Biplane wing dihedral

[vincent p. norris]

Friend of mine said at lunch today that the upper wings of biplanes
have no dihedral. Hementioned specificlaly the Stearman PT-17.

I believe he was mistaken. I know the Sopwith Camel upper wing was
flat but I think the PT-17 and most other biplanes have dihedral in
both wings.

Any expert comments?

Thanks. vince norris

[Ron Wanttaja]

On Sat, 11 Jun 2005 00:04:10 -0400, vincent p. norris > wrote:

>Friend of mine said at lunch today that the upper wings of biplanes
>have no dihedral. Hementioned specificlaly the Stearman PT-17.

Think he's right about the Stearman, but it's not universal. See:

http://www.miramarevents.com/dreammachines/media-images/WacoBiplane-300dpi.jpg

http://hillcrestcottage.com/images/murwillumbah/flying.jpg

http://www.geocities.co.jp/Playtown-Dice/2996/raf-be2.jpg

http://www.airwar.ru/image/i/other1/be2c-i.jpg

http://www.raf-upper-heyford.org/UH_AC_Bristol_Fighter.jpg

http://www.airmuseumsuk.org/airshow/2003/Shut030907/800/images/179%20Bristol%20F.2b%20Fighter.jpg

http://www.airmuseumsuk.org/airshow/2003/Shut030907/800/images/001%20Sopwith%20Pup.jpg

http://www.airmuseumsuk.org/airshow/2003/Shut030907/800/images/009%20De%20Havilland%20DH.87b%20Hornet%20Moth.jpg

http://www.aviation-history.com/raf/se5a-6.jpg

Not even triplanes are immune:

http://www.airmuseumsuk.org/airshow/2003/Shut030907/Triplane.jpg


Ron Wanttaja

[Brian Whatcott]

On Sat, 11 Jun 2005 00:04:10 -0400, vincent p. norris >
wrote:

>Friend of mine said at lunch today that the upper wings of biplanes
>have no dihedral. Hementioned specificlaly the Stearman PT-17.
>
>I believe he was mistaken. I know the Sopwith Camel upper wing was
>flat but I think the PT-17 and most other biplanes have dihedral in
>both wings.
>
>Any expert comments?
>
>Thanks. vince norris

If you realise that monoplanes have been designed with various
anhedrals and dihedrals, why would you suppose that there are no
similar examples in biplanes?

Brian Whatcott Altus, OK

[vincent p. norris]

>If you realise that monoplanes have been designed with various
>anhedrals and dihedrals, why would you suppose that there are no
>similar examples in biplanes?

I didn't suppose that, Brian, I supposed the opposite.

vince norris

[vincent p. norris]

Thanks, Ron. I'll forward those to my friend--who, btw, is a retired
747 captain with many thousands of hours, but not terribly well
informed about ragwings.

vince norris

[Brian Whatcott]

On Sat, 11 Jun 2005 19:17:06 -0400, vincent p. norris >
wrote:

>>If you realise that monoplanes have been designed with various
>>anhedrals and dihedrals, why would you suppose that there are no
>>similar examples in biplanes?
>
>I didn't suppose that, Brian, I supposed the opposite.
>
>vince norris

Then I guess your position was well-founded?

Brian W

[vincent p. norris]

>Then I guess your position was well-founded?

Did you look at the web sites Ron sent?

vince norris

[Brian Whatcott]

On Sun, 12 Jun 2005 20:36:59 -0400, vincent p. norris >
wrote:

>>Then I guess your position was well-founded?
>
>Did you look at the web sites Ron sent?
>
>vince norris

Not initially - but I just did - some live examples of biplane and
triplane -hedral, just as you would expect - you say you did
expect this, didn't you?

Best

Brian Whatcott

[vincent p. norris]

>... I just did - some live examples of biplane and
> triplane -hedral, just as you would expect - you say you did
>expect this, didn't you?

Yes, here's the essence of my original post:

"Friend of mine said at lunch today that the upper wings of biplanes
have no dihedral. .... I believe he was mistaken. ..... I think the
PT-17 and most other biplanes have dihedral in both wings."

My friend insists the PT-17, properly rigged, has no dihedral in the
top wing. My photo collection shows SOME PT-17s that clearly have
some dihedral, but perhaps they were modified.

