January 5, 2008 16:37 - Delta Stunt Kite Carves Hot Summer Breeze
There was just enough time, we decided, to give the delta stunt kite a fly before lunch. The day was hot, very hot by most standards, at around 39 degrees Centigrade. That's over 100 on the old Fahrenheit scale. There was hardly any cloud cover either, so we slapped on some sunblock.
Down at the reserve near the school, we set up the kite out on the grass, a fair distance from the surrounding trees. The breeze was in the 3 Bft range most of the time, as far as I could tell. We must get a wind meter soon...
The first few launches weren't successful, with the kite getting knocked out of the air by tree turbulence in most cases. Spins and stalls led to fairly gentle contacts with the ground. I have to admit to one actual crash, where the kite sped off sideways, at a height of only a meter or 2. It took a dive, and my correction was too little, too late. It sat there on the ground, a forlorn twisted heap of nylon and fiberglass. Critically injured and fighting for life... well actually, it didn't turn out so bad after all. Although most of the fiberglass-to-plastic connections had popped apart, no damage was done. There was a tiny hole in the sail, which might have been there before.
It was time to let out more line, and get further away from those pesky trees and their turbulence. With about 35 meters of line out, and better air, the kite was soon soaring up and away. With a bit of height and ample wind, the kite proved fairly easy to control. Even so, I was concentrating hard to avoid unexpected landings and making my poor wife run around after the kite like before!
With a nice safe line angle of 40 degrees or so, I felt for the edge of the wind window in both directions. In between, I cautiously flew from side to side, trying to keep a constant distance from the ground. Climbing the kite higher, I was delighted to see how steep it would fly, easily more than a 60 degree angle. Just when I was doing this, the wind gusted even stronger, keeping the lines almost straight and exerting a decent pull on my hands. OK, so much for flying in straight lines... let's try a loop!
Starting at about 50 degrees above the horizon, I pulled in some right line and watched the kite circle round clockwise, diving towards the ground. The turn radius opened up a bit, so I pulled in some more as the kite shot around close to the ground and back up the other side of the loop. Success! My first loop! Now for the other direction. Much the same thing happened, except I turned too sharply at the bottom and so the loop was more like a spiral. Anyway, practice makes perfect... At least the kite didn't hit the ground.
This final flight was a good long one, by our standards anyway. Nearly five minutes in the air. Hey, this is only the second time we've been out with a stunt kite!
Now for a few notes on the flying during that last flight. Line tension varied a lot, which was mainly due to thermal turbulence I think. We were flying high enough and far enough from the trees to be unaffected by their wake most of the time.
I learnt to act quickly when the kite's pull died! A few quick steps backwards kept just enough tension to keep the kite under control and fly it somewhere else. Sometimes quite big movements on the control lines were required.
Whenever there was plenty of tension in the lines, I trotted off downwind to keep some distance from the trees. This drove my wife nuts, since she was trying to video the kite and kept losing it straight overhead. We did end up with some reasonable footage though.
When the kite was speeding sideways, the feel was spongy but only a few centimeters of line movement were required to steer it. However, when way off to the left or right, much bigger movements were required to turn the kite back to the center again. I was never game to turn toward the ground when doing this! If misjudged, the kite would really hit hard.
To sum up, I had a lot of fun even if May, my wife, didn't. As my skills improve though, she will be doing more photography, which she enjoys, and less retrieving, which is no fun at all. It was nice to keep the kite in the air for a few minutes, which gave opportunities to plan what to try next. Maybe we'll try flying at a beach next time, and attempt some figure eights and triangles! Forget deliberate stalls for now, this kite stalls on me often enough already, and I don't want to encourage it! ;-)
January 7, 2008 15:49 - New Rok Kite Floats Up And Glides Down
Gee, this Rok kite saga just continues. We are now onto MBK Skewer Rok number 3, in our quest to make it fly well and be reasonably easy to make. The bowed cross spar tensioning has caused numerous problems during construction. It's just very awkward for the Rok design on this small scale. Fiddly beyond belief. This time, I experimented with a dihedral design, rather than a curved bow.
With Aren in his pram, the 2 of us headed off to the Old Reynella reserve. The weather was warm, with a gusty breeze. Soon the little Rok was up, and it looked promising. Stability was a bit marginal though, so I went out to it and bent, yes bent, a little more dihedral angle into the rear cross spar. Up it went again, and I was able to let out quite a bit of flying line this time.
Still a few problems in the fresh gusts that came through, so I slipped that fancy Prussik knot up a bit to decrease the kite's angle of attack and tried again. A bit better perhaps, but the kite had a tendency to nose down in lulls and fly around like a model glider. It managed to get upwind of me at one point!
In stronger gusts the Rok kite would sometimes enter a long dive to the ground, with a 50-50 chance of recovering and flying back up.
