From: krnet-bounces@mylist.net To: John Bouyea Subject: KRnet Digest, Vol 346, Issue 237 Date: 12/12/2004 8:59:16 PM Send KRnet mailing list submissions to krnet@mylist.net To subscribe or unsubscribe via the World Wide Web, visit http://mylist.net/listinfo/krnet or, via email, send a message with subject or body 'help' to krnet-request@mylist.net You can reach the person managing the list at krnet-owner@mylist.net When replying, please edit your Subject line so it is more specific than "Re: Contents of KRnet digest..." Today's Topics: 1. kr wings (Don Chisholm) 2. Re: kr wings (GavinandLouise) 3. Re: more kr1 questions (RENOSADLER@aol.com) 4. Re: kr wings (Martindale Family) 5. RE: kr wings (Stephen Jacobs) 6. Re: kr wings (Orma) 7. Gs and aerodynamic lift (Colin & Bev Rainey) 8. Re: kr wings (VIRGIL N SALISBURY) 9. Re: kr wings (larry severson) 10. Re: kr wings (Orma) 11. Simple lift (Colin & Bev Rainey) 12. Re: Gs and aerodynamic lift (larry severson) 13. Neg Gs (Colin & Bev Rainey) 14. RE: Simple lift, or maybe not simple (Ron Freiberger) 15. AS504x wing sections for KR-1? (Russell Bell) 16. Static load testing of KR wing (Orma) 17. Re: Static load testing of KR wing (Dan Heath) 18. Re: Static load testing of KR wing (Mac McConnell-Wood) 19. Lift (Colin & Bev Rainey) 20. Re: Static load testing of KR wing (Orma) 21. Lift - BS debunked (Stephen Jacobs) 22. Re: Lift - BS debunked (larry severson) ---------------------------------------------------------------------- Message: 1 Date: Sun, 12 Dec 2004 00:49:13 -0500 (EST) From: Don Chisholm Subject: KR> kr wings To: krnet@mylist.net Message-ID: <20041212054913.91771.qmail@web88002.mail.re2.yahoo.com> Content-Type: text/plain; charset=us-ascii seems to me if you followed the plans you would have foamed and glassed your center section first to the division line between the center section and the outer wing panel line on a plane that corresponds to the wing attach bolts you could have used the butt end of the foamed and glassed center section airfoil profile as your sanding guide for your outer wing panel root end sanding guide. otherwise you will have to extend the 48 inch AS50whatever template to the attach bolt line to be able to use as a sanding or hot wire guide. however you have determined to shape your foam cores . I hope I read Your problem correctly Don Chisholm chizmsupholstery@rogers.com ------------------------------ Message: 2 Date: Mon, 13 Dec 2004 16:49:07 +1000 From: "GavinandLouise" Subject: Re: KR> kr wings To: "KRnet" Message-ID: <000701c4e0df$d7cd47a0$0100000a@vic.bigpond.net.au> Content-Type: text/plain; charset="iso-8859-1" Yes you have read properly, and no I haven't added the foam and glass to the so called butt end of the centre section as yet. maybe I should do that and that will fix my problem. It's just that the plans call for the ply rib to be used as the guide and it also says that the rib should be a little way in from the end as well, which doesn't work out. Gav . > I hope I read Your problem correctly > Don Chisholm chizmsupholstery@rogers.com > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > > please see other KRnet info at http://www.krnet.org/info.html > ------------------------------ Message: 3 Date: Sun, 12 Dec 2004 02:48:19 EST From: RENOSADLER@aol.com Subject: Re: KR> more kr1 questions To: krnet@mylist.net Message-ID: <197.33f0c346.2eed51c3@aol.com> Content-Type: text/plain; charset="US-ASCII" John if you ever find any premolded parts for KR1 I'd like to be the seconed person to know!! Thanks Bill ------------------------------ Message: 4 Date: Sun, 12 Dec 2004 22:08:31 +1100 From: "Martindale Family" Subject: Re: KR> kr wings To: "KRnet" Message-ID: <001601c4e03a$ea93db60$e9bcecdc@athlon2400> Content-Type: text/plain; charset="iso-8859-1" Gav The KR2 (not S) centre main spar is 83" long and the centre rear spar is 84" long. To run your 48" template at right angles on the end of the former will place it 1/2" in from the end of the rear on each side. The difference in spar length compensates for the fact that the rear outer spar sweeps forward and allows for the bends in the outer rear WAFs to align in parallel with the inner rear WAFs. In my view you