Soft Kite Posts—Octopus

It's an archive of sorts, although there are no dates and times. Kite flying is timeless, don't you agree?

I trust there is plenty in here to educate, inform, and often entertain!

These short flight reports once appeared as posts in the site-blog page, although that page is no longer present on this site. Below, the latest posts come first. Just scroll down and stop at any heading that appeals :-)

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MBK Octopus Kite

Octopus #3 Loves Final Bridle

With plenty of flying and bridle mods done, it was time to test a new set of lines.

The existing bridle was getting rather short with all the retying and cutting. So, a complete new set of lines was fitted. The basic configuration was a copy of the old lines, but one final tweak was incorporated too.

Octopus #3 Holds 45 Degrees

For an inflatable octopus kite, 45 degrees of line angle in smooth horizontal air will definitely do.

After giving the #3 kite a 50% boost in tail length, it flew very well today, down at a beach. I was even able to back off a bit on the pulled-in bottom corners in order to reduce drag somewhat.

Wind strength was in the gentle range almost completely. Occasionally, it would dip to light but by the time I left, the breeze was gusting to 13 kph.

Most of the time, the kite would fly smoothly and drift small distances from right to left and back again.

After some minutes on 100 feet I let the 20-pound Dacron out to 200 feet and shifted position. Due to the wind direction, space was a little tight. The waves were lapping near me, and cars were driving by atop a small rocky incline, beneath the kite!

A few slightly anxious moments ensued when the wind speed seem to creep up a little, causing the octopus to veer more emphatically to the left and right. Mmmm perhaps even more tail might be required, if the kite is to cope with moderate winds as well.

Octopus #3 First Flights

It didn't go as well as hoped.

MBK Octopus #3 looks just brilliant on paper, but it's the flying that counts! Today I got down to a local beach to take advantage of smooth winds that were almost moderate in strength. They were close to 18 kph.

Upon getting the kite into the air, there was a big problem. The head would not inflate fully, instead choosing to fold itself in half across the middle! That inessential bridle line I had removed from the #2 design had turned out to be very necessary after all. So it was back home to add the needed bridle line.

Later in the day, at a local park, I headed out with both #2 and #3 kites. This time, although #3 refused to fly initially, a 20-degree sweep forward of the bridle lines enabled it to take flight at last. However, the rear two bridle lines seemed way too short, which produced excessive drag and kept the kite low. Meanwhile, #2 got some good high flying in, in the gusty breeze!

The list of #3's problems goes on. The upper edge of the air intake was causing the middle ribs to buckle at the cross-flow vents, so it's going to get trimmed back more in line with the lower edge.

The MBK Octopus should still be a desirable DIY kite project once all the wrinkles are ironed out!

Octopus Kite Tune-up

It was down to the beach today to fly in solid moderate winds from the north.

At last, a chance had come up to push the octopus harder! Initially the breeze was a bit soft; this was handy for unfurling and launching the kite. It wasn't long though, before the breeze freshened, with gusts hitting 28 kph at shoulder level.

There were troubles immediately, with the kite showing a tendency to tuck one shoulder under and flip onto its back. The sheer wind-speed seemed to be doing it, time and time again. I tried shortening the bottom two bridle lines a little, to give the kite more weathercock stability. This helped but more was needed.

Getting a bit desperate now, I tried increasing the kite's angle of attack by retying the bridle lines back at the towing point. Success! The octopus now charged around left and right, occasionally reaching 50-degree line angles from horizontal.

Despite the success, it was clear that at around 30 kph of wind speed, the kite was at the limit of stability. A couple of times it was forced right down to the sand, off to one side. But that's OK. The kite, with careful trimming, can now fly from the high end of light right through to the top of the moderate range of wind speeds. That will do!

Pelican Out-climbs Octopus

I'll get to that pelican in a moment.

Winds over the large long reserve were plumb in the gentle range, varying between 12 and 20 kph, roughly. I've been itching to see how the MBK Octopus handles moderate-strength wind though. So that will have to wait for another day.

At ground level, the lulls were long and the gusts were barely able to sustain the kite in the air, let alone loft it higher up. After quite a few attempts, however, a particularly fresh thermal gust got the double-blue octopus away. No time was wasted in letting out many meters of line to give the kite its best chance of staying up there.

The octopus did well, although some thermal turbulence did cause it to dive suddenly on one occasion. As is its custom after an upset, the plastic octopus just lolled around on its back for a while. The kite even maintained height momentarily in some rising air. Eventually, as all the plastic drifted close to the ground, my tugs on the line managed to flip the kite right-way-up and off it climbed.

While flying steadily on 60 m (200 ft.) of line, a lone pelican approached, having seen the kite climb earlier. The pelican cruised around the kite expecting to find rising air. However, the graceful bird was disgusted to find that it needed a few flaps just to maintain height!

Leaving the thermally incompetent eight-tailed "bird" to its own devices, the pelican shortly found some actual rising air. This happened less than 100 meters away and slightly upwind of the octopus.

Many minutes later, with the octopus now flying at around 250 feet above the grass, I noticed the pelican in the distance, far downwind. It was climbing through 800 feet at least, on motionless wings!

Octopus Bridle Mod Magic

To save time, I just walked down to a nearby reserve today with a simple bridle mod done on the kite

Just as I held the kite up for its first launch, a healthy gust of breeze came through the trees. After a brief wallow at low level, up shot the MBK Octopus to a remarkable line angle. Amazing! Plus, it only took moments to observe that the kite was much more stable at higher wind speeds now.

