you were = Kelly Johnson and I was Ben Rich I'd collect a quarter from you. = Allowing for extreme inflation lets call it $100 and I'll post you my = address....) It won't fly because the wings have fallen off. Actually that's not = technically correct, the wings have clapped...at 18,500lbs of wing lift = because that's what the wings were designed to lift and that's what they = will lift....well, sort of. We'll get to that little "gotcha" shortly. Lets look at Data, from the horse's mouth. The best source of = information on LIVs I know of are Martin Hollman's book "Modern = Aeroplane Design" vols I, II, and also "Boogie with a Turboprop". Should = be required reference books for ALL LIV builders/owners/pilots but I do = digress.... In "MAD" vol I, Chp 6, is a section describing the LIV wing. = Page 106 gives some pertinent information, (I'll only quote that which = is pertinent for the purpose of this discussion). Limit Flight load = factor =3D 4.4gs. Gross Weight =3D 2,900 lbs, minus the wing weight of = 310 lbs =3D 2,590 lbs. Limit Flight maneuvring speed, Va =3D 200 mph. = design dive speed Vd, 360 mph. (both speeds at SL). Safety Factor =3D = 1.5 for ultimate loads. Page 111 of Vol I shows a copy of an engineering drawing of the Lancair = IV wing layup schedule. In the bottom right hand corner in the notes = section are notes I & II, as follows: 1) Gross wt 3,000lbs less wing = panel wt 160lbs/panel. 2) Limit load factor =3D 4.4 gs, Safety Factor = 1.50. (interesting is it not? ...Safety factor of ONLY 1.5 Kinda blows = the 200% Ultimate Load Factor myth out of the water...no?) Let's skip to page 113, Fig 6.15, Wing Deflection, skin shear stress, = etc. Quote "An actual wing structural test was performed for the load = condition of Vd =3D 360 mph. The wing failed under a total load of 9,250 = lbs and a deflection of 15 inches. The wing load at 4.4 Gs is: Load =3D = 2590 x 4.4 x (154.5/360) =3D 4891 lbs". Therefore with 4.4 Gs load = equaling 4891 lbs wing panel lift we can easliy calculate the max G load = at the wing panel point of failure of 9,250 lbs =3D 8.32 Gs. What a great design! Nearly 200% ultimate load factor...lot's of margin = built into this wing... let's up the gross weight and our wing can carry = it for sure! =20 Yeah right...sucker! ....myths based on assumptions based on wishfull = thinking.... Let's backtrack to page 107, top of the page "...Structural Dimensions = for an airspeed of Va =3D 200 mph and an angle of attack of 14 degrees, = and for an airspeed of Vd =3D 360 mph and an angle of attack of 2 = degrees are determined". Then para 1: "Figures 6.10 & 6.11 show that the = maximum bending moment is expected for Va =3D 200 mph since the tip is = loaded more than at Vd =3D 360 mph" So what's this then? what does it = mean? Let's go look at Figs 6.10 & 6.11... a couple of graphs and a = couple of tables of, wait for it.... DATA!!! The graphs on page 108 are self explanatory and show clearly that at Va = the wing tip is loaded more than at Vd. Then page 109 gives = numbers...lots of them but it easy to make sense of it. Our interest are = the lines (wing station) WS2 on both tables. Firstly for Va, 200 mph, = 14' AoA, the wing panel lift =3D 4952 lbs outboard of BL 18 ie. and wing = bending moment at BL 18 is 28,554 ft-lbs. For Vd, 360 mph, 2' AoA, the = wing panel lift is 4709 lbs outboard of BL 18 and the wing bending = moment at BL 18 is 22,436 lbs. In other words, for nearly identical wing = panel lift for Va and Vd conditions, the wing bending moment at Va, ... = ie the force that breaks the wings, is 28,554/22,436 =3D 1.27 times = greater than at Vd. Got your attention now I'll bet! To tie it all together, to know the G load achievable at the point of = wing failure at Va, divide the 8.32Gs achievable at Vd by 1.27 =3D = 6.55Gs=20 So there you have it: At 2,900 gross weight at Va your wings will clap = at 6.55 Gs or thereabouts. Perhaps you lead sled builders might want to = play in the margins and in the edges of the bell curve of the wing = failure test (a test sample of 1 to date), maybe your wing are = stronger...but maybe not, maybe Lancair Company has redesigned and = strengthened the wing since this data was published...or maybe not, = maybe you think fuel load in the wing alleviates the wing bending moment = and these numbers don't apply to you...but for the purpose of = calculating wing bending moments weight of fuel in the wing is not = permitted. If you think that way you're relying on lots of "maybes" = Best of luck to you and I hope the "maybes" line up in your favour as I = don't wish to read more Lancair accident reports thank's very much. In this recent once again iteration of Lancair IV weights on LML others = have covered pretty much all the negative points of increasing gross = weights but I'd just briefly like to put some numbers to increasing = stall speeds with increasing weights. Stall speed increases with the = square root of the load factor. If the stall speed @2,900lbs is 66 = knots, increase the weight to 4,000lbs and the increase in load factor = is 4,000/2900 =3D 1.379. Square root it =3D 1.174. multiply by the = original 66 knots stall speed =3D 77.5 knots. Lets look at the clean = configuration and a stall speed of lets say 80 knots... multiply by = 1.174 =3D 93.92 knots. Pull a 2 g turn (clean) and the stall speed =3D = 132.8 knots. Build 'em light, Really Light!! (it's not hard) ....and straight... ciao Roberto d'Italia. ps, lead sled builders...don't forget to redo the white/green/ arcs on = your ASI. ------=_NextPart_000_008A_01C4F817.4EFA9DC0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Salutti tutti,
 
