I wanted
to build something spectacular, and decided that, in terms of bang for
your buck, a large snowflake would be hard to beat. In spite of its complicated
appearance, this kite is actually quite easy to make. Nevertheless, I wouldn't
recommend it as a first kite to build unless you are already competant
at machine sewing, and if I'd had any sense I'd have built a pely-box
first, which presents similar challenges in tensioning the sail, but on
a smaller scale. But as a second or third kite to build, you couldn't do
much better, judging by the number of admiring looks and comments I got
on the maiden flight. (If you're looking for a first kite to build, try
Charlie Charlton's Jewel
Kite ©Charlie Charlton which will give you
all the experience you need.)
Here is a picture of it, flying with a spinsock and a pig windsock (purely for effect). (Someone else's shark is in the background.)
The constructional details in these plans are entirely original, but the design is based on a picture of a snowflake on the cover of Morgan's book.
This is a light to moderate wind kite. Being big, it moves slowly and majestically, responding well to a strong but slow pull on the line. Once you get it airborne it just sits in the sky as steady as a rock, looking like a huge chunk of crystal.
First some vital statistics. The diameter is 2m, as is the front-to-back depth. The total raw sail area is 12.67m2, but since many of the panels are vertical or at a high angle, the effective sail loading area is 3.85m2. The total weight is around 1100gm, giving an effective sail loading of 285gm/m2.
From a close look at the sketch, you will see that it is made up entirely of squares: three large ones, six two-thirds the size, and six one third the size. Each square of the smaller sizes is sewn across a diagonal to a corner of a square of the next larger size. Study the sketch until you can see this clearly, otherwise much of the following discussion and instructions will be hard to follow. The kite is supported by a circular external frame made out of 6 lengths of fibreglass, and by a 2m length running through the centre perpendicular to the plane of the external frame.
I wanted to make a big one, and 2m seemed a good size. It also turns out to make particularly good use of standard 1.5m width ripstop. Talking of which, you will need the following materials:
Cut two test squares of ripstop, each about 50mm square, the first with the diagonals along the grain of the fabric, and the second with the sides so aligned. Take each one in turn, place it on a table and hold it down, in slight tension, with three fingers of one hand on just three corners, which we will call A, B and C. Now take the fourth corner, D, between thumb and forefinger of the other hand, and pull it in different directions to see in which directions it has any freedom of movement.
You will find, with the first square, corner D moves fairly freely in a direction parallel to AC but resists stretching along BD. My first thought was to cut the ripstop in this orientation on the grounds that the main tension would be diametrically through the kite, and hence through the diagonals of the squares from which it is build. But this experiment shows that this would be disastrous, allowing three of the vertices of the external frame to move in one direction out of its plane, and the alternate three in the other, so relieving the diametrical tension and causing the kite to collapse.
In the second test square, you should have found that the fourth corner was much more stable, provided you kept the edges in tension. My design therefore tries to concentrate tension along the edges of the squares, using edge-binding rather than simple hemming to allow them to take extra tension. Another point you will have noticed is that as you stretch the square along one diagonal it contracts along the other. This means that if the external frame of a snowflake kite is of fixed size, the sail can be tensioned within it by stretching it along the central spar. I used straight stitches on the edge binding which is not meant to stretch, and a small zigzag stitch on sewing parallel to the central spar, to allow a little stretch. This stretch can only be used for fine-tuning though. Try giving the second test square a good tug along a diagonal and then lay it flat on the table. You will see that it has distorted irreversibly.
The basic problem with a hexagonal frame is that each side of the hexagon has 2 sail attachment points pulling on it and tending to bow it inwards. What is more, the 6 main sail attachments place the whole frame in compression, which tends to encourage any bowing once it starts. I have seen a bigger snowflake than mine (about 2.5m, built by Phil Tolman(?) of the Great Ouse Fliers) using a hexagonal frame, but this used much thicker dowelling. To keep the weight down, my solution is to use a circular frame made out of 6 lengths of fibreglass. Each needs to be 4.7% (2*pi/6) longer than the sections of a hexagonal frame for the same size sail. They need to be joined by rigid joiners, which have to be quite strong.
