Gurney flaps + plain flaps?

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

addaon

Well-Known Member
Supporting Member
Joined
Feb 24, 2008
Messages
1,984
Location
Kanab, UT
Anyone have a reference (NACA or otherwise) for combined Gurney flaps and plain flaps? (Also might come up as dCL and dCM effect of highly-deflected trim and servo tabs I suppose.) Couldn’t find anything with search.
 

addaon

Well-Known Member
Supporting Member
Joined
Feb 24, 2008
Messages
1,984
Location
Kanab, UT
Yeah, looking specifically for Gurney-on-the-end-of-a-plain-flap. One of the interesting things about that geometry would be that the Gurney angle can't be perpendicular to the flow at all times as the plain flap deflects; I'm hoping to see numbers (especially hinge moment and dCm/d(deflection)) for the combined system as the Gurney deviates from perpendicular.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
17,641
Location
Memphis, TN
I’m sure your Google Fu came up with this NASA Technical Memorandum 4071
It in its self was really designed to be a trim tab for a fixed airfoil. Usually the need for it on an airplane means you picked the wrong trailing edge thickness.
 
Joined
Nov 14, 2009
Messages
8,599
Location
Rocky Mountains
for the combined system as the Gurney deviates from perpendicular.
I'm guessing that if the flow separates from the flap/aileron before getting to the trailing edge then the Gurney would have no effect. If the flow stays attached then the angle of the Gurney to the relative airflow would be unchanged from that of a non-deflected control device?

Edit:
Using a Gurney as a method of controlling the aileron/flap is an interesting idea I have pondered. It would require a very small actuator to do the work - if it actually worked.
 

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
7,403
Location
krakow,poland
the Gurney angle can't be perpendicular to the flow at all times as the plain flap deflects;

=in case of KASPERWING "G Flap" is mooving 0-90 gegree .

(last video)...

"It would require a very small actuator to do the work - if it actually worked."

=simple pushrod,X-crossed !

-for clarity...
 

Attachments

  • Zrzut ekranu (18).png
    Zrzut ekranu (18).png
    615.7 KB · Views: 0
Last edited:

Victor Bravo

Well-Known Member
Supporting Member
Joined
Jul 30, 2014
Messages
11,113
Location
KWHP, Los Angeles CA, USA
Tony Blair - "Brexit!"
Henryk - "Kasperwing!"

Albert Einstein - "Relativity!"
Henryk - "Kasperwing!"

Beatles - "Dear Prudence!"
Henryk - "Kasperwing!"

Abraham Lincoln - "Emancipation!"
Henryk - "Kasperwing!"

Pythagoras - "Triangle!"
Henryk - "Kaspewring!"

Mother Theresa - "Kindness!"
Henryk - "Kasperwing!"

Dalai Lama - "Enlightenment!"
Henryk - "Kasperwing!"
 

dog

Well-Known Member
Joined
Dec 29, 2019
Messages
741
a bit more reading has led to the rabbit hole of
TED's ,trailing edge devices,of which aluminum angle is but one of many,including various
longitudinal notches,grooves and gutters,angles,
triangles,blocks and tabs,each changing the lift
and drag depending on all of the usual factors
none that I have found yet are flapped,flaps which is what the op is looking for
though I suspect that flapped flaps will flutter and
thats not going to fly
 

addaon

Well-Known Member
Supporting Member
Joined
Feb 24, 2008
Messages
1,984
Location
Kanab, UT
Yeah, I'm aware of the reputation of the Gurney flap as a "fix". I happen to be in a particular case where I'm looking at a rigidly-driven flap (so no flutter concern) where I need more nose-down moment per unit lift at, specifically, high flap deflections, and wanted to see if something like a deployable Gurney flap (or perhaps something like a 1% chord split flap) would satisfy the somewhat odd requirements.
 