All I had done was to shift the two lowest bridle lines to the bottom corners of the kite. By shortening the lines as well, the sail corners were drawn in and up, causing the trailing edge to curve like that of a sled kite. This created extra drag and extra side area, right where needed. It worked so well that I'm going to forget about using thicker Dacron for these two lines after all.

Being close to the middle of the day and sunny, most of the air movement was highly influenced by thermals in the area. So there were lulls from time to time that kept sending the kite to the grass. And occasionally, rough air would upset the kite and flip it upside down.

On one flight I had more than 50 m (150 ft.) of line out and the plastic octopus was quite a sight, flying steadily, high up with tubular tentacles flailing away.

Winds at the Noarlunga weather station were 14 kph gusting to 22 kph. They were gentle while gusting into the moderate range, in other words. Getting the kite to fly in those wind speeds was the aim; it looks like it has been achieved.

Octopus Loves Light Line

Down at the beach, the latest octopus prototype enjoyed ideal winds and did much better on 20-pound Dacron, compared to the 50-pound line used last time.

First up, the kite took to the air upside down ... and surprised me with how stable it was in that position! With bridle lines draped right over the leading edge from the upper side of the inflated shape, the kite hung at a low line-angle but looked very comfortable. This was even when the breeze gusted up a bit!

Round the right way, the blue octopus went on to confirm the flying characteristics I had observed inland. Only this time, line angles were much higher at 40 to 45 degrees. Also, the line sag was quite minimal thanks to the lighter Dacron. As icing on the cake, a couple of people (at different times) took an interest in watching the kite and its tails as they walked along the sand. I smell a few extra e-book sales, when the time comes :-)

This kite reaches its upper wind-limit very soon after exceeding the optimum wind-speed. I hope to extend the wind range a lot by shifting the bridle points around and using heavier line for the lower two bridle legs. That's not so much for the weight but for some extra drag back there. It worked wonders for the MBK Parasail!

MBK Octopus #2 Floats

I'm still getting used to how far forward the towing point has to be on "fat" kites.

First, it was the MBK Parafoil; the towing point needed to be level with the leading edge. Now, with the octopus, just like the big ones, the best position seems to be way forward of the leading edge.

With the average wind-strength somewhat lower than yesterday, it was a chore trying to get much line out. Eventually, I tried raking the bridle lines forward by an extra 15 degrees or so. This was done as the kite flew on the bridle only, giving me a chance to tweak individual lines to even it all up. Carefully, I tied a new knot into the bunch of lines, just a few centimeters closer to the kite than the old knot.

Immediately, the octopus was able to gain height in slower air than before. And it seemed quite stable. An extra meter on all the tails was helping out there!

Unfortunately, the kite still struggles with extra wind-speed, tending to loop at not much more wind pressure than it takes to climb.

On the plus side, the MBK Octopus is currently capable of sitting up there for minutes at a time in the right wind. Looking "like a bought one" except for the yet-to-be-marked eyes and suckers!

MBK Octopus #2 Does Better

The second octopus prototype was put in the air at the big kite festival last week.

But it was a case of going back to the drawing board. The kite was not quite stable, even in smooth air at an ideal strength. It was clear though, that once stable, this octopus was going to fly at a much steeper line angle than #1. So, after shifting two unnecessary bridle lines from the top corners to a couple of lower positions and allowing more air into the side cells, it was time for another try.

Today was moderately windy with small rain showers drifting through. The gusts pushed into the mid or high 20s in kph. Enough sun had come out to dry the grass to a reasonable state, so out I went.

After a brief fly, some plastic loops were attached to the middle two tubular tails, just to check the effect of more tail drag. Stability was now reasonable, although excessive wind-strength kept looping the kite—just like a kid's diamond on a far too windy day.

The outline around the top of the octopus needs a bit of work. When fully pressurized, the shape around the top was far from smooth. In fact, it was somewhat unlike an octopus!

For a few seconds at a time when the wind strength was not too strong, this kite soared up high. The angle was at least 45 degrees, which is great for an octopus.

So, longer tails are needed. Making the central two from heavier plastic will help too. However, adding 3D suckers—while very effective—would be a big burden on people wanting to make the kite for themselves. Hence I won't go there!

Octopus Flies First Try!

After an initial try in the backyard a few days ago, today was the day to take advantage of smooth beach-winds.

The backyard was no place to test a soft kite design, so the results were not encouraging. However, today's beach breeze proved ideal for evaluating the MBK Octopus #1. The kite at first wanted to circle constantly to the left, but I was able to trim this out by shortening a top right bridle-line. Next, the kite exhibited the classic signs of "towing point too far aft"—no climb!

Again, I gathered the bridle lines through one hand and was able to adjust the towing point as the kite flew. The method was to make a coarse adjustment, then let the tight lines pull through until all have no slack. This would be a bit tricky for a beginner, so the e-book will document another way, indoors. In the air, the bridle lines seemed to sweep forward past the leading edge by 10 or 15 degrees.

To my surprise, the octopus ended up quite stable, with all 10 bridle lines tight. Before arriving, I had thoughts of flying on a subset of lines, thinking some might be unnecessary. But after getting a closeup look at the kite fully inflated and stable over the sand, it seemed wise to not to "fix" what was evidently working very well! There were no dimples, creases, or flappy bits :-)

Like all my first attempts at a new soft design, this octopus is presently a dismal performer. The kite was struggling to make 20 degrees of line angle most of the time. It's just a bit heavy and a bit draggy, I think. Stand by for octopus #2!

 

 

 

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