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Flying Dowels & Plastic, Mar 2013 - The Rok Keeps Rollin'.
March 27, 2013
Fresh Kite-Making And Kite-Flying News
As Winter draws nearer, the hot days are fewer and further between. The weather has been generally quite windy. What's new - this is the windiest state in one of the windiest countries on the planet! And I decided to create a stable of light-wind kites... Never mind, there's plenty to do in a kite-related business when it's too windy to fly one's Best Kites.
As long-term subscribers to this newsletter know, the occasional box kite gets pulled out on windy days. Which leads nicely into the most recent building project (trumpet fanfare) ... The Multi-Dowel Box kite!
Yes, the Multi-Dowel Box kite is all made up and sitting (de-rigged) on the floor behind me as I write. However, yesterday the wind was a bit too wild for an initial test flight. Even for a sturdy Box kite, since I am somewhat conservative in my approach to testing kites. I'll give it a first try when the wind is blowing in the teens (kph) and gusting into the 20s.
For anyone in a light-wind locality, the Multi-Dowel Rokkaku is now tested and documented as the Bonus design in the e-book Making The Dowel Rokkaku Kite. This means it is also present in the Making Dowel Kites e-book and the Bundle products.
This month a whole bunch of people made and flew kite designs from the MBK site, and then posted about the experience. Sometimes with photos - just have a scroll through the Kites: Site Blog page.
My apologies for the slight lateness of this newsletter. The only excuse is forgetfulness...
"Every new kite is an adventure!"
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Table of Contents
Visitor Contribution Of The Month
One contribution in particular seemed to really capture the delights of light-wind flying. From high line angles and low line tension through to glide-in landings as only Deltas tend to do. Also, the four photos gave good support to the story.
Check out Craig's story titled A Dowel-Delta-Kite Success Story! Can you relate to this kind of flying? Why not give it a shot one day when there doesn't seem to be enough air movement to fly anything!
Flight Report Of The Month
Well, there were a few unexpected struggles with getting the huge Multi-Dowel Rokkaku design into shape. Finally, the design seems sound but uneven timber from the hardware store has prevented a really good high flight so far.
Yesterday I spent some time with the wood file and ruler, getting both horizontal spars into a more even curvature. Checking the distance between the bow-line and the bridle attachments points beneath it is a good first-approximation method of checking the curvature on the left and right side.
Here's what happened on the second-last time I went out to fly...
MkIV - Multi-Dowel Rokkaku Refined
"Although the wind was very gusty, the strength seemed to be just within limits for the huge Rokkaku kite. The next few days will produce some rather windier weather, so it was a case of fly now or wait for quite a while.
I went out with this kite a couple of days ago and came to the conclusion that an upper bow-line was a necessity. At least in these gusty inland conditions!
Perhaps in a location with very smooth winds you could fly again and again with no problems. But the moment the kite goes horizontal, it's in trouble. There is nothing to stop the nose sliding sideways, which soon develops into a dive. Then, you just have to hope the tail swings down in time to effect a recovery!
Today, the winds seemed fairly ideal for the big 2.4 meter (8 feet) span Rok, and it easily climbed out to 100 feet or so. Typical of this flying location though, winds aloft were a lot stronger than near the ground. The bowed upper horizontal spars made the kite much more manageable and predictable during lulls in the rough air.
Although the wind meter recorded a maximum gust of only 13.6 kph, some strong thermal activity soon started tugging at the sail and distorting the frame. A fluffy seed pod floated by, also caught up in the rising air.
The kite line was not vertical, so it seemed like there was also a reasonable breeze blowing. Looking around, the tree tops had started waving around and producing some leaf noise. Not good! At the same time, the line reel had decided to jam so it was impossible to let some line out to release tension. I immediately started walking out to the kite, bringing it down slowly but steadily.
A couple of minutes later the kite was safely on the ground and quickly de-rigged. Going back to the hose reel which stored the flying line, I found the cause of the jam. The line had looped itself around one of the tent pegs which were holding the reel in place. Maybe it would be a good idea to drive the pegs all the way into the ground, if it's not too hard!