If your fibreglass rod comes in metre lengths (or 2 metre or 3 metre lengths) you may like to scale down all dimensions by 5% to save a lot of wastage. If you have the choice of rod or tube, take the rod; fibreglass tube may well split at the ends. But if tube is all you can get, get some fibreglass rod (or any other kind) which is a snug fit inside the tube, and glue a short length into each end of each section of tube, using epoxy adhesive. This prevents the tube from being crushed by the bending force at the ends.
The choice of material for the frame joiners is critical. Flexible tubing simply won't hold the frame circular, even with the 6 main sail attachment points pulling them in. I tried aluminium tubing of about 1mm wall thickness, but this fractured on the first field assembly attempt. If you can find two sizes of aluminium tubing, one of which snugly fits inside the other, you could try a double joiner.
I settled upon steel tubing - I found some just the right size in a hardware superstore (B&Q in UK). The only disadvantage is that it rusts - salt water contamination is particularly bad, and you must always make sure the kite is bone dry before you pack it away. You could try a rust treatment; look for a rust converter, and one that claims to add a hard protective (phosphate) layer and doesn't insist you overpaint it as soon as possible.
8mm brass ferrules are available from kite stores, but they're not cheap when you need 6 of them. I have heard that they can fracture when used in a very similar way for the frame of a circoflex. Another possibility is to contact the after sales service department of a manufacturer of dome tents - these are framed with bowed fibreglass rods joined with just the right sort of ferrule. It has also been suggested that a sockist of hydraulic parts would have various types of tubing. Whatever your source, the ideal would be stainless steel tubing - if you can get it then go for it - and get me some too while you're there!
You will need templates. For the larger two sizes, cardboard is not suitable.
I made up a triangle of 18mm hardwood strips, with two sides 1426mm and
the hypotenuse 2016mm, as shown in Fig 1. I mitred all ends of the strips
before but-joining them by placing small triangles of hardboard over the
corners and fixing them to the strips with a staple gun.
You can use the template to draw half a large square on the fabric, then turn it round with the hypotenuse against the already-drawn hypotenuse in order to trace out the other half. Mark points 955mm from the apex of the template on each of the equal sides in order to use it to mark out the middle size squares. Check the diagonals for equality before cutting out. The smallest size squares can be marked out using a 482mm square of card.
Cut two of the largest squares in half along a diagonal. Don't cut the third!
The first step is to assemble all the large squares, as shown in Fig 3.
Lay the uncut largest square on the floor. Take one of the halved squares
and crease a 6mm fold along the cut diagonal edge (which you didn't edge
bind, did you). Now place this on top of the uncut square and line up the
corner and the edges. This should leave the folded edge 6mm from the diagonal
of the uncut square, and the fold folded under. Temporarily hold it in
place with pins inserted at right angles to the fold. Carefully turn over
the uncut square with the halved square attached, and similarly fold and
pin another halved square on the other side. Taking care to avoid bloodshed
from the pins, you can now sew both halved squares onto the uncut square.
Use a small zigzag stitch to allow a small amount of stretch. You can sew
over the pins without difficulty, removing them afterwards. Repeat with
the other two halved squares on the other half of the uncut square.
For the closed pocket (Fig 4), cut a piece of dacron tape (as used for
the leading edge of delta sports kites) 25 by 100 mm. Also, cut a piece
of ripstop 37 by 112 mm, the same colour as the uncut large square. Use
this to cover the dacron, folding 6mm of ripstop along each edge over the
edge of the dacron, and sticking the folds down with seamstick tape.
Place the strip over the end of the diagonal of the large square, ripstop-covered side up and overlapping the diagonal by 60mm. Sew it on. Some of the stitches will go through the cut diagonal edges of the other two large squares, giving it extra strength.