By this stage, I noticed that the top cross spar had a lot of dihedral angle. On checking it, I found the joint had weakened, so it was time to go home and see about reinforcing it. But this design should work well. My feeling is that with enough dihedral on both top and bottom spars, plus a properly adjusted bridle, this kite should do just fine in moderate breezes. Like its bigger 2 meter cousins, it might also cope well with strong wind with a tail attached.
January 8, 2008 21:29 - Rok Kite Flies High At Last
We just needed a photo of the Rok being launched, for the How To Make A Rok Kite page on the website. The tops of the trees were moving around, so it seemed like perfect conditions for this little medium-wind kite.
Down at the Old Reynella reserve, we soon had the kite up without any tail. A few short flights later, it was clear that in smooth air of just the right strength, the Rok would indeed fly well without a tail. It would soar up straight from time to time, but then give in to rough air or gusts which were a bit strong for it. In lighter air that wasn't quite enough to raise it above shoulder level, it would hover quite steadily.
With a meter of tail, the kite had much longer and higher flights. However, it still needed a bit more, so I added another meter of looped plastic tail. Then, it soared eagerly above the treetops, and I was able to let about 40 meters of line out.
This won't be a long post, so I'll close with a few comments about this Rok kite.
Although Roks are meant to fly without tails, this relies a lot on accuracy of the sail surface and the bridle lines. Both of these are hard to achieve in a very small kite!
The Rok kept flying off to the right, before I noticed one of the knots in the bridle wasn't dead-center. I moved it maybe a millimeter, and the kite flew much better!
The cross spar reinforcements have added a bit of glue weight, so there goes the light-wind performance of the kite. Oh well, it will still be a fun medium-wind kite with its tail...
This Rok flies similarly to a delta in some ways. For example, it can reach very high line angles, and is prone to float and fly around like a paper plane during lulls in the wind.
Unlike a delta, this kite seems to have a fair amount of pull for its size.
That'll do for today!
January 17, 2008 10:20 - Delta Stunt Kite In A Spar-Bending Breeze
Yes, it was windy out at the reserve near the Old Reynella school. Quite cool too, so we didn't stay too long. By Adelaide standards there was a bit of chill factor to contend with.
The delta stunt kite leapt eagerly into the air and was soon high up in the strong breeze. It wasn't super-gusty, but still there were times when the kite would lose speed very suddenly. At these times, a few backward steps were necessary to keep control. There was some wind gradient too, where the wind was much slower near the ground. However, it was fun getting the feel of the kite in stronger wind than it had flown in for the other 2 times we have been out. Climbing straight up with the full force of the wind, I could see the leading edge spars bending quite a bit!
This time I managed to get a bit more adventurous, and tried some straight-line climbs and dives. Diagonal and vertical. They'll get straighter with practice... Plus a few loops, in both directions. Again, getting them nice and round is going to take some extra practice! A big wobbly figure eight as well. I guess this stuff will be a bit easier down at the beach with a smooth breeze off the ocean, and fewer gusts.
I was surprised that the kite didn't have a heavier pull, considering the strength of the wind. A small parafoil stunter might be a different story! We might get one later on.
A couple of unexpected landings resulted from sudden wind drops while the kite was low. I did my best to make them soft, by throwing both hands towards the kite when it looked like crashing, to keep its speed down. One time, my loss of control near the ground resulted in some tight looping and spinning before I managed to get some airspeed into the kite while it was pointing away from the ground. This little display, plus the recovery, impressed my wife no end. She thought it was deliberate!
Anyway, this short flying session left me hankering for more. However, we might head down to Brighton beach next time! This inland stunt kite flying is a bit dodgy...
January 19, 2008 21:37 - Delta Kite 4 - Promising Light Wind Floater
With the end of the month approaching, it was time to test fly the latest kite in the MBK Skewer series. Finally, I have returned to one of the first types of kite I ever made out of bamboo skewers and plastic, the Delta. However, this time I incorporated a couple of standard features that were missing from my first 3 versions. Firstly, floating leading edge spars. Floating since they are not attached rigidly to the nose of the kite. Secondly, a keel to aid directional stability. Also, since the bamboo spars are not flexible enough for a really genuine delta kite of this size, some bow is held into the cross spar with a draw string.
Out at the Old Reynella reserve, the wind was fresh and moderately gusty. Most likely a bit too fresh for the Delta. I was right, it turned out, but the little kite still managed to strut its stuff in the lulls. I knew it was a touch nose heavy, but still wanted to see how it would fly.
Initially, it showed signs of gliding around instead of settling back on its tail to catch the wind. Yep, too nose heavy alright. To fix this, I attached a paper clip to the tail end. This did improve its flying, so I will replace the paper clip with strips of tape later.
Stability was a bit marginal so I added another meter of tail. The keel seemed to be about in the right spot. Perhaps it could go back a tiny bit in light winds. The amount of bow in the cross spar would probably be enough in steady light winds, but it wasn't quite enough in the fresh breeze.
Although the kite kept diving to the ground, I had fun doing recoveries by suddenly letting all tension out of the line. The kite would just settle on its belly, drifting down, before recovering straight into a vertical climb. If it was off to one side, it would also drift or fly back to the middle of the wind window.