need a 48" ply template at right angles to the main spar both on the outer end of the centre section and another on the inner end of the wing. They are essential when it comes to sanding down your foam to shape with a very long board. Regards John The Martindale Family 29 Jane Circuit TOORMINA NSW 2452 AUSTRALIA phone: 61 2 66584767 email: johnjanet@optusnet.com.au ----- Original Message ----- From: "GavinandLouise" To: "KRnet" Sent: Monday, December 13, 2004 5:49 PM Subject: Re: KR> kr wings > Yes you have read properly, and no I haven't added the foam and glass > to the > so called butt end of the centre section as yet. maybe I should do > that and > that will fix my problem. > It's just that the plans call for the ply rib to be used as the guide > and it > also says that the rib should be a little way in from the end as well, which > doesn't work out. > > Gav > > . > > I hope I read Your problem correctly > > Don Chisholm chizmsupholstery@rogers.com > > > > _______________________________________ > > Search the KRnet Archives at > > http://www.maddyhome.com/krsrch/index.jsp > > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > > > > please see other KRnet info at http://www.krnet.org/info.html > > > > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > > please see other KRnet info at http://www.krnet.org/info.html ------------------------------ Message: 5 Date: Sun, 12 Dec 2004 13:32:49 +0200 From: "Stephen Jacobs" Subject: RE: KR> kr wings To: "'KRnet'" Message-ID: <000701c4e03e$55e2d620$1d64a8c0@stephen> Content-Type: text/plain; charset="us-ascii" No big deal, but a thought that may be maybe worth expressing. My concern with pre-fab wing skins (any wing skins) is the quality of bond with the spars. We need to remember that the airplane is literally being picked up by the skin of its wings (well 2/3 of it is). That may not translate to a great force per sq. ft - a typical KR has a wing load of maybe 10 lbs /sq. ft. At say 4G that is 40 lbs /sg Ft - so maybe 27lbs of actual tug on each square foot of wing. We know that the load distribution is not even over the entire wing and the bit covered by the fuselage is counted, but carries zero aerodynamic load, so some areas must handle a bit more - say 38 lbs /sg ft for those parts in a heavy G turn /pull-up. On the face of it, no big deal - that is a mild 1.3G load for a piston twin. Consider the KR wing structure (below the skin) and imagine dividing the top surface of the wing into 1' x 1' squares and screwing a cup hook into each square. Turn it over and hang 38 lbs on each of the 80 or so cup hooks. How comfortable will we be with the bond between the skin and the spar(s)? How about coming back and hanging these weights on the wing after the bird gets to be 20 years old and sees many great gatherings sitting in the sun. The point is that the combined load is transferred to the wing structure via a much smaller area - for a KR this is essentially the spars. The COP moves around a lot, but typical numbers would suggest that the main spar carries the bulk of the load - particularly under high G loads when the COP tends to sneak fwd - maybe even ahead of the main spar. The typical, KR main spar (top surface area) amounts to maybe 2 sq ft. that could well be carrying up to 700 lbs or more. Still not a very big deal, that is only 700/288 = 2.4 lbs /sq ft, but we do need to keep this in mind when bonding the top skin. With his wing skins DD suggests that we taper the spar in section only and leave the plan view (width) constant for more glue area Have a great Sunday Steve J Mark J - Yeeee Haaa (hee haw) ????? ------------------------------ Message: 6 Date: Sun, 12 Dec 2004 10:11:46 -0500 From: "Orma" Subject: Re: KR> kr wings To: "KRnet" Message-ID: <002901c4e05c$e69fc560$4b32d445@ROBBINS1> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original "Consider the KR wing structure (below the skin) and imagine dividing the top surface of the wing into 1' x 1' squares and screwing a cup hook into each square. Turn it over and hang 38 lbs on each of the 80 or so cup hooks." Hello Net This is long, if you have a KR to work on, repair , or fly, don't waste your time on this!! It's 29 and snowing here