Now turn the kite over, and fold over the free end (40mm long) of the dacron strip, and sew the edges to make a pocket. Sew to within 10mm of the fold in the dacron strip only. You need plenty of stitches here so sew up and down several times. (On the prototype, this pocket burst open on a heavy landing with the kite a little over-tensioned.)
The closed pocket is also used as the main towing point for the kite, as follows. Cut a piece of 6mm dowel 35mm in length, and cut notches in each end. This should slip comfortably into the fold of the dacron strip, perpendicular the spine. (Now you know why you weren't to sew the dacron all the way to the fold.) Take it out again and burn a small hole in the centre of the fold of the dacron such that if you insert the spine into the pocket you can see the end of it through the hole. (A soldering iron with a small bit is suitable for buring holes.) Cut 150mm of 110lb line, fold it in half and tie an overhand knot to make a loop. Pass the fold of the loop through the burnt hole, up through the pocket and out of the open end. Larks head this to the piece of dowel and then pass it carefully back down the pocket, pulling the knot as it goes, and locate it in its position in the fold of the dacron. The notches in the two ends of the dowel will now be protruding either side of the pocket. The dowel can be prevented from slipping out by taking a short length of line, passing it over the notches in the ends of the dowel (outside the pocket), and tying it. Secure the knot with a drop of superglue.
First cut a piece of dacron tape 120 by 50mm, and a piece of ripstop 132
by 62mm. Fold the ends of the ripstop over the ends of the dacron and sew.
The velcro should be 25mm wide. Cut a piece 40mm long. Sew one half of
it to each end of the dacron, along the edge and covering half the width
of the dacron (on the ripstop-covered side). The dacron will be folded
in half along its length, but before doing that, sew it onto the kite,
half its length overlapping the spine of the kite and half its width (the
half with the velcro on) free to fold over. You can use plenty of stitching
to make it strong. Now fold the dacron over along its length and sew the
edges together to make the tube. You should now be able to fold it over
and secure it with the velcro. You should have sewn it to the same side
of the kite as the opening in the pocket at the other end.
Finally, burn two small holes either side of the pocket. You can thread a short piece of line or chord through these and then tie it over the folded pocket to prevent the velcro coming undone under pressure - it's barely strong enough without.
You can now cut the spine, initially 2020mm. You will probably want to cut it in half for easy transport and storage, joining the two halves with a ferrule (a piece of metal tube into which the dowelling fits snugly). Anyway, leave it in one piece until the end, and if storage and transport aren't a problem, don't cut it at all.
You will also need to sew some pieces of ripstop to the kite along the length of the spine to make small tunnels to hold the dowel in place. I used four, each made from 75 by 50mm strips of ripstop folded in three to give 25 by 50mm patches, sewn to the kite along their 50mm edges. In fact, five would have been better. Before sewing the patches to the kite, sew along the 50mm edges so the spine can only pass between the patch and the kite, and not between layers of the patch. Make sure the middle patch allows the plastic tubing to pass through, if you are using that method - you will need to sew quite close to the edges of the patch.
Lay the kite flat on the floor and place a middle size square over the corner of one of the large squares, carefully positioning it so that two of the sides and one corner coincide. Place a long straight edge (such as a strip of the wood used for making the template) between the large and middle sized squares, along the diagonal of the middle size square parallel to the spine. Removing the middle sized square, mark this diagonal on the large square with a coloured pencil. Also mark the diagonal of the middle size square. Either side of this line, place pieces of double sided tape (as sold in stationary shops). The pieces should be in pairs, either side of the line, at frequent intervals, and leaving sufficient space between them to sew. Now reposition the middle size square, and when exactly in the right place, firm it down onto the double sided tape. You can now sew the middle size square onto the large one.
My experiment suggested that you should use a small zigzag stitch, but I think a straight stitch is less likely to tear the ripstop, so I suggest you only use the zigzag along the spine. Even a straight stitch has sufficient stretch for the remainder of the kite.
Sew the other five middle size squares similarly.
