Aerodynamics Discuss the concepts of aerodynamics here

Dihedral effect on swept wing

Old 02-15-2019, 02:57 PM
  #1  
Abuelo
Member
Thread Starter
 
Abuelo's Avatar
 
Join Date: Sep 2013
Location: Arizona desert
Posts: 292
Default Dihedral effect on swept wing

A buddy built a powered glider type plane with forward swept wings and had some stability and turning issues with it. We got most of these sorted but still have a question we don't know then answer to.

"Miss Tempe" has a 60" span ( two 30" panels), 8" root chord, 5" tip chord, flat bottom conventional airfoil, 4 per panel dihedral, and 5 forward sweep as measured at the leading edge. No tip plates or fences, high wing, rudder, elevator, and throttle only. As built the C/G was about 33% of the MAC but she flew better with the C/G moved forward to around 25%. Weight all up was 19 oz. See the rather poor photo.

I understand that rear sweep adds effective dihedral, found references to anywhere from1 per each 5 to 10 sweep. (References are inconsistent but may represent unknown factors in the overall design.) But what about forward sweep? Does that add effective dihedral or subtract dihedral? I'm thinking it subtracts which would account for the turning difficulty as the effective dihedral was down to 3.5 or 3.0, depending. I also think a fence along the root would have kept any span wise air flow on the wing.

The builder is leaning toward replacing the wing with a 0 dihedral KF2 and ailerons. I'm thinking he could cut the original wing and add a couple more degrees dihedral and would be OK. Another option is a second KF2 with dihedral and no ailerons.

Thoughts and comments? All appreciated.
Attached Thumbnails Click image for larger version

Name:	Miss Tempe.JPG
Views:	19
Size:	101.1 KB
ID:	187372  
Abuelo is offline  
Old 02-15-2019, 04:10 PM
  #2  
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 12,161
Default

I can confirm from actual flying a model that sweep-back does add 'dihedral' effect.

I had a Pavel Bosak 20 powered Mig17 back in the 80's that had very little dihedral but the sweepback made her effective rudder / elevator machine.

If sweepback aids the turn ... then logic would say sweep forward would detract from the turn ... I know the couple of sweep forward wing models I have flown - I don't like ... which includes the 540 racer which has a forward taper wing ...
solentlife is online now  
Old 02-15-2019, 04:39 PM
  #3  
Abuelo
Member
Thread Starter
 
Abuelo's Avatar
 
Join Date: Sep 2013
Location: Arizona desert
Posts: 292
Default

Thanks, Nigel.

I found there are a couple sailplanes with forward swept wings but they were thus designed to get the main spar out of the cabin area. Forward sweep may work best in high speed designs and just be a novelty with ours.

The buddy also tried a flying wing design with forward sweep. To the best of my knowledge it would snap roll at the slightest hint of a stall and the longest flight I saw must have been under 10 seconds.
Abuelo is offline  
Old 02-15-2019, 09:23 PM
  #4  
Panther
Super Contributor
 
Panther's Avatar
 
Join Date: Oct 2012
Location: South East Queensland, Australia
Posts: 1,462
Default

The Blanik has forward swept wings because it is a 2 seater. This is to move the CG position forward for the extra weight.
Panther is offline  
Old 02-20-2019, 08:32 PM
  #5  
Abuelo
Member
Thread Starter
 
Abuelo's Avatar
 
Join Date: Sep 2013
Location: Arizona desert
Posts: 292
Default

Thanks.
Abuelo is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Flite-Metal
Electric Ducted Fan Jets
276
03-22-2019 12:49 PM
Flite-Metal
Electric Ducted Fan Jets
544
10-12-2018 01:18 PM
AEAJR
Beginners
165
06-28-2017 04:22 PM
guapoman2000
Scale E-Powered Aircraft
22
05-26-2016 09:36 PM
piercethesky
Delta & Flying Wings
17
12-11-2015 04:04 AM

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


Quick Reply: Dihedral effect on swept wing


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

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

Page generated in 0.07638 seconds with 14 queries