in SE Michigan. For me it's a good day to learn something new. About this G loading of a KR wing, I guess I really would like to learn more, especially since my KR is over 20 years old. It doesn't have wing skins, just the one's I made. I thought that in flight the air traveling over the curved upper surface caused low pressure on the bottom surface and that's what caused lift. As a pilot I learned that in a climbing turn, that one wing is closer to stall then the other, and also that in a pull up, the wing panels transfer the lifting force, what ever the G's to the spars and in particular for the KR, the attach fittings. Such that in an overloaded +G condition the force acting on the wing would be downward as the fuselage trys to pull up. In this situation I always thought the forces were pushing down on the top of the skin. Following that in a -G condition, the wing would try to continue to fly with lift from the bottom while the fuselage trys to force downward, causing the wings fold in failure. I would think that as the spar bends, that the adhesion of the skin to the spar would act to prevent the bending. I can see where gluing the wing skins really good is important. I can't see where the force to lift the skin from the spar comes from. As you will note, I present this as things I would like to learn, since I don't have much aerodynamic training. In a practical since I'm not sure that if I attached a 38 pound weight on the unsupported wing skin, say the space between the spars and ribs, that the thing would not drop through. I'm positive that my original wing covering of one layer of Dynel would not. I have seen pictures and read articles about load testing of wings where nearly a ton a sand bags have been stacked on the aircraft wing to simulate the G loading and read of some that have continued to stack till failure. There tests looked for the destruction of the wing as whole. Over the years the only non straight and level flying that I do is the occasional high speed pass with a pull up. I have no idea at what amount of G's. Orma Southfield, MI N110LR celebrating 20 years Flying, flying and more flying http://www.kr-2.aviation-mechanics.com/ Do not Archive ------------------------------ Message: 7 Date: Sun, 12 Dec 2004 11:18:50 -0500 From: "Colin & Bev Rainey" Subject: KR> Gs and aerodynamic lift To: "KRnet" Message-ID: <006a01c4e066$448724d0$2d432141@RaineyDay> Content-Type: text/plain; charset="iso-8859-1" Orma and netters First off lift is NOT created by a tugging of the wing panel up into the air. It is created by a combination of the deflected air PUSHING the bottom wing panel up (Newton's Law) and the airflow being increased over the top creating a pressure differential from under to over causing the air on the bottom to push up into the now low pressure area above the wing (Bernoulli's Law). The only force "sucking" on the wing skin is the small semi-vacuum created by the low pressure area of the airflow over the upper wing. Negative Gs are simulated by adding weight to the UPPER wing panel, simulating the reverse G force hence negative of the wing attempting to produce lift downward in relationship to the pilot. Positive Gs are tested with the wing inverted, simulating the increased lifting force beyond 1G that is created when one increases the load on the wing during say a steep turn, pull-up, snap roll, etc... 1G is created when the aircraft is in equilibrium in straight and level flight, and this is increased when you decide to make a turn, which you can feel is the force pulling down on you during the maneuver. You have increased the amount of lift required over straight and level because now you are "borrowing" some other lift for straight and level to apply in the direction of the turn, so to remain level, lift must increase. There is a good chart in the Airplane Flying Handbook which illustrates very clearly the increasing Gs for the angle of bank of a given "level" non descending coordinated turn. Orma you are right, that the outside wing increases lift, with the down application of aileron, while the inboard wing decreases lift, each having an associated change in drag which causes adverse yaw. Application of the rudder