Ever heard of a Winged Tetrahedral Kite
by Craig Ensey
(The Willamette Valley, Oregon, USA)
Hi, I'm quite interested in learning about "tetras". I mean tetrahedral kites, not the tropical fish. Over in the Willamette Valley, where I live, we rarely see winds that top 10mph. I can always go to the coast if I want to fly in a STRONG offshore wind, but that's quite a ways away. So, my question: "Is it possible to combine a high aspect ratio Delta with a four celled Tetrahedron?"
At first it seemed like a no brainer, but then I took into account the different angles that these two kites fly at. I'm referring to "Angle of Attack" as they say in the airplane world. Deltas fly at a very high angle and Tetras fly at a lower angle according to the research I've done. Will the two different angles counteract, or meet in the middle, or will it be a problem? The "Delta Conyne" works good and is similar to my idea.
I'm hoping this will work, 'cause I like the look of a big tetra "nailed to the sky." I just don't have the wind to fly one.
I've done a little mock up of the frame I'm thinking of building for it. It's just a regular delta with a four celled tetra hooked on the bottom. Please excuse the mess of hot glue and skewers.
Thanks for your advice.
I'll address a number of your points in turn...
"Is it possible to combine a high aspect ratio Delta with a four celled Tetrahedron?"
I'm pretty sure this would work, since as you have observed, a Triangular Box kite is often combined with a Delta wing to form a Delta Conyne - a great stable lifting kite. Here are two kite types with very different operating angles on their own!
"Angle of Attack"
You have this term a little confused with line angle :-) In aeronautical terms, the angle of attack of a wing is the angle it makes with the airflow approaching it. A kite sitting at a low line angle usually has a rather high angle of attack to the airflow. Kites which tend to 'ride on top' like Deltas and Genkis have rather low angles of attack to the airflow, while maintaining a very steep flying line angle. (My apologies if I mis-read you, and you don't actually have the 2 concepts confused. Anyway...)
"I just don't have the wind to fly one."
Weeeeeeell... That depends entirely on the 'wing loading' of the kite! In other words, the ratio of total weight to total (effective) sail area. A high wing loading requires plenty of wind to get the kite flying, but if you manage to get the weight right down - any design will fly in light winds.
Hence, rather than fiddle around with a Delta wing, I think the 'ultra lightweight' path might be simpler to follow for a first attempt. However, I would suggest doing a little further research to find a design that uses more than 4 cells. For the sake of stability! Although work-intensive, one straight-forward way is to simply connect four 4-cell tetras together to make one big 16 cell design.
Here are my tips for a very light-weight tetrahedral kite:
- Thin 12" bamboo skewers for spars. (The ones in the photo look very thick)
- Try to be accurate and sparing with the glue - the weight adds up.
- Find the thinnest possible plastic for sail panels.
- Attach each fold-over tab with just 3 or 4 squares of clear sticky tape, rather than running the tape the full length of each tab.
Do all that, and watch your tetrahedral kite float way
up in the first thermal that comes through!
Looking forward to hearing how it all goes...
You might have noticed that this site has a monthly newsletter...
For single-line kite fliers and builders, it's always been a good read. But if you are interested in KAP and/or large home-made kites you won't want to miss it!
So sign up today, and download the free 95-page e-book "What Kite Is That?" straight away. Info-packed and fully photo-illustrated.
And there are even more free resources, such as a kite-making e-course, waiting for you in the next issue of this newsletter.
Aug 25, 14 03:57 AM
Last week I came home from a KAP (Kite Aerial Photography) session down at Brighton beach, here in Adelaide, South Australia. The photos were a disaster, being totally washed out. Over-exposed, to be a little more technical. At the time I thought the problem was purely the position of the sun, relative to the direction of the camera...
Well guess what. Down at the same beach today, the photos had the same problem - and this time it definitely wasn't the sun. Camera damage seemed a small possibility since the rig had hit the sand at some speed last time, during a white-knuckle experience with the kite in rough air! Which turned out OK, but that's another story.
Anyway, once back home today, I did a little investigating with the camera, taking some test pictures from the back yard. It was a great relief to find the explanation for the bad images...
It seems that setting a fixed ISO is not a good idea for this camera in very bright lighting conditions. It can cause the camera to run out of adjustment room for other parameters, like shutter speed or aperture. When the camera was allowed to set ISO automatically, the exposure problem disappeared. Whew!
The Tyvek-sailed Carbon Diamond performed wonderfully today. It was, for the first time, hoisting the KAP rig into the air. Never has the rig been so steady for so long. Sway was almost non-existent. But whenever I handled the line the camera twisted back and forth due to the rather steep line angle from the rig to the kite. Without enough horizontal separation, the suspension lines do not provide the maximum resistance to twisting. It might be an idea to separate the attachment points even further, on the flying line.
The 2 meter (7 ft) Diamond was struggling to lift the camera in the fairly light winds coming off the ocean. At times, people on the beach had to duck under the line from me to the camera! The camera was behaving as a sort of aerial tether point, with the kite flying at a steep line angle from there.
Measured at shoulder height, the on-shore breeze was about 4.5kph gusting to just under 7kph. More of a day for the Multi-Dowel Sled really, which hardly feels a 280g weight on the line!
"Simplest Dowel Kites": A free but very useful kite-making e-book. Make a super-simple Sled, Diamond and Delta - step-by-step with photos. Sign up for the e-book and get an emailed series of messages called "MBK Tips'n'Ideas". If you don't need the e-book, consider signing up anyway... You won't believe what's on offer in that message series!