Leading Edge shape

[staudman]

`I have been involved in IMAC for some few years now and have seen some airframes outfitted with a rather sharp leading edge at the tip and as it makes it way to the root it transituions gradually to the conventional rounded profile.
I was of the impression that this was a useful design element to assist spin/snap entry.
Is this still a viable design when we consider todays airframes??
MIke Sotomayor
THE Staudman
Miguel Sotomayor
THE Staudmans Builder !!!

[thewrap]

I'm not sure but I had a friend experement with something similar. He taped a piece of tri stock to the LE. He said it helped to be more precise in rolls and such.

[3ddd]

sharper is faster on pitch changes and not quite as stable on a straight flyby if you wiggle the sticks at all.rounded is more forgiving and smoother on pitch changes,that is why most good imac planes do not have a sharp leading edge

[Surly_Schmidt]

SHarper will transition into alpha flight easier. I dont think they are faster in pitch changes. JMO

[Shaker]

	Quote: Originally Posted by 3ddd
	sharper is faster on pitch changes and not quite as stable on a straight flyby if you wiggle the sticks at all.rounded is more forgiving and smoother on pitch changes,that is why most good imac planes do not have a sharp leading edge

Actually that's incorrect and is some bad information that's been passed around as long as I've been flying (34 years now). The leading edge shape of a wing has little to nothing to do with pitch rate.

A sharp leading edge WILL allow the airflow to detach quicker making snap entries a bit sharper. It still takes the same angle of attack to depart, but when it reaches critical AoA, the flow detaches MUCH faster with a shapened leading edge.

[somethnextra]

Shaker is right. Take a look at Abbott and Von Doenhoff data. The thickness of an airfoil affects post stall characteristics. That is, after the airfoil reaches max lift/aoa. For a given airfoil of varying thickness both are the same.

[somethnextra]

thewrap: The tri stock would only affect airflow over the wing at high angles of attack. Some GA planes use the same technique as a stall warning. At high aoa it creates a buffet that warns the pilot a stall is close.