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Old Jul 10, 2014, 01:48 AM
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rudder responsiveness with little dihedral

im almost done building a 1.5m electric glider, but i have only made the wing dihedral 4 degrees total. i realize that this make the rudder less responsive, and i cant change the angle of the wings anymore since they are epoxied together, so i have two questions:

1: will a bigger rudder make it more responsive with such a small dihedral angle?

2: some slope gliders/ aerobatic gliders have no dihedral, what makes the rudder responsive? is it the air speed, a bigger rudder or a combination of both?

here are some specs

span:60in
chord: 6.5in
length: 40in
weight is going to be around 13oz with motor esc etc.
total dihedral angle: 4 degrees
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Old Jul 10, 2014, 02:29 AM
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Yes, it's a combination of how fast the air is flowing over the displaced rudder and how large the rudder is.
Just make it bigger in small increments till you feel you have enough control authority.
Control surface sizing questions/issues seem to be coming up a lot lately on this site.
Personally, I'd rather have too much authority than not enough.
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Old Jul 10, 2014, 05:12 AM
An itch?. Scratch build.
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South Wales U.K.
Joined Mar 2003
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Quote:
Originally Posted by greenlight149 View Post
...........................................

2: some slope gliders/ aerobatic gliders have no dihedral, what makes the rudder responsive? is it the air speed, a bigger rudder or a combination of both?

.................................................. .
If they have no dihedral, they will be using ailerons in combination with elevator to turn. Rudder can be used with ailerons to try and get a flatter turn.

Go for a big rudder with that reduced dihedral. You can always reduce the amount of throw if you feel it is over controlling, (yawing).
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Old Jul 10, 2014, 06:15 AM
gpw
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A Taller rudder is more effective in causing “roll".. rather than just deflecting the tail ...that may help ...
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Old Jul 10, 2014, 01:03 PM
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I'll make the rudder bigger and if that doesn't work I'll have to make the wing a polyhedral...
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Old Jul 11, 2014, 11:02 AM
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Originally Posted by gpw View Post
A Taller rudder is more effective in causing “roll".. rather than just deflecting the tail ...that may help ...
Which is why many rudders have more area toward the bottom ......so that they don't
Induce roll the wrong way Keeping the weight as low as possible will help with the turning
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Last edited by hiko; Jul 11, 2014 at 11:09 AM.
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