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Computing Wing Lift

Posted: Wed Oct 04, 2017 9:44 am
by lightandfrost
For those designing wings here is a rough guide to compute approximate lift based on wing surface area.

Lift in Pounds = Surface Area in Square Feet * Velocity in fps * Velocity in fps * coefficient of Lift

or

L = S * (( V * V ) * C)

Where:
* = times or multiples of
L = Lift in Pounds(lbs)
S = Square Area in feet(ft)
V = Velocity in feet per second(fps)
Note: V * V is the square root of V

C = Coefficient of Lift

Note: For purposes here the coefficient of lift is equal to one(1).

To obtain a Square Area in feet of your wing go here:

http://www.airfieldmodels.com/informati ... g_area.htm

The measurement process computes one(1) side of the total wing area so remember to double the area before applying to the formula to obtain total lift.

Conversions

1 cm2 = .00107639 ft2

cm2 = square centimeters
ft2 = Square feet

Knots(kts) to fps Chart

kts fps

1 1.68781
2 3.37562
3 5.06343
4 6.75123
5 8.43904
6 10.12685
7 11.81466
8 13.50247
9 15.19028
10 16.87808
11 18.56589
12 20.2537
13 21.94151
14 23.62932
15 25.31713

Using the L = S * (( V * V ) * C) formula a 0.7 square foot wing surface area provides the following lift.

Kts Lift in lbs

1 1.99
2 7.97
3 17.94
4 31.90
5 49.85
6 71.78
7 97.71
8 127.62
9 161.52
10 199.40
11 241.28
12 287.14
13 337.00
14 390.84
15 448.67

In closing readers should remember that a hydrofoil wing/mast combination probably obtains two(2) types of lift. The lift generated by the wings and lift generated by the mast under certain conditions. For list from the mast cross reference the centerboard hydrofoil effect.

Light and Frost

Re: Computing Wing Lift

Posted: Wed Oct 04, 2017 10:14 am
by evan
1st grade aeronautical engineer trying to apply his college knowledge to hydrofoiling?

Deriving the lift from a given lift coefficient isn't the hardest part, obtaining that coefficient is and for those who know what you are talking about explaining the basic stuff feels a bit weird when you leave out half the the variables unexplained. What CL and density did you use for example?

L = (1/2) d v^2 s CL

L = Lift, which must equal the airplane's weight in pounds
d = density of the air. This will change due to altitude. These values can be found in a I.C.A.O. Standard Atmosphere Table.
v = velocity of an aircraft expressed in feet per second
s = the wing area of an aircraft in square feet
CL = Coefficient of lift , which is determined by the type of airfoil and angle of attack.


Oh, and try keeping everyting metric without elbows, thumbs and snail speeds for measurements.