From: "Kevin Russert Walsh" Date: Tue, 23 Jan 1996 10:42:28 +0000 Subject: Re: AeroCanard vs. Cozy: Lower Winglets > From: Marc J. Zeitlin > Howard Bernstein writes: > > >My question: What function do the lower winglets serve, and why are they > >missing on the AeroCanard? > > According to Nat, the lower winglets assist in preventing span-wise flow > in low speed flight, which helps in preventing stalling, especially > deep stalls, as well as preventing wing drops near stall. Nat found the > winglets to be very important in his deep stall tests. Furthermore, the recent Berkut airshow accident has been blamed on an aft CG and the elimination of the lower winglet. The aft CG contributed to a high G pullup main wing stall and the lack of winglets contributed to a rolloff to one side after the main wing got into trouble. It seems silly given the facts to remove the lower winglets for a dubious speed (either in the air or building in the shop) gain. Kevin R. Walsh Mechanical Engineer Intelligent Automation Systems 149 Sidney Street Cambridge, MA 02139 TEL 617.354.3830 FAX 617.547.9727 From: "Howard Bernstein" Date: Tue, 23 Jan 1996 09:34:35 -0500 Subject: AeroCanard vs. Cozy: Lower Winglets I'm in the process of deciding which to build (Cozy or AeroCanard) and noticed that in a photo sent by AeroCad that there are no lower winglets. I remember seeing some discussion in this group about construction issues related to joining the upper and lower winglets. My question: What function do the lower winglets serve, and why are they missing on the AeroCanard? Thanks! -- Howard Bernstein - Atria Software, Inc. (howie@atria.com) 20 Maguire Road, Lexington, Massachusetts 02173-3104 (617) 676-2607 [direct], -2400 [main], -2600 [fax] From: Marc J. Zeitlin Subject: AeroCanard vs. Cozy: Lower Winglets (fwd) Date: Tue, 23 Jan 96 9:52:43 EST Howard Bernstein writes: >My question: What function do the lower winglets serve, and why are they >missing on the AeroCanard? According to Nat, the lower winglets assist in preventing span-wise flow in low speed flight, which helps in preventing stalling, especially deep stalls, as well as preventing wing drops near stall. Nat found the winglets to be very important in his deep stall tests. Burt Rutan says that the lower winglets protect the wings and upper winglets in case of a backwards tipover, as well as redistributing the wing stress (in an advantageous manner) due to side loads on the upper winglets. He also says the same thing about the lower winglets that Nat does regarding span-wise flow. Considering the sources and the testing, it seems unwise to remove the lower winglets, given that they really don't cost anything other than a few hours of time, and those that have done so have seen NO speed increase. With apologies to Cliff Cady, I think Shirl Dickey's opinions on deep stall and lower winglets (the E-racer also has none) is complete nonsense. -- Marc J. Zeitlin Email: marcz@an.hp.com From: "Kevin Russert Walsh" Date: Tue, 23 Jan 1996 15:08:49 +0000 Subject: Re: AeroCanard vs. Cozy: Lower Winglets > > From: Marc J. Zeitlin > > Howard Bernstein writes: > > > > >My question: What function do the lower winglets serve, and why are they > > >missing on the AeroCanard? > > > > According to Nat, the lower winglets assist in preventing span-wise flow > > in low speed flight, which helps in preventing stalling, especially > > deep stalls, as well as preventing wing drops near stall. Nat found the > > winglets to be very important in his deep stall tests. > > > Furthermore, the recent Berkut airshow accident has been blamed on an > aft CG and the elimination of the lower winglet. The aft CG > contributed to a high G pullup main wing stall and the lack of > winglets contributed to a rolloff to one side after the main wing got > into trouble. It seems silly given the facts to remove the lower > winglets for a dubious speed (either in the air or building in the > shop) gain. I'd like to clarify what I have said here as someone contacted me about this information. The explanation of the Berkut accident is a paraphrase from Nat in the most recent newsletter (52?) I do not know his source of information. The Experimental Aviation folks have evidentally explained the crash as a aileron torque tube failure due to the high G maneuver. A deep stall was not suspected, thus the fact that lower winglets were not installed is not suspected to be a contributing factor. On the issue of lower winglets, Dave is of the opinion that the addition of lower winglets will only help to keep the plane pointed straight in a deep stall. This will keep the airplane locked in the deep stall as it has been demonstarted both in the Velocity and the Cozy MK IV tests