The nominal size of a conventional RC airplane should follow this rule for a good and stable flight.
(Flying wings and other designs do not follow this rule)
All the size ratio start with the wingspan. Determine your wingspan and start calculating the other sizes as follow.
The fuselage length should be 70% - 75% of the wing span:
• Example: If the wing is 36" long, then the fuselage should be 25" - 27" long.
The ratio of the wing span to wing root chord should be 5 or 6:
• Example: If the Wing span is 36"then the wing root chord should be 6"
Note: The wing root chord is that portion of the wing that attaches to the fuselage, measured from the leading
edge to the trailing edge of the wing.
The wing thickness should be 12% to 14% of the wing root chord:
• Example: If the wing root chord is 6" then the widest part of the wing should be 3/4" thick.
Note: Foam profile planes do not follow this rule of thumb but still fly.
The aileron surface area should be 10% - 12% of half of the wing surface:
• Example: If half a wing is 6" x 18" then the wing surface is 108 sq inches. The aileron shape should
equal 11 - 13 square inches of surface area.
The distance from the leading edge of the wing to the back of the prop should be 15% of the wingspan:
• Example: If the wingspan is 36" then the distance from the back of the prop to the leading edge of the
wing should be 5.4".
The leading edge of the wing to the stabilizer should be 3 times the wing root chord:
• Example: If the wing chord is 6" then leading edge of the wing to the stabilizer should be 18".
The horizontal stabilizer should be 25% of the wing area:
• Example: If the wing is a rectangle, 36"L x 6"W, it has a wing area of 216 sq inches. 25% of 216 = 54
sq inches. The shape of your horizontal stabilizer should equal 54 sq inches.
The elevator (attached to the horizontal stabilizer) should be 25% of the horizontal stabilizer surface
area:
• Example: If the Horizontal Stabilizer is 54 sq inches then the elevator surface area should equal
13.5 sq inches.
The vertical stabilizer should be 10% of the wing area:
• Example: If the wing is a rectangular 36" x 6" shape it has a surface area of 216 sq inches. 10% of 216
= 21.6 sq inches. The shape of your horizontal stabilizer should equal 21.6 sq inches of surface.
The rudder (attached to the vertical stabilizer) should be 25% of the vertical stabilizer surface area:
• Example: If the vertical stabilizer is 21.6 sq inches then the rudder surface area should equal 5.4 sq
inches.
The plane should balance at 25% - 33% of the wing root chord:
• Example: If the wing root chord is 6" from the leading edge to the trailing edge of the wing then the
Center of Gravity (COG) should be located 1.5" - 2" from the leading edge of the wing.
(Flying wings and other designs do not follow this rule)
All the size ratio start with the wingspan. Determine your wingspan and start calculating the other sizes as follow.
The fuselage length should be 70% - 75% of the wing span:
• Example: If the wing is 36" long, then the fuselage should be 25" - 27" long.
The ratio of the wing span to wing root chord should be 5 or 6:
• Example: If the Wing span is 36"then the wing root chord should be 6"
Note: The wing root chord is that portion of the wing that attaches to the fuselage, measured from the leading
edge to the trailing edge of the wing.
The wing thickness should be 12% to 14% of the wing root chord:
• Example: If the wing root chord is 6" then the widest part of the wing should be 3/4" thick.
Note: Foam profile planes do not follow this rule of thumb but still fly.
The aileron surface area should be 10% - 12% of half of the wing surface:
• Example: If half a wing is 6" x 18" then the wing surface is 108 sq inches. The aileron shape should
equal 11 - 13 square inches of surface area.
The distance from the leading edge of the wing to the back of the prop should be 15% of the wingspan:
• Example: If the wingspan is 36" then the distance from the back of the prop to the leading edge of the
wing should be 5.4".
The leading edge of the wing to the stabilizer should be 3 times the wing root chord:
• Example: If the wing chord is 6" then leading edge of the wing to the stabilizer should be 18".
The horizontal stabilizer should be 25% of the wing area:
• Example: If the wing is a rectangle, 36"L x 6"W, it has a wing area of 216 sq inches. 25% of 216 = 54
sq inches. The shape of your horizontal stabilizer should equal 54 sq inches.
The elevator (attached to the horizontal stabilizer) should be 25% of the horizontal stabilizer surface
area:
• Example: If the Horizontal Stabilizer is 54 sq inches then the elevator surface area should equal
13.5 sq inches.
The vertical stabilizer should be 10% of the wing area:
• Example: If the wing is a rectangular 36" x 6" shape it has a surface area of 216 sq inches. 10% of 216
= 21.6 sq inches. The shape of your horizontal stabilizer should equal 21.6 sq inches of surface.
The rudder (attached to the vertical stabilizer) should be 25% of the vertical stabilizer surface area:
• Example: If the vertical stabilizer is 21.6 sq inches then the rudder surface area should equal 5.4 sq
inches.
The plane should balance at 25% - 33% of the wing root chord:
• Example: If the wing root chord is 6" from the leading edge to the trailing edge of the wing then the
Center of Gravity (COG) should be located 1.5" - 2" from the leading edge of the wing.
Very useful
ReplyDeletethank dear
ReplyDeleteWhat about weight
ReplyDeleteIf rudder area is 5.4 sq inches
ReplyDeleteand elevator area is 13.5 what should be the length and width of rudder and elevator?
How do All Flying Tail surfaces affect these values, or combined role surfaces like Elevons? I would assume AFT could be made slightly smaller than conventional if stability is acceptable, down to about 15% for a very stable aircraft, 20% otherwise.
ReplyDelete