Horizontal stabelizer size vs. Wing size
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Master_cheif
- Posts: 3
- Joined: Sat Apr 14, 2007 6:52 am
Horizontal stabelizer size vs. Wing size
I am making a glider and have wings that measure 36". What should the size of the horizontal stabelizers be? 1/4 wings? 1/2?
Eggnaut. Like Astronaut. Haha. I get it
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Craig_Bridge
- Former Expert
- Posts: 1297
- Joined: Mon Oct 16, 2006 11:47 am
Have you tried a search?
I put "Model glider horizontal stabilizer" in and found several interesting hits. Among them was http://www.nasa.gov/pdf/58321main_X1Glider1b.pdf
Look at the model dimensions for some guidance.
Assuming the center of lift and gravity is at the center of the wing attachment, the surface area of a rear horizontal stabilizer should be much smaller because the pressure times its area is a force that is multiplied by the distance between the center of the wing and the center of the stabilizer to apply a torque to control pitch. If the stabilizer is too big for its placement, the effective center of lift will move backwards and increase the stall speed. If it is too small, the pitch will not be controlled. Both are bad for the Egganaut.
These are things you are supposed to determine experimentally!
Try searching "Pitch Roll Yaw" and you should get a hit in the Nasa teaching series on flight.
I put "Model glider horizontal stabilizer" in and found several interesting hits. Among them was http://www.nasa.gov/pdf/58321main_X1Glider1b.pdf
Look at the model dimensions for some guidance.
Assuming the center of lift and gravity is at the center of the wing attachment, the surface area of a rear horizontal stabilizer should be much smaller because the pressure times its area is a force that is multiplied by the distance between the center of the wing and the center of the stabilizer to apply a torque to control pitch. If the stabilizer is too big for its placement, the effective center of lift will move backwards and increase the stall speed. If it is too small, the pitch will not be controlled. Both are bad for the Egganaut.
These are things you are supposed to determine experimentally!
Try searching "Pitch Roll Yaw" and you should get a hit in the Nasa teaching series on flight.
-Craig
When designing your glider, keep in mind that the goal is to protect the egg. Flight worthiness is secondary.
Why is this important? Because you want your craft to land in the way that maximally protects the egg. A nose first crash landing, with the whole front of the glider crushing, absorbing kinetic energy that would otherwise get delivered to the egg, is not at all a bad design goal. This is how Indy Cars are designed, to protect their drivers. Their fronts get destroyed, but the occupant survives.
For stability in a glider, you want your weight at the center of gravity of the glider (and yes, the egg position will dramatically change the glider's center of gravity.)
So unless your design elegantly skids to a landing each time, think of making a large dependable crush zone at the front to help protect the egg, and make the glider a little nose heavy.
Anyway, enough hints for now. Keep us informed as your building proceeds with problems / questions you might have.
Why is this important? Because you want your craft to land in the way that maximally protects the egg. A nose first crash landing, with the whole front of the glider crushing, absorbing kinetic energy that would otherwise get delivered to the egg, is not at all a bad design goal. This is how Indy Cars are designed, to protect their drivers. Their fronts get destroyed, but the occupant survives.
For stability in a glider, you want your weight at the center of gravity of the glider (and yes, the egg position will dramatically change the glider's center of gravity.)
So unless your design elegantly skids to a landing each time, think of making a large dependable crush zone at the front to help protect the egg, and make the glider a little nose heavy.
Anyway, enough hints for now. Keep us informed as your building proceeds with problems / questions you might have.
Alan Lichtenstein, MD
Anesthesiologist
Mens et manus
Veritas
He who laughs last...Thinks slowest.
Anesthesiologist
Mens et manus
Veritas
He who laughs last...Thinks slowest.
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Craig_Bridge
- Former Expert
- Posts: 1297
- Joined: Mon Oct 16, 2006 11:47 am
zzzdoc mentioned a slightly heavy nose which is probably a good thing to prevent stalls. What he didn't mention are considerations of where the center of gravity of the glider should be with respect to the glide slope and center of lift.
High wing planes have a high center of gravity. When they do emergency landings in fields, they tend to flip tail over wing and end upside down even when the pilot does a tail drag flare stall to attempt to avoid the flip.
You may or may not want to intentionally take advantage of this flip behavior; however, you should plan for it as a possibilitity.
Uncontrolled low wing gliders have a tendency to have a wing touch down first and can do a cart wheel (wing, nose, flip, wing, tail, ...).
High wing planes have a high center of gravity. When they do emergency landings in fields, they tend to flip tail over wing and end upside down even when the pilot does a tail drag flare stall to attempt to avoid the flip.
You may or may not want to intentionally take advantage of this flip behavior; however, you should plan for it as a possibilitity.
Uncontrolled low wing gliders have a tendency to have a wing touch down first and can do a cart wheel (wing, nose, flip, wing, tail, ...).
-Craig