It was another shopping trip outing. The wife and small son were left at the supermarket while I had exactly 1 hour to get a decent flight out of the new Multi Dowel Barn Door kite. This time, unlike the first outing, I had rolled and folded the package down to its designed length of just 1.2 meters (4 feet). An easy stow in the boot (trunk), even in our fairly small vehicle.
Some odd behavior during the first test flight had me thinking about the bridle configuration.
The original bridle had left a lot of sail area between the upper and lower attachment points. Strong air pressure was popping the diagonal spars concave, bending them away from me in the middle, which should never happen!
No wonder the huge blue kite did a wobble-board impression up there, while being subjected to a particularly strong thermal gust from underneath...
So, it was decided to return to the conventional Barn Door arrangement of having a single line to the crossing-point of the diagonal spars.
However, I retained my earlier idea of also adding a bridle attachment point near the upper tip of each diagonal spar. Hence there are now 3 bridle loops near the upper portion of the sail. One oblique loop on each side, connecting a diagonal spar and the horizontal spar. Plus a horizontal loop in the middle, connecting the other 2 loops. This gives great rigidity to the whole upper portion of the kite.
Stability was a bit marginal on the first test flights too. This time, a couple of knots in the bow-line were jacking the tips up to 24cm away from horizontal. A good increase on the original 18cm.
The weather was less severe today, only averaging 5 or 6 kph near the ground. Perfect for another test fly, even factoring in much more breeze higher up. After all, this is supposed to be my 'moderate wind' kite in the Multi-Dowel series.
Down on the grass, the Multi Dowel Barn Door kite was fairly straightforward to rig, although harder than indoors, definitely! Placing my kite bag over the leading edge of the sail helped prevent things from blowing around.
A few attempts were made to launch, since the kite was unable to support itself during the lulls. Finally an 8kph gust came through and the huge blue craft was away! Steadily pulling line off the hose reel, the kite was soon floating around on 30 meters (100 feet) of braided Dacron. Some turbulence from the buildings upwind jolted the kite at one point, but it soon settled down.
So far, so good and it was also a handy time to whip the camera out. Taking video was steadier with 2 hands, so I trod the line underfoot to secure the kite.
I looked down at one point to discover that the kite was steadily letting itself out! There was the hose reel, rotating at a good pace as the line slipped between my foot and the grass, making no vibration and hardly any sound.
The Barn Door seemed to have a bit of a lean to the right. As well, it was pulling rather hard considering its slow climb rate. The lower sections of the diagonal spars were bending noticeably. Tsk tsk - not good in such light wind!
This necessitated bring the kite down to fiddle with the bridle knots. One knot was shifted across by a centimeter (1/2 inch) or so, and the towing point knot was shifted a couple of centimeters (1 inch) towards the nose.
With the kite in better trim, I felt confident letting it up on 60 meters (200 feet) of line this time. Well, what do you know - there was much more wind speed up there! Heavy tension in the line now. There was still a slight tendency to tip to the right, but I left it since the kite was going up to quite good line angles.
It was time, probably a bit late really, to put on a glove and put a couple of wraps around my hand to help stop the line slipping through. I just enjoyed seeing the big kite doing its thing for a while.
Sometime after this, I slipped a few wraps of line around the spring-scales hook and held the other end to check the tension. Hard to know the exact wind speeds aloft, but the Multi Dowel Barn Door kite was only pulling between 3 and 5.5kg (up to 12 pounds). About the same as the huge 2D Sled in a rather lighter breeze! Perhaps there was around 15kph up there today.
Everything on the kite seemed to be holding, so why not push on to 90 meters (300 feet) of line...
However, not long after, some nasty strong gusts started coming through. Sure enough, the kite started to bog down under the pressure. The big blue craft started to lose height, ominously tipping far over to the right. Even worse, it was close to the road and directly over a line of trees!
I decided to ground the kite immediately, which proved difficult! Being on my own, and nowhere near an anchoring point of any kind, I started to pull the kite down hand over hand. There was no choice but to take a couple of wraps around each hand in turn, shaking the loops off the rearward hand at each change-over. My left hand, un-gloved, soon turned pink all over from all the painful squeezing by the 200 pound Dacron line. There didn't seem to be a centimeter of sag in the line! Who knows what the spring-scales would read now...
Soon, there was no danger of going down in the trees. Whew! Also, below 100 feet or so, the tension started to ease up somewhat. The effect of descending into the wind gradient.
For the last 30 meters (100 feet) or
so I started to tread the line down foot after foot onto the green
grass, walking towards the kite. Much easier! There was no harm done
since the grass was reasonably soft and springy after recent rain.
With the kite in hand I made an adjustment to the upper bride loop to further correct the leaning tendency. Also, I shifted the towing point forward a little more to give even more relief from fresher winds. If this is over-done, the kite will become less stable though.
Despite the drama near the end, I'd have to call the outing a success! The aim was to make a kite which would handle up to 30kph winds. With the bridle nearly perfectly adjusted, I think the Multi Dowel Barn Door kite is close. Later on, I will be putting up the Windtronic wind meter near the kite itself in flight, to get more accurate checks on wind speeds aloft.
Today, near ground level, the readings were 5.5kph average and a maximum gust of 14.8kph. High up, judging by some tree branches moving around quite a lot, it might have hit 25 - 30kph during the freshest gust at 250 feet.