March 3, 2008 10:17 - Latest Dopero Kite - All Bamboo Skewers Were Not Created Equal!
The other day we went down to the Old Reynella reserve to test fly the latest Dopero kite. This one was made with freezer plastic, and its construction provided all the photos for the new How To Make A Dopero Kite page. I expected it to be a touch lighter than the black Dopero due to the lighter plastic.
The first hint that I was wrong about the weight was actually when I found the skewers much harder to snip with the scissors than usual. However, I didn't think much about it at the time. You see, we had gone through almost an entire packet of skewers and had bought a new one - from a different shop.
The second hint was when the kite was reluctant to climb, even after trying several different towing points. Stability was a problem too. This was a slight surprise since this kite had larger keels than the original black kite. Also, there was a small gap between each keel and the lower sail. This was meant to make them more 'draggy' when the kite yawed, to help directional stability. However, I had tried to get away with much less tail, and the kite just didn't like it! On top of this, the reserve was being used by a few kids. Hence we were attempting to fly in the wind shadow of a bunch of trees, near the edge of the reserve! That doesn't help at all.
'I'm not writing this up' I was thinking to myself as we came home. But here it is, from yours truly, a compulsive kite blogger...
Anyway, after arriving home I did a little test to see which kite was heaviest. On one side there was the clear plastic kite, suspended by its bridle from the 1 inch mark on my plastic ruler. On the other side, the black garbage bag plastic kite, suspended from the 11 inch mark. In between was my finger, which ended up near the 5 inch mark to get the kites to balance! So the clear kite was indeed quite a bit heavier. My ruler has both inches and centimeters by the way. This has to be the only time I can remember using the inches scale!
I'm not at all worried about the success of this kite. All it needs is a touch more wind than the other one, plus a bit more tail for stability. However, there's a lesson here for kite builders. Identical materials from different sources aren't always as identical as you think!
March 6, 2008 21:45 - Heavy Dopero Kite Buffeted By Evening Thermal Turbulence
But at least it got up there! Even after climbing way past tree height down at the Old Reynella reserve, there was enough turbulence to test the stability of the little Dopero. Some of the gusts coming through were moderately fresh, and that was just as well with those rather heavy bamboo skewer spars! Most bamboo skewers are great, but the last packet we bought turned out to be quite a bit more dense, and therefore heavier, than most.
Not happy with how the kite was coping, I waited for the next forced landing before making some changes. The tail was lengthened by undoing one end from the spar, knotting in another loop, then re-attaching the tail to the spar. That made things much better. However, the wind was constantly varying between almost calm and just enough to climb the kite. Hence I ended up doing a series of short flights. Climbing to about twice tree height in the gusts then reeling it in during the lulls. Sometimes walking back to keep it in the air a bit longer. Since the wind was marginal, I also moved the towing point back a centimeter or so. So easy to do with that fancy Prussik knot! (It's about 3/4 of the way down the page.)
This kite has a tendency to drop its nose and dive at times, so I might take a paper clip or 2 along next time. I'll see how its behavior changes when it's slightly more nose heavy, or tail-heavy. Slipping the clips on the leading or trailing edge will achieve this.
Finally, I tired of this semi-flying that was going on, and pulled out the MBK Sode kite. I've only made one of these, and it's looking a bit the worse for wear! Particularly since that gale it flew in down at Brighton Beach... Up it went, with its long thin tail just starting to catch the rays of the setting sun. Aren, my 2 year old, held it for a while before we reeled it in and headed home.
Once home, I patched up the Sode with a few extra pieces of tape. I also shortened the very long tail. However, I made the remaining length more efficient by adding pieces of tape to hold the plastic loops open to catch and drag against the wind better. We'll see how this kite goes next time!
March 18, 2008 14:00 - Box Kite Smashes World Altitude Record!
Our little box kite world that is! Aren and I trundled off to the Old Reynella reserve with the clunky little foam box kite stashed in the bottom of the pram. For those who can remember earlier posts on this blog, the kite was now all repaired and re-bridled to fly on its narrow sides. Also, some foam was scraped away near the bridle attachment points to shift the towing point forward as far as possible.
