Effects of sharp leading edge?

[dvint]

I am building a delta with an approx.45 degree swept back leading edge.The
leading edge is rather sharp. Span is 29" with 350sq.".Wil this be pitch sensitive ?
Thanks

[Sail 'n Soar]

I am building a delta with an approx.45 degree swept back leading edge.The
leading edge is rather sharp. Span is 29" with 350sq.".Wil this be pitch sensitive ?
Thanks

Deltas are different. They tend to roll up a vortex from that high sweep leading edge. This vortex keeps flow along the upper surface to very high angles of attack, making them almost stall proof. That said, I'm not sure what will happen at small angles of attack.

[banktoturn]

I am building a delta with an approx.45 degree swept back leading edge.The
leading edge is rather sharp. Span is 29" with 350sq.".Wil this be pitch sensitive ?
Thanks

dvint,

I doubt that the sharp leading edge will cause pitch sensitivity. There seems to be a widely held view that a sharp leading edge has this effect, but I don't believe that this is the case. One thing that will certainly cause pitch sensitivity is high aspect ratio. Your delta will have a very low aspect ratio, which should actually make it fairly insensitive to pitch.

banktoturn

[Ollie]

Airfoils are designed to perform in two dimensional flow. A low aspect ratio delta wing operates entirely within the tip vortex with lots of spanwise flow which varies over the span. The induced angle of attack at stall can be as large or larger than the airfoil section angle of attack. Therefore, the effect of the leading edge shape on stalling angle of attack is far less important than for a high aspect ratio wing. Airfoil selection for low aspect ratio wings is not as important because of induced drag and induced angle of attack affects which tend to dilute drag and angle of attack differences between airfoils especially at high coeffients of lift in tight turns or slow landing approaches.

A flat plate airfoil stalls at about 7.5 degrees angle of attack. An S8020 airfoil stalls at about 9.5 degrees angle of attack. Yet, when you add the 10 or 15 degrees induced angle of attack of a low aspect ratio delta, the airfoil differences will be barely noticeable.