Light carbon frames in R8s
Testing the R7
Carbon frames in the R7
Standard fiberglass frame for R8
New frames for scaled-up Trooper (Trooper 8)
New frames for standard Trooper RS
Scaled up Wildcard
New frames for R5 Rustler
OC345 lightweight carbon version
Our first Whirlwind, called at the time the Wycombe Widespan, was our second kite to use RBJ's 6.35x3.2mm pultruded fiberglass tubing in 1981. (The first one was the prototype destined to become the Trooper.) Experiments in the early-to-mid 1990s showed that RBJ's pultruded 5.5mm thin-wall carbon tubing would have been the perfect substitute for the 1/4 inch (6.35mm) fiberglass, should the need arise. But one day one of the wing spars split in flight in light wind, and then a few years later it was dropped from their catalog. Further experimenting 15-20 years ago pointed to 5mm carbon rod as a replacement for the original 1/4 inch fiberglass, being almost as stiff. But while it was good in light winds, it proved to be not as good in gusts as fiberglass. Consequently our first re-scaled Whirlwind was smaller (by 4%) and sparred with 5mm carbon rod in the leading edges. Currently it has 6mm spiral-wound fiberglass. It's been pretty good in tests over the last three years, but we have yet to confirm a frame for it. (Incidentally, it is fundamentally different from the rest of the current batch of test kites — the only one whose scallops are not to scale; the radius should have been 57.625 inches, not 60.)
First Group Test — Whirlwind, Wildcard and R7 (in lightish but very gusty conditions, on 80lb Ockert Climax Dacron)
The first test in this latest series involved three existing deltas we've always made: Whirlwind, Wildcard and R7. Two had previously been sparred up with RBJ's 5.5mm thin-walled pultruded carbon tubing, which was perfect for these deltas, but no longer made. Just prior to this latest round of tests the three kites all had 5mm carbon rods in their leading edges. It was very durable, but a bit too bendy. Then most recently they were all sparred up with an exciting new 6.35x3.2mm pultruded fiberglass from a different manufacturer. It was our last hope at keeping the original designs alive, but unfortunately it has proved to be no use. It was very nicely made, clean to handle, inexpensive, but just way too darned heavy. It had so much momentum in the air, flying was a continual battle with dives, spins and impossible landings. In spite of identical cross section dimensions, due to its different composition it was 16% heavier than our old fiberglass! My hope, of course, had been to be able to use existing patterns and carry on with our existing designs, but none of the kites flew well at all, and the Wildcard couldn't fly at all until we changed to a lighter spreader.
Second Group Test — 4 Sizes of Whirlwind (in most the most ideally perfect wind conditions for many, many years, on 80lb TUF-Line)
We used Whirlwinds for this test in an attempt to zero in on a scale-up factor. In addition to the smaller Whirlwind above, we had test kites in standard size, plus two more larger than standard. The latter two used 5.5mm carbon tubes in their leading edges.
The day was sunny with a forecast wind of 4mph during the hours we were on the hill. Not since we lived in London (almost 40 years ago) did we have such perfect flying conditions. It was glorious, and all four kites flew magnificently. The smallest one, with fiberglass spars, was surprisingly good. We had a pair of 6mm spiral wound fiberglass wing spars cut to fit our original Whirlwind and it, too, flew brilliantly in the light wind (it would fold up in a gust, though). The +5% kite was the steadiest (+5% = the sweet spot) and stood out as the best all-round flyer of the bunch. It was the creme-de-la-creme, somehow the most steady, true and stable one of the four. The +8% size, which I expected to be a dream in light wind, was very good going up, but then sometimes unexpectedly paid no attention to control inputs from the flyer... so we're currently making some new parts for it. All four jumped into the sky with shortish launches and would have taken all 900 feet of my line had I let it.
Third Test — 2 Sizes of Whirlwind (wind conditions light dropping off above about 400 feet, low level turbulence, on 80lb Ockert Climax Dacron)
The big one (+8%, 9 foot span) wasn't much better after shortening the spreader, which was too tight. The +5% one again behaved impeccabably.
These kites are built from scratch — we don't have templates or space in the workshop for drawing new trailing edge scallops. Also, they may not be able to achieve the wide wind range of the originals, but should be able to surpass them at the light wind end, which is after all what delta kites are all about. Now that the new Whirlwind's scale-up factor is considered final, the R7 and hopefully the Wildcard can be scaled up by the same percentage. If all goes well we will pick up testing the smaller one with 6mm spiral wound fiberglass and 5mm carbon rod at a later date. We are thinking about the Trooper, too, but it may prove to be quite a project...
A few days later...
There was a thin layer of sporadic lift just above the tops of some nearby conifers, just enough to take out short lengths of line before needing reeling, but not enough to hold for more than about a minute. With no wind at ground level and only those few puffs at the tops of the conifers, we gave the +8% (9 foot span) kite a goodly number of long launches and just reeled. We were using the 80lb dacron line — not the ultralight TUF-Line, which didn't help.
During this series of test flights the +8% 9-footer exhibited no more handling problems in the same conditions where they showed up before, when on one occasion the kite ended up in the top of one of the aforementioned conifers (which did not particularly endear it to me).
So, the new parts worked. They were: 1, a lighter center spine, and 2, a heavier spreader. The center of gravity moved forward and up. This was more like the original Whirlwind with wood spine and spreader, where in testing the 7/16" (11mm) hardwood spreader was better than the 3/8" (10mm). Unfortunately there were only two lengths of the thick-walled 8mm carbon tubing left, and the last few times we ordered it, RBJ substituted thin-walled. I can test it with a 10mm carbon spreader, which though ~3 grams per meter lighter would approach the weight of the thick-walled 8mm tubing, but that will have to wait until we can get some 10mm stock. The +5% Whirlwind is the better all-rounder, so that will be the focus of our attention in the foreseeable future, though a 10mm spreader may well be tried on this one, too, at some point.
