The Rokkaku dako (六角凧) is a traditional six-sided Japanese fighter kite. Traditionally, it is made with bamboo spars and washi paper. The rokkaku kite is often hand painted with the face of a famous Samurai. The structure is a vertically stretched hexagon with a four-point bridle. One spar runs from tip to toe, and there are two cross-spars. Flown on a taut string, the kite is stable and rises rapidly. When the line is released, the kite tumbles until tension is put on the line, at which point it takes off in the direction of the spine. Fighting two or more of these kites involves tipping over or destabilizing the opposing kite or cutting its kite line or bridle. The frame of a Rokkaku kite looks similar in shape regardless of the overall size. The thickness and strength of the spars are just scaled up or down depending on how big the kite is. Most Roks are just under 2 meters (6 feet) in height, since this is the most common size in a kite battle. These types of kites are everywhere, from small ones turned out from children's kite-making workshops right through to large expensive air-brushed versions for sale in kite shops. There's always a few big Roks floating around at our local kite festival each year!
Stability can be increased by bowing the cross spars, making the kite stable enough to fly without a tail. The rokkaku kite is often used for kite aerial photography and in atmospheric science, thanks to its large surface area and simple construction. Some guys working for the Institute for Marine and Atmospheric Research Utrecht (I.M.A.U.) have used a couple of Roks for scientific purposes, way down in Antarctica. Due to the extreme cold, these kites were specially designed to be rigged while the flier is wearing thick gloves. Their 2 meter and 1.5 meter Roks were used separately or stacked together, to provide the required lifting force in a variety of wind conditions. The payload was atmospheric measuring equipment, hoisted to the considerable height of 600 meters (2000 feet).
Having corrected the spar curvatures, I just couldn't resist flying the Dowel Rokkaku kite again. The results? Well, the sub-title up there says it all! The sizeable Rok is now a delight to fly, in any part of its wind range.
On our way to the reserve, it seemed that conditions were very light indeed. Hazy mid-level cloud covered much of the sky, although plenty of sunlight was getting through.
On arrival, the Dowel Rokkaku kite was soon rigged. Then it took off willingly in the first light puff of breeze to come through. I had adjusted the towing point well back, to get the most light-wind performance out of the kite.
However, there seemed to be a sharp increase in wind speed above 40 feet or so! This often happens in this location with some wind directions.
Today there was a Westerly, which was slowed down near the ground by a grove of trees a short distance upwind. I flew the Dowel Rokkaku on just 60 meters (200 feet) of line for a while.
It was very satisfying to see how the kite reacted to gusts, now that the horizontal spar curvatures were fixed. There was no tendency to pull left, as it used to do even with some hefty adjustments in the bridle loops.
All it took was some careful rubbing away at the spars on one side, with a wood file. This reduced the diameter of the dowel just a fraction. Hence, the bend on that side matched the other side more closely, with the spar under tension from the bow-line.
Occasionally there were some lulls with not quite enough wind to keep the kite at a high angle. So, a little 'working the line' had to be done to keep the kite out of trouble. I had just started to enjoy some higher flying by letting out even more line, when the bottom right spar cap pulled away! The first indication of this was when the kite started slowly looping to the left.
The Dowel Rokkaku kite had been getting thrashed by some very fresh thermal gusts. Thermals were getting more active, as you can see by those juicy Cumulus clouds in the photo down there on the right!
Looping to the left? That didn't make sense at first, since normally a kite will loop towards the side with less effective sail area. With the bottom-right part of the sail flapping away loose, that was the right hand side!
When I thought about it again, after getting home, a possible reason occurred to me. Without the sail being anchored to the lower spar on the right side, perhaps the vertical spar was being bowed to the left. This, plus some sail billow, would have acted like a rudder, steering the kite into a loop to the left, and overcoming the sail area imbalance.
Anyway, enough of the technicalities, which tend to make most people's eyes glaze over...
The Dowel Rokkaku kite was right over power-lines and a road. Not a problem at over 300 feet, if you are monitoring it. But now it was time to move quickly. I also needed to clear the trees at the edge of the reserve. The wind direction was not helping, since it had shifted more towards the North.
To summarize the next few nerve-wracking minutes... I moved cross-wind which gave the kite a little more room, while also pulling down line onto the grass. The sail problem also affected the trim of the kite, increasing the tension in the flying line! But I had no choice, since every loop was losing several meters of altitude. Just keep hauling it in, and hope none of the spars snap!
