Trailing Edge Fences

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This question seems to come up every couple of years, which suggests there’s a need to have a database somewhere of what works and what doesn’t. See Also VG Installation

Trailing edge stall fence.gif

On my xlrg,

1. vg’s provided a 3kt lower stall speed (dropped from 66 to 63) and approximately a 1.5 - 2 kt drop in cruising airspeed. The cruise speed drop measurement was imprecise, - used flying in triangles to measure.

2. vg’s on the canard add lift and drag during cruise, with a noticeable increase in down stick pressure needing to be applied. I clipped the length of the canard vgs in half and that seemed to solve the problem. Previously (I’ve done this twice) I removed half of the vgs on the canard, both seemed to have negligible effect on the lift during slow speed produced by the canard and beneficial effect at cruise speed. My anticipation is that the pattern needs to be re-engineered for the canard.

TEFence2.jpg

3. vg’s on top in front of the naca scoops helped reduce engine temps. Although in a steep climb, I did not see the improvement, anticipated that the air is detaching further ahead in a steep climb. I tried attaching vg’s at the door line on top as well. Haven’t noticed that it helps significantly.

Trailing edge stall fence on the inside of the ailerons reduced take off distance by 15% - and gave significant increase in control at low speeds. No reduction in cruise speed. This should be a standard on the wing.

Trailing edge fence on the inside and outside of the aileron produced significant climb improvement. I went from a sustained 1,200 to 2,000 with two large adults in the front seat. But I removed them because of the adverse effect on turning. Basically it wants to fly straight ahead with four fences on the wing – sure goes up quick though.

Have attached a couple of pics. Hope that helps.

Rodney Brim,