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 09-02-2011, 09:06 PM   #1
GreenAce92
RAWR!!! Lets fly...
 
GreenAce92's Avatar
 
Join Date: Apr 2007
Location: Fredonia Ny
Posts: 4,302
View GreenAce92's Gallery36
Thanked 96 Times in 95 Posts
iTrader: (0)
Friends: (21)
Default Does anyone put the extra washout on their wing tips?

I was told that it is important to either stall the wing tips first (in a turn) or not to stall I can't remember which one.

The idea though is having the washout get over extended, so that the wing tips are down facing (if that makes sense).

Here is an image of what I'm trying to describe.

I'm not sure if I drew it right, but basically it's like over "feathering"


Attached Thumbnails
Click image for larger version

Name:	Washout.jpg
Views:	433
Size:	33.8 KB
ID:	152507  

Do life with optimism

GreenAce92 is offline  
  Reply With Quote
Old 09-02-2011, 09:15 PM   #2
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,314
View rcers's Gallery57
Thanked 517 Times in 506 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

You want the wing tips to stall last so the plane won't snap as easily. A small amount is all that is needed or desired.

I can't make heads or tails of your drawing sorry. You don't want to over do the washout as that starts to create other issues (especially in aerobatics and inverted flight).

Mike
rcers is offline  
  Reply With Quote
Old 09-02-2011, 09:29 PM   #3
NJSwede
3D wannabe
 
NJSwede's Avatar
 
Join Date: Nov 2010
Location: New Jersey, USA
Posts: 1,892
View NJSwede's Gallery1
Thanked 127 Times in 124 Posts
Club: Somerset Signal Senders & GCA
Awards Showcase

2kW  1kW 
iTrader: (1)
Friends: (11)
Default

Originally Posted by GreenAce92 View Post
I was told that it is important to either stall the wing tips first (in a turn) or not to stall I can't remember which one.
Doesn't that depend on what flying characteristics you're after? If you want to do crazy snap rolls and stuff, you may want the tips to stall first. Also, if you're after insane speed, you may sacrifice some low speed stability in order to reduce the tip vortices. But if you want a stable plane that's easy to land and that flies well at slow speeds, you definitely don't want the tips to stall first.

YMMV, I'm no expert and all other disclaimers apply...

AMA #959089
NJSwede is offline  
  Reply With Quote
Old 09-02-2011, 10:01 PM   #4
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,314
View rcers's Gallery57
Thanked 517 Times in 506 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

My point exactly on some planes you want aggressive snap and spin characteristics. Aerobatic airplanes for sure. But.....you would want to be mighty careful with having the tips stall first. That would mean slow down too much and the wing snaps and spins.

I had a plane like that once. A snappy Cap. It had a short but spectacular life.
rcers is offline  
  Reply With Quote
Old 09-02-2011, 10:26 PM   #5
GreenAce92
RAWR!!! Lets fly...
 
GreenAce92's Avatar
 
Join Date: Apr 2007
Location: Fredonia Ny
Posts: 4,302
View GreenAce92's Gallery36
Thanked 96 Times in 95 Posts
iTrader: (0)
Friends: (21)
Default

that would explain the flat constant chord wings on 3d planes

sorry not chord but taper

yeah i apologize about the drawing

Do life with optimism

GreenAce92 is offline  
  Reply With Quote
Old 09-02-2011, 11:36 PM   #6
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,696
Thanked 58 Times in 57 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award 
iTrader: (0)
Friends: (6)
Default

GreenAce92
It is worth remembering that washout becomes 'washin' when flying inverted which will ensure the tip stalls first!

Washout does cause a slight reduction in the wings efficiency however you can use other aerodynamic effects to ensure that the wing root stalls before the tip.

The most obvious is to use a different wing section on the outer portions (ie one that stalls at a greater angle of attack) or by aerodynamic 'additions' such as leading edge slots or stall strips at the root.
quorneng is offline  
  Reply With Quote
Old 09-02-2011, 11:51 PM   #7
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 6,047
Thanked 617 Times in 581 Posts
Awards Showcase

125mph Speed Demon  5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (10)
Default

Washout is a useful trick in many ways but as others have said needs to be used with extreme caution if the model is intended to fly inverted.

BTW.. washout does not necessarily always reduce a wing's efficiency. On un-tapered wings washout can actually increase efficiency because it can be used to optimise the spanwise lift distribution to be closer the elliptical... Elliptical being the ideal for reduction in induced drag.