that application of roll controls or full power or both are not capable of pulling either plane out of the deep stall. The only satisfactory recovery from this maneuver is to slide the CG much forward, which was done in the testing with a sliding weight. In the case of having no winglets, it is therefore possible to roll out of the maneuver to one side. Having winglets will evidentally not allow this to be done. This was a demonstrated characteristic of the Cozy tests. Thus the arguement becomes that with the lower winglets you have a better chance of not getting into the deep stall position at a rear CG (though the data are not complete on this) and the lack of winglets will allow one to roll out of the stall if one is encountered. In my original post I had no intention of discrediting the Berkut or the work Dave Ronneberg has done. It is a fine aircraft and I very heavily considered one before deciding that I would rather have the increased room of the Cozy. As far as deciding for yourself if winglets should or should not be added, I would follow the designer's recommendations to a T, unless you have significant information to lead you to believe otherwise. I hope I have not wasted too much space or stepped on too many toes. Kevin R. Walsh Mechanical Engineer Intelligent Automation Systems 149 Sidney Street Cambridge, MA 02139 TEL 617.354.3830 FAX 617.547.9727 Date: Tue, 23 Jan 1996 09:39:58 -0600 (CST) From: Mark J Turner Subject: Re: AeroCanard vs. Cozy: Lower Winglets (fwd) On Tue, 23 Jan 1996, Marc J. Zeitlin wrote: > Howard Bernstein writes: > > >My question: What function do the lower winglets serve, and why are they > >missing on the AeroCanard? > > According to Nat, the lower winglets assist in preventing span-wise flow > in low speed flight, which helps in preventing stalling, especially > deep stalls, as well as preventing wing drops near stall. Nat found the > winglets to be very important in his deep stall tests. > > Burt Rutan says that the lower winglets protect the wings and upper > winglets in case of a backwards tipover, as well as redistributing the > wing stress (in an advantageous manner) due to side loads on the upper > winglets. He also says the same thing about the lower winglets that Nat > does regarding span-wise flow. > > Considering the sources and the testing, it seems unwise to remove the > lower winglets, given that they really don't cost anything other than a > few hours of time, and those that have done so have seen NO speed > increase. > > With apologies to Cliff Cady, I think Shirl Dickey's opinions on deep > stall and lower winglets (the E-racer also has none) is complete > nonsense. I gave Jeff Russell a call this morning... He agrees at least in part with all that Nat/Burt has to say about span-wise flow... However, he also says: 1. Without lower winglet the airplane will have a better roll rate than an airplane with lower winglets. 2. An airplane with lower winglets will only yaw with rudder, one without lower winglets will roll as well as yaw with rudder. Jeff says that there was someone (I didn't write down his name) who took a 'smart inclomometer' (sp) around and checked several airplanes on the line at Oshkosh... The report is that Nat's airplane was one of the worst as far as his wings being out of alignment?? Something like 1/2 degree off in washout or something like that... What does this say for the validity of testing?? If the wing dropoff that was reported during the deep-stall testing was due to that particular airplanes rigging vs a generic design issue... My purpose here is not to stir up the issue, but to provide the feedback from Jeff... He also says that you can install the lower winglets on the AeroCanard, it is up to the individual builder... Mark... Date: Tue, 23 Jan 96 13:48:20 EST From: "Wilhelmson, Jack" Subject: Re[2]: AeroCanard vs. Cozy: Lower Winglets (fwd) My input on the reported fact that a Cozy with winglets only yaws with rudder and does not roll. My Cozy rolls quite well with application of rudder only. It has per plans lower winglets. In fact it takes cross control to make it slip. From: Marc J. Zeitlin Subject: Re: AeroCanard vs. Cozy: Lower Winglets (fwd) Date: Tue, 23 Jan 96 16:04:52 EST Kevin Walsh writes: >Thus the arguement becomes that with the lower winglets you have a >better chance of not getting into the deep stall position at a rear >CG (though the data are not complete on this) and the lack of >winglets will allow one to roll out of the stall if one is >encountered. Yes. I would remind people, however, that the only experiments that have been done, or at least published (Shirl Dickey and Dave Ronnenberg's opinions to the contrary notwithstanding) are Nat's, and the