Looking carefully at the picture, you will see that each large square has to be sewn to an adjacent middle size square, a third of the way in from the tip of the large square. On each large square, measure along each edge and mark a point 472mm from the corner. Join the two marks on a large square with a coloured pencil line. Lay the adjacent middle size square over the corner of the large square, secure with double sided tape and sew, as before. You have to do this 6 times.
You can now sew on the smallest size squares, using the same method as for the middle size squares.
The external frame is made out of six 105cm lengths of 8mm fibreglass rod,
joined with 4cm lengths of steel or brass tube, as shown in Fig 6. Actually,
you should initially cut the fibreglass 107cm long and trim them later.
A small piece of dowel inserted in each piece of tube prevents the metal
cutting through the fixing lines.
For each frame joiner, cut 4cm of tubing. Also cut 1cm of 8mm dowel (or 8mm dowel sanded down to a snug fit) and insert it into the tubing, pushing it to the middle. Drill a 3mm hole through the tubing and the dowel inside it. Temorarily remove the dowel and enlarge the hole in the tubing to 4mm. Carefully deburr the hole.
There are several possible methods of attaching the corners of the sail to the frame, but the method I used worked very well. My sewing machine has a special foot for sewing a cord onto cloth, but you can make one by filing a groove in the underside of a standard presser foot, exactly in line with the line of sewing. A piece of line can then be located in the groove and sewn onto a piece of fabric.
Cut a 15cm length of 80lb line and sew it to the edge binding of a corner of a square, with 7.5cm running down each edge of the corner. Sew to 1cm of the corner but no closer. Another short piece of 80lb line can now be passed through this loop and through the hole in one of the frame joiners, or around one of the frame rods, as appropriate. Initially tie this second piece of line so that the corner of the square is 1cm from a frame joiner, or just touching a frame rod. This will give approximately the right tension.
If you find it impossible to assemble the final connector, measure how much you would have to shorten one of the frame rods by to do so, then cut a sixth of this off each. Adjust the length of the spine, if necessary, so that there is sufficient overlap of the velcro to hold reliably.
You should be able to adjust the tension of the whole kite by adjusting the velcro spine adjuster. Get the spine as tight as you can, then check the remainder of the sail. If any parts of it are slack, adjust some of the loops which hold the corners to the frame. Unless your sewing is a lot more accurate than mine, you may not be able to get the whole sail absolutely taught, partly because the weight of the sail and the spine will result in greater tension in the upper parts. This doesn't seem to matter too much.
The bridle is not critical, the dimensions I give being simply what I ended up with rather than the result of any sophosticated design process. I used 110lb line. For the 3 leg bridle, the lower legs are around 180cm each. Tie one end of each to a frame joiner, passing the line through the loop which attaches it to the sail, so that it can't slip off the joiner. Tie them together with an overhand knot near their free ends, making sure the knot is the same distance from the two frame joiners. The upper leg should be around 220cm. At each end, fold it over and tie an overhand knot to make a loop. Larkshead one loop to the knot joining the lower legs, and the other to the knot attached to the closed pocket at the front of the spine. Finally, larkshead a small aluminium ring to the upper leg, initially about 160cm from the closed pocket. After final adjustment, convert the larkshead to a prussic knot.
If you want to use a 2 leg bridle, it should consists of around 4m line, attached to the kite in the same way.
Offer the kite up to the wind by holding the bridle near the aluminium ring. Try different positions until you find the point at which it seems to lift best. If it fails to lift, try positions closer to the fixed pocket; or if it seems unsteady, try moving away from it. Move the ring to the position you find best and let it go!
The snowflake is normally a very stable flyer but may veer to one side if the sail is unbalanced or slack. It should fly fairly quietly but if the sail goes slack it can make a noise like a large gas burner. If the wind drops, it falls quite slowly. A firm pull on the line just before it lands effects a gentle touch-down.
Whilst a tail or drogue is completely unnecessary, it can add to the visual effect. I've used a tubular plastic tail, a small pig windsock and a small spinsock - I think the spinsock looks best.
