Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > R/C Electric Topics - General > Aerodynamics
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

Aerodynamics Discuss the concepts of aerodynamics here

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 06-18-2014, 02:35 AM   #1
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 2,949
View mclarkson's Gallery4
Thanked 179 Times in 177 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default Gull Wings - pros / cons / nasty habits?

I'm playing around with a design with a lot of polyhedral for a trainer-type slow flyer. But I keep thinking of flipping things sideways, sort of, to produce a gull wing polyhedral wing.

What I don't know is if that's a good, bad or indifferent thing. There are 'gull wing' planes out there, especially a lot of older gliders, but also the Stinson Reliant and Corsair.









I'm not talking about planes with anhedral (although the wing tips will be anhedral to the inner wings, they will still have a dihedral tilt with respect to the ground.)

I know that the various planes I've mentioned use the gull wing arrangement for various reasons (e.g. landing gear clearance) and the Corsair is actually an inverted gull wing, but is there any particular reason to not use them on a trainer / slow flyer?

mclarkson is online now  
  Reply With Quote
Old 06-18-2014, 02:58 AM   #2
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 2,949
View mclarkson's Gallery4
Thanked 179 Times in 177 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

Examples from some 3D 'sketches' I've been playing around with:




mclarkson is online now  
  Reply With Quote
Old 06-18-2014, 03:41 AM   #3
Wrongway-Feldman
Member
 
Join Date: Jan 2011
Location: Govan, Saskatchewan
Posts: 621
Thanked 34 Times in 34 Posts
iTrader: (0)
Friends: (5)
Default

I've had both a corsair and a reliant and both were very stable flyers.
I can't remember where I read it but I understand a polyhedral wing is best suited in a high wing configuration. I'll try to find the page where I read it. If I remember correctly it has something to do with the pendulum of the fuselage under the wing.

----------------------------------------------------------
Dumas Ecroupe, MM EVA, E-flite L4 Grasshopper, Sig Kougar, Sig Kobra, Top Fight Contender, top flite mini contender, Carl Goldberg Skylark mark II, M&H Sportster 40.
Wrongway-Feldman is offline  
  Reply With Quote
Old 06-18-2014, 04:06 AM   #4
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 2,949
View mclarkson's Gallery4
Thanked 179 Times in 177 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

That'd be great. It's my understanding that, the lower the CG is relative to the wing, the greater the dihedral effect is. That's why high-wing heavy lifters like the Antonov AN-255 have significant anhedral to prevent them becoming too roll resistant. Nonetheless, I see old free-flight models, and newer trainer types, all the time that feature a bunch of tip polyhedral, or a bunch of dihedral, with very low relative CG.




mclarkson is online now  
  Reply With Quote
Old 06-18-2014, 05:45 AM   #5
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,431
Thanked 490 Times in 456 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

Polyhedral (like the Old Fogey or the first of your 3D sketches) is a little more efficient that conventional 'straight dihedral because it places the dihedral close to the tips where it is more effective due to having a longer lever arm to work on. This is why you see it often used on RC sailplanes.

True gull wing like the Minimoa is less efficient than conventional dihedral because the dihedral is inboard where it only has a short moment arm. Gull wing is usually used for 'non-aerodynamic' reasons, such as raising the wings up to increase ground clearance.
JetPlaneFlyer is offline  
  Reply With Quote
Old 06-18-2014, 08:52 AM   #6
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 2,949
View mclarkson's Gallery4
Thanked 179 Times in 177 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

Or cuz it looks wicked cool!

mclarkson is online now  
  Reply With Quote
Old 06-22-2014, 04:31 AM   #7
Abuelo
Member
 
Abuelo's Avatar
 
Join Date: Sep 2013
Location: Arizona desert
Posts: 124
Thanked 10 Times in 10 Posts
Club: Open flying at the Chandler Bowl
iTrader: (0)
Friends: (1)
Default

From what i've read on the Corsair, the inverted gull wing was intended to accomplish two things:

- To get the wing to fuselage angle close to 90 for reduced drag.,
- And to get the fuselage up higher for ground clearance for the prop.

"Treason doth never prosper. What's the reason? For if it prosper, none dare call it 'treason.' -- Sir John Harrington
Abuelo is offline  
  Reply With Quote
Old 06-22-2014, 04:52 AM   #8
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,175
Thanked 217 Times in 208 Posts
iTrader: (0)
Friends: (1)
Default

Inverted gull of the Corsair was mostly for prop clearance while keeping the landing gear short. Essentially the airplane was designed around the most powerful engine available.

The way the Corsair's wing meets the fuselage creates issues with stall and spin recovery.
fhhuber is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > R/C Electric Topics - General > Aerodynamics

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Pros and cons: which would you get? kikaida01 Warbird Electrics 7 11-16-2011 05:29 AM


All times are GMT +1. The time now is 09:35 AM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.20249 seconds with 33 queries