Gurney flaps + plain flaps?

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Tiger Tim

Well-Known Member
Apr 26, 2013
Thunder Bay
If you need more nose-down pitching moment with more flap, could Fowler flaps be rigged in such a way that they keep pushing the center of pressure aft the further they deploy? Not exactly the same but it would leave you with an airplane that’s more nose heavy the more flap you put on.

Protech Racing

Well-Known Member
Jul 10, 2020
AS aero adviser for Trans am cars. The Gurney was a huge tuning tool . Changing the size from 3/8 in to 1/2 in resulted in almost 100# down force change at 125MPH. I have never seen any data testing that showed that they did not work .

Bille Floyd

Well-Known Member
Sep 26, 2019
Billie, that’s the idea, just hoping to find some numbers so I can do sizing.

My numbers will come from actual empirical data . Start
with a 2.5% cord gurney , and adjust the
timing so as to get near 0 effect , and keep adding more AOA, until
it gets uncomfortable. Next change the gurney % cord , for both - first
then +.

I can make an adjustable mechanism , so as to get all the data
for one size gurney , in one flight ; get rid of it when size and
optimum AOA timing is found.

Lots and lots of altitude please ; one hand ready to grab my reserve.

Thanks for the Idea "addaon" ; it's a Really good one , and
I'm definitely gonna do it !!!! ... ...



Well-Known Member
Aug 9, 2005
Cresson, TX
I've experimented with Gurney Flaps on my CH601XL-b, both on the elevator, and on the rudder. Anecdotally, and not having any "performance numbers", from the seat of the pants feel I can tell you that these are a lot more effective than you may realize, especially in yaw. With Gurney Flaps, start a lot smaller than what you think you need, and adjust from there in small increments.