is used to correct the adverse yaw. In the KR the differential ailerons, those that deflect up different from down, "tunes" out most of this adverse yaw for us making it simpler to fly coordinated. The confusion may have come from looking at drawing that illustrate the lift "vectors" which are showing the resulting forces, and their direction of action, and misinterpret this to mean that that is where the force originates from. 2 Books for further reading that will enhance a pilot's understanding, and should be read completely, are the Pilot's Handbook of Aeronautical Knowledge, and the Airplane Flying Handbook. Both available at any decent pilot store, King School and Sportys Catalog and online ordering. They run about $14.95 each and will answer most of these questions in greater detail. If anyone has any other pilot questions like this, or related to flying, e-mail off the net and I will be glad to discuss them with you. FLY SAFE!!! Colin & Bev Rainey KR2(td) N96TA Sanford, FL crainey1@cfl.rr.com http://kr-builder.org/Colin/index.html ------------------------------ Message: 8 Date: Sun, 12 Dec 2004 11:23:38 -0500 From: VIRGIL N SALISBURY Subject: Re: KR> kr wings To: krnet@mylist.net Message-ID: <20041212.112359.2064.0.virgnvs@juno.com> Content-Type: text/plain; charset=us-ascii > It's 29 and snowing here in SE Michigan. For me it's a good day to > learn > something new. About this G loading of a KR wing, I guess I really > would > like to learn more, especially since my KR is over 20 years old. It > doesn't > have wing skins, just the one's I made. I thought that in flight > the air > traveling over the curved upper surface caused low pressure on the > bottom NO! THE TOP SURFACE! > surface and that's what caused lift. As a pilot I learned that in a > > climbing turn, that one wing is closer to stall then the other, and > also > that in a pull up, the wing panels transfer the lifting force, what > ever the > G's to the spars and in particular for the KR, the attach fittings. > Such > that in an overloaded +G condition the force acting on the wing > would be NO! UPWARD! > downward as the fuselage trys to pull up. In this situation I > always > thought the forces were pushing down on the top of the skin. > NO! PULLING UP! Following that > in a -G condition, the wing would try to continue to fly with lift > from the NO! TOP! > bottom while the fuselage trys to force downward, NO! UPWARD! causing the wings > fold in > failure. I would think that as the spar bends, that the adhesion of > the > skin to the spar would act to prevent the bending. I can see where > gluing > the wing skins really good is important. I can't see where the > force to > lift the skin from the spar comes from. > Please rethink your + and - G Forces > As you will note, I present this as things I would like to learn, . Orma> Always good to keep learning, Virg > > > _______________________________________ > Search the KRnet Archives at > http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > > please see other KRnet info at http://www.krnet.org/info.html > > Virgil N. Salisbury - AMSOIL www.lubedealer.com/salisbury Miami ,Fl ------------------------------ Message: 9 Date: Sun, 12 Dec 2004 08:28:57 -0800 From: larry severson Subject: Re: KR> kr wings To: KRnet Message-ID: <5.2.1.1.0.20041212082602.02f726e0@pop-server.socal.rr.com> Content-Type: text/plain; charset="us-ascii"; format=flowed > I thought that in flight the air >traveling over the curved upper surface caused low pressure on the >bottom surface and that's what caused lift. I think that you were tired when you posted. The low pressure is on the top surface. Larry Severson Fountain Valley, CA 92708 (714) 968-9852 larry2@socal.rr.com ------------------------------ Message: 10 Date: Sun, 12 Dec 2004 11:36:23 -0500 From: "Orma" Subject: Re: KR> kr wings To: "KRnet" Message-ID: <003401c4e068$b8bbc2f0$4b32d445@ROBBINS1> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original "The low pressure is on the top" Thanks Larry, you and Virg are correct, that was a typo of the mind. Orma ------------------------------ Message: 11 Date: Sun, 12 Dec 2004 11:38:38 -0500 From: "Colin & Bev Rainey" Subject: KR> Simple lift