From what I saw today, the kite is ready to be written up and published as the bonus design in the Rokkaku e-book. Perhaps not the most versatile of the Multi-Dowel kites to date, but should be a real treat to fly in fairly smooth winds. Gusting up to about 18 kph. Perhaps into the mid-20's if you manage to find some harder and stiffer dowel than I used!"
MBK Kite-Making News
Fiddling about with the Multi-Dowel Rokkaku through 4 different versions was an interesting exercise. However, it's certainly good to be finished at last.
The huge Rok started as a super-light-wind design which soon turned into a monster with no less than 8 bridle legs and a 3-piece vertical spar. Quite a fiddly set-up on the field! After all that, the wind range was tiny. I knew I could do better for my valued e-book purchasers...
There's the current version in the photo. With a 5-leg bridle and 2-piece vertical spar, the setup task is much simpler. The wind range is still modest, but that seems to be a feature of large light-wind Roks. I hope to post a long-format flight report or 2 for this kite as soon as the weather is suitable.
The mechanics of the Rokkaku design are fascinating and unlike most other kites. A complex interplay between aerodynamic forces, frame stiffness and bridle leg angles and tensions.
To give an example: if the lower bridle loop is too short, it can actually contribute to horizontal spar bending when enough flight load is added! And the further apart the attachment points on the horizontal spar are, the worse it gets. This is easier to see if you imagine the vertical spar tips bending a lot, in the down-wind direction. Do a few little thought-experiments of your own.
Here's a useful little bit of tape engineering knowledge... Over the months, I have occasionally seen the edge tape fail, right next to the attachment tie on the top corner of the sail. This is because the sudden transition from several layers of tape to just one sets up a stress point there.
Solution: just make sure all the tape layers don't line up exactly. When you finish all the taping, you should be able to see a progression from 1 layer to many layers, symmetrical on the left and right side of the top corner. Packing tape gets darker with every layer added, so the effect is clear.
Darn it, the weight tests still have not happened, due to all the effort being put in on the MD Rokkaku and Box. However, the MD Box is ready to fly, and it should have a great wind range. In proportions, it is quite similar to the fresh wind Dowel Box. Also, I'm itching to get the MD Barn Door trimmed for moderate winds which should provide more opportunities for hanging the weights.
An intriguing possibility is mounting the camera directly in the Box kite, just a shade behind and below the center of gravity. Hopefully this approach might not affect the flying characteristics much, apart from raising the minimum wind strength required to fly. The camera would need to be panned to one side or the other of the bridle spar. Or perhaps not - images from left and right could just be cropped from the full-width original!
These are advertised in the right hand columns of the My Best Kite website, and occasionally referenced in the body text of some pages. I'm sure you have seen them.
In recent months, the number of people accessing e-books on all kinds of topics has exploded, thanks largely to the Amazon company and its increasingly popular Kindle e-reader. In fact, the term 'e-book' might soon be so well known that I can stop referring to mine as 'downloadable, printable books'!
My books are of the PDF file variety, which you can view and / or print off from PCs, Macs and other computers. A bit 'old-school' now, but still pretty handy. There are even ways to access them on the Kindle. But the way of the future is with hand-held devices that are as easy to read as paper.
A little reminder...
An MBK book is a PDF file containing text and photos which can be downloaded to your computer's hard drive. These 'e-books' are handy for either reading on-screen, or printing off to paper, which is preferable for some. With a PDF, it's very easy to just print out the pages you want. For example, a couple of Appendices plus the instructions for a single kite.
Almost the entire book-published content of this site is contained in the MBK Book Bundle. Of course, the cost is much less than buying all the books separately. Also, as time goes on, the value will increase as new products are added or existing ones extended. For example, the recently-added Multi-Dowel Rokkaku kite.
Plenty of people are signing up for the MBK Beginner eCourse. Feel free to reply to this email if you have tried it and have a comment or 2. A more advanced course is in the pipeline.
Issued (belatedly) on Wednesday, March 27th 2013 Issue #0068
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