Go Back  RCU Forums > RC Airplanes > Aerodynamics
Reload this Page >

Dihedral/anhedral effect on lift?

Notices
Aerodynamics Discuss the physics of flight revolving around the aerodynamics and design of aircraft.

Dihedral/anhedral effect on lift?

Old 11-02-2010, 06:13 PM
  #1  
hfb
Member
Thread Starter
 
Join Date: Jan 2010
Location: Shreveport, LA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default Dihedral/anhedral effect on lift?

I am right in thinking that Dihedral/anhedral will decrease lift in proportion to the COS of the angle. IE, a 20deg dihedral angle will reduce lift by 0.9396?
Harold
Old 11-02-2010, 10:28 PM
  #2  
soarrich
My Feedback: (98)
 
soarrich's Avatar
 
Join Date: Feb 2002
Location: Middletown, NJ
Posts: 4,676
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Are you saying less than 1%? Maybe, but you would never be able to tell a 1% loss in lift, that 20* dihedral will be keeping you pretty busy I would think.[X(]
Old 11-02-2010, 10:40 PM
  #3  
MTK
Senior Member
 
Join Date: May 2004
Location: Whippany, NJ
Posts: 5,386
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?


ORIGINAL: hfb

I am right in thinking that Dihedral/anhedral will decrease lift in proportion to the COS of the angle. IE, a 20deg dihedral angle will reduce lift by 0.9396?
Harold
It's nothing to worry about even if you are flying a glider. Correct Dihedral on a wing has so many positive attributes that you should ignore any tiny loss in lift
Old 11-03-2010, 01:00 AM
  #4  
Shoe
 
Shoe's Avatar
 
Join Date: Sep 2003
Location: Stuttgart, GERMANY
Posts: 336
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Harold,

Multiplying by the cosine of the dihedral angle should get you close. In most cases, I would expect the lift curve slope (increase in lift per degree of angle of attack) of a wing with dihedral to be a little steeper than for a wing without dihedral of the same span. This is because the wake of a wing with dihedral will be non-planar. In effect, dihedral gives some winglet-like benefits. Bottom line: I would expect the lift to be a little more than 0.94 at 20 degrees.
Old 11-03-2010, 02:06 AM
  #5  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,373
Likes: 0
Received 11 Likes on 9 Posts
Default RE: Dihedral/anhedral effect on lift?

Due to the changes in airflow I'd say that it's not as accurate as your four significant figures. But yeah, the angle of the wings will slightly reduce the overall lift due to the simple geometry of the situation as well as how the angle affects the spanwise airflow. And no, I don't know of any equations that would predict what the loss would be.
Old 11-03-2010, 02:46 AM
  #6  
pimmnz
 
Join Date: Nov 2005
Location: Auckland, NEW ZEALAND
Posts: 1,961
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Actually, any di/anhedral does not change the amount of lift one whit. The rules remain the same, ie in S&L flight lift equals weight, banked turns, L=acceleration x W, etc. There might be a very small change in projected wing area, but we don't usually take that into account in area calculation either. So, no, no changes you you need to even think about.
Evan, WB #12.
Old 11-03-2010, 03:34 AM
  #7  
bogbeagle
Senior Member
 
Join Date: Apr 2003
Location: York, UNITED KINGDOM
Posts: 1,296
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?


ORIGINAL: pimmnz

Actually, any di/anhedral does not change the amount of lift one whit. The rules remain the same, ie in S&L flight lift equals weight, banked turns, L=acceleration x W, etc. There might be a very small change in projected wing area, but we don't usually take that into account in area calculation either. So, no, no changes you you need to even think about.
Evan, WB #12.

Spot on.

It'd be true to say that dihedral affects wing-loading ... if your calculation is based upon projected wing area. (I think!)
Old 11-03-2010, 06:05 AM
  #8  
hfb
Member
Thread Starter
 
Join Date: Jan 2010
Location: Shreveport, LA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Thank you all for your comments and insight.. I have a big, 75 inch wing span, new F4U Corsair model and the bent wing is my interrest. I I know at 90 degrees lift with respect to the ground will be zero. But for small angles off horizontal I could see it might not make any difference at all. I will plan on landing with flaps and trust the wing to do its part.
Thanks again to all,
Harold
Old 11-03-2010, 10:40 AM
  #9  
MTK
Senior Member
 
Join Date: May 2004
Location: Whippany, NJ
Posts: 5,386
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Not specifically related to dihedral but rather the wetted area of wing that is exposed in S&L versus other flight angles besides S&L:

I recall seeing a military plane being flown fairly close to the ground in an aggressive manner by its pilot. High speed passes and extreme banking of the wings to wow an audience it seemed. This was a rather large plane but with a pencil thin fuselage.