Soon the Dowel Rokkaku kite was safely on the grass, just a few meters inside the row of trees. During the last few loops I had watched the kite's shadow flitting across the trees' foliage. This gave me a clue that all was going to end well!
After fixing the spar cap, I reinforced all the others too, just in case. You can see the black bits of extra tape in the photo over there.
Immediately after re-launching the Rok, I backed off just a short way, put the line underfoot and snapped off a few photos.
Following the line back a bit more, I had the kite on about 20 meters (70 feet) of line. This time, the kite posed for some video. There's some of it near the top of this page.
We walked all the way back to the original tether-point. The winder was still lying near the tree, the line wrapped a couple of times around the trunk.
From here on, it was an enjoyable high flight. Strong thermals were passing through, but the Dowel Rokkaku kite took them all in its stride. Sinking air occasionally made things interesting with sudden losses of altitude! Wind direction tended to shift around quite a bit too.
Despite extremely light winds at ground level, thermal gusts occasionally bent the Rok severely. Impressively though, the kite remained true, with not a hint of wanting to loop left or right.
I wished I had shifted the towing point forward a little when I had the chance. Still, the kite was coping. We left it up there for at least half an hour, still tethered to the small tree.
Once in a while I had to grab the line to keep it clear of the leaves of a nearby large tree.
Naturally, some of the time was spent craning our necks to appreciate the kite wandering around almost directly overhead on 120 meters (400 feet) of line! This got mildly interesting in one case where it decided to head directly down-wind for a while. Of course, this soon became a steep dive towards the ground... Don't worry, it pulled out by itself.
Just before deciding to take the kite down, 2 pelicans flew over at a fair height. They were probably higher than the Rok. As usual, they were not flapping, preferring to soar on any scrap of rising air they encountered along the way.
A nice way to finish a great flight with the Dowel Rokkaku kite
Bridle. When it comes to bridles, there is some variation. Generally a 4 point bridle is sufficient for the standard 2 meter Rok. The bridle lines attach to the cross spars, midway between the vertical spar and the edge of the kite. Kites this size or larger can benefit from an extra 1, 2 or even 3 bridle lines attached to the vertical spar. This helps the spars resist bending out of shape in strong winds.
Most artistic Japanese kites were developed in the Edo period from 1603 to 1867. At this time, Japan was closed to foreigners. Different designs originated from different regions of the country, including, presumably, the Rokkaku. Since the earliest times, some Roks have been adorned with the faces of heroes from Japanese folklore. In 1649, the Sanjo Rokkaku fighting kite festival began at Niigata Prefecture in Japan.
There is actually a Rokkakudo Temple located in central Kyoto. Since the rokkaku part of the name refers to the hexagonal shape of the temple, there seems to be some connection. Only historians would know which came first - the kite or the temple! Sanjo is a location in Kyoto Prefecture, hence the traditional name, the Sanjo Rokkaku.
Size. Most plans and write-ups for Rokkaku kites feature a vertical spar around 1.8 meters (6 feet) long. This is because the most commonly accepted size for Rok Battle kites is 6 feet. Kites bought from stores vary a bit more with one well known shop selling sizes from 1.2 meters (47 inches) tall through to 2 meters (78 inches) tall. There's that 6 foot measurement again! There also seems to be the occasional bigger home-made Rokkaku kite, say 7 or 8 feet tall, flown for recreation. And of course, the Kite Aerial Photography crowd have always loved their super big, stable Roks!
Shape. Rokkaku kites all look pretty much the same in outline, with six corners, a long vertical spar, and two bowed cross spars. There are 2 widely used proportions in particular, named 4,5,6 and 3,4,5. For example, 3,4,5 means that the kite is 5 units tall, 4 units wide, and the main body - the rectangular bit - is 3 units tall. That means the cross spars are 1 unit in from the top and bottom.
Construction. The Japanese like to refer to the kite frame as the 'bones', and the sail material as the 'skin'. A modern Rokkaku kite might have pockets in the sail, into which the ends of the spars are inserted. Then the cross spars are bowed, and the kite is ready for flight. Not much to it really, a small price for having something collapsible and easily transportable. Browsing around, I came across 3 separate methods for holding a bow in a cross spar...
- Kite aerial photography page of Scott Haefner describing his rokkaku and other kites
- Using a kite to measure wind speed
- Rokkaku designed for kite aerial photography
- http://www.my-best-kite.com/rokkaku-kite.html this is a genious site!
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