Victor Bravo

Well-Known Member
Supporting Member
Joined
Jul 30, 2014
Messages
11,113
Location
KWHP, Los Angeles CA, USA
If you are looking for more nose-down moment at a high deflection, the trailing edge of a standard 90 degree gurney Flap may now be pointing too far forward to do what you want. It could start thinking it's an air scoop :)

I am guessing that bending the Gurney Flap to some angle at which it becomes vertical at full main flap deflection will get you closer than a "textbook" Gurney???

With a Gurney Flap, you're of course living with the drag for the whole flight, and you might not be able to get rid of all of it even by reflexing the flap at cruise.
 

addaon

Well-Known Member
Supporting Member
Joined
Feb 24, 2008
Messages
1,984
Location
Kanab, UT
Yeah. I'm thinking of that tiny split flap, or a 1% TE plain flap / tab that deflects to Gurney levels (90° to free stream, so 90° - main flap deflection); in either case, only deployed as the main flap passes 20° or so. I'm just trying to find some numbers that would describe either of those cases, since a tiny flap buried in a boundary layer is not something I can really model easily.
 

dog

Well-Known Member
Joined
Dec 29, 2019
Messages
741
put a deployable gurney flap outboard of the main
flaps,designed to deploy as part of the main flap mechanism,added lift and nose down moment and drag that is separate from the rest ,those numbers aret here now,though it will likely require a rework of the outer wing
 

cluttonfred

Well-Known Member
Supporting Member
Joined
Feb 13, 2010
Messages
9,629
Location
World traveler
Tony Blair - "Brexit!"
Henryk - "Kasperwing!"

Albert Einstein - "Relativity!"
Henryk - "Kasperwing!"

Beatles - "Dear Prudence!"
Henryk - "Kasperwing!"

Abraham Lincoln - "Emancipation!"
Henryk - "Kasperwing!"

Pythagoras - "Triangle!"
Henryk - "Kaspewring!"

Mother Theresa - "Kindness!"
Henryk - "Kasperwing!"

Dalai Lama - "Enlightenment!"
Henryk - "Kasperwing!"

I think there was time you could have made the same joke about me with either “Pou-du-Ciel!” or “Volksplane!” as the answer to everything. 😜
 

Victor Bravo

Well-Known Member
Supporting Member
Joined
Jul 30, 2014
Messages
11,113
Location
KWHP, Los Angeles CA, USA
I've also been accused of answering "Taylorcraft" or "Sailplanes" to many questions as well. But Einstein's theory of relativity (and My Cousin Vinny's theory of relevance) do have their limits... I must humbly admit that our dear friend's way of promoting his religion just happened to have that 36 grit sandpaper effect at that one moment.
 
  • Like
Reactions: BJC

Victor Bravo

Well-Known Member
Supporting Member
Joined
Jul 30, 2014
Messages
11,113
Location
KWHP, Los Angeles CA, USA
a bit more reading has led to the rabbit hole of
TED's ,trailing edge devices,of which aluminum angle is but one of many,including various
longitudinal notches,grooves and gutters,angles,
triangles,blocks and tabs,each changing the lift
and drag depending on all of the usual factors
none that I have found yet are flapped,flaps which is what the op is looking for
though I suspect that flapped flaps will flutter and
thats not going to fly

Depending on where you draw the line between a flap tab and a whole 'nother flap, "Flapped Flaps" work well on the deHavilland series of bushplanes, and we see double/triple slotted flaps are on many large airliners. But there is indeed a lot of structure and engineering at the early design stage that goes into making these safe and flutter-resistsnt.
 

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
797
... I must humbly admit that our dear friend's way of promoting his religion just happened to have that 36 grit sandpaper effect at that one moment.

Just at that moment ?
When I drink too much coffee ; that's when ("I") have that
36 grit effect on Everybody !! LOL

Hooking up deploy-able Gurney flaps, for just 1/2 span
or less , as the normal flaps go down ; would be a doable
solution. Time them to Not go past 90-deg ; when fully deployed.

It's such an easy Idea ; I just decided to do that to my Atos VRX
and chop about 1/5 the flap span off , for the same effect as
the 5/8-th span flap gives me now

Bille
 
Last edited:
Top