To give you an idea of the small size of this kite, it's sitting on a swivel-chair in the photo above. This kite needs almost gale force winds to have any hope of flying well, but the gusts coming through seemed pretty fresh. Small branches were moving around, and there was plenty of leaf noise. Even some larger branches were moving at times. It was worth a shot! We arrived, and the flying line was soon attached to the bridle with a Lark's Head knot.
Well, the kite managed to hover at shoulder height a few times. The air not being particularly smooth near the trees, the kite sometimes darted from side to side in the stronger gusts rather than climbing. I even did the little kid thing, running upwind and towing the kite a bit higher. Bit of a role-reversal really, with my 2 year old watching on, from his pram! Eventually I gave up and took Aren across to the play equipment.
After some time I realized that the wind had actually picked up again. Now, it was seriously stronger! Aren was conveniently parked in a swing, all cute in his hat and blue sunnies (that's sunglasses to non-Aussies). Hoping he wouldn't mind too much, I quickly got the box kite ready again. This time, it caught a massive gust and willingly swirled around several meters up. Well well! I moved away from the swings to let the kite have some more room.
With the next gust whistling around my ears and humming the flying line, the little foam box kite actually soared up and clung to a height of around 10 to 15 meters for a short while. Stability could be better, but this kite definitely flies! Box kites aren't known for high line angles, particularly small ones, so I was reasonably happy with the 20 to 30 degree angle of this rather heavy foam kite. The foam slabs came from the packaging of our microwave oven.
We'll be on the lookout now for thinner slabs of foam to make an improved model of this kite. We'll make the gap between the upper and lower cells bigger for extra stability, and perhaps use sandpaper to round off all the square edges. Onwards and upwards!
March 21, 2008 20:37 - New Roller Kite Soars Over Suburbia
Well, over our roof and briefly over the neighbor's property anyway! This is the new MBK kite for this month, although on the website it will actually be second-last in the series. That leaves the relatively complex and fiddley Dopero as the ultimate single-skewer-span MBK kite.
As a reader of this blog you are now privileged to know that a new round of MBK kites is just around the corner. Starting from next month, the basic types will repeat. All the way from simple diamond to the Dopero. However, they really are new kites because they will all be ... wait for it ... two-skewer-span kites! This will involve a little more snipping and gluing of bamboo than usual, but the reward will be more accurately made kites with considerably better light wind performance. I'm hoping that some of the tail-less types will actually fly without tails this time!
Back to the Roller kite! It was breezy outside, but nothing too wild. Having read about Londoners flying their German Roloplans out of small parks in the 1930s, I wondered if the MBK Roller might be ok out of our small backyard... It wasn't long to sundown, but out I went with the new Roller hitched to a 50 meter Dacron line.
The kite was soon up, and it was indeed promising! A couple of times I let it out to above roof height, but the stronger gusts always sent it down onto the lawn or the roof. It was easy to drag off the roof and into the air again. A couple more loops of tail improved stability in the fresh gusts. Also, I shifted the towing point forward a centimeter or so. These 2 changes resulted in the little Roller happily flying between 2 and 3 times roof height! Believe me, I had very little room to move on the ground. Danger lurked in every direction if the kite decided to go down suddenly.
There were a few lulls where the kite had to be reeled in quickly to avoid losing it in someone else's property. Or the rose bushes. Or the TV aerial. In the end, it did snag on a tree. No drama however, since it was a small one in our spare driveway, and I managed to pull the kite free. Not wanting to take any more chances, I went inside, very happy that the Roller Really Rocks!
March 23, 2008 21:17 - Roller Kite Reaches For The Sky At Semaphore
We've just been to 3 days of the Adelaide International Kite Festival, and taken a lot of photos and video. However, rather than blogging them here, most of our kite festival experiences will end up as new web pages on My Best Kite. Of course, you can just visit the site every few days and click on What's New to catch up on all the kite festival action!
