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Zenith 750

 

With your VG's installed, 2600 rpm (O-200A) I was able to get 102 mph. Without VG's and without slats I could only get 97.5 mph. With original setup slats top speed was 93 mph. Fuel consumption is down from 6 gph to 5.4 gph.  Take off roll was better with the slats, 200 ft without flaps or brakes, 400 ft with VG's no flaps. With brakes 350 ft. This is based on observation from the plane using our runway lights as a measure. They are 200 ft apart. 

The VG's are doing what I was looking for: better fuel economy and a higher cruise speed. I'm not a bush pilot, I was looking for a Cessna 150 LSA type kit, first time builder, with good support and the Zenith CH750 fit the bill. The only disappointment had been the fuel economy and cruise spd which your VG's have cured. I'm 100% happy with my Zenith CH750 and your VG's 


Clemens, Florida

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Measured my (slatless) 750’s wing today and the chord was 1330 mm.

I calculated that 7% was 93mm. By the way, that’s 155mm forward of the main spar rivet line, measuring directly on the skin with a flexible ruler. I aligned the VG tips to a string line at 7% chord. Worked great! Takeoff seems just as short as previously with the slats – I can rotate as I accelerate through about 25 kts and I’m gone! Low speed handling is superb – with the VG’s and very slight crosswind, I flew down a long runway at about 35 kts and could raise the wheels on and off the strip at will with no problem from the crosswind – excellent control authority.

Without slats, cruise @ 2900 rpm was exactly the same before and after VG installation (80 kts.), so no drag penalty there!


John, 


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The easiest and tidiest way to remove the slat brackets, is just to cut them off about 12mm from the skin, along the profile of the leading edge.  Then they look like miniature stall fences, and you don't have to fill the holes in the skin.
Tip from John Austin (750)  Cut the brackets at 20mm out from the skin, so that you could re-attach the slats again, if desired.
(I'll be offering a kit to do be able to do just that, sometime in the new year).

For the main wing, place the VGs with their front tips 155mm in front of the main rivet line on the top of the wing.  The first 15 VGs in from each wingtip are at 60mm spacing, and the rest at 90mm.

For the tail, place the VGs on the elevator rather than the horizontal stab.Place the front tips of the VGs 120mm in front of the rivet line on the underside of the elevator spar, at a spacing of 30mm.  The curvature of the elevator increases at this point, and basically you are just trying to get the VGs as far forward as possible.


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