Lift Forces On A Box Kite

by Des
(Ottawa, ON, Canada)

Q:

Can you explain how a box kite generates lift? I have trouble visualizing how it acts like a wing. It has a space in the middle that offers no resistance to the air flow.

I have read and think I understand your description of how a diamond shaped kite generates lift.

Thanks

A:

The key to understanding this is to consider the individual rectangular panels of the box kite cells. Each one, like a rectangular Korean fighter kite, is a 'wing' in its own right. Each one is held at an 'angle of attack' to the breeze, by the kite's bridle. So, you have 8 wings connected together, each of them subjected to the same forces as described for the Diamond kite example. Of course 'line tension' is a bit hard to compare, since the panels experience tension through the connections to the rest of the kite, rather than having individual bridle connections.

If you add up all these individual forces, they are equivalent to the same 4 forces described for the Diamond kite. Lift, Drag, Weight, Tension. The Box kite as a whole lifts a certain amount, drags at the air a certain amount, weighs a certain amount and pulls a certain amount of tension into the line.

A slightly simpler way of visualizing all those 'wings' is to consider each cell to have just 2 wings. A lower one, with 45 degree dihedral. Plus an upper one, with 45 degrees of anhedral. The 4 forces on each of the 4 wings would add to the same overall Lift, Drag, Weight and Tension.

A bit wordy, but I hope that helps!

Comments for Lift Forces On A Box Kite

Click here to add your own comments

Oct 12, 2011
Forces On A Box Kite
by: Des

Thank you. The last paragraph was most helpful.

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to About Kites.




E-book special of the month (25% off)...

This printable e-book takes you step-by-step through making a 120cm (4 ft) diameter Parasail kite. This kite performs well in gentle to moderate wind speeds. That's from 12 to 28 kph or from 8 to 18 mph. It pulls hard for it's size, so should not be flown by very small kids!

Every kite design in the MBK Soft Series satisfies the following points...

  • Materials are plastic sheet, tape and line – and nothing more!
  • Tools are a ruler, scissors and a marker pen - and nothing more!
  • All cuts are along straight lines.

For the greatest chance of success, I make recommendations regarding the materials. For example, the type/weight of plastic, type/width of tape and line type/strength. Close enough should nearly always be good enough, since the design is well-tested and should be tolerant of small differences from my original.

Get the e-book for making the MBK Parasail kite. After making your first one in plastic and seeing how it performs, you can try soft Tyvek or rip-stop nylon for your next build.

The e-book is a PDF file - which means printable instructions to refer to while you make the kite. It also means convenient off-line access if that suits you better.



What's New!

  1. The Adelaide Kite Festival

    Apr 26, 17 06:00 AM

    Coincidentally, this previously published page has recently been updated. The Adelaide International Kite Festival for 2017 was held earlier this month...

    Read More









 


E-books


Kite-making e-book: Simplest Dowel Kites

This one's FREE
Download it now!



More E-books...





Testimonials
(unedited)

"Love the easy to understand step by step instructions, made from next to nothing materials and above all so much fun to fly... cheers Tim for sharing your well thought out pdf kite designs with the whole world.

Very satisfying making your own and watching them get air-born for the first time."

_________________

"I've just bought your super e-book and spent most of last night pouring through all the great stuff in it!

Very detailed and USEFUL information - thanks for such a great book."

_________________

"30+ years ago, I tried making a kite using the 'instructions' in a free kite-safety booklet. What a disappointment for a young boy.

 Your instructions and methods are wonderful. You help the builder to focus on accuracy, without making it hard. Also, you use materials that are durable, yet cheap!"

_________________

"omg i made a kite from this site and i fly it ....... booom i didnt expect this bc in the other sites instuction are trash

thank you"




Kite-making e-book: Simplest Dowel Kites

This one's FREE
Download it now!



More E-books...





Wind Speeds


Light air
1-5 km/h
1-3 mph
1-3 knots
Beaufort 1

Light breeze
6–11 km/h
4–7 mph
4–6 knots
Beaufort 2    

Gentle breeze
12–19 km/h
8–12 mph
7–10 knots
Beaufort 3    

Moderate breeze
20–28 km/h
13–18 mph
11–16 knots
Beaufort 4    

Fresh breeze
29–38 km/h
19–24 mph
17–21 knots
Beaufort 5    

Strong breeze
39–49 km/h
25–31 mph
22–27 knots
Beaufort 6

High Wind
50-61 km/h
32-38 mph
28-33 knots
Beaufort 7