 
Time for some myth = busting:
 
...data data Data!  where to = start?  How=20 about with tonight's LML Digest and and Brent R's assertion that "you = could load=20 a IVp to 28,500lbs and it would still fly" Well, sorry Brent, it = won't. =20 (Brent, if you were Kelly Johnson and I was Ben Rich I'd collect a = quarter from=20 you. Allowing for extreme inflation lets call it $100 and I'll post you = my=20 address....)
 
It won't fly because the wings have = fallen off.=20 Actually that's not technically correct, the wings have clapped...at = 18,500lbs=20 of wing lift because that's what the wings were designed to lift = and that's=20 what they will lift....well, sort of. We'll get to that little "gotcha"=20 shortly.
 
Lets look at Data, from the horse's = mouth. The best=20 source of information on LIVs I know of are Martin Hollman's book = "Modern=20 Aeroplane Design" vols I, II, = and also=20 "Boogie with a Turboprop". Should be required reference books for ALL = LIV=20 builders/owners/pilots but I do digress.... In "MAD" vol I, Chp 6, is a=20 section describing the LIV wing. Page 106 gives some pertinent=20 information,  (I'll only quote that which is pertinent for the = purpose of=20 this discussion). Limit Flight load factor =3D 4.4gs. Gross Weight =3D = 2,900 lbs,=20 minus the wing weight of 310 lbs =3D 2,590 lbs. Limit Flight maneuvring = speed, Va=20 =3D 200 mph. design dive speed Vd, 360 mph. (both speeds at SL). Safety = Factor =3D=20 1.5 for ultimate loads.
 
Page 111 of Vol I shows a copy of an = engineering=20 drawing of the Lancair IV wing layup schedule. In the bottom right hand = corner=20 in the notes section are notes I & II, as follows: 1) Gross wt = 3,000lbs less=20 wing panel wt 160lbs/panel.  2) Limit load factor =3D 4.4 gs, = Safety Factor=20 1.50. (interesting is it not? ...Safety factor of ONLY 1.5 Kinda = blows the=20 200% Ultimate Load Factor myth out of the water...no?)
 
Let's skip to page 113, Fig 6.15, Wing = Deflection,=20 skin shear stress, etc. Quote "An actual wing structural test was = performed for=20 the load condition of Vd =3D 360 mph. The wing failed under a total load = of 9,250=20 lbs and a deflection of 15 inches. The wing load at 4.4 Gs is: Load =3D = 2590 x 4.4=20 x (154.5/360) =3D 4891 lbs". Therefore  with 4.4 Gs = load equaling 4891=20 lbs wing panel lift we can easliy calculate the max G load at = the wing=20 panel point of failure of 9,250 lbs =3D 8.32 Gs.
 
