Another Question about Flaps

Reading the "airfoils again" thread, there is one thing I'm not
clear on. There are some designs with a constant chord wing, and
a flat STATIONARY flap, with the trailing edge of the flap
tapered. The Flight Streak & Brodak Lightning Streak come
to mind. Does a flat stationary flap add lift, or is it
strictly cosmetic?

It is not cosmetic. It adds lift in virtually the same amount, per area, as any other part of the wing structure.

Ed,

That's how I plan to add a small about of wing area to my Skyray. The wing is elongaged by two inches, stab/elevator area are increased - I think that will make the Skyray a slightly better flyer than the stock version.

As I recall, one of the thoughts about airfoils that goes back pretty far has to do with the idea of avoiding stall at the tips, which may introduce rolling, so the tip airfoil is intentionally thicker than the root airfoil. Tapered flaps fulfill this theory nicely.

K.

>Lightning Streak come
>to mind. Does a flat stationary
>flap add lift, or is
>it
>strictly cosmetic?
>
>
>Ed N.

Thin objects stuck in an airflow can run, but they can't hide. And they cannot abrogate their natural tendencies.

One of which is to provide lift.