calulation for stabilizer area ?
09-13-2002, 06:30 AM
#1
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calulation for stabilizer area ?
Does anyone know what the rule of thumb is for calculating the size of the stab area to the wing.?
I am scratch building a project and the stab/elevator will be between two tail booms.
Thanks
Rod
I am scratch building a project and the stab/elevator will be between two tail booms.
Thanks
Rod
09-13-2002, 10:01 AM
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calulation for stabilizer area ?
See:
http://www.aalmps.com/tv.htm
It depends not only on the wing area. The longer the tail moment arm, the smaller the tail area for a given CG and stability.
http://www.aalmps.com/tv.htm
It depends not only on the wing area. The longer the tail moment arm, the smaller the tail area for a given CG and stability.
09-13-2002, 01:34 PM
#4
Stab Size
For powered RC planes use 20%-25% of the wing area.
For all practical purposes, there is no down side for a large stab. The old Dirty Birdy pattern plane had a 30% stab and a long fuselage and flew great. Generally, a large stab gives you more lattitude in CG placement, whereas a small stab tends to narrow the CG range.
I generally use 23%-25% for planes I design. I had an 80 inch sport design with a 23% stab that I removed a Quadra 42 and replaced it with a ST 3000, moving the CG back to about 50%. I flew it for 6 flights before fixing the CG. It required you to watch it all the time and it would loop on its own if you blipped the elevator and released. It was flyable, but I wouldn't recommend it to a novice flier. I finally got tired of using down elevator on final approach to keep the plane descending.
For all practical purposes, there is no down side for a large stab. The old Dirty Birdy pattern plane had a 30% stab and a long fuselage and flew great. Generally, a large stab gives you more lattitude in CG placement, whereas a small stab tends to narrow the CG range.
I generally use 23%-25% for planes I design. I had an 80 inch sport design with a 23% stab that I removed a Quadra 42 and replaced it with a ST 3000, moving the CG back to about 50%. I flew it for 6 flights before fixing the CG. It required you to watch it all the time and it would loop on its own if you blipped the elevator and released. It was flyable, but I wouldn't recommend it to a novice flier. I finally got tired of using down elevator on final approach to keep the plane descending.
09-15-2002, 02:11 AM
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calulation for stabilizer area ?
For a 3.74-78 tail moment arm, wich I experimentally use, a 10 to 15% area of wing should do! It gives great performance when quick reactions are needed.
09-15-2002, 05:09 PM
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Stab Area 'rule of thumb'
I think thumbs come in lots of sizes...
Another dimension that I think gets into the calculus for for elevator area is that of the wing chord. I think that all wings are not created equal in their need for downforce to stabilize the airplane. I suspect the wing chord plays an important part in establishing the elevator authority needed. I think that sailplanes with skinny chords and long spans need different elevator force to stabilize the aircraft than 'pattern' aircraft with the same wing area, for example. But I am only a layman speculating on his own, and wiser heads than mine could shed light on this.
Another dimension that I think gets into the calculus for for elevator area is that of the wing chord. I think that all wings are not created equal in their need for downforce to stabilize the airplane. I suspect the wing chord plays an important part in establishing the elevator authority needed. I think that sailplanes with skinny chords and long spans need different elevator force to stabilize the aircraft than 'pattern' aircraft with the same wing area, for example. But I am only a layman speculating on his own, and wiser heads than mine could shed light on this.
