Box Kite: A Single Brace Prototype
Here is a box kite I just made. There are tons of kite plans online, but my kite has some major differences. My box kite just has a single central brace instead of two end braces. I also used balsa instead of spruce or pine.
These changes from the norm created issues, which I dealt with, to create a really small and light weight flyer.
Traditional, flat diamond-shaped kites are harder to manage in the wind. As the wind speed rises, they'll need a longer and longer tail. Tails stabilize kites by adding drag (it's not really the weight that helps).
I wanted to design a kite that was easy to keep up and that could handle rougher winds without the need for longer and longer tails-all in as small a kite as possible.
This led me to a box kite, because multi-planed kites are easier to fly and usually don't require any tail.
I also wanted to go extremely light and small. I replaced the usual spruce and pine with balsa wood.
Weight per cubic foot
Spruce = 28lbs
Pine = 26-45lbs
Carbon Fiber = 106lbs
Aluminum = 168lbs
Balsa = 4-24lbs
Steel is heavier than aluminum but an aircraft part made of aluminum the size of a pencil can be redesigned and made out of steel the size of a toothpick. Making an aluminum part as an exact copy in carbon fiber doesn't save you much weight, but you can make it thinner and in a different (smaller, thinner, shorter) shape and that's where the real weight savings begin to appear.
My redesign? Well, I didn't just replace the spruce with balsa. I also radically modified the traditional box kite design by getting rid of the end braces and creating a single, central brace.
Wind passing over a plane wing creates lift. An airplane propeller creates wind over the wing. The Wright Brothers took box kites in a cellular / modular design and added an engine to create wind on demand. Boom: a hard to steer airplane!
Then the Wright Brothers came up with something awesome: make the boxes super-flexible! This really helps catch and keep the wind.
Instead of a rock solid brace at both ends of the box, my design has a slightly flexible central brace! It will catch the wind more easily. Also, I'm now using lighter wood-and a lot less of it. [edit: I oddly used heavy newspaper instead of lighter materials like plastic grocery bags to cover this].
Basically, I just scaled down everything. I came up with the above numbers and used the third column-except for the string lengths (E and F) leading to the bridle.
Balsa cuts and saws very easily.
I notched the center brace components using the little Xacto saw and then just cleaned up the notch with an Xacto blade.
My new, experimental one-of-a-kind Logusz Brace. It joins together tightly even without glue.
The other joints were notched as well.
Clamps! I highly recommend you don't do what I did by using heavy clamps. Also, don't use alligator clips because they'll damage the balsa. Go online and order some "panel clamps" for $2 each. They're perfect for this type of thing and are made for clamping thin bits of metal together for welding. Mine are arriving in a few days.
To true up the frame I used the paper skin to pull things into shape. I wrapped the end around a rail with glue and let it dry. This let me pull really hard on the paper and thus keep things taut and straight.
Here's the first joint that anchors the skin. I let it dry before continuing with construction so I could pull the paper tight.
Notice the center brace isn't (yet) straight like a + sign. It will be!
Strings for the bridle. A string passes through a ring and connects two rail ends. The other string also passes through the ring and connects to two points in the halfway point of the opposite ends' paper skin.
The metal wire shown is pulling on the clamp, which makes the central brace straighten out into a perfect "+" sign shape.
Nice and straight!
A bread tie used as a glue brush. I ran it between each rail and the paper skins.
I put 4 layers of transparent tape on the skins where I drilled holes for the strings using apin vice drill.
Curved tweezers / forceps are indispensable for knot tying.
Both strings get looped around a plastic ring twice. This forms a bridle which self adjusts, allowing the kite to stay with the wind-eliminating the need for a tail.
There she is: a single brace box kite! Single, central brace. Quarter size balsa. Ultra light. Tail-less.
I ain't got no tail either... but then again, I can't fly. Meow.
My redesign? Well, I didn't just replace the spruce with balsa. I also radically modified the traditional box kite design by getting rid of the end braces and creating a single, central brace.
Wind passing over a plane wing creates lift. An airplane propeller creates wind over the wing. The Wright Brothers took box kites in a cellular / modular design and added an engine to create wind on demand. Boom: a hard to steer airplane!
Then the Wright Brothers came up with something awesome: make the boxes super-flexible! This really helps catch and keep the wind.
Instead of a rock solid brace at both ends of the box, my design has a slightly flexible central brace! It will catch the wind more easily. Also, I'm now using lighter wood-and a lot less of it. [edit: I oddly used heavy newspaper instead of lighter materials like plastic grocery bags to cover this].
Another change I made is to scale down the traditional box kite measurements. Box kites were used to lift things like emergency radio antennas in life rafts. Almost and other box kite plan you'll see online the standard 40" long rail variety or larger. This box kite is only 10" long!
A (Braces) 17" 8.5" 4.25" 2.125" 1.7"
B (Rails) 40" 20" 10" 5" 4"
C (Skins) 12" 6" 3" 1.5" .75"
D (String offset) 6" 3" 1.5" .75" .375"
E (End String) 60" 30" 15" 7.5" 3.75"
F (Offset String) 50" 25" 12.5" 6.25" 3.375"
Basically, I just scaled down everything. I came up with the above numbers and used the third column-except for the string lengths (E and F) leading to the bridle.
Balsa cuts and saws very easily.
I notched the center brace components using the little Xacto saw and then just cleaned up the notch with an Xacto blade.
My new, experimental one-of-a-kind Logusz Brace. It joins together tightly even without glue.
The other joints were notched as well.
Clamps! I highly recommend you don't do what I did by using heavy clamps. Also, don't use alligator clips because they'll damage the balsa. Go online and order some "panel clamps" for $2 each. They're perfect for this type of thing and are made for clamping thin bits of metal together for welding. Mine are arriving in a few days.
To true up the frame I used the paper skin to pull things into shape. I wrapped the end around a rail with glue and let it dry. This let me pull really hard on the paper and thus keep things taut and straight.
Here's the first joint that anchors the skin. I let it dry before continuing with construction so I could pull the paper tight.
Notice the center brace isn't (yet) straight like a + sign. It will be!
Strings for the bridle. A string passes through a ring and connects two rail ends. The other string also passes through the ring and connects to two points in the halfway point of the opposite ends' paper skin.
The metal wire shown is pulling on the clamp, which makes the central brace straighten out into a perfect "+" sign shape.
Nice and straight!
A bread tie used as a glue brush. I ran it between each rail and the paper skins.
I put 4 layers of transparent tape on the skins where I drilled holes for the strings using apin vice drill.
Curved tweezers / forceps are indispensable for knot tying.
Both strings get looped around a plastic ring twice. This forms a bridle which self adjusts, allowing the kite to stay with the wind-eliminating the need for a tail.
There she is: a single brace box kite! Single, central brace. Quarter size balsa. Ultra light. Tail-less.
I ain't got no tail either... but then again, I can't fly. Meow.
