Large (16-sail) Portable Tetrahedral Kite With 3D Printed Connectors

A tetrehedral box kite using wooden dowels, Tyvek paper, and connectors printed in PLA on a 3D printer. Much larger and more durable than similar kites made out of plastic straws and string.

Supplies:

Wooden dowels, 3/16" diameter, 88 plus a few spare in case there are breaks

Connectors:

• 30 6-way connectors printed on a 3D printer
• 4 3-way corner connectors printed on the same printer
• 4 small metal eyelets

Sufficient Tyvek paper to create the foils (each foil requires about 2 sq. feet of paper, there are 16 of these, so 32 sq. feet of Tyvek)

Glue or other means of binding the tyvek to itself. I used a Food Saver heat sealer for many of my seams, spots of hot glue for others. Tyvek can supposedly be bound with regular white Elmer's type glues as well, though these take some time to dry. Rubber cement will also work quite well, as will contact cement. I have not tried urethane glues, but I can't imagine they won't work, just require much too long to dry/ cure. The heat sealer took only a few seconds per seam, though there were some overmelts that could not be fixed. These sails could also be sewn on a sewing machine fairly quickly.

Recommended Tools:

• Rotary cutting tool (you can use a scissors, but see below)
• Self-healing cutting board that is marked with 30 degree and 60 degree angles, and is at least 12" square
• Pencil/ pen to mark your lines (optional)
• Measuring tape/ ruler (also optional if your cutting pad is marked with ruler markings)
• 3D printer and printing filament (I used a Monoprice Mini Delta printer and PLA filament)
• Small butane torch
• Hot glue gun/ sewing machine/ heat sealer
• Hair dryer (for softening the hot glue when necessary and for disassembly)

This Instructable presupposes that you already own or have access to a 3D printer and are able to use it to print off the connectors used here. Learning how to use such a printer is beyond the scope of this kite project, and is a skill that must be acquired separately, though the printed parts are relatively few and pretty simple.

Note that this kite must be built either in a garage or in some outdoor space: once assembled, it will be too big to fit through even a large single-door doorway. Which is already inconvenient, but there's more: if you use any amount of hot glue to hold the kite together, you will need to reheat this hot glue during disassembly. If you are indoors, you can use a hair dryer to do this. But as I already said, the kite must be assembled outside, and access to an outlet and a hair dryer may not be realistic. In this case, you may need to use the butane torch to VERY gently warm up the parts of those connectors that have hot glue in them in order to loosen up the dowel rods. Otherwise the only way to disassemble the kite will by by breaking the dowels, which is less than ideal. See more on this in Step 7: Disassembly, below.

A tetrahedral/ tetragonal kite is a 3-dimensional kite like a box kite which has been around for centuries. The theory of the kite works on the principle of an airfoil: each of the V-shaped Tyvek cutouts, when folded along the middle, bent, and stiffened sufficiently, will create an airfoil. Multiple airfoils assembled correctly and with sufficient wind will enable the assemblage to become airborne. This particular kite uses 16 airfoils. In theory, you can create a kite with any number of such airfoils,in almost any combination, though flying a kite with only 4 will prove pretty difficult and having just 1 airfoil will require quite a breeze! But imagine a kite made of over 60, over 100 little airfoils... It could be done, with enough patience and resources.

When making this particular kite, or any tetrahedral kite, there are some things to keep in mind. One of these is how exactly it is gong to fit together. Because there are so many airfoils, and because they need to fit together rather precisely, assembling them can be a challenge. I am including with this Instructable the files I used to create the kite connectors using my 3D Monoprice Mini-Delta printer.

Here's what I mean: the connectors produced by the printer each has several holes I call "ports" for the dowels to go into. However, if the dowels are not placed within these ports to more or less the exact same depth, then one side of your kite may be longer than the other. This will not do! Also, my printer (which is low-end) has a hard time printing tubes horizontally because of the internal overhang. Therefore some shenanigans was required. More on that in a bit.

The estimated realistic build time for this kite is around 30 hours. That includes printing off the connectors, fiddling with them, drawing out the airfoils, cutting these out, gluing/ sealing their seams, inserting the dowels, and assembling the entire kite. The cost for the wooden dowels (in 2022) is around $20, and you can get Tyvek from the Post Office for free (not that I am encouraging this). Hot glue is cheap. I used a kite reel for flying my kite which was about $16.