What a great design! Nearly 200%=20 ultimate load factor...lot's of margin built into this = wing... let's=20 up the gross weight and our wing can carry it for = sure!  
 
Yeah right...sucker! ....myths based on = assumptions=20 based on wishfull thinking....
 
Let's backtrack to page 107, top of the = page=20 "...Structural Dimensions for an airspeed of Va =3D 200 mph and an angle = of attack=20 of 14 degrees, and for an airspeed of Vd =3D 360 mph and an angle of = attack of=20 2 degrees are determined". Then para 1: "Figures 6.10 & = 6.11 show=20 that the maximum bending moment is expected for Va =3D 200 mph since the = tip is=20 loaded more than at Vd =3D 360 mph"  So what's this then? what does = it mean?=20 Let's go look at  Figs 6.10 & 6.11... a couple of graphs = and a=20 couple of tables of, wait for it.... DATA!!!
 
The graphs on page 108 are self = explanatory and=20 show clearly that at Va the wing tip is loaded more than at Vd. Then = page 109=20 gives numbers...lots of them but it easy to make sense of it. Our=20 interest are the lines  (wing station) WS2 on both tables. = Firstly for=20 Va, 200 mph, 14' AoA, the wing panel lift =3D 4952 lbs outboard of BL 18 = ie. and wing bending moment at BL 18 is 28,554 ft-lbs.  For = Vd, 360=20 mph, 2' AoA, the wing panel lift is 4709 lbs outboard of BL 18 and the = wing=20 bending moment at BL 18 is 22,436 lbs. In other words, for = nearly identical=20 wing panel lift for Va and Vd  conditions, the wing bending moment = at Va,=20 ... ie the force that breaks the wings, is 28,554/22,436 =3D 1.27 times = greater=20 than at Vd. Got your attention now I'll bet!
 
To tie it all together, to know the G = load=20 achievable at the point of wing failure at Va, divide = the 8.32Gs=20 achievable at Vd by 1.27 =3D 6.55Gs
 
So there you have it: At 2,900 gross = weight at Va=20 your wings will clap at 6.55 Gs = or=20 thereabouts. Perhaps you lead sled builders might want to play in = the=20 margins and in the edges of the bell curve of the wing failure test (a = test=20 sample of 1 to date),  maybe your wing are stronger...but maybe = not, maybe=20 Lancair Company has redesigned and strengthened the wing since this data = was=20 published...or maybe not, maybe you think fuel load in the wing = alleviates the=20 wing bending moment and these numbers don't apply to you...but for the = purpose=20 of calculating wing bending moments weight of fuel in the wing is not = permitted.=20 If you think that way you're relying on lots of "maybes"  Best of = luck to=20 you and I hope the "maybes" line up in your favour as I don't wish to = read more=20 Lancair accident reports thank's very much.
 
In this recent once again iteration of = Lancair IV=20 weights on LML  others have covered pretty much all the negative = points of=20 increasing gross weights but I'd just briefly like to put some numbers = to=20 increasing stall speeds with increasing weights. Stall speed increases = with the=20 square root of the load factor. If the stall speed @2,900lbs is 66 = knots,=20 increase the weight to 4,000lbs and the increase in load factor is = 4,000/2900 =3D=20 1.379.  Square root it =3D 1.174.  multiply by the original 66 = knots=20 stall speed =3D 77.5 knots. Lets look at the clean configuration and a = stall speed=20 of lets say 80 knots... multiply by 1.174 =3D 93.92 knots. Pull a 2 g = turn (clean)=20 and the stall speed =3D 132.8 knots.
 
Build 'em light, Really = Light!! (it's not=20 hard)  ....and straight...
 
ciao
 
Roberto d'Italia.
 
ps, lead sled builders...don't forget = to redo=20  the white/green/ arcs on your  ASI.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
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