Date: Thu, 16 Jan 1997 03:19:31 -0500 From: INFINITY Aerospace <72124.347@compuserve.com> Subject: COZY: Winglets Hi Cliff and All, >Cliff Cady wrote:< >I had lower winglets on a Long-Ez and none on my E-Racer MKII. The Long-Ez had more apparent wing rock and I less yaw stability too. The only difference that might account for this might be a more aft cg for the Long-Ez and almost 200 lbs more empty weight on the E-Racer. Also the winglet cant angle is 90 degrees vs the inward cant angle on the Long-Ez. The roll effect of the rudders appears to be less with the E-Racer which surprised me as I remember this alot from the Long-Ez.< Info: As you may know, about 2/3 of the height of the winglet is like having that much more wing span per side. Winglets canted outward 110 degrees, to straight out (180 degrees, if you will), have no drag increase between the juncture of the winglet and the wing tip through this 70 degree outward cant angle band. Look at the winglets on airliners, other jets (and there fillets) - the winglets are there to help increase stability on these aircraft, yet are still canted outward about 110 degrees to remain within the optimum drag band. As the winglet cant angle decreases towards the fuselage to vertical, this will also increase roll rate. A vertical winglet (90 degrees) has a little less/will allow less roll rate than a winglet canted inboard a little. The Long-EZ wing rock and faster roll rate Cliff experienced is probably from the inward cant of the winglet (not having a wide flat bottom fuselage may have been a small factor somehow, also). You may be right about the yawing; i.e. - more aft Long-EZ CG and E-Racer being heavier. I wanted a little more maneuverability. That's why the Infinity 1 winglet is canted inboard even a little more (ala SR-71), coupled with longer ailerons and full span split-flap type rudders, should net a 50% increase in roll rate and more drag from the rudders - I'll let you know how it all turns out (Rutan's CM-44 winglets cant inboard about the same). The problem with progressively decreasing the cant angle towards the fuselage (from 110 degrees to vertical to leaning towards the fuselage) is that the drag between the winglet and wing tip juncture increases. This is why I talked about the need for fillets between all junctures, and the fillet equations in my 11/06 /96 post concerning Winglet Alignment, Vortilons and Airfoils. Also, don't forget to make sure the winglet chord and/or the vortilons are parallel to fuselage center line, or you may get some undesired yawing action meaning more drag. >Another difference between the two is the E-Racer winglet leading edge is forward to the leading edge of the wing.< As you all know, the purpose in sweeping the wings on a canard without a long fuselage to put a vertical and rudder is to get the winglets as far aft of the CG as possible so the rudders can drag you about the yaw axis in a turn. The original Long-EZ winglet leading edge is 2.7" aft of the wing tip leading edge (4.5" at the winglet to wing surface intersection) probably to get the original small Long-EZ rudder door hinge line aft of the wing trailing edge, and to get the small rudder door as far aft as possible for maximum yawing from this small rudder. As in the Italian Piaggio Avanti with the canard in the nose, for example, the thought behind the idea of placing the leading edge of the winglet to the leading edge of the wing tip may be/is an attempt to cut down on drag by having the 2 airfoils break the air only once at a single point (see Infinity 1, CM-44, StarShip, JetCruzer, E-Racer). Whether or not moving the winglet helps that much to cut down on drag, the winglet sure looks better moved to the leading edge of the wing (at least Cliff and I think so :-) ). Rudder yaw effectiveness would not be any less since the Big Rudders tip sweep aft to well aft of the same Fuselage Station (FS) of the original Long-EZ small rudder tip. I hope all this helps, is clearly explained, and is of interest. If not, let me know. A few more topics I have been asked to discuss that are in work: rudders, canard, ailerons, and HOT. Infinity's Forever, EAA Member EAA Technical Counselor JD EAA Flight Advisor AOPA Member Test Pilot James D. Newman, President LCDR F-14 USNR INFINITY Aerospace Mailing Address: P. O. Box 12275 El Cajon, CA 92022 Shipping Address: 1750 Joe Crosson Drive, D-2 El Cajon, CA 92020 (619) 448-5103 PH & FAX 72124.347@compuserve.com OR INFINITY_Aerospace@compuserve.com Checkout our Stick Grips, Retractable Main Landing Gear and the Infinity 1 at: Home Page http://ourworld.compuserve.com/homepages/INFINITY_Aerospace Date: Thu, 16 Jan 1997 06:24:29 -0500 (EST) From: CCady@aol.com Subject: Re: COZY: Winglets In a message dated 97-01-16 03:24:38 EST, you write: <> Interesting post. The application of rudder with aileron on the Long-Ez would just about double the roll rate, ailerons alone were pretty slow. I haven't tried rolling the E-Racer. The increased roll effect of the canted winglet is a safety factor because you could more easily compensate for a aileron control disconnect. From: "Rob Cherney" Organization: Ellicott City, Maryland Date: Thu, 16 Jan 1997 20:09:24 -0400 Subject: Re: COZY: Winglets >INFINITY Aerospace <72124.347@compuserve.com> wrote: > > The problem with progressively decreasing the cant angle towards > the fuselage (from 110 degrees to vertical to leaning towards the fuselage) > is that the drag between the winglet and wing tip juncture increases. This > is why I talked about the need for fillets between all junctures, and the > fillet equations in my 11/06 /96 post concerning Winglet Alignment, > Vortilons and Airfoils. Also, don't forget to make sure the winglet chord > and/or the vortilons are parallel to fuselage center line, or you may get > some undesired yawing action meaning more drag. Certainly, the vortilons should be parallel to the center line, but I think there is some intentional inboard alignment of the winglet leading edges to provide a bit of dynamic stability. If I remember correctly, one canard builder removed this "misalignment" to increase speed and found that his yaw stability suffered. While his speed marginally increased, his plane slowly wanders about the yaw axis. When in doubt, stick to the plans. Rob- +--------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@clark.net | +--------------------------------------------------------+ Date: Fri, 17 Jan 1997 00:52:30 +0000 From: John Meernik Subject: Re: COZY: Winglets (snip) > >Cliff Cady wrote:< > >I had lower winglets on a Long-Ez and none on my E-Racer MKII. > The Long-Ez had more apparent wing rock and I less yaw stability too. The > only difference that might account for this might be a more aft cg for the > Long-Ez and almost 200 lbs more empty weight on the E-Racer. Also the > winglet cant angle is 90 degrees vs the inward cant angle on the Long-Ez. > The roll effect of the rudders appears to be less with the E-Racer which > surprised me as I remember this alot from the Long-Ez.