Slats/slots for sheet wings

[Terry Caron]

The caption to the pic below says "The slot makes the flat wing act like a proper airfoil. Simple."
How about a slat on both sides of a sheet wing? Simple?

[Brett Buck]

The caption to the pic below says "The slot makes the flat wing act like a proper airfoil. Simple."
How about a slat on both sides of a sheet wing? Simple?

   I don't know about "proper airfoil" but a very neat way to make a slat that works in both directions is to put a flat sheet in front of the LE, hinge it from a frame on the front, and put stops to prevent it from moving more than about 30 degrees either way. Just let it float free - when you need positive lift, it flop up, and creates a slot to channel the air over the top, and when inverted, the opposite. Where you put the stops, and whether you want to let it free-float or put a spring on it, is an interesting experiment. The same principle could be used to create a drooped  leading edge with a little more work.

   I have seen an airplane with the free-floating slot/flap in front of the wing LE. The problem appeared that it worked far too well, and far too abruptly, at least with a conventional airfoil. Of course, you could create a variable slot/drooped LE that was driven by the controls, too. That, I haven't seen aside from some thought experiments I did.

      I very strongly suspect that anything you can do with slots/slats/flaps and a flat-plate wing would be better solved with a built-up wing and a conventional airfoil, but it would still be interesting to see.
 
     Brett

[Terry Caron]

Thanks for the reply, Brett. We're getting into an area I know little of (airplanes!  ) and not visible in that pic is that the slat has an airfoil. I don't know if it matters.
Am I correct in thinking the angle between the 2 surfaces determines the AoA at which the slot begins to take effect?
I'm guessing there's a useful angular range, and a range of useful slat area (or chord?), maybe as a function of wing area or MAC.
Slot height's another variable.
!/2A sheet profiles are quick building - I may play around with it a bit.

[Phil Krankowski]

Might as well read about sailboats.  There is a similar relationship between the jib and main on small yachts.  The first big difference is that the sails form a true airfoil.  The second is the direction of said airfoil being rather vertical. 

Phil
 

[Terry Caron]

Right, Phil, I'm somewhat familiar with sailing.
The significant difference here is the fixed surfaces, which can't be adjusted on the fly as a jib can be.
So slat & slot size & angle must be designed in, so if I can get info on design parameters it would be a great help in any attempt to play around with the idea.
I've also discovered that a slat refers to a movable surface while a "fixed slat" as discussed here is referred to as a slot.
Live and learn, as long as I can.