You can demonstrate this with the little application here: http://aero.stanford.edu/WingCalc.html

Put in an unswept wing with no taper (taper ratio 1) and you can achieve about 4% increase in efficiency by adding 2.5 -3 deg of washout. Wing efficiency factor is the 'e' value.
JetPlaneFlyer is offline  
  Reply With Quote
Old 09-04-2011, 11:45 PM   #8
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,696
Thanked 58 Times in 57 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award 
iTrader: (0)
Friends: (6)
Default

How the ailerons perform can have a big influence on a plane's stall behaviour.
I shot this video of my Wing Dragon with separate flaps to demonstrate its speed range.
It has a tapered wing with no washout so might be expected to stall aggressively but it actually retains adequate roll control at very slow speeds with only a gentle and controllable wing drop if taken too slowly.

Note the planes angle of attack remains more or less the same when the flaps are down so the wing tips do not stall and the aileron remain effective albeit with progressively less authority as the airspeed reduces.
quorneng is offline  
  Reply With Quote
Old 02-05-2012, 05:00 PM   #9
norcalwelder
Member
 
Join Date: Jan 2007
Posts: 41
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Basically you only need to worry about washout if you have a wing plan form other than a rectangular wing. (tapered, delta, elliptical) An aircraft's stall characteristics are determined by its wing plan form, with some stalling at the root, (rectangular) some stalling at the tip (tapered, delta) and some stalling all at once (elliptical). If you don't want to use washout, you can force a stall at the root with stall strips and a few other devices.
norcalwelder is offline  
  Reply With Quote
Old 02-10-2012, 09:44 AM   #10
simonrich
New Member
 
Join Date: Feb 2012
Posts: 1
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

hi just a quick message for me inlaw.. he's building a fast slope soaring plane of a 5m wingspan..he's using the programme compufoil, with this cord and settings.... 30%>2.40"-> HN218PRO.COR/8"c/.0625"s/0.3"k/ .875"h/9.84%thk/2.33%cmb....... 10inch rootcore for the first metre, and from 10-5inch for a 1.5mtres thinned 25% on the outter pannel.. wht he wants to no is does he have to put wash out in.... or does he need the tip cord broader or not to get away without putting wash out in? any help is much appreciated, thanks Simon
simonrich is offline  
  Reply With Quote
Old 02-12-2012, 08:49 PM   #11
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,696
Thanked 58 Times in 57 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award 
iTrader: (0)
Friends: (6)
Default

As a fast glider the performance will be marginally improved without wash out, providing the wing has sufficient torsional stiffness to hold its incidence accurately all along the wing when at speed.
With such a high aspect ratio the way the structure of the wing performs at various loads and speeds is likely to be just as important as the static wing geometry.
There is no easy answer.
quorneng is offline  
  Reply With Quote
Old 06-27-2017, 04:42 AM   #12
F22trainer
Member
 
Join Date: Apr 2017
Location: Sun City, Az
Posts: 59
Thanked 6 Times in 6 Posts
iTrader: (0)
Friends: (0)
Default

If the plan calls for it - do it, someone already figured out the why. Just depends what you want the airplane to do. Low wing full size trainers have stall strips and washout, in addition to stronger dihedral than high wing. Cessna high wings have a a nice surprise for the student that is not coordinated when stalling the plane - Pipers on the other hand don't break as hard. The nose drops and you accelerate. Wing root stalls first while the tips maintain some control beacause the are at a lower AoA. Put washout in a swept wing design and bad things happen at high speeds. Good discussion!
F22trainer is online now  
  Reply With Quote
Old 06-27-2017, 09:13 AM   #13
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 10,826
View solentlife's Gallery47
Thanked 486 Times in 478 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (17)
Default

Wash out ? I never add more than the kit / model has. I believe that unless its deformed by shipping - that designer may have had an idea what he was doing when he set the wing.

On this subject - lets take the HK Lancaster. Out of box with no damage, the washout is hard to see, because its set by the aerofoil used in the outer section. But some people go to the lengths of 'steaming in' or even shaving off foam to create visible washout.
Does it add any advantage to the model ? Being human - we will always 'perceive' improvement and then claim its worked. But in all honesty - small models in full size air ? This modification to the HK Lanc is work for very little reward. But another model that may not have washout / twisted in shipment will benefit.

My 2c's worth ...

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is offline  
  Reply With Quote
Reply

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


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
Electric Zero..Any suggestions on how to add some washout. liposucker Beginners 14 08-20-2011 08:48 AM
Crazy idea? WayneG Hi-Performance and Sailplanes 21 05-29-2011 08:37 PM


All times are GMT +1. The time now is 03:32 AM.


Powered by: vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

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



Page generated in 0.13241 seconds with 47 queries