HorizonHobby.com Shop our Airplanes Products Shop our Surface Products
Thread Tools
Old Nov 12, 2015, 08:20 AM
georgy is online now
Find More Posts by georgy
Allways the hard way!
georgy's Avatar
South Africa, GP, Germiston
Joined Jan 2012
733 Posts
Discussion
Advice: Anhedral wings..

I've been reading what i could find regarding anhedral wings on park jets... found a thread on a Harrier/AV8 where i get the impression the designer had dis hands full to get it to fly properly.. used a lot of mixing to tame the beast!

Is this an inherant issue with the droopy wings... or a Harrier thing... or a combination?

To make it worse, i think the Harrier has rather smallish wings, and a chubby fuse to boot!

Your opinion/experiance appreciated...
georgy is online now Find More Posts by georgy
Last edited by georgy; Nov 12, 2015 at 02:37 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 12, 2015, 08:43 AM
eflightray is offline
Find More Posts by eflightray
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
16,038 Posts
Have you got a model with dihedral ?, try flying it inverted.

Swept back wing can give a similar effect to a small amount of dihedral, i.e. a bit of lateral stability. That could be cancelled with some anhedral.

Often there can be a problem in copying the same size and layout of a full size aircraft. Tail ends can sometimes be a little too small if made to scale, (you can scale a model, you can't scale air).

There are many things that can make a model difficult to fly, initially. But generally those problems can be solved, though may need a non-scale change.

Biggest problem is usually weight, too much of it.

Ray.
eflightray is offline Find More Posts by eflightray
Reply With Quote
Old Nov 12, 2015, 08:54 AM
flypaper 2 is online now
Find More Posts by flypaper 2
I use foam to hold my hotglue
flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
15,342 Posts
Don't know about the Harrier, but in one of the books I have on the Avro Arrow, they put a bit of anhedral in the wings in order to shorten the gear legs.
Most of these high tech planes are computer controlled/ stabilized, so don't really need dihedral or anhedral. Sooner have neutral stability.

Gord.
flypaper 2 is online now Find More Posts by flypaper 2
Reply With Quote
Old Nov 12, 2015, 09:05 AM
compressor man is offline
Find More Posts by compressor man
Professional tree finder
compressor man's Avatar
GA,USA
Joined Jul 2010
266 Posts
I heard that the big cargo planes have anhedral wings to make them more 'unstable' and that if they did not have this then they would be much more difficult to turn. Not sure if this is actually true.
Chris
compressor man is offline Find More Posts by compressor man
Reply With Quote
Old Nov 12, 2015, 09:36 AM
georgy is online now
Find More Posts by georgy
Allways the hard way!
georgy's Avatar
South Africa, GP, Germiston
Joined Jan 2012
733 Posts
Some interesting thoughts!

As far as scale is concerned... i love profile and semi-profile planes so i guess claiming "scale" would be a bit daft of me!

I just love the look of those droopy wings, and think even on a semi-profile would just be wrong to have "flat" wings on a Jaguar or Harrier... or....or!

My main concern is some sort of evil inherent instability demon on anhedral wings?

Swept wings with anhedral... maybe that why my Sabre swept-wing with dihedral is such a cow!
georgy is online now Find More Posts by georgy
Last edited by georgy; Nov 12, 2015 at 02:39 PM.
Reply With Quote
Old Nov 12, 2015, 09:54 AM
FiftySlicks is online now
Find More Posts by FiftySlicks
Registered User
United Kingdom, Scotland, Edinburgh
Joined Jun 2014
261 Posts
Quote:
Originally Posted by compressor man View Post
I heard that the big cargo planes have anhedral wings to make them more 'unstable' and that if they did not have this then they would be much more difficult to turn. Not sure if this is actually true.
Chris
I'm thinking the anhedral in this case is to cancel out the high wing effect. If you have the wing mounted on top of the fuselage it creates an effect similar to dihedral that resists turning. There's 2 explanations for this that I know, the first is 'pendulum stability' in that the CG of the plane is under the wing attachment point, giving a self leveling tendency. Thing is this does not apply to multirotors or helicopters, even though intuitively you'd think it would, so I genuinely don't know if fixed wing aircraft benefit from it at all. Open question to anyone that knows the answer. A quick search tells me 'pendulum stability' gets quoted an awful lot even when it may not apply.....

What I do know is that a high wing fuselage has an aerodynamic property similar to dihedral that resists turning and provides a real self-levelling tendency. It's a 3d airflow effect related to the aircraft slipping sideways slightly when it rolls and this airflow hitting one side of the fuselage and acting to push the fuselage back 'under' the wing if it makes sense. Hurts my head to visualise it if I think about it too long. Low wing has the same property in the opposite sense, acts against stability and the same as anhedral.

There's also the concern that wings bend upward when they lift, so you might have a long wing with anhedral when stationary, that bends up to become effectively flat in flight. Or a dihedral wing gains more dihedral in flight. As said sweep effectively acts as dihedral as well so that's something else to factor in. So you could have a swept wing with anhedral that would be about the same as a low mounted straight wing with dihedral, that would be about equivalent to a high mounted straight wing with anhedral. Things can never be simple can they?
FiftySlicks is online now Find More Posts by FiftySlicks
Reply With Quote
Old Nov 12, 2015, 11:25 AM
gpw is online now
gpw
Find More Posts by gpw
gpw
“There’s no place like Foam”
gpw's Avatar
United States, LA, New Orleans
Joined Jul 2002
25,110 Posts
We’ve also had planes with top mounted wings and anhedral , and it was no problem ... Even the Cylon Raider (SGT) flew fine with slight anhedral ... but we are an experienced pilot .... maybe beginners should stay away from this till confident ...

