January 1, 2009 20:55 - 2-Skewer Sled Kite Tests 20 Pound Line
We went down to Christies Beach for a New Year's Day lunch on the sand with our trusty ermm... tent thingy, shelter, whatever it is. It uses built-in sand anchor bags, which was just as well today. The sea breeze was pumping, powering up the rocky slopes and giving a free ride to dozens of slope-soaring sea-gulls.
Eventually, after some family time with wife and 3 year old boy, out came the 2-Skewer Sled Kite. Wasn't game to try the Dowel Sled, I think it would attempt to rip my arm off in the stiff wind. It's meant to be a light-wind kite after all. Soon, after the usual tantrums my Sled kites are prone too low down, the 2-Skewer kite was high and stable. Only just stable mind you, while exploring the extreme limits of its flight envelope! Line angles were around 60-65 degrees. The only reason it ever went lower was when wind strength increased still further, forcing the kite back down or to one side or the other as it struggled to point upwind.
The flying line, despite being as taut as a banjo string, did not make a huge amount of noise. Putting my ear next to it, it was whistling though. Perhaps the noise of the surf, and wind flowing past my ears drowned out the noises from the line. I tried an experiment. I held the winder tightly but let my arm dangle loosely by my side. In the strongest gusts, this very modestly-sized Sled managed to pull my arm up past 45 degrees, maybe 50, from my body! You'd be surprised how much weight there is in a human arm.
Well, the 20 pound twisted Dacron held, I'm glad to say. I don't think it's ever been loaded so far for so long as during today's flight. My wife May grasped the line at one stage, intending to fly the kite for a few moments. She made a face after barely moving the line at all! To bring the kite down, winding straight on just wasn't an option. I pulled the line down onto the sand, a meter at a time, and finally got the kite down.
The 2-Skewer Sled has a decent wind range for something made out of bamboo and plastic. Oh yes, a bit further down the beach, a kid was having trouble keeping a small shop-bought Delta in the air. I could see the leading edge spars flexing massively, as it got forced to the sand time after time...
January 9, 2009 11:02 - Dowel Eddy Kite Imposter
You see, it was actually an MBK Dowel Diamond up there in the fresh Southerly blustering across the Wilfred Taylor Reserve in Adelaide's southern suburbs. However, the resemblance to an Eddy is no coincidence. I actually researched the Eddy design in order to make this Diamond quite similar in dimensions and bridling. Every Dowel kite in the series is going to be tail-less. Also, every kite will break down into a slim roll-up package like the Sled. So far, so good with the Sled and the Diamond!
The setup procedure went smoothly... almost. I managed to break off part of one of the insulation tape ties on the vertical spar when tightening them. Another small re-design effort might be needed there. The horizontal spar seemed pretty secure in its pocket. At the other tip of the spar, it proved much trickier than anticipated, to tie off the sail corner strap. I ended up just looping it round the bow-line and then looping it around itself several times, back towards the spar tip. Would it actually hold?
At this date, the How To instructions for this kite show my first effort at securing the sail wing tip corners to the spar. I'll be updating the page shortly, to reflect the much more practical Pocket-and-Strap method which the current kite uses.
As you might tell from the video, the wind conditions were trying. The Dowel Diamond was at the top end of its wind range, occasionally being forced into horizontal flight to the left and right, and even into a loop once. At other times, the kite was perfectly balanced, exactly downwind, when it would get hit by gusts so strong that the bow line would momentarily slacken off! That's scary, given that the horizontal spar is so tight you could use it as a bow and fire an arrow with it! At those moments, the billow in the sail was so extreme that the kite seemed to shrink to half it's usual size in the sky. Luckily the spar didn't snap.
Overall impressions of the Dowel Diamond? It's not fair to say too much yet, since it hasn't had a chance to shine in smoother and more moderate breezes. However, its stability is impressive, no tail and all! I was expecting it to be a bit temperamental low down, like the Roller or Dopero 2-skewer kites. The generously bowed spar and lower sail billow combine to make this kite very predictable in the air. On the other hand, I think I've been spoiled with those super high-performance 2-Skewer kites! This Diamond flies at lower line angles and responds much slower to changes in the wind.
Oh yes, after all that drama in the air, the sail strap did hold! Not only that, but also through a number of bumpy ground-launches after forced landings. Quite surprising, but also really nice, since how can you get a simpler system? It's perfect!
January 12, 2009 21:39 - Dowel Diamond Starts To Show True Colors
Well, you know what I mean, despite it being just a plain pale orange Diamond to look at! It went high yesterday, in a gusty moderate Southerly breeze down at the reserve near the school.. The first few times out with this kite were disappointing. The previous blog entry describes the initial test flight in which the tail-less Dowel Diamond was battered by very fresh and gusty winds. I persisted, since I need to know the kite's limits in order to pass that information on!
The next couple of flying sessions were in more moderate winds, but a problem showed up. The kite would persistently turn to the left, but at times mysteriously straighten up for a while. This was surprising, since I had taken the usual care with cutting the sail and fitting the spars. Not only that, but this was a sizable kite, and it's not hard to be accurate at this size. Eyeballing the whole kite while it was in my hand and billowing in the breeze offered no clues. The sail seemed to billow evenly on both sides. Looking down the vertical spar like a pool queue, it looked straight as an arrow. The bowed horizontal spar looked fine too. What the heck was wrong?