inadvertent and purposeful Velocity ones. When Shirl and/or Dave can demonstrate extraction from a Deep Stall via rolling in an aircraft without lower winglets, and CANNOT demonstrate said extraction on EXACTLY the same plane WITH lower winglets, then their hand waving theories will mean something. Until then, I'll trust Burt and Nat. >As far as deciding for yourself if winglets should or should not be >added, I would follow the designer's recommendations to a T, unless >you have significant information to lead you to believe otherwise. Seconded. -- Marc J. Zeitlin Email: marcz@an.hp.com Date: 23 Jan 96 19:45:55 EST From: Chuck Wolcott <75501.356@compuserve.com> Subject: RE: Lower winglet + Roll rate Mark Turner quoted Jeff Russell as having said: >2. " An airplane with lower winglets will only yaw with rudder, one > without lower winglets will roll as well as yaw with rudder." I have to agree with Jack Wilhelmson's comments : > " My input on the reported fact that a Cozy with winglets only > yaws with rudder and does not roll. My Cozy rolls quite well > with application of rudder only. It has per plans lower > winglets. In fact it takes cross control to make it slip." My Mark IV was built per plans with the lower winglets and has a significant roll along with yaw during rudder only application. My suggestion is to keep them. There are a whole lot more EZ's and Cozy's flying with lower winglets than without. Chuck Wolcott - N154CW Date: 24 Jan 96 08:43:30 EST From: Ken Miller <75202.3245@compuserve.com> Subject: See attached ---------- Forwarded Message ---------- Sender: swrothert@aol.com Subject: More "shaving off the lower winglets" From: burtrutan@aol.com (Burt Rutan) Date: 20 Nov 1995 02:20:16 -0500 Message-ID: <48pa7g$bur@newsbf02.news.aol.com> The Long-EZ lower winglets have several functions: 1. Add important directional stab, at high angle of attack. 2. Balance some of the winglet moment, to reduce the stress on the outer wing during sideslips. 3. Protect the rudder and wing for wing strike during landing or for tip-back while parked. Only the plans config has had the rigorous flight testing for departure, about 14 years ago. Vortilons help the wing lift and thus aid directional stab at low speeds and reduce susceptibility to departure. This is a small help with the Long-EZ and a BIG help for the VariEze. Do not fly a Long at aft CG without Vortilons. Do not fly a Varieze at all, without Vortilons. They do not reduce cruise speed, and they can save your life! Date: Wed, 24 Jan 1996 06:22:10 -0800 From: brimmer@ix.netcom.com (Kenneth Brimmer ) Subject: Hot Stuff - Lower Winglets It was all the rage to cut off the lower winglets when I was building my plane (finished 3 yrs.) but I was not sure so I only cut half of them off - I WISH I HAD LEFT ALL THEM ON. On a high wing turn at low speed the plane gets real mushy. May be I have a real sensetive pucker meter but you will have to make some landings that are tight and you will wish to hell you had them. From: "Howard Bernstein" Date: Wed, 24 Jan 1996 13:55:19 -0500 Subject: Re: Lower winglet... (was AeroCanard vs. Cozy, etc.) I'm pleased to see that my first submission to this group generated such interesting discussion. Thanks for all the responses. When I *do* get to the winglets, whether it's an AeroCanard or a Cozy, the lower winglets will definitely be there! -- Howard Bernstein - Atria Software, Inc. (howie@atria.com) 20 Maguire Road, Lexington, Massachusetts 02173-3104 (617) 676-2607 [direct], -2400 [main], -2600 [fax] Date: Fri, 26 Jan 1996 12:54:02 -0500 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: RE: lower winglets Shirl Dickey wrote an interesting article about a year ago and he comments that although the lower winglets delay stall of the main wing there are no pilot queues warning of the pending stall. With the lower winglets removed the stall occurs at a higher speed but the aeroplane tells you that it is unhappy before the stall occurs, and when it does, it does not lock in so deeply. I have the lower winglets on my wings but I am seriously considering cutting them off for this reason. Fortunately the design of the eze's allows one to make these changes relatively easily. Phillip Johnson From: Marc Zeitlin Date: Fri, 26 Jan 96 15:25:08 EST Subject: Re: Lower winglets People; I know we've beat this "Lower Winglet" thing into the ground, but I just came across an interesting Q&A in the 3rd quarter 1995 issue of the "Velocity Views" newsletter (a VERY nice newsletter, by the way). John Bros asked "What is Velocity Co. position on leaving off the lower winglet"? To paraphrase Scott Swing: We have never done extensive testing on a plane without the winglet bottoms...... Those