< > > Info: As you may know, about 2/3 of the height of the winglet is > like having that much more wing span per side. For anyone thinking about changing the winglets a word of caution. Any such changes will effect the allowable aft center of gravity. The reason for this is that the prevention of a deep stall depends upon many things. Two of them are the relative wing loading of the canard compared to the main wing, and the stall characteristic of the main wing. The winglets effect both of these things. First as stated above the winglets make the main wing have a larger effective span. This changes the effective wing loading of the main wing and thus changes the aerodynamic balance between the main wing and the canard. Secondly, the winglets change the stall behavior of the main wing by protecting the outer portion of the main wing. In a swept back wing like we have on our birds, the outer portion of the wing is the first to stall. In a canard this tendency is aggrevated by the fact that the center portion of the main wing is flying in the downwash of the canard. This downwash causes the center part of the main wing to be flying at an angle of attach that is effectivly less than the outer portions of the main wing which are not flying in the canards downwash. The winglet does not erradicate this tendency, but it does change the angle at which the main wing will stall. This is a seperate effect from the winglets increase in main wing area. As I stated in a posting I made several months ago, this is a very short word of caution on something which is fairly complex. Experimental aircraft are great because we really can "experiment". However if you chose to experiment with something as basic as the design of the wings in order to increase speed, change roll characteristics, fix a yaw problem, etc. be aware that even small changes can have some unintended, sometimes nasty effects. As an example, from what I can gather, I think that the most important contributing factor to the recent deep stall crash of one of our bretheren was probably the removal of the vortilons. This has a profound effect on the stall behavior of the main wing at critical angles of attack. Flying at or near the aft CG without the vortilons is a sure fire way of falling out of the sky. Same goes for flying at or near aft CG after changes to the winglets. Some changes will have more effect that others, but all changes will have some effect. (some changes might even improve stall behavior, but not many of the ones that I have seen discussed) I am a firm believer in freedom. If anyone wants to make changes more power to you. Just be careful because some of the effects may not be what you want. John Meernik Date: Thu, 16 Jan 1997 17:15:36 -0800 From: berkut@loop.com Subject: Re: COZY: Winglets >>INFINITY Aerospace <72124.347@compuserve.com> wrote: >> >> The problem with progressively decreasing the cant angle towards >> the fuselage (from 110 degrees to vertical to leaning towards the fuselage) >> is that the drag between the winglet and wing tip juncture increases. This >> is why I talked about the need for fillets between all junctures, and the >> fillet equations in my 11/06 /96 post concerning Winglet Alignment, >> Vortilons and Airfoils. Also, don't forget to make sure the winglet chord >> and/or the vortilons are parallel to fuselage center line, or you may get >> some undesired yawing action meaning more drag. > To which Rob Cherney replied > >Certainly, the vortilons should be parallel to the center line, but I >think there is some intentional inboard alignment of the winglet >leading edges to provide a bit of dynamic stability. If I remember >correctly, one canard builder removed this "misalignment" to >increase speed and found that his yaw stability suffered. While his >speed marginally increased, his plane slowly wanders about the yaw >axis. When in doubt, stick to the plans. > The "waterline" on the winglet template in the Long EZ plans (and I assume the Cozy plans, please correct me if I'm wrong) is NOT supposed to parallel the aircraft centerline. Follow the WPRP numbers in the plans, there is supposed to be a specific positive AOI built in. I saw Burt work out the difference on his calculator watch and he said it wouldn't be a critical error, but it does affect yaw stability. The line on the template is only there so you can hotwire the winglet without any twist. -- Czech Sikhs! Richard Riley "Heavier than air flying machines are impossible." Lord Kelvin, President, Royal Society, c 1895 See the Berkut at http://www.berkut.com Date: Fri, 17 Jan 1997 09:19:44 -0500 (EST) From: SWrightFLY@aol.com Subject: Re: COZY: Winglets John Roncz covered this subject (mounting winglets parallel to BL-0) in the most recent issue of the CSA newsletter. John has agreed to answer similar technical questions in the newsletter. Bottom line of this subject- Stick to the plans. Date: Fri, 17 Jan 1997 18:21:34 -0500 (EST) From: CCady@aol.com Subject: Re: COZY: Winglets In a message dated 97-01-16 19:31:43 EST, you write: << Certainly, the vortilons should be parallel to the center line, but I think there is some intentional inboard alignment of the winglet leading edges to provide a bit of dynamic stability. If I remember correctly, one canard builder removed this "misalignment" to increase speed and found that his yaw stability suffered. While his speed marginally increased, his plane slowly wanders about the yaw axis. When in doubt, stick to the plans. >> Funny one of the first things I noticed about my Long-Ez was a small wander of the nose. One person mentioned to me that some of this dutch roll is common on swept wing airplanes. I had the winglets mounted per the plans. I wonder if this was severe or similar to what I experienced. Cliff