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Ron's Web Site
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Date: 11-6-2011
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Number of Hours: 2.50
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Manual Reference:
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Brief Description: Wing Vortex Generators
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I wanted to try vortex generator's as they appear to allow increased angle of attack during approach; on my BH, I can't use 3 or more notches of flaps easily, as I'm unable to get the nose up during the flare without popping throttle. I used Hall Bros. VG's which currently go for $184 from AC Spruce. They are a bit easier to install as they have two generators on each piece of aluminum, which means I was able to "only" install 36 generators. Further, their broad base allows provisional fixation using white electricians tape. I used 9.176 inch spacing set at 7 inches aft of the leading edge (10.6% chord), spanning 13 feet of each wing, measured on the VG centers. The width of each vortex expands to 4.5 inches from the VG center, according to Hall Bros. wind tunnel data, so the 13 feet is centered 4.5 inches inboard of the wing tip and 4.5 inches outboard of the wing root fairing edge seams. I used a taut fishing line as the straight edge, and a long tape for the measurements.
Iniitial flight test was done on a calm, smooth day. Stall KIAS with full fuel decreased from 51 to 41 clean, and from 48 to 40 with two notches, both with noticeably higher angle-of-attack. With 3 notches, I was able to achieve 39 KIAS stall with a sufficiently higher nose, such that I felt 3 notch landings were feasible. Flight feel was quite different; the aircraft feels heavier in pitch and more attention to trim was needed. Ailerons were somewhat more effective. Using 50 KIAS for landing gives a nose high approach all the way down, and it's very easy to three point with a slight flair and taking the power off. "Parachute Mode" shows a stable phugoid at 40 KIAS with power off and stick fully aft and a descent rate of 1000 fpm. Ground roll on takeoff (as well as landing) is also decreased.
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Laying out of VG's.
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Provisionally installed VG's.
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Fully installed.
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