To: "KRnet" Message-ID: <007701c4e069$0806ae60$2d432141@RaineyDay> Content-Type: text/plain; charset="iso-8859-1" Simple illustration of lift can be seen in a commercial aircraft such as a 767 on takeoff. On the takeoff roll the wings are basically straight out from the fuselage. As the takeoff run continues the lift is increased and gradually applied to the wing, causing the tips to rise as the wing bends by design to handle the lifting loads. Depending on the weight the tips may rise 3-5 feet as the wing takes the lifting loads on takeoff. This clearly illustrates the lifting force in positive Gs is applied to the bottom. The fuselage is attempting by gravity to stay on the earth and the wing is lifting it up, hence positive Gs. Negative Gs is where the fuselage is repelled from the earth and/or the wing makes negative lift (such as inverted flight). Colin & Bev Rainey KR2(td) N96TA Sanford, FL crainey1@cfl.rr.com http://kr-builder.org/Colin/index.html ------------------------------ Message: 12 Date: Sun, 12 Dec 2004 08:44:38 -0800 From: larry severson Subject: Re: KR> Gs and aerodynamic lift To: KRnet Message-ID: <5.2.1.1.0.20041212083255.02fd3e30@pop-server.socal.rr.com> Content-Type: text/plain; charset="us-ascii"; format=flowed >First off lift is NOT created by a tugging of the wing panel up into >the >air. It is created by a combination of the deflected air PUSHING the >bottom wing panel up (Newton's Law) Very slight, unless at high speed (much higher than a KR2). > and the airflow being increased over the top creating a pressure > differential from under to over causing the air on the bottom to push up > into the now low pressure area above the wing (Bernoulli's Law). Significant, and the reason that wing profiles change based on the speed range that the plane is designed to operate under. >The only force "sucking" on the wing skin is the small semi-vacuum >created >by the low pressure area of the airflow over the upper wing. True, but not slight. >Negative Gs are simulated by adding weight to the UPPER wing panel, >simulating the reverse G force hence negative of the wing attempting to >produce lift downward in relationship to the pilot. I do not understand. Negative Gs are the result of changing the direction of the plane's nose in a downward direction at a pace that exceeds 32 ft/sec squared. That is why one can encounter negative Gs with an abrupt leveling off at the end of a climb. >Positive Gs are tested with the wing inverted, simulating the increased >lifting force beyond 1G that is created when one increases the load on the >wing during say a steep turn, pull-up, snap roll, etc... Positive Gs are the result of pulling the nose up from the existing line of flight. A 60 degree level turn requires a 2G force applied to the plane by the pilot back pressure on the stick. An inside loop results in constant positive Gs, but an outside loop is all negative Gs. >1G is created when the aircraft is in equilibrium in straight and level >flight, True. >FLY SAFE!!! Larry Severson Fountain Valley, CA 92708 (714) 968-9852 larry2@socal.rr.com ------------------------------ Message: 13 Date: Sun, 12 Dec 2004 11:52:20 -0500 From: "Colin & Bev Rainey" Subject: KR> Neg Gs To: "KRnet" Message-ID: <000c01c4e06a$f22bf9e0$2d432141@RaineyDay> Content-Type: text/plain; charset="iso-8859-1" The negative Gs from an abrupt level off come from the fuselage attempting to continue upward while the control force input makes the airplane change direction, hence the force going up changed to downward. The wing and aircraft structure "force" the airplane down into a level flight or below that from a climb, which causes the reverse Gs, or repelling feeling, like being momentarily weightless, which is the negative Gs. However, the force is applied to the wing and fuselage where the wing is attempting to stop the fuselage from continuing upward so the wing creates a downward force, while fuselage tries to continue upward, attempting to bend the wing down away from the pilot. The inside loop positive Gs are keeping the loop going by creating more lift, while the fuselage wants to keep going straight, positive Gs even though we go inverted through part of the maneuver. Colin & Bev Rainey KR2(td) N96TA Sanford, FL crainey1@cfl.rr.com http://kr-builder.org/Colin/index.html ------------------------------ Message: 14 Date: Sun, 12 Dec 2004 12:05:49 -0500 From: "Ron Freiberger" Subject: RE: KR> Simple lift, or maybe not simple To: "'KRnet'" Message-ID: <000001c4e06c$d5d851b0$d23aca0c@Disorganized> Content-Type: text/plain; charset="us-ascii" Clearly it's lifting, but how do you imply that it's pushing up from the bottom or LIFTING from the top? Did you ever feel negative G's at the top of some aerobatic maneuvers, clearly not being "repelled" by the earth. Ron Freiberger mail to rfreiberger at swfla.rr.com <- substitute an @ sign ;o) Depending on the weight the tips may rise 3-5 feet as the wing takes the lifting loads on takeoff. This clearly illustrates the lifting force in positive Gs is applied to the bottom. The fuselage is attempting by gravity to stay on the earth and the wing is lifting it up, hence positive Gs. Negative Gs is where the fuselage is repelled from the earth and/or the wing makes negative lift (such as inverted flight). ------------------------------ Message: 15 Date: Sun, 12 Dec 2004 09:13:23 -0800 (PST) From: Russell Bell Subject: KR> AS504x wing sections for KR-1? To: krnet@mylist.net Message-ID: <20041212171323.8406.qmail@web51404.mail.yahoo.com> Content-Type: text/plain; charset=us-ascii I've been lurking for a few weeks. Just bought a KR-1 project and I have a couple of questions. Has anyone used Ashok Gopalarathnam's airfoil on a KR-1? Any reason not to? Russ Bell > > > >Ashok designed that airfoil specifically for the > KR2S, but the set of > >points > >he generated was for a standard "unity" profile, > based on the chord length > >being 1.000. Not that it won't work just fine on a > KR2, but at the time, I > >couldn't imagine anybody wanting to build a KR2 > wing if they were starting > >from scratch, so the templates are also designed > for the KR2S, rather than > >the KR2, hence the lack of a 36" chord tip > template. The S wing planform __________________________________ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail ------------------------------ Message: 16 Date: Sun, 12 Dec 2004 12:47:52 -0500 From: "Orma" Subject: KR> Static load testing of KR wing To: "KRnet" Message-ID: <007101c4e072$b4bf8380$4b32d445@ROBBINS1> Content-Type: text/plain; charset="iso-8859-1" Does any one know if the KR wing (original or skins) ever underwent static load testing. Has Dan ever load tested his wing skins. Orma Southfield, MI N110LR celebrating 20 years Flying, flying and more flying http://www.kr-2.aviation-mechanics.com/ ------------------------------ Message: 17 Date: Sun, 12 Dec 2004 13:00:59 -0500 (Eastern Standard Time) From: "Dan Heath" Subject: Re: KR> Static load testing of KR wing To: "krnet@mylist.net" Message-ID: <41BC875B.000001.03524@DANHOMECOMPUTER> Content-Type: Text/Plain; charset="iso-8859-1" Don't know, ask Dan. See N64KR at http://KR-Builder.org - Then click on the pics There is a time for building and a time for FLYING and the time for building has expired. Daniel R. Heath - Columbia, SC See you in Mt. Vernon - 2005 - KR Gathering -------Original Message------- From: KRnet Date: 12/12/04 12:48:18 To: KRnet Subject: KR> Static load testing of KR wing Does any one know if the KR wing (original or skins) ever underwent static load testing. Has Dan ever load tested his wing skins. Orma Southfield, MI N110LR celebrating 20 years Flying, flying and more flying http://www.kr-2.aviation-mechanics.com/ _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net please see other KRnet info at http://www.krnet.org/info.html ------------------------------ Message: 18 Date: Sun, 12 Dec 2004 21:11:50 -0000 From: "Mac McConnell-Wood" Subject: Re: KR> Static load testing of KR wing To: "KRnet" Message-ID: <013501c4e08f$331250c0$d63c9c51@tinypc> Content-Type: text/plain; charset="iso-8859-1" I read somewhere that KR wings were tested to destruction in Australia and they failed at the wing/fuselage transition. Mac KR2 G-BVZJ ----- Original Message ----- From: "Orma" To: "KRnet" Sent: Sunday, December 12, 2004 5:47 PM Subject: KR> Static load testing of KR wing > Does any one know if the KR