Its pilot made the fatal error of driving the plane to knife edge in one of those passes, with insufficient height to recover back to S&L, even at the fairly high speed it was flying at. The plane lost much of its lift and slid sideways into the ground. It was a horrifying end to some very careless flying.
Old 11-03-2010, 12:15 PM
  #10  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,056
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Copied from:

http://en.wikipedia.org/wiki/Wing_configuration
http://en.wikipedia.org/wiki/Gull_wi...rted_gull_wing

"Inverted gull wing has anhedral on the root section, dihedral on the main section. The opposite of a gull wing. Typically done to reduce the length and weight of wing-mounted undercarriage legs. Two well-known examples of the inverted gull wing are World War II's American F4U Corsair, and the Nazi German Junkers Ju 87 Stuka dive bomber.

The inverted gull wing was developed at the same time and for the same reason as seaplanes.
More powerful engines generally require larger propellers, but clearance between the propeller tip and ground must be maintained.
Long landing gear legs are heavy, bulky, and weaker than their shorter counterparts.
The Vought F4U Corsair, designed from the onset as a carrier-based fighter, not only had the largest propeller of any U.S. fighter, but was also expected to face rough landings aboard a pitching carrier deck.
The inverted gull wing allowed the landing gear to be short, tough, and to retract straight back, improving internal wing space."

Old 11-03-2010, 12:34 PM
  #11  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,373
Likes: 0
Received 11 Likes on 9 Posts
Default RE: Dihedral/anhedral effect on lift?


ORIGINAL: pimmnz

Actually, any di/anhedral does not change the amount of lift one whit. The rules remain the same, ie in S&L flight lift equals weight, banked turns, L=acceleration x W, etc. There might be a very small change in projected wing area, but we don't usually take that into account in area calculation either. So, no, no changes you you need to even think about.
Evan, WB #12.

DANG! You busted us! Yeah, of course this is right. It would be the wing LOADING that would be affected by the projected area reduction effect.
Old 11-03-2010, 05:40 PM
  #12  
Tall Paul
Senior Member
 
Join Date: Jun 2002
Location: Palmdale, CA
Posts: 5,211
Likes: 0
Received 1 Like on 1 Post
Default RE: Dihedral/anhedral effect on lift?


ORIGINAL: hfb

Thank you all for your comments and insight.. I have a big, 75 inch wing span, new F4U Corsair model and the bent wing is my interrest. I I know at 90 degrees lift with respect to the ground will be zero. But for small angles off horizontal I could see it might not make any difference at all. I will plan on landing with flaps and trust the wing to do its part.
Thanks again to all,
Harold
.
With warbirds, WATCH YOUR SPEED!
These things love to tip-stall or just plain give up and quit flying!
Don't expect the flaps to make landings easier.
All they really do is add drag, so the approach can be steeper (safer) without coming down too fast.
Old 11-03-2010, 05:47 PM
  #13  
hfb
Member
Thread Starter
 
Join Date: Jan 2010
Location: Shreveport, LA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Thank you. A point to be well taken,
Harold
Old 11-03-2010, 08:56 PM
  #14  
buzzard bait
 
Join Date: Jan 2003
Location: Ithaca, NY
Posts: 3,279
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Some SE-5 pilots had their wings rigged with most of the dihedral taken out. They got a few mph speed increase. My recollection is 5 mph, but that seems like a lot. My guess is that with less dihedral they could get the same lift with fractionally less incidence in flight, so drag was less.

Jim
Old 11-04-2010, 01:44 PM
  #15  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,373
Likes: 0
Received 11 Likes on 9 Posts
Default RE: Dihedral/anhedral effect on lift?

Harold, the old pilot's adages definetly applies here.

1- Speed is like money in the bank.
2- All testing and possibly dangerous maneuvers will be practiced at least 3.5 mistakes high.
Old 11-04-2010, 06:52 PM
  #16  
Foxman
Member
 
Join Date: Mar 2005
Location: Banglamung, THAILAND
Posts: 78
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

It is an interesting subject but why do you care about the dihedral when it's on a scale model.
Surely you are making it as scale as possible so the dihedral has to be replicated exactly whatever it is.
Apparently the Corsair had a very good fuselage to wing joint due to the anhedral and the circular fuselage so the angle was quite large, more than 90 degrees giving it lower drag than a conventional set up. Hope that makes sense?
Jim
Old 11-05-2010, 07:00 AM
  #17  
hfb
Member
Thread Starter
 
Join Date: Jan 2010
Location: Shreveport, LA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

Pure intellectual curiosity.
Harold
Old 11-05-2010, 04:00 PM
  #18  
hfb
Member
Thread Starter
 
Join Date: Jan 2010
Location: Shreveport, LA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

One last comment. I found data indicating the F6F and the F4U, full size, have very close stall speeds for both empty and fully loaded. This indicates to me the bent wing is not much of a problem.
Harold
Old 11-05-2010, 05:34 PM
  #19  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?


ORIGINAL: hfb

One last comment. I found data indicating the F6F and the F4U, full size, have very close stall speeds for both empty and fully loaded. This indicates to me the bent wing is not much of a problem.
Harold

And yet, the Hellcat was known to be an easy plane to fly while the Corsair wasn't. The Corsair in fact had bad stall characteristics. They improved it after it had been in active service awhile. A stall strip was added to a section of the leading edge of one wing.

