Design > Stunt design

Stabilizer Location Question

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Harleyman:
Is there a rule of thumb for Horizontal Stabilizer location related to the wing centerline?
I am building my own profile, semi scale stunt T-38 Talon, .35-.40 size.  The full scale Jet has a very low stabilizer location; it’s pretty much mounted on the underside of the Fuse.  I have only seen and built airplanes with the stab mounted higher than the enterline of the wing.  Is this done for pushrod clearance issues?  Can the stab be mounted in line with the wing?  How does engine Thrust line influence stabilizer position?  Also, please assume typical nose and tail moments, similar to Nobler numbers.

Thanks.

RC Storick:
I will try a "stab" at your question. The stab will work in any relation to the thrust line or center line of the wing. However if you loft out the push rod you should try to keep it parallel to the TL. The reason for this is the mechanical advantage or swing of the control horns cause UN equal throw in one direction or the other. Hence it would cause unsurmountable trimming problems.

Ironbomb:
Would the same trimming issues be present if the elevator horn were above the surface, and the flap horn below the flap surface? Could the difference in throw be canceled like that?

The elevator pushrod could then be kept parallel to the thrust line, keeping a T-38 stab/elevator configuration more to a scale appearance. Yes?

Just wondering

 ???

Greg

Bill Little:
Hi Greg,
There have been a few ships set up with the horns as you describe.  Vic Macaluso did 2 versions of the F-8 Crusader with the elev. horn on top.  In fact, you will not need to reverse the bellcrank to get the up line in front.   Both flew great!

Ted Fancher:
Besides the mechanical and alignment issues already addressed, you do need to be aware of the effect of a very high or low location and the effect on the pitch axis caused by the drag of the surface.  The position of the stab will effect the vertical location of the center of drag of the ship and, when producing lift for maneuvering that drag will increase dramatically.  Most successful ships that have been designed with "high" or "low" tails have been quite modest in the degree of vertical offset from the wing and centerline of the fuse.

Ted

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