Area of a Kite Calculation

A Practical Guide for Sticked Designs

Perhaps you have looked up how to find the area of a kite before. There's the familiar diamond shape, plus some info that looks or sounds like it came straight from a mathematics textbook.

---

 

 

---

Method For Two Simple Kite Shapes

If you just want to find the area of a simple delta or diamond, there is a very quick and easy way!

The distance from the vertical spar out to the "wingtip" multiplied by the kite's height (nose to tail) gives the total area of the kite. That's it!

Delta. For example, if your delta is 70 cm from nose to tail, and 80 cm from vertical spar to wingtip, along the trailing edge. The whole sail has an area of 70 x 80 = 5600 square centimeters. Or 5600 / 10000 = 0.56 square meters. Just over half a square meter.

In inches, let's say your delta was 40 inches from nose to tail and 45 inches from vertical spar to wingtip. The whole sail has an area of 40 x 45 = 1800 square inches. Or 1800 / 144 = 12.5 square feet.

Diamond. Suppose you have bought yourself a diamond that is 110 cm tall and 100 cm across. The total area is the length from where the spars cross, out to the tip, multiplied by the height (nose to tail). So in this case, the total sail area is 110 x 50 = 5500 square centimeters. Or 5500 / 10000 = 0.55 square meters.

In inches, let's say your diamond was 60 inches from nose to tail and 35 inches from vertical spar to wingtip. The whole sail has an area of 60 x 35 = 2100 square inches. Or 2100 / 144 = 14.6 square feet.

Note that some deltas actually have a diamond shape, with the trailing edge swept forward a little instead of going straight across. The calculation still works!

---

Now let's look at two more complex examples, using the following straightforward four-step process:

1. Identify triangles, if any, in the half-sail template. Calculate the area of each one.
2. Identify the remaining rectangles, if any. Calculate the area of each one.
3. Add all those area figures together, to get the template area.
4. Multiply the template area by two, to get the area of the whole kite. Done! Convert to other units if desired.

Both the "area of a kite" examples are worked in centimeters and inches, so you can follow in whatever system you are most comfortable with.

---

Area of a Kite
The Dowel Rokkaku

Step 4. Double the template area, and convert to other units if needed.

That's 6048 x 2 = 12096 square centimeters. Divide by 10000 to get square meters, if you want to. 12096 / 10000 = 1.21 square meters. Well over 1 square meter.

Now for inches. 972 x 2 = 1944 square inches. Divide by 144 to get square feet, if you want to. 1944 / 144 = 13.5 square feet.

---

Area of a Kite
The Dowel Dopero

Step 4. Double the template area, and convert to other units if needed.

That's 5270.4 x 2 = 10540.8 square centimeters. Divide by 10000 to get square meters, if you want to. 10540.8 / 10000 = 1.05 square meters. Just over 1 square meter.

Now for inches. 848.85 x 2 = 1697.7 square inches. Divide by 144 to get square feet, if you want to. 1697.7 / 144 = 11.79 square feet.

So, this dopero has significantly less area than the rok and more spar material. But you wouldn't know it, from how well it flies in light wind!

---

Quicker Calcs With Rounding

Don't need great accuracy for your sail area figure? The dopero kite shape example contains some awkward measurements. In the case of metric measurements, working with decimal places just means a few extra keystrokes on the calculator before the answer pops out. Still, it can be useful to round the figures to make the "area of a kite" calculations quicker and easier.

For example, take a triangle that is 60.2 cm wide and 5.8 cm high. 20.2 is near enough to 20 and 5.8 is near enough to 6, so the area is 60 x 6 / 2 = 180 square centimeters. Compare that with the exact area of 174.58 square centimeters. 180 is close enough!

Rounding measurements is even more of a time saver when working with inches. Imagine a triangle with a width of 25 1/8 inches and a height of 4 3/4 inches. 25 1/8 is near enough to 25 and 4 3/4 is near enough to 5, so the area is 25 x 5 / 2 = 62.5 square inches. Compare that with the exact area of 59.67 Not very far off!

Furthermore, when adding several area figures together, the errors tend to cancel each other out. The resulting overall area of a kite figure is often much more accurate than you might expect!

---

Flat Versus Projected Area of a Kite

In the real world, kites don't fly with perfectly flat sails of course. The effective, or projected sail area of a kite is somewhat smaller, affected by:

1. Dihedral or bow of the horizontal spar(s)
2. Billow in the sail due to air pressure in flight

The easiest way to visualize projected area of a kite is to imagine holding it with nose and tail the same short distance off the ground. Gravity causes some billow in the sail, similar to when the kite is flying. This is on a sunny day, with the sun directly overhead. (I won't go into all the circumstances that need to come together, for this to be the case!) Now, look at the shadow of the sail on the ground. This is the projected area of the sail.

My guess is that for most flat or bowed kites, the projected area is somewhere between 2 and 20 percent less than the flat area. So, if you are calculating the area of a kite for the purpose of selecting line strength, you could factor this in, to be even more accurate.

---

Finally...

If you've had a bit of fun finding the area of a kite by running these calculations, you could try one of my barn door or sode designs just as an exercise. Apart from that small nose section, there are no triangles at all in the MBK Dowel Sode!

I hope you have found this discussion about finding the area of a kite useful. May your flying line never snap!

 

---

 

 

---