It appears that the N3N, F3F and SBC had no dihedral in the top wing,
along with the Fokker D VII, Albatros D III and D V, but most WW I
biplanes and most biplanes in the museum at Pensacola did.

vince norris

[Ed Sullivan]

On Sat, 11 Jun 2005 00:04:10 -0400, vincent p. norris >
wrote:

>Friend of mine said at lunch today that the upper wings of biplanes
>have no dihedral. Hementioned specificlaly the Stearman PT-17.
>
>I believe he was mistaken. I know the Sopwith Camel upper wing was
>flat but I think the PT-17 and most other biplanes have dihedral in
>both wings.
>
>Any expert comments?
>
>Thanks. vince norris


Some biplanes have sweptback wings which provide the same effect as
dihedral. My parasol Jungster II has sweepback and no dihedral.

Ed Sullivan

[Gord Beaman]

Ed Sullivan > wrote:

>On Sat, 11 Jun 2005 00:04:10 -0400, vincent p. norris >
>wrote:
>
>>Friend of mine said at lunch today that the upper wings of biplanes
>>have no dihedral. Hementioned specificlaly the Stearman PT-17.
>>
>>I believe he was mistaken. I know the Sopwith Camel upper wing was
>>flat but I think the PT-17 and most other biplanes have dihedral in
>>both wings.
>>
>>Any expert comments?
>>
>>Thanks. vince norris
>
>
>Some biplanes have sweptback wings which provide the same effect as
>dihedral. My parasol Jungster II has sweepback and no dihedral.
>
>Ed Sullivan

Why is that Ed?...dihedral provides lateral stability by making
the 'downgoing wing' increase it's lift while the 'upgoing'
wing's lift decreases, so how does the 'sweep-back' provide
lateral stability?
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

[Ed Sullivan]

On Thu, 16 Jun 2005 02:09:30 GMT, Gord Beaman >
wrote:

>Ed Sullivan > wrote:
>
>>On Sat, 11 Jun 2005 00:04:10 -0400, vincent p. norris >
>>wrote:
>>
>>>Friend of mine said at lunch today that the upper wings of biplanes
>>>have no dihedral. Hementioned specificlaly the Stearman PT-17.
>>>
>>>I believe he was mistaken. I know the Sopwith Camel upper wing was
>>>flat but I think the PT-17 and most other biplanes have dihedral in
>>>both wings.
>>>
>>>Any expert comments?
>>>
>>>Thanks. vince norris
>>
>>
>>Some biplanes have sweptback wings which provide the same effect as
>>dihedral. My parasol Jungster II has sweepback and no dihedral.
>>
>>Ed Sullivan
>
>Why is that Ed?...dihedral provides lateral stability by making
>the 'downgoing wing' increase it's lift while the 'upgoing'
>wing's lift decreases, so how does the 'sweep-back' provide
>lateral stability?

The reference escapes me, but I have read that so many degrees of
sweep back is the equivalent of an estabilished amount of dihedral.
All I know for sure is that this little sucker only has a 21' span and
it is as steady as a rock. It will go for miles without touching the
stick.

[Gord Beaman]

Ed Sullivan > wrote:

>On Thu, 16 Jun 2005 02:09:30 GMT, Gord Beaman >
>wrote:
>
>>Ed Sullivan > wrote:
>>
>>>On Sat, 11 Jun 2005 00:04:10 -0400, vincent p. norris >
>>>wrote:
>>>
>>>>Friend of mine said at lunch today that the upper wings of biplanes
>>>>have no dihedral. Hementioned specificlaly the Stearman PT-17.
>>>>
>>>>I believe he was mistaken. I know the Sopwith Camel upper wing was
>>>>flat but I think the PT-17 and most other biplanes have dihedral in
>>>>both wings.
>>>>
>>>>Any expert comments?
>>>>
>>>>Thanks. vince norris
>>>
>>>
>>>Some biplanes have sweptback wings which provide the same effect as
>>>dihedral. My parasol Jungster II has sweepback and no dihedral.
>>>
>>>Ed Sullivan
>>
>>Why is that Ed?...dihedral provides lateral stability by making
>>the 'downgoing wing' increase it's lift while the 'upgoing'
>>wing's lift decreases, so how does the 'sweep-back' provide
>>lateral stability?
>
>The reference escapes me, but I have read that so many degrees of
>sweep back is the equivalent of an estabilished amount of dihedral.
>All I know for sure is that this little sucker only has a 21' span and
>it is as steady as a rock. It will go for miles without touching the
>stick.