wing (original or skins) ever underwent static load testing. Has Dan ever load tested his wing skins. > > Orma > Southfield, MI > N110LR celebrating 20 years > Flying, flying and more flying > http://www.kr-2.aviation-mechanics.com/ > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > > please see other KRnet info at http://www.krnet.org/info.html ------------------------------ Message: 19 Date: Sun, 12 Dec 2004 15:30:25 -0500 From: "Colin & Bev Rainey" Subject: KR> Lift To: "KRnet" Message-ID: <001f01c4e089$69a74dd0$2d432141@RaineyDay> Content-Type: text/plain; charset="iso-8859-1" I give up CR ------------------------------ Message: 20 Date: Sun, 12 Dec 2004 16:42:19 -0500 From: "Orma" Subject: Re: KR> Static load testing of KR wing To: "Mac McConnell-Wood" , "KRnet" Message-ID: <007c01c4e093$7602b600$4b32d445@ROBBINS1> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original and they failed at the wing/fuselage transition That would make for interesting reading. If you ever find the source material, I hope you will provide the net with a link. Orma Southfield, MI N110LR celebrating 20 years Flying, flying and more flying http://www.kr-2.aviation-mechanics.com/ ------------------------------ Message: 21 Date: Mon, 13 Dec 2004 01:01:46 +0200 From: "Stephen Jacobs" Subject: KR> Lift - BS debunked To: "'KRnet'" Message-ID: <000401c4e09e$94ea63a0$e264a8c0@stephen> Content-Type: text/plain; charset="us-ascii" Jeez guys - never wanted to start a big issue here, just felt it important to stress the importance of the skin /spar bond - it has killed a few folks and it will probably kill a few more. I would be happy if I can do something to prevent just one future accident. I considered leaving it alone, but I have seen so many constructive contributors give up that I do feel compelled to stay with it a bit longer. Let me be clear - I do not feel compelled to comment on everything that is said - even when I know little about the topic. I can happily do without defending my earlier post with what is really basic stuff, but it is important to me that this message gets across - is that not what KRnet is all about? Some folks seem to feel obliged to have the last word and that would be great if they would build on the post and develop the point - add some value. In this case an important point may get lost in a meaningless exchange - so let us dump the conjecture and opinion and deal with hands on, seeing is believing, raw reality - OK. Please - take a desert spoon and go to the sink. Open the tap until you have a nice steady stream of water. Hold the handle (stem?) of the spoon gently between two fingers, with the scoop hanging vertically down - the bulge facing the running water. A bit like the top of a wing about to enter an air stream. Slowly move the spoon closer until the bulge contacts the running water. Get the message? I really need say no more. Orma, you sincerely said you were out to learn and I would be really pleased if I can contribute something to that. Do this little experiment and you will immediately understand where that 2/3 of lift comes from. The spoon will be aggressively "sucked" (tugged?) into the stream and you will have no doubt that 2/3 of the weight of your airplane is being suspended by the upper wing skin - sucked into the air. The spoon has no "bottom surface" that is being influenced by the flowing water, so the under-camber aspect is NOT at work here. We could leave it there, but for those who are now curious. The spoon has no "bottom" as such, so that blows any verbiage about: "the airflow being increased over the top creating a pressure differential from under to over causing the air on the bottom to push up into the now low pressure area above the wing" I read the above a few times and I have no clue what he is trying to say - with great respect, I honestly tried. In any case, there is no water moving under the "wing" in this demonstration. If the stream of water from the faucet was in fact a thick sheet of water, the spoon would continue to be "sucked" through the water until it came out the other side - the upper "camber" is developing "lift". >From airplane to airplane (depending on configuration, loading etc.) the