of you who do not put the bottom winglets on, are on your own. Even though we haven't seen any problem with this change, sufficient testing has not been done to allow us to say - do it..... The statement "As I understand it, Velocity Co. now approves of their builders leaving off the lower winglet on either of the wing models" is NOT the case. We have never made this statement. Just thought you'd be interested in another company's viewpoint. -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Fri, 26 Jan 1996 19:27:06 -0500 From: StetsonE@aol.com Subject: Re: AeroCanard vs. Cozy: Lower Winglets (fwd) In a message dated 96-01-25 06:23:10 EST, Marc wrote: >>As far as deciding for yourself if winglets should or should not be >>added, I would follow the designer's recommendations to a T, unless >>you have significant information to lead you to believe otherwise. I would also agree. I also went through this decision process. Peer pressure made the decision especially difficult because the current trend for So Cal Long-EZ builders/flyers is to remove the lower winglets. I installed the lower winglets anyway, reasoning that during first flights with little time in type, the last thing I want is reduced stability and stall margin. Now I'll have the best of both worlds - greater safety margin with a potentially hamfisted pilot (Me!). And, if I later decide to remove them, I can remove a little at a time and flight test to determine when to stop. A friend recently removed 80 percent of his lower winglets. He said it only took a couple of hours per side, so we're not talking about a huge retrofit job here. He did report a little reduced directional stability at low speeds. He's now not sure he made the correct choice, a question he probably ponders the most when his 2 year old is in the back seat. Stet Elliott Perpetual Long-EZ builder From: Lee Devlin Subject: Removing lower winglets Date: Sat, 27 Jan 96 2:28:59 MST Phillip wrote: > Shirl Dickey wrote an interesting article about a year ago and he > comments that although the lower winglets delay stall of the main wing > there are no pilot queues warning of the pending stall. With the lower > winglets removed the stall occurs at a higher speed but the aeroplane > tells you that it is unhappy before the stall occurs, and when it > does, it does not lock in so deeply. Testing... who needs it when you can have arrive at answers so much cheaper and faster by conjecture and speculation? By the same logic one can argue that cutting a few feet off of each wing will cause the stall to occur at even a higher speed and thus give an even earlier warning of your impending stall condition. (Not that I don't admire Shirl's flying abilities, he is, after all, probably the best dead stick lander in the universe.) What do Rutan and Puffer really know anyway? They only have 1000+ planes flying between them and the E-Racer has what? Three? I'm still waiting for Shirl's test data on deep stall. I've read Rutan's, Puffer's, Swing's, but nothing from Dickey other than pure speculation. Sorry for the sarcasm, fellow readers, but I vehemently disagree with what Phillip has posted here and I think it would be irresponsible if I didn't say so. > I have the lower winglets on my > wings but I am seriously considering cutting them off for this reason. Maybe you should remove them on the principle of giving Nat more reason to vilify this forum as a means of disseminating bad advice. It's OK, folks, Phillip and I have been through this before and I have no beef with him personally. It's just that I don't agree with his approach of trying to convince others of the merits of modifications without having test flown them first. Lee Devlin Date: Fri, 03 May 1996 10:56:00 From: JRaerocad@gnn.com (Jeff Russell) Subject: COZY: AeroCanard: Lower winglet?? Not to my surprise was the results of adding lower winglets to the AeroCanard. At normal weights and CG not a lot of differences were seen. At 101.8 - 102.2 the biggest change was seen. Without the lower winglets the airplane would wing rock about 10 degrees right and left at 70 knots. This went away with the lower winglets installed. The AeroCanard feels more stable at these CG ranges. The lower winglets that are on this airplane are smaller than the Long-EZ style. The 8.5 inch tall lower winglets from L.E. to T.E. have been changed to 5 inches L.E. to 2 inches at the T.E. I like this change over not having lower winglets because it makes pattern work safer at these speeds and CG. I still like the look of no lower winglets then with them on, but safety is more important. Hope this helps someone. AeroCad Inc. Jeff Russell 1445 Crater Lane Yadkinville, NC. 27055 910-961-2238 E-mail: JRaerocad@gnn.com