Ok, thanks...I know that sweepback will increase fore and aft
stability by making the critical fore and aft CG limits 'farther
apart' but I sure can't see how it affects lateral
stability...anyhoo...if you find out could you tip me off?
Thanks Ed.
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

[Ed Sullivan]

On Fri, 17 Jun 2005 01:06:53 GMT, Gord Beaman >
wrote:


>>stick.
>
>Ok, thanks...I know that sweepback will increase fore and aft
>stability by making the critical fore and aft CG limits 'farther
>apart' but I sure can't see how it affects lateral
>stability...anyhoo...if you find out could you tip me off?
>Thanks Ed.

This is not a complete explanation, but it might help.

http://avstop.com/AC/FlightTraingHandbook/LateralStability.html

[Brian Whatcott]

On Fri, 17 Jun 2005 00:20:28 -0700, Ed Sullivan >
wrote:

>On Fri, 17 Jun 2005 01:06:53 GMT, Gord Beaman >
>wrote:
>
>
>>>stick.
>>
>>Ok, thanks...I know that sweepback will increase fore and aft
>>stability by making the critical fore and aft CG limits 'farther
>>apart' but I sure can't see how it affects lateral
>>stability...anyhoo...if you find out could you tip me off?
>>Thanks Ed.
>
>This is not a complete explanation, but it might help.
>
>http://avstop.com/AC/FlightTraingHandbook/LateralStability.html

It does help - but in a disconfirming sense - let me quote:

"The contribution of sweepback to dihedral effect is important
because of the nature of the contribution. In a sideslip the wing into
the wind is operating with an effective decrease in sweepback while
the wing out of the wind is operating with an effective increase in
sweepback. The reader will recall that the swept wing is responsive
only to the wind component that is perpendicular to the wing's leading
edge. Consequently, if the wing is operating at a positive lift
coefficient, the wing into the wind has an increase in lift, and the
wing out of the wind has a decrease in lift. In this manner the swept
back wing would contribute a positive dihedral effect and the swept
forward wing would contribute a negative dihedral effect. "

This suggests that sweepback is directionally destabilizing..... (?)

Brian Whatcott Altus, OK

[Gord Beaman]

Brian Whatcott > wrote:

>On Fri, 17 Jun 2005 00:20:28 -0700, Ed Sullivan >
>wrote:
>
>>On Fri, 17 Jun 2005 01:06:53 GMT, Gord Beaman >
>>wrote:
>>
>>
>>>>stick.
>>>
>>>Ok, thanks...I know that sweepback will increase fore and aft
>>>stability by making the critical fore and aft CG limits 'farther
>>>apart' but I sure can't see how it affects lateral
>>>stability...anyhoo...if you find out could you tip me off?
>>>Thanks Ed.
>>
>>This is not a complete explanation, but it might help.
>>
>>http://avstop.com/AC/FlightTraingHandbook/LateralStability.html
>
>It does help - but in a disconfirming sense - let me quote:
>
> "The contribution of sweepback to dihedral effect is important
>because of the nature of the contribution. In a sideslip the wing into
>the wind is operating with an effective decrease in sweepback while
>the wing out of the wind is operating with an effective increase in
>sweepback. The reader will recall that the swept wing is responsive
>only to the wind component that is perpendicular to the wing's leading
>edge. Consequently, if the wing is operating at a positive lift
>coefficient, the wing into the wind has an increase in lift, and the
>wing out of the wind has a decrease in lift. In this manner the swept
>back wing would contribute a positive dihedral effect and the swept
>forward wing would contribute a negative dihedral effect. "
>
>This suggests that sweepback is directionally destabilizing..... (?)
>
>Brian Whatcott Altus, OK

Yes, I see your point Brian and on a slightly different tack, I
always saw dihedral like this.

A wing has max lift when it's 90 degrees to gravity, (or 'down')
it has zero lift when pointed straight 'up'...now, when a gust
knocks a wing (with dihedral) 'down' (towards level) then it's
lift increases while the other wing's lift will decrease (as it
goes upwards 'toward' the 'zero lift angle'. Hell, if you had
'enough' dihedral then you couldn't roll the a/c because of this
powerful effect, the ailerons wouldn't have enough authority to
overcome it. Taking things to a ridiculous extreme you could have
say, 45 degrees of dihedral where it'd be possible to have a gust
of wind take one wing 'down' to 90 degrees so that it has the max
lift that it's capable of while the other wing is pointed
straight up and has 'no' lift at all.

