stall speed at gross

[KWK]

Have any builders established using GPS the clean stall speed at gross of their Sonex/Waiex?

The nominal wing loading of the Sonex is higher than average among the LSA, so the fuselage must be providing some of the lift.

[gammaxy]

I never set out to measure this number to the precision you want, but I did find a gross-weight flight where I performed two stalls and I flew in enough directions that I believe I can estimate the wind speed.

Aircraft weight: 1125lbs (took off at 1150lbs and burned ~25lbs of fuel; this flight was performed at greater than Sonex's recommanded gross weight for the Aerovee engine.)
Density altitude: 4000ft
Tailwind during the stall: 7mph (my greatest uncertainty, but I did record GS and TAS while flying around in several circles, so feel like this is a reasonable estimate)
Minimum GPS ground speed during the stalls: 43mph (35mph IAS)
Estimated clean stall TAS: 50mph (43mph+7mph)
Stall speed corrected to sea level density altitude: 50mph * sqrt(1.088/1.225) = 47mph

Sonex lists the clean stall speed as 46mph. I feel like my estimate of 47mph agrees remarkably well with theirs. Both are comfortably within the LSA rule of 51mph.

Here's a recent quote from John Monnett about the fuselage lift:

“They’re basically a box with a lifting body that’s created by a smooth canopy and cowling transition. That contributes tremendously to its performance at both low-speed and high-speed operations.”

I'd be interested in seeing a comparison against other more rounded fuselage designs.

[KWK]

47? I'd have bet it was closer to 51. Impressive performance. Thanks for the info.

[mike.smith]

At 950 lbs (aerobatic weight) my stall speed is 26 kts indicated. There is probably some pitot error due to a high angle of attack, but I can keep flying straight ahead with rudder, and it won't start nosing down until 26 kts. At that weight I break ground on take off at 36 kts indicated.

[Darick]

Is that with any flaps down?

[mike.smith]

No flaps.