horz stab may or may not be contributing to lift and some parts of the fuselage may sometimes contribute a bit (it is reported that the GP4 canopy generates 400lbs of lift??) but for the purpose of this discussion, the wing provides the lift. The following is not my opinion, speculation, assumption or a product of thumb sucking - it is well established, simple, basic old hat fact. Approx 1/3 of the lift produced by a wing is generated from pressure under the wing and the other 2/3 of lift is created by the top surface of the wing. You have just proved the 2/3 bit with the spoon. We have all stuck our hand out the car window at 50 mph, so we know all about the 1/3 bit. (Even then, we are actually also seeing some of the 2/3 bit). If you want, you can do a second test to really make sure that your airplane is being sucked into the air (by the top skin) even it there is NO BOTTOM SKIN. This is more difficult to explain. This time we deal with air flow, not water. Take a sheet of typing paper and hold it by the bottom corners, one corner in each hand, between two fingers - sort of like you wanted to read it without smudging it. Bottom corners OK - the page is above your fingers. Try to hold the sheet near vertical (like you were reading it), then without changing the position of your hands, allow the paper flop over backwards (away from you). The bit you are holding is nearly vertical and the rest of the sheet is sort of hanging backwards over your hands - right. Now blow over the curve of the paper. Amazing how it rises up. The harder you try to blow it down, the more it rises up. The flow of air is "sucking" the trailing paper up - even without any airflow around the "bottom". The lift created by the top surface of a wing is indeed a function of Bernoulli's Law - also known as the venturi effect. The vacuum created in a venturi (Bernoulli's Law) is substantial, venturis were developed in days gone by to power vacuum instruments. Call it negative pressure, call it vacuum, call it what you like - in simple terms Bernoulli's Law is all about "suction". We really could leave it alone now, but in the interest of completeness. I am not sure why negative G came into the original discussion or why the explanation became so convoluted. Negative G is no different from positive G, just goes the other way. G forces have little to do with which way up the airplane is - an inverted airplane can pull positive G's Load testing a wing - if we wish to establish if the wing structure as a whole is strong enough (were our calculations correct). To establish the positive G capability we turn the wing over and pile sand bags on the upward facing lower surface until we are satisfied that we have represented a load of how ever many G's we want to demonstrate. Or keep going until it fails (to establish the ultimate load capability). This has zip to do with establishing if the skin spar bond is Ok - the topic of this discussion. I will be happy to take heat on any statement above that is demonstrated to be blatant, unsubstantiated conjecture and I will be delighted to expand on anything that may be vague. I will be equally happy to leave it alone, knowing that at least one buddy is going to make darn sure his /her wing skins stay put. Anyone who distracts from the importance of this matter is in sad need of help. My Sunday is done - enjoy what is left of yours. Steve J ------------------------------ Message: 22 Date: Sun, 12 Dec 2004 16:40:49 -0800 From: larry severson Subject: Re: KR> Lift - BS debunked To: KRnet Message-ID: <5.2.1.1.0.20041212163833.02e73ae0@pop-server.socal.rr.com> Content-Type: text/plain; charset="us-ascii"; format=flowed Yep. Push stick forward - get light. Pull the stick back - get heavy. But, only if you are flying above the stall speed.. Larry Severson Fountain Valley, CA 92708 (714) 968-9852 larry2@socal.rr.com ------------------------------ _______________________________________________ See KRnet list details at http://www.krnet.org/instructions.html End of KRnet Digest, Vol 346, Issue 237 *************************************** ================================== ABC Amber Outlook Converter v4.20 Trial version ==================================