I imagine that the correction then would be somewhat sudden.
:)


-Gord.

"You are completely focused on RPM as the
single factor producing rotational velocity"

-Dude Henrickles

[Brian Whatcott]

On Fri, 17 Jun 2005 20:07:30 GMT, Gord Beaman >
wrote:

>>>This is not a complete explanation, but it might help.
>>>
>>>http://avstop.com/AC/FlightTraingHandbook/LateralStability.html
>>
>>It does help - but in a disconfirming sense - let me quote:
>>
>> "The contribution of sweepback to dihedral effect is important
>>because of the nature of the contribution. In a sideslip the wing into
>>the wind is operating with an effective decrease in sweepback while
>>the wing out of the wind is operating with an effective increase in
>>sweepback. The reader will recall that the swept wing is responsive
>>only to the wind component that is perpendicular to the wing's leading
>>edge. Consequently, if the wing is operating at a positive lift
>>coefficient, the wing into the wind has an increase in lift, and the
>>wing out of the wind has a decrease in lift. In this manner the swept
>>back wing would contribute a positive dihedral effect and the swept
>>forward wing would contribute a negative dihedral effect. "
>>
>>This suggests that sweepback is directionally destabilizing..... (?)
>>
>>Brian Whatcott Altus, OK
>
>Yes, I see your point Brian and on a slightly different tack, I
>always saw dihedral like this.
>
>A wing has max lift when it's 90 degrees to gravity, (or 'down')
>it has zero lift when pointed straight 'up'...now, when a gust
>knocks a wing (with dihedral) 'down' (towards level) then it's
>lift increases while the other wing's lift will decrease (as it
>goes upwards 'toward' the 'zero lift angle'.///
>I imagine that the correction then would be somewhat sudden.
>:)
>-Gord.

I think that I must have read this thread once too many times...in
that when I read what I posted, I see that the "Traing" text implies
just the opposite of what I thought it did. Oh my: he says sweep
back is like dihedral, but the argument seems to point the other way.

Think I will shut up, now!

Brian W

[Ed Sullivan]

>
>I think that I must have read this thread once too many times...in
>that when I read what I posted, I see that the "Traing" text implies
>just the opposite of what I thought it did. Oh my: he says sweep
>back is like dihedral, but the argument seems to point the other way.
>
>Think I will shut up, now!
>
>Brian W

I'm really sorry I started this. Perhaps my parasol also benefits from
the pendulum effect. It does have a slight dutch roll tendency, but
the controls are so light that this is overcome easily. According to
what I have read my aircraft has far more sweepback ( 15 degrees )
than is healthy subsonic, but it doesn't seem to care. It does very
reliable moderate aerobatics and yet is not a monster on cross country
trips.

Ed Sullivan, me too

[Ed Sullivan]

On Fri, 17 Jun 2005 15:45:41 -0700, Ed Sullivan >
wrote:

>
>
>>
>>I think that I must have read this thread once too many times...in
>>that when I read what I posted, I see that the "Traing" text implies
>>just the opposite of what I thought it did. Oh my: he says sweep
>>back is like dihedral, but the argument seems to point the other way.
>>
>>Think I will shut up, now!
>>
>>Brian W
>
>I'm really sorry I started this. Perhaps my parasol also benefits from
>the pendulum effect. It does have a slight dutch roll tendency, but
>the controls are so light that this is overcome easily. According to
>what I have read my aircraft has far more sweepback ( 15 degrees )
>than is healthy subsonic, but it doesn't seem to care. It does very
>reliable moderate aerobatics and yet is not a monster on cross country
>trips.
>
>Ed Sullivan, me too
>
I take it back here is some more confusing
info:http://www.av8n.com/how/htm/roll.html

[vincent p. norris]

>This suggests that sweepback is directionally destabilizing..... (?)
>
Aren't a/c with sweptback wings subject to dutch roll?

vince norris

[Ed Sullivan]

On Fri, 17 Jun 2005 21:45:18 -0400, vincent p. norris >
wrote:

>>This suggests that sweepback is directionally destabilizing..... (?)
>>
>Aren't a/c with sweptback wings subject to dutch roll?
>
>vince norris

Yea verily, some worse than others.