Today we went to Semaphore beach specifically to catch the Rokakku Challenge - a traditional Japanese Rok Battle! Again, this will end up as a new web page. The page will feature a movie of the entire thing from airborne start to the last Rok flying triumphantly at the end! After this was all over, we ended up flying the new Roller kite a few hundred meters north of the festival site, in the low sand dunes near the beach.
At first, the Roller insisted on flying left, even looping into the sand during the stronger gusts. The wind was a light to moderate but gusty South to South-westerly, and not a cloud in the sky. With the kite flying, it was obvious that the left upper sail panel was slacker than the right panel. Taking down the kite, I pulled the right side tethering line through the tape a little to even things up. Up went the kite again, a bit better but still leaning left.
Oh well, it obviously needs more. So I took the kite down yet again and adjusted some more. At this point it was clear that both sides of the upper panel were far too slack, which was affecting performance. The kite went up quite straight this time, but never flew at better than a 50 degree line angle. However, it flew nice and stable, only looping around once or twice in particularly strong gusts. We were able to let out nearly all the 50 meters of line. We all had a fly. Myself, my wife May (in the photo) and 2 year old son, Aren!
The process of making and flying 3 Roller kites, that's including the first 2 Dopero kites, has taught me a thing or 2 about making and flying this double-sail style of kite on such a small scale. Firstly, the gap between upper and lower sails needs to be bigger, proportionally, than on larger scale kites. Also, adjustable tether lines on the upper sail are useful for trimming out any tendency to hang left or right, near the top of the wind range for the kite.
March 30, 2008 08:16 - Roller Kite Frolics In Fresh Conditions
Having tightened up the tether lines on the new Roller kite, I was curious to see how the kite's performance was improved. Off we went, all 3 of us, to the Old Reynella Reserve. The weather was breezy, with the rain clouds of the previous few days finally starting to clear from the North West. After connecting the flying line to the Roller, it went straight up but was soon on the ground again.
To summarize the next series of short flights, I found it necessary to move the towing point forward to cope with the wind strength. Also, with the tether lines re-done, I had to to pull one of them through the tape a bit to trim out a tendency for the kite to loop to the right. Eventually the kite behaved itself, and flew reliably with about 30 meters of line out. Mind you, the little Roller was pulling strongly, and the line trembled and twitched as the wind tore at the kite.
Performance-wise, this kite was still a bit disappointing, hanging around the 30 to 45 degree mark a lot of the time. Kites do hang a bit lower when flown near the top of their wind range, since drag forces start to dominate. I won't get into the aerodynamics here, let's move along... Occasionally, higher line angles would result when some rising air came through. There was plenty of sunshine to generate thermals, despite the considerable cloud cover all around. At one stage, the kite behaved like the black MBK Dopero did a few weeks ago, floating almost overhead in rising air, the flying line quite slack and bowing all over the place. It's like having a little model glider on the end of a string!
So why the poor performance? Well, for one thing, the lower wing is quite small, with a relatively thick spar across its leading edge. Also, I could have attached the sail to the spar a bit more accurately and neatly! All in all, I think that lower sail is contributing a lot of drag. Plus, a fair length of tail is being used to keep the kite stable in fresh wind. The Pearson Roller is a great kite design, but it was never meant to be made this small!
Also, the trailing edge of the upper sail vibrates in strong wind, which creates extra drag. I've read about this problem, as it sometimes affects standard sized Roller kites.
On the plus side, with careful trimming and enough tail, this is really a fun moderate wind kite! Somehow, the vibrating trailing edge sound effect can add something too, as stronger gusts come through. The kite moves over a large area of sky in response to thermals coming through. Sitting low and pulling hard in sinking air, soaring much higher in rising air, with a slack line as it glides down. Being forced far to the left and right when it's close to the limits of its stability in stronger gusts. You have to work harder with a little kite, making sure it doesn't end up in surrounding trees!
With just the right wind speed, and with the towing point set a bit further back, I'm sure this kite will have a flying line angle of around 50 degrees or so. Not great, but respectable, in other words!