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Old Nov 04, 2012, 01:05 PM
Registered User
Joined Oct 2012
42 Posts
Question
Dihedral

Do aircraft need dihedral? Be it positive or negative I've read it's used to offset another overbearing part of the plane's design. I've built a couple foamies with no dihedral or a zero degree dihedral and they seem to fly fine. They do tend to roll much faster though, which I kinda like. My newest foamy I want to have a good glide aspect, so is dihedral something that will help that or are good gliding characteristics just more wingspace?
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Old Nov 04, 2012, 01:54 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
12,451 Posts
You really could do with some dihedral if you fly rudder only. Models with aileron control do not need dihedral.
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Old Nov 04, 2012, 01:54 PM
Gone Fly'n
planecrazy1969's Avatar
USA, NV, Las Vegas
Joined Jan 2007
282 Posts
Hi pizatio...my understanding is that dihedral is not necessary, but helps in stabilizing level flight...kind of helps the plane self right itself...if you understand what I'm saying...great thing to have for a beginner or an RET (rudder, elevator, throttle) setup.
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Last edited by planecrazy1969; Nov 05, 2012 at 05:58 PM.
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Old Nov 05, 2012, 03:46 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
1,311 Posts
On a side note, I have a pusher that I've been working on for the past few months. One version of the plane has canards with a dihedral to them, while the main wing is level. Just the dihedraled canards are enough to get the plane to self level out of a turn. So you dont need the main wing to have that aspect. Ive herd that diherdran has a detromental effect aswell, something beyond roll rate, but cant remember what it was right now.
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Old Nov 05, 2012, 10:31 PM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,044 Posts
You need dihedral on a RET RC model and for a free-flight model.
You don't need dihedral on an AET or ARET model. A flat wing is (slightly) easier to build and can be made (slightly) lighter and they fly beautifully.
You can use dihedral on these to provide a measure of self-correction in the Roll Axis, but this will come at the price of more rock and roll due to cross-winds and wind turbulence. Landings can therefore become difficult in turbulent conditions when the wind direction and speed are unpredictable.
Dihedral is bad for aerobatic planes. These need to go where they are pointed and not ever want to self-correct.
Dihedral reduces the efficiency of a wing, so for planes designed for the best L/D ratio flat (or almost flat) wings are the choice here.
Please use the right dihedral on a scale model. It is such a large part of the "look."
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Last edited by Whiskers; Nov 05, 2012 at 10:43 PM.
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Old Nov 06, 2012, 04:14 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
12,451 Posts
The really noticeable difference comes when you fly your first low winger aileron job with a flat wing.

Fly it straight out in front and give rudder. Most models of that type will carry on in a fairly straight path but crabbed, (side slipping), they do not turn like a wing with dihedral. They will eventually start to turn in a horrible way as the thrust line is now pointing to one side.

Likewise, trying to fly a RET without any dihedral will give very poor quality turns, plus it will lose the natural ability to recover itself with wings level if you let go of the sticks.

Dihedral is there to make the RET plane much easier to fly when aileron isn't available to keep the wings level.

Having too much dihedral can make for a very wallowy flight as the rudder control end up fighting the dihedral.
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