Area ratio, wing to H. Stab??  
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Area ratio, wing to H. Stab?? - 3/24/2002 10:42:23 PM   
Murphey


 

Posts: 114
Joined: 3/4/2002
From: Aurora, CO, USA
Status: offline 		Is there a rule of thumb to size the horizontal stab/elevator based on the area of the wing?
       Post #: 1

Stab area relative to wing area - 3/25/2002 2:45:03 AM   
Mike James



Posts: 2464
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Most typically-configured aircraft have the horizontal stabilizer area (including elevators) at about 20 to 25 percent of the wing area.

Try collecting lots of 3-views of different types of aircraft and measuring yourself. Then you'll see what designs user larger or smaller percentages.

The fuselage length has a bearing on this too.


_____________________________

Mike James
RC Design and Building - www.nextcraft.com

(in reply to Murphey)
       Post #: 2

Area ratio, wing to H. Stab?? - 3/25/2002 5:31:20 AM   
Murphey


 

Posts: 114
Joined: 3/4/2002
From: Aurora, CO, USA
Status: offline 		Mike: Thanks for the info!! I did check out the relationship between wingspan and fusalage length. Seems that most are 1.2 when I divide the span by length, except for pattern planes which seem to be .93. This current adventure is a profile twin with a 58" WS and 48' length. Still on the drawing board!!

(in reply to Murphey)
       Post #: 3

tailplane area - 3/25/2002 6:08:02 AM   
majortom-RCU


 

Posts: 1583
Joined: 12/11/2001
From: Merrimack, NH, USA
Status: offline 		There is a design concept known as "tail volume" which is the area of the horizontal tailplane (stab + elev) as % of the main wing, multiplied by the fuselage length from main wing TE to tailplane hinge-line expressed as ratio to wing chord.

Ex: wing chord 12", fuse 24" from wing TE to stab/elev hinge-line, gives tail-length/chord ratio of 2.0; tailplane area 22% of main wing area; tail volume = 2 x 22 = 44 (which is a realistic number).

If you take a given tail volume and distribute it to a long tail/ smaller tailplane surface area you get more pitch stability (like an arrow in flight); if you shorten the tail and add tailplane surface area you get snappy, more aerobatic pitch response (like a combat or bat bat). You can further modulate this characteristic by dividing your horizontal tailplane between fixed and movable surface, then further still by degrees deflection of control surface.

I have not made a deliberate study of the matter, but for sport models I'd stay in the range of 40-45% tail volume. If you are looking for a high scale speed then you could go down into the 30's, or for slow 3D stuff go 50% or more. If you did a statistical survey of this measure on various types of models with great reputations, I expect you'd come up with a fairly small standard deviation. I wish someone would do that and tell us the numbers.

(in reply to Murphey)
       Post #: 4

Tail Volume Coefficient - 3/25/2002 8:42:07 AM   
Ollie


 

Posts: 958
Joined: 12/8/2001
From: Punta Gorda, FL
Status: offline 		The stability associated with a given tail volume coefficient depends on the CG position. The larger the tail volume coefficient the farther aft the CG will be for a given static stability. Also, the pitch and yaw damping varies with the square of the tail moment arm length. Longer is smoother.

_____________________________

Regards, Ollie

(in reply to Murphey)
       Post #: 5

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