Glider Design

[Easy226]

Hi everyone,
As part of my 2nd year main project for my degree, I have to design (and fly) a glider that will be able to fly roughly 25 metres inside a sports hall and hit a target.
We have investigated various designs as to what shape the glider should be and also wing design but have one problem. We are not sure weather it iss worth taking the extra time to build a dihedral wing to make it more stable or just use a straight wing to fly the glider the 25 metres. Is it really worth the hassle?
I know the topic is a bit vague, but would appreciate any help!
Many Thanks
Dan

[avoman]

If you Google on model glider plans or similar, observe very marked dihedral on nearly all. This could be a clue.

[qwertyuiop]

Dihedral gives stability and ease of flight. Agree with avoman, check out all the other designs.

[Genghis the Engineer]

You need lateral stability - dihedral being the most common way to achieve that.

There are two other ways however - one is to use pendular stability - in other words a CG reasonably well below the wing, the other is to use wing sweep.

Personally I'd go for a combination of a small dihedral value and a high wing (so giving at-least a little pendular stability). You probably also, to ensure post stall controllability, want to try incorporating a little washout - somewhere in the order of 2-4°. Sweep I'd not bother with, since that does become slightly difficult and you're unlikely to need the directional stability advantages if you put a reasonable fin on it.

Don't forget by the way that for a degree project, you really need to be able to justify what you're doing by reference to a good stability analysis. I'd suggest you get hold of a copy of Darrol Stinton's "design of the aeroplane" which should help a lot in that regard.

G