One little detail did appear. The spar pocket had stretched a little, plus perhaps it was misplaced a tiny amount to start with. Result - the horizontal spar was off-center by a significant amount when tensioned up. Maybe a full centimeter, which would cause a small weight shift to one side. Aha! A small staple near the crease of the pocket fixed the problem, so out I went to fly. Problem solved? Nope. The Diamond got in the air, and promptly sat on its side again! Grrr. Most of the time while in flight, the flying line would bow out to the right, indicating that the kite was always off-center to the left.
OK, time to get serious. I decided to check the curvature of the horizontal spar as best I could. Back home, I tensioned up the spar then laid it down on the cement floor of the veranda. Using the spar as a curved ruler, I drew a line from tip to tip using green chalk. Then, I swapped the spar around, and draw again, this time with yellow chalk. If the curvature was even, the 2 lines should line up exactly. And so they did. Ummm .... hang on .... not quite! There was indeed a subtle difference, but I had a hard time believing it was enough to explain the flying problem. Only one way to find out. Rig the kite with the spar swapped around the other way and see what happens!
That's what we did. By the title of this post, it might appear the problem was solved since the kite 'went high' for the first time. However, that was only because of the weaker breeze. Whenever a stronger gust tugged at the kite, around it went. To the right! So, the spar was the problem. All that needs to be done now is for a little wood to be filed off the spar on the 'stiff' side, so its curvature matches the other side. Less wood = less stiffness = more bending when tensioned up. When that job is done to perfection, maybe with a little trial and error, this kite should have a very respectable wind range. The weight of the removed wood should hardly make any difference. Even if it did, it would be an easy matter to re-balance the kite by adding a bit more tape on one side.
I'm looking forward to seeing this kite on the full 150 meters of line, sometime in the next few days. Not tomorrow, the temperature is going to be 41 C (105+ F) in the shade! The method for tying the spars where they cross has also been re-designed, since it kept coming loose in flight. Quite spectacular really! All of a sudden, the kite would dive for the ground, sail fluttering, with the bow line touching the vertical spar. This actually caused a tree landing on the kites most recent flight, but we managed to extricate it with only minor damage to the sail near the nose...
P.S. A trait of this kite which is probably common to any Eddy design, is that the sail billow below the horizontal spar increases considerably in strong wind. This does seem to give the kite more directional stability, which explains why the Dowel Diamond would sometimes straighten up just when I expected it to loop even tighter in a strong gust!
January 23, 2009 21:57 - Refined Diamond Kite Flies High, Pulls Like A Bull
Think I've got Blogger's Bottle-neck (Never heard of it? Neither had I...) A bunch of things to say, no idea what to put first. OK, let's go for a Stream-of-Consciousness approach...
The original Dowel Diamond kite flew OK for a while, although the horizontal spar had a slightly uneven curvature. This was corrected and we had a couple of reasonable flights with it despite overly strong winds. However, it had a couple of design flaws that soon showed up. One of which caused the sail to gradually go asymmetrical in area. That was my great idea of a Pocket and Strap approach. Beautifully simple and practical in theory, but caused much hair-pulling and gnashing of teeth in practice! Lesson - if something even looks asymmetrical on a kite, perhaps it isn't a great idea! Pockets on both sides work for some kites, straps on both sides... well, that brings me to the New Improved Dowel Diamond. (The video and photo actually show the original). I simply went with identical straps on each wing tip, and taped the sail to the vertical spar where the spars cross. No chance of any significant shifting of sail area from one side to the other now! One more strap to do up, but heck - how can it go wrong?
Indeed, when I went out today near sun-down, it was a pleasant experience from start to finish. With the kite still rolled up, I walked over to a green patch of grass on the reserve near the school and started setting up. At this point I might mention that the original method of lashing the spars together didn't turn out so well either. However, the current approach of using a single long tie to weave around the spar crossing - just once - seems to be working well. A wonderful property of electrical insulation tape is that it has very high friction with itself. Hence, a simple Granny knot, tightened only a little, is enough to keep the spars lashed together for a long flight. Afterwards, it's easy to un-pick when packing up the kite.
There was a gusty moderate breeze blowing, and the Diamond showed signs of the towing point being a bit far back.for an easy take-off. Still, I left it where it was since the kite soon floated up, pulling hard. With 20 or 30 meters out, there was a hint of a tendency to fly to the right, but the kite was generally flying well. Letting the line out to 60 meters was effortless, in the sense that the kite behaved itself and dutifully started climbing straight up as soon as I stopped the line flying off the reel.
Now it was time to start walking back towards the trees at the perimeter, to allow more room in case the kite got in trouble. I needn't have worried. Even with strong gusts coming through, the Diamond just flew higher, wagging its wing-tips harder and fishtailing a bit. Also, a bit of trailing-edge flutter could be heard! All this with NO TAIL. Somehow, there was a slight sense of the bizarre here - a big Diamond kite just flying around on its own. It's not the image people generally have.
In no time at all, out went the 90 meter marker, then the 120 meter marker, then the empty winder. I left about 4 winds on, just to be safe. As the wind strength ebbed and rose, so did the kite. At times floating vertically down on its face, slowly and gracefully, at other times wriggling like a large hooked tuna, climbing quickly and pulling like a bull. When at a comfortable wind strength, the kite sat at around a 50-55 degree angle from the horizontal. Wing tips wagged slowly, perhaps a couple of times per second.
Interestingly, when under stress the kite headed off to the left a little. At a somewhat lower wind strength it headed off to the right a bit. Generally though, it went straight up! That's good enough for me, considering this sizable Diamond costs less than $3 in materials!