Also fun was getting it to hover down low, with so little tension in the line that for some moments the kite was actually tethered by the line at my end just sitting in the grass! No tension at all in the reel. Then, with a little tension applied to the line, the kite would slowly accelerate straight up and find faster air.
A couple sitting on a bench nearby seemed mesmerized by the antics of the Delta. Perhaps it will inspire them to make or buy a kite...
At one stage, the little Delta kite got snagged on a tree when it flew way off to the side. I made the wrong snap decision. By releasing all tension in the line, the kite would have recovered for just long enough for me to run to one side and fly it away from the tree. Instead, I tried to pull in line to get the kite in front of the tree, whereupon it dived into the leaves on the down-wind side of the tree! I managed to pull the kite away, with the line still threaded through the tree. Eventually, the kite managed to free itself by flying the line out of the top of the tree. Whew!
After some more flying, it was time to walk home. My wife May and little boy Aren met me halfway, wondering where the heck I had gone! Dadda! screeched Aren at the top of his lungs, while I was still 100 meters away...
January 24, 2008 22:17 - Delta Kite 5 Bravely Soars Higher In Blustery Breeze
Another Delta already! Yes, I knocked this one together I mean very carefully constructed the MBK Skewer Delta in order to take all the pics for its How To... website page. Delta Number 4 proved the concept. The only real difference is that the cross spar on delta number 5 is slightly closer to the nose than on number 4. I think this is the most satisfying skewer kite to build in the series so far. It takes some time to do it accurately, but the reward is a high performance kite. For its size and humble materials anyway! Now, on with the test flight report...
Earlier in the afternoon, the wind seemed quite light with just a little movement in the trees. Great I thought, perfect for the delta! However by the time we arrived at the Old Reynella reserve, the wind had picked up considerably with gusts of really fresh wind moving through. Still, it should be possible to see if the delta is in good trim. Several loops of tail plastic were tucked away in my pocket, just in case a bit of extra drag was required on one side of the kite. May, my wife, had brought the camera since we needed a flying shot of the kite for the bottom of the How To... page.
MBK Skewer Delta kite The first few launches were ok, but the little delta was still a touch nose-heavy and tended to glide right back to my feet in every lull! Also, like delta number 4, it pulled right every time with too much wind under its sail. So, I added a few extra strips of tape to the tail to correct the balance. Also, I taped just a single loop of tail plastic to the right wingtip, to correct the turning tendency. On the next flight, no more gliding upwind, but it pulled left quite violently! How sensitive is this kite?! To cut a long story short, the wingtip tail ended up being just a centimeter or 2 long to properly correct the turning problem! Quite surprising. With a short main tail, this is a finely balanced little aircraft.
Then followed a few longer flights where I let out 20 or 30 meters of line. Unfortunately, the delta couldn't cope with the wind strength and soon ended up on the ground again after being forced into a dive. However, the dive was not always in one direction, so that confirmed it was in good trim. We are really looking forward to a light wind day now, to see the little MBK Delta strut its stuff!
January 28, 2008 22:29 - MBK Delta Kite Hovers and Soars In Light Gusts
On the way back from Aren's grandparents' place we stopped at the Holden Hill reserve off NE Road. We were prepared with 3 kites in bags, all with their own flying lines. With a fairly light breeze outside, we took out the MBK Delta and the MBK Kids Diamond. The little barn door kite would have had a hard time getting airborne!
The delta went up first, with the wind gusting right up close to its limit. At last I was able to give this kite a really good fly inside its wind range. It was fun hovering near the ground and climbing to max height, depending on the wind strength. Sometimes hauling in, sometimes letting line slip out with the kite climbing during long gusts.
Although the breeze was light and variable, the kite actually got into trouble quite often during lulls. It was prone to long rolling dives if the nose happened to dip too far during a lull, or perhaps straight after being upset by some turbulence.
The kite would begin gliding slowly upwind, then down would go the nose until the kite was diving straight at the ground and rolling left at the same time. Usually, it would recover just before contacting the ground. A couple of times I released all the line tension to force it to recover quicker. Letting the bowed cross spar do its stuff, righting the kite as it drifted straight down. To fix the diving, it should just be a matter of adding yet more weight to the tail end. A few more strips of tape on the trailing edge.
This kite should really be flying on 3kg nylon, since the 20 pound Dacron is definitely too heavy for it in its comfortable wind range.
We also flew the MBK Kids Diamond for a while. Aren flew it briefly, but kept running downwind towards it! Whereupon the kite promptly settled down on the grass of course...
The diamond could be reliably looped to the left by pulling hard on the line. After my experience several days ago with trimming the delta to fly straight, I knew what to do when we got home.
All it needs is a small bit of tape sticking out from one wing tip to produce a bit of extra drag when the airflow past the kite speeds up. With just the right amount of tape, it should balance things out nicely, and enable the little diamond to fly in much stronger wind than it does now. A more efficient fix than just bunging on another meter of tail!
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