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Nov 09, 2017, 10:07 AM
average user
Discussion

biplane drag


If the wings are farther apart, is drag reduced?
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Nov 09, 2017, 10:23 AM
Piscine Promulgator
surfimp's Avatar
At least as regards parasitic drag, I don't believe the distance between the wings is as significant as the fact that there are two wings, along with the requisite bracing. That adds up to a lot of drag.

Separating the wings further means that the amount each wing interferes with the airflow (and hence lift) generated by the other is reduced. Positive stagger (top wing ahead of bottom wing) is designed to help reduce the negative influences of this interference, although I don't believe it does much to reduce the amount of induced (through the action of creating lift) or parasitic drag.

However, I am far from an expert on the subject

PS I hope to have the Buzz Bipe flying soon!
Latest blog entry: Of Fish, France, FPV, and Fun!
Nov 09, 2017, 05:54 PM
It's time for me to fly
JimZinVT's Avatar
What about 2 high aspect ratio wings that add up to a similar surface area as a monoplane? No idea, just throwing it out there, maybe a fun experiment. I am an armchair aeronautic engineer
Nov 09, 2017, 06:19 PM
Registered User
Daemon's Avatar
My suspicion is that the same thing that causes "ground effect" to produce a higher L/D
when plane is less than half span from the ground is what causes interference between the two airfoils.
Basically the high pressure under the upper wing interferes with the lower wing's ability to generate
low pressure and accelerate the air over it.

To this point I think that a reverse stagger (lower wing forward of the upper wing) is
better than conventional stagger, and this plane seems to bear that out.
https://en.wikipedia.org/wiki/Beck-Mahoney_Sorceress
200mph biplane racer with a 125hp powerplant.

There appears to be quite a number of other reverse stagger biplanes including the
Sopwith Dolphin
Beech Staggerwing,
Sorell SNS-2, SNS-7 and Hiperlight

For a PSS project though the Sorceress certainly looks like the one to build.
Nov 09, 2017, 09:09 PM
It's time for me to fly
JimZinVT's Avatar
Beech Staggerwing is one of my all-time favorites. But that Sorceress is sick! Trying to imagine how that lower wing is structurally sound though..
Nov 09, 2017, 09:41 PM
Theoretical balsa dust maker
plane_tech's Avatar
Here are a couple more pictures for you.
I saw this at the Udvar-Hazy air and space museum a few years back. Not sure where I found the 3-view. Top View i grabbed from Airliners.net
Nov 09, 2017, 10:00 PM
Brett
bjaffee's Avatar
I recall a foamie Staggerwing sloper. I think someone else tried flying a Byron Staggerwing as a sloper.
Nov 09, 2017, 10:28 PM
average user
Thank you guys, really great info and cool planes. I am trying not to use staggered wings so the plane flies the same inverted. I have noticed a small difference with staggered vs. non staggered, it could be an optical illusion.

I figure I can reduce drag while adding more side area. Some people state that the total area of biplane wings is up to 40% less effective than a mono wing with the same area.

I watched a youtube video of a burt rutan style airplane build, the guy was talking about airfoiled landing gear struts and how they were less draggy if placed farther apart. I figured it would be the same for biplanes - so I guess I'm wondering what a good ratio would be, and hopefully without needing to build 20 models to find a ballpark range. I'm no math wiz.
Last edited by mr.zagi5c; Nov 09, 2017 at 10:36 PM.
Nov 09, 2017, 10:35 PM
Registered User
chip.greely's Avatar

Beechcraft Staggerwing


I always seem to Photo-bomb this subject

Anyways, 2 wings should increase drag, as well as lift. Reducing chord and airfoil thickness will help minimize the drag.

I've got a pair of wings cut for a Biplane version of my Bonefish, for one of these days.
Last edited by chip.greely; Nov 10, 2017 at 10:38 AM.
Nov 09, 2017, 10:38 PM
Person of interest
KiwiKid's Avatar
I have seen a few bipe slopers, Staggerwing, a Stearman and a Tiger Moth. They are never going to be slope racers, but add another dimension to the fun.

Here's some info on the Tigger: https://www.rcgroups.com/forums/show...postcount=2937

And a vid - the Tigger features from 00:56 to 2:10

HERMANUS 2016 DAY 3 (3 min 17 sec)
Last edited by KiwiKid; Nov 11, 2017 at 03:31 AM.
Nov 09, 2017, 10:57 PM
It's time for me to fly
JimZinVT's Avatar
One of the guys on the Port Elizabeth, South Africa thread built a foam profile version of the Ultimate 40 aerobatic biplane a few years back. It flew very well as I remember. You might try searching that thread. I have a *.dwg file of the parts ( but no program that will open it ) if you're interested.
Nov 10, 2017, 07:58 PM
Registered User
TFLG's Avatar
I fiddled with bipes a couple of times. As slopers they have some serious drawbacks. The additional drag from the bracing is one but the biggest hurdle is getting the two wings aligned. Many builders can't get the wing tail incidence right. Now add in another wing. If the top wing is off even a little bit to the bottom wing the performance falls off quick. Second problem is keeping them aligned. Even if you do manage to get them set perfectly, keeping them there is a real pain. Especially on a bendy foam plane (which I did one of).
Nov 10, 2017, 10:00 PM
average user
This is my best so far, however it is a sesquiplane. The other biplane worked pretty well too but had staggered wings and had an issue with multiflips.

Crazy Gliders !! (3 min 24 sec)


In no way is it optimized. I like the aesthetics of biplanes, and the way they roll, feels more locked in to me.
Nov 14, 2017, 07:26 AM
Rock Breaker
gazasmith's Avatar
This is my biplank.
Basic spec is 2 rock Breaker wings joined 100mm apart at LE 105mm at TE 150mm cord. Bottom wing is upside down so should have same performance inverted. Fly well just need more tuning time with the big control surfaces. Crashed landed and blew a few servos so has been put on the back burner for now.

Gaza
Nov 14, 2017, 02:14 PM
average user
that thing really does fly awesome gaz. love it! interesting method with the bottom wing upside down.


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