In order to make the kite you will need connectors. You will need to print off 4 corner connectors and 30 six-way connectors.

Once the connectors are printed off, you need to make sure the dowels fit inside them. For the 6-way connectors included with this Instructable, the holes in the connector have already been designed wide enough to accommodate the 3/16th inch dowel rods used for the build. But even with these, there is sometimes a hole that gets printed too small or too large (at least, with the Monoprice 3D printer). When too small, I found I could use a butane torch to soften the plastic just enough to accommodate a dowel. Make sure you do not change the orientation of the hole when you soften it. Do not burn the PLA plastic! When too large, well, that is coming later.

Also, now that you are done printing off the connectors, it is time to insert the metal eyelets into the corner connectors: take a metal eyelet, hold it with a pliers, and hit it with the butane torch until quite hot, then gently screw it into the connector's point until it is well secured there. Cool it off with a spritz of water and test it: it should not come out. Be carefuk while heating and inserting these that you do not heat the whole connector so much that it becomes distorted. If you make a 3-sided pyramid with other connectors and some dowels with the corner connector at the top, you will be certain not to change anything important about it when you melt the eyelet into place.

Once you have all the connectors ready to go, you can start the airfoils. You could also do these first: the order of operations does not matter.

The picture provided is exactly proportional to the airfoils required. The gray area represents the physical airfoil; the dotted lines represent the dimensions of a theoretical diamond shape from which the airfoil is made; the dashed lines represent fold lines.

If making a kite with 12" dowels, then the measurements given here for the airfoils must be cut and folded accurately in terms of angle of cut and of fold. Even small deviations might make the resulting airfoil impossible to mount without breaking dowels. Once the folds have been made, each of the four side flaps must be held down. They can be sewn, held with hot glue, or sealed using a heat sealer: tyvek makes a neat bond when treated with heat, but you must not heat it too long or it will liquify. I used my Food Saver to create these seams, for just over 5 seconds per seam. At 6 seconds the tyvek would melt and ruin the entire airfoil. At 4 seconds it would not make a secure bond. Timing this just right was tedious, but it beat sewing each of these seams in place.

Note that if you have a rotary cutting tool you can save a LOT of time by first folding all of your tyvek or other paper in half and then stacking all 16 folded sheets together before cutting. Tyvek is slippery, so if you use it and you decide to cut as a stack you need to be careful that none of the folded pieces slips out of position as you are cutting. Also note that you will not be able to accomplish this with a handheld scissors-- only a rotary cutter can cut stacks of materials this way and have them all come out the same.

Having said this, "all come out the same" is a perilous outcome because a single error means everything in the stack is affected. But a rotary cutter will make the production time for the airfoils into a fraction of what it would be otherwise. I highly recommend using one.

There are 16 airfoils in this kite. Creating them took over an hour. Sixteen is a lot.

There are no real tricks here. Imagine you are beginning at the lower left of the diagram (A). The airfoil here will require one 3-way corner connector at its left vertex (corner), and then a six-way connector at its right vertex and two more connectors at its top (one left, one right). Run the dowels through the seams of the airfoil and press the dowel tips into the connector. The result should look like a V. Make four of these V's in a row. This is the leading edge (A-B) of the kite.

As you insert the dowels into the ports, if the connection is too loose and you can turn the dowel easily in the port, you will want to secure the connection with a bit of hot glue by putting the hot glue on the tip of the dowel and then ramming it into the port while still molten. Do this after you have run the dowel through the seam of the airfoil, not before. Use no more glue than necessary, however, as this will make later disassembly very difficult.

Return to the left side of the kite and complete the next row, sliding dowels into airfoils and then pushing the tips into the connectors and using hot glue wherever called for, until you reach the top of the kite (C-D). As you go you will need to make sure you are orienting the connectors correctly. This is especially important if you are securing the dowels using hot glue, as fixing the problem may require you to turn a hair dryer onto the connector to loosen up the glue.

There's a thing about tetrahedral kites: because of the way they are structured, they are very difficult to make come apart: the airfoils naturally hold the dowels in place in the connectors with surprising firmness. Taking the kite apart is actually somewhat risky as you may find you need to tear an airfoil to get its dowels out.