This brings up a point where the vertical area is large enough to compensate such as on SGT’s Colonial Viper , with much anhedral and a huge Vertical fin ... which seems to fly just fine ...
gpw is online now Find More Posts by gpw
Reply With Quote
Old Nov 12, 2015, 12:02 PM
georgy is online now
Find More Posts by georgy
Allways the hard way!
georgy's Avatar
South Africa, GP, Germiston
Joined Jan 2012
733 Posts
Seems there are sufficient proof of good flying anhedral winged park planes not to worry too much about the concept...

As far as pilot experiance.. i've done enough "un-usual" planes to atleast expect some success...

Thanx gents
georgy is online now Find More Posts by georgy
Last edited by georgy; Nov 12, 2015 at 02:40 PM.
Reply With Quote
Old Nov 12, 2015, 02:23 PM
eflightray is offline
Find More Posts by eflightray
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
16,038 Posts
There is a bit on anhedral here -- https://en.wikipedia.org/wiki/Dihedr...tics)#Anhedral

Ray.
eflightray is offline Find More Posts by eflightray
Reply With Quote
Old Nov 13, 2015, 10:13 AM
DuPageJoe is offline
Find More Posts by DuPageJoe
Registered User
USA, IL, Wheaton
Joined Oct 2010
774 Posts
That's an interesting article, with a lot more on dihedral, but it shows how a force analysis helps figure out these things. The Chance Vought Crusader has quite a bit of anhedral in its high mounted wing, but dihedral in the stab. I think a lot of it has to do with placement of the center of drag with respect to the CG. For maneuvering, they should be pretty close as you look head on to the plane.

http://richard.ferriere.free.fr/3vue...rusader_3v.jpg

Some of the anhedral in big cargo planes might be canceled out by wing flex, with less anhedral in the air than when parked. B-52's droop a bit on the ground, too.

Remember that the original Wright Flyer used anhedral for some lateral stability, The Wright brothers got the idea from observing gulls.
DuPageJoe is offline Find More Posts by DuPageJoe
Reply With Quote
Old Nov 13, 2015, 12:01 PM
dayhead is offline
Find More Posts by dayhead
SlingWinger
San Bernardino, California, United States
Joined Oct 2004
2,005 Posts
If your swept-aft wing is displaying dutch roll or "wing walking" or "wing rocking", add some directional stability, or add anhedral.

I've added anhedral to combat wings with great success. I had one with perhaps too much of it, and while thermalling it was roll unstable.

However, I found that while circling, the "high siding" of the stick gave me camber on the lower wing and the reflex was concentrated on the high wing. It felt as though I was getting a better sink rate/climb rate with this set-up.
dayhead is offline Find More Posts by dayhead
Reply With Quote
Old Nov 13, 2015, 10:36 PM
SGTalon is offline
Find More Posts by SGTalon
SG Talon... Super Genius.
Lenox, Michigan
Joined Nov 2005
3,242 Posts
I have a Harrier I built with Anhedral wings and everyhing. It flew fine. If your control surfaces are large enough and you have a decent sized tail you are good.
http://www.rcgroups.com/forums/showthread.php?t=1466697

On my Harrier, I did increase the vertical tail by about 25% to increase the stability. And as GPW mentioned the Battlestar Galactica Viper and Cylon both have anhedral but I don't think it makes them unstable. I think CG position helps that a lot too. My Harrier has the CG very low vertically on the plane. Helps keep the plane flying right side up.

So are you working on a plane? I wasn't really sure from the original post.
SGTalon is offline Find More Posts by SGTalon
Reply With Quote
Old Nov 14, 2015, 12:44 AM
georgy is online now
Find More Posts by georgy
Allways the hard way!
georgy's Avatar
South Africa, GP, Germiston
Joined Jan 2012
733 Posts
Quote:
Originally Posted by SGTalon View Post
I have a Harrier I built with Anhedral wings and everyhing. It flew fine. If your control surfaces are large enough and you have a decent sized tail you are good.
http://www.rcgroups.com/forums/showthread.php?t=1466697

On my Harrier, I did increase the vertical tail by about 25% to increase the stability. And as GPW mentioned the Battlestar Galactica Viper and Cylon both have anhedral but I don't think it makes them unstable. I think CG position helps that a lot too. My Harrier has the CG very low vertically on the plane. Helps keep the plane flying right side up.

So are you working on a plane? I wasn't really sure from the original post.
SGTalon, i've seen your Harrier, and it's the inspiration for my own version. Kinda mix between your design and my own taste..

Somewhere you mentioned with mixing its now flying right.. that's what got me asking about the inherent stability of anhedral wings.
georgy is online now Find More Posts by georgy
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Gallery Advices for a second quad or an upgrade macfurax Multirotor Beginner 16 Oct 08, 2015 03:27 PM
Discussion Electrifying an Ivory Gull ... need practical advice bogbeagle Vintage & Old-Timer Designs 31 Jul 28, 2015 07:30 AM
Discussion Wing repair advice cityevader Sailplane Talk 5 Jun 28, 2015 05:53 AM
Discussion Falcon 880 - Wing build advice needed jjscott Sailplane Talk 15 Jun 25, 2015 12:14 PM
Discussion Want advice on fixing an Elapor wing dmt Foamies (Kits) 19 Apr 22, 2008 10:18 AM