One design aspect doesn't make or break most designs.

The bent wing really wasn't much of a problem for sure. It might have contributed to the fact the F4U was faster than the P47 by a whisker and both were significantly faster than the F6F. And all 3 used the same engine.
Old 11-06-2010, 11:58 AM
  #20  
Tall Paul
Senior Member
 
Join Date: Jun 2002
Location: Palmdale, CA
Posts: 5,211
Likes: 0
Received 1 Like on 1 Post
Default RE: Dihedral/anhedral effect on lift?

ORIGINAL: hfb

One last comment. I found data indicating the F6F and the F4U, full size, have very close stall speeds for both empty and fully loaded. This indicates to me the bent wing is not much of a problem.
Harold
.
The Corsair was deemed unsuited for carrier use by the US Navy, but not by the Royal Navy.3
And the Marines used theirs as land-based.
And after a battle in the South Pacific when Marines landed their Corsairs on a carrier, the Navy decided, well, OK....
The approach to the boat was different with the Corsair, requiring a short base/final turn so the pilot could see the deck looking alongside the long nose.
Old 11-06-2010, 02:25 PM
  #21  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,056
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

ORIGINAL: da Rock

The bent wing really wasn't much of a problem for sure. It might have contributed to the fact the F4U was faster than the P47 by a whisker and both were significantly faster than the F6F. And all 3 used the same engine.
Interesting, indeed.
Differences in airfoils and frontal profile may have been important as well.

That Corsair must have been a handful to land with that long nose blocking the view.
Old 11-06-2010, 03:56 PM
  #22  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

ORIGINAL: Lnewqban

ORIGINAL: da Rock

The bent wing really wasn't much of a problem for sure. It might have contributed to the fact the F4U was faster than the P47 by a whisker and both were significantly faster than the F6F. And all 3 used the same engine.
Interesting, indeed.
Differences in airfoils and frontal profile may have been important as well.

That Corsair must have been a handful to land with that long nose blocking the view.

Yes, and the surface finish probably was a major factor. As was placement and area of radiators and intercoolers.

And let's not forget propellers. All 3 had different ones and changed them around a bit.

Bottom line is a LOT of things make up the performance envelope of an individual airplane. The main problem the Corsair had with the Navy's decision to not use them on carriers when the 1st squadron had just completed qualifications was politics... and logistics. The fact the oleo's were too stiff combined with a bad stall tendency provided the brass reasons to re-think the decision to deploy the squadron that'd just qualified (VF-12) F4Us for carrier use and about to head west on the Saratoga. They swapped them for F6Fs. It must have dawned on the brass when they heard the Corsairs were heading for the Pacific on a carrier that there were no spares for the airplane in the supply line to the carriers. Duh..... That was the real reason, but many others could have been part of the decision.

So, does dihedral affect lift? Yeah.
Old 12-23-2010, 04:19 AM
  #23  
davidej
 
Join Date: Nov 2002
Location: West Mersea, UNITED KINGDOM
Posts: 138
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?

But why do modern jets have lots of anhedral, particularly on the tail surfaces?
Old 12-23-2010, 05:55 AM
  #24  
guille2006
Senior Member
 
guille2006's Avatar
 
Join Date: Jan 2006
Location: MaranelloModena, ITALY
Posts: 646
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Dihedral/anhedral effect on lift?


ORIGINAL: hfb

I am right in thinking that Dihedral/anhedral will decrease lift in proportion to the COS of the angle. IE, a 20deg dihedral angle will reduce lift by 0.9396?
Harold

Yes; so 100 of lift will become 93.96

Diehedral or anhedral matters to stability and shall be considered together with the position in heigh of the wing with respect to the mid-line of the plane.

High wing => adds roll stability (and the opposite)
Dihedral => adds roll stability (and the opposite)

So: you can have a high wing anhedral plane still roll stable...

Military planes uses to have anhedral in order to get more roll-maneuvrability while an IMU assists the pilot for flying.
Old 12-23-2010, 10:40 AM
  #25  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,373
Likes: 0
Received 11 Likes on 9 Posts
Default RE: Dihedral/anhedral effect on lift?

Davidej, dihedral or anhedral on the tail is usually there for reasons other than stability or maeuverability.  For example on the F4 Phantom from the Vietnam era the anhedral was put in to get the tail down below the wing's wake during high Alpha (angle of attack) flight.  On the old WW2 Bristol Beaufighter it was to raise the stabilizers out of the prop wakes so that the surfaces were subjected to less vibration due to avoiding the prop "waves" in the wake of the props.  Each dihedral or anhedral stabilizer story carries something of the sort with it.  Also in the case of modern jets there's the supersonic shockwave effects that need to be cated to.  Again angling the stabilizer can affect this.  But that's not something we need to worry about with our models.

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.