Also, there is this: as you assemble the kite, you may discover that one or another of your airfoils wasn't folded quite correctly or was glued at an incorrect angle and that you cannot get its dowels to reach its corresponding connectors. This usually means the airfoil must be discarded and regenerated. I found that in some instances I was able to patch over the problem by creating paper "saddles" over the offending edge of the airfoil and running the dowel through these instead of the airfoil's original channel.

You may also find that one of your connectors "splits" as you are inserting a dowel tip into it. This may happen if the PLA was not laid down heavily enough during printing, but could result from any number of printing errors. These connectors will need to be discarded and replaced. This is one of several reasons why you should print several replacement connectors-- you will never know if a connector will split until you try to use it, and sometimes a connector that worked fine the first time you used it will come apart the second or third time. You need to have spares ready to go, because you can't very well fly the kite if it is missing even a single connector.

Once done, run some thick string through all four of the metal eyelets. When you tighten this string, it should pull the entire kite taught. Do not overtighten or you may break a dowel. The main purpose of this strng is to keep the kite from flying apart, not to compress it into place. There are six edges to the kite, each just over four feet long, so you will need at least 26' of string to do this.

Assembly is not fast, nor can it really be rushed.

Now it is time to attach the kite string. First, attach a piece of string a bit over 4.5' in length along the "bottom" or leading edge of the kite (A-B) by tying one end into the metal eyelet at A and the other into the eyelet at B. This string needs to attach at these two corners of the kite, and needs to be able to withstand all of the considerable tension that will be placed on the kite once it is airborne.

Next, secure this to your actual kite string about 2/3rds of the way up. You want this string to make the kite fly at a sleight angle here. You may also want to attach one or even two "tails" to the kite. If so, these should go on the other two points (C and D). Tails are often made of a series of bows-- these bows create drag, and this drag pulls the back part of the kite back. Tails run about 8' long for a kite of this size, with a bow every 12" or so, but the more bows in general the better. Not big floppy heavy bows, tight stiff little bows!

Kite launching can be tricky. Ideally, you will want a friend to help with this. What follows is a summary of what this experienced tetrahedral kite flyer has to say about launching: choose a day with steady and fairly strong (though not blustery) wind and a location free from telephone poles/ lines, trees, and other people. Have your friend stand with the kite downwind from you about 40 feet or so. Have them hold the kite so that the spine along which you have attached your strings is vertical, with the shortest part of the V shape of the string on the uppermost part (this is pretty intuitive, but see diagram if you have questions). When you are ready and a solid bit of wind comes along, give your friend a signal (like, "NOW!") and have them launch the kite upward while you pull back forcefully on the string. This should launch the kite into the air! Remember that if you are waiting for a gust, this gust will hit you a second or two before it reaches your friend-- this is how you take advantage of a gust to launch. Timing might be important, and it is on your side.

Good luck! Happy flying!

To disassemble the kite for storage, simply take it apart dowel rod by dowel rod until all of the pieces have been taken apart. Then fold the airfoils in half and store them together with the dowels and the connectors. I used a small fabric bag with a draw string for my connectors, which works great. As I mentioned in the beginning, if you used hot glue to hold any part of your kite together when assembling it, you will need to reheat this hot glue to get the dowels out of their sockets again. While reheating, take care that you do not get the PLA connector so hot that it, too, begins to soften-- it is important that these connectors retain the exact same angles on each of their ports, or the kite won't go back together again very well and maybe not at all. The ports are at very specific angles for a reason, and a few degrees this way or that will make them useless for future kites. Using a butane torch to soften the hot glue is very likely to get the PLA too hot along the way. You will need to get the connector hot quickly, but not too hot, and if the PLA softens as you pull out the dowel then let it cool with a clean dowel rod inside it to help it retain its shape. Even if it cools bigger than it was before, this is fine-- if it cools too small, however, then you will have to reheat it with butane to get it to accept a rod again, and this may cause it to go out of alignment. Just, be careful, yes? These PLA connectors are far from ideal, but they serve the purpose here well enough, and they are cheap and easy to replace.

There is a very good chance that while disassembling the kite you will either break a dowel or tear a sail. That will happen. The dowel rods are only made of wood, and the tyvek is just tyvek-- tough, but not indestructable. It is important to have enough leftover fabric and spare dowels to replace the few that will become damaged during assembly or disassembly. I broke three dowels during my first assembly, and another during disassembly. Since I had spares, this was no problem.