Hi Guys Does anyone have a good simple for calculating the necessary fin area for a rocket?
Thanks
Fred
The normal fin rules of thumb...
3 fins
Fin Area (each) = 0.17 * [(rocket_diameter+0.5)*rocket_length]
4 fins
Fin Area (each) = 0.13 * [(rocket_diameter+0.5)*rocket_length]
Those are in inches and square inches
Root chord = 2 x rocket_diameter
Tip chord = 1x rocket_diameter
So for a BT-80 Root cord is 5.2 inches.
Tip cord is 2.6 inches.
Semi span would be 5.2"
This is aproximate of course
Thanks
fred
Hmm, I get different numbers... how long is this rocket? Assuming a 10:1 ratio, the rocket would be 26 inches in length.
Root = 5.2 in
Tip = 2.6 in
Area(3) = 13.7 in^2 (each)
area(4) = 10.48 in^2 (each)
The formula for area would be:
area = (root+tip) * span / 2
Therefore:
span = area*2/(root+tip)
For 3 fins, that'd be 3.51 in.
For 4 fins, that'd be 2.69 in.
Also remember that a span increase is more effective than a chord increase when considering the fin's overall effectiveness... OL JR
Hmm, I get different numbers... how long is this rocket? Assuming a 10:1 ratio, the rocket would be 26 inches in length.
Root = 5.2 in
Tip = 2.6 in
Area(3) = 13.7 in^2 (each)
area(4) = 10.48 in^2 (each)
The formula for area would be:
area = (root+tip) * span / 2
Therefore:
span = area*2/(root+tip)
For 3 fins, that'd be 3.51 in.
For 4 fins, that'd be 2.69 in.
How do these formulas change if at all when using metric measurement. I can use imperial but find it confusing. I mean inches no disrespect either
Cheers
Bill
How do these formulas change if at all when using metric measurement. I can use imperial but find it confusing. I mean inches no disrespect either
Cheers
Bill
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