Although I made 6.35mm carbon tube wing spars for my R8 quite a few years ago, it retained the original 11mm (7/16 inch) wood spine, weighing about 84 grams, and its original heavy dowel spreader (described below). I hadn't quite considered the R8 as a candidate for an all-out light wind role.
Pat Snodin made the frame that inspired me to go lighter. He and Marilyn (The K Team) made a set of 6mm carbon tube wing spars and spine, leaving the stock pull-wound carbon tube spreader as-was. Their photos of zero-wind kite flying on their flicr pages show that kite.
The K Team
Since then I have made a few light R8s for other people, but have yet to finish altering my own. All it needs is finishing the new spine. Meanwhile, another customer (thanks Hussam) has posted photos on flicr of his experimental Light R8 in very light wind... inspiration.
"Wind has finally died down and I have taken the Lightweight R8 Cruiser on its maiden flight. Wind could not be felt, but the kite flew right out off my hand. After 30 minutes of fly time, it was too hot (44°C/111°F, in the shade) to wait patiently for the kite to catch stronger wind, but the kite managed to be 'suspended' on its own for in under 2MPH ground wind speed. The kite was up the whole time." -H. Qasem
Light R8 on H Qasem's flicr pages
"Your R8 felt like a tripod in the sky. I've never handled a kite that stable."
The kite in the photos uses CC345 wing spars, plus the stock 10mm spreader and a solid spine of 6mm carbon rod to lower the center of gravity a bit.
More flicr links to Hussam's photos
A new approach has resulted in a new drawing, and a new R series kite; it's a bit bigger than an R6 (and smaller than an R8). It's been on the back burner for many months, but I had high hopes for it. It's being called the R7. It's very much a small R8, but its ultimate character will be defined by how much its wing spars bend at what wind speed.
The prototype was ready three months ago, but we never had a decent day free to test fly it - until now. It's had a half dozen flights and so far I haven't felt that anything needed changing. The construction could be simplified at the expense of reinforcements, but past experience has shown that this layout favors this particular grain direction. The leading edge sleeve linings and the diagonals could conceivably be left off. Judging by the look of the wings in the air, the diagonals will stay. The leading edges might manage without stretch linings with the fabric I'm using now, but those linings do prevent distortion when things get fraught. I'd only leave them off if this were a light wind kite. (In my experience R series kites won't work with the fabric grain aligned with the leading edges, leaving the center sleeve to stretch.)
How does it fly?
In light ground winds, and no more than a medium breeze at height, we have had nothing from this kite but good flying. Easy flying. Stable flying. I like this sort of safe kite more and more the older I get. I may try it with a heavier spreader, bucking the trend set by the latest R5 and R10 (but not the R6), but I can't think of anything else to do with it other than make a light wind frame for it.
This is an R7 everywhere except the nose angle, which is 90° instead of 94. The one difference structurally is the measurement to the wing tips, but that has knock-on effects on the rest of the kite. The M7's towing point is almost identical to that on an R7, but the stock R7 wing spars used are relatively longer in proportion to the length of the leading edge, putting the spreader relatively closer to the nose. This short spreader is thus very strong and light. The wing's surface area is somewhat smaller than the R7's, but the 90° layout is very steady, very stable, especially in pitch. All told it means the M7 is good in strong breezes by virtue of its overall stiffness*, and it sits level in lulls thanks to its 90° nose angle.
*I refine designs by scaling them down in 2% steps from a bendy starting setup down to successively smaller prototypes and test fly them, changing the kite's size without changing the frame materials. Eventually one of these prototypes will show signs of being too stiff by spinning around uncontrollably rather than flying. So I go one 2% step back to the previous size, and that's usually the one I keep, as long as the wing spars are not too long for shipping. In the case of the M7, I doubt if it would pass even a 1% downscaling; it's that close to the edge. It has about the widest flyable wind speed range possible, though with its standard frame it is a not a dedicated light wind kite.
The first R-series kite was a fiberglass-and-wood R5, which was one of 4 protypes, and the one I judged to be the best all-round flyer. Second best at the time was a 90° kite, based on 90° deltas from the '70s. I always preferred something a little broader than 90° for the handling and the look, the appearance of the shape in the sky. Practical kite designers used 90° designs for all-purpose deltas ever since the 70s, while I used 90° only for small kites, like the little Fringed Delta. Mark Cottrell's original 90° delta is still in production today in a scaled-up version.
The guinea pig in the photo doing the test-flying reported worry-free flying in challenging wind conditions, no stalling in lulls, and easy landings.
Along with the Trooper, the R7 and M7 will need new framesets now that the 6.35mm PT fiberglass used in their leading edges and spines has been discontinued. All three kites have had heavy-ish frames. The only carbon options are lightweight rod and tube. The rod is the toughest; the tubes are probably too stiff. The 8mm spreader stock for the Trooper also seems to be unavailable at the moment. The kite that eventually evolved into the Trooper used ¼" PT fiberglass rod, so there may be some light at the end of the tunnel with rod, at least for the Trooper. As for the R7 and R8, the experimental kites described below will have to be revisited.
A flight with an R6 that hands-down out-flew a Whirlwind in light wind, plus a report from an R8 owner of his modified light wind R8, planted the seed. And now the R7 has a second frame with carbon tube wing spars and spine. The spreader is the lightest 8mm carbon.
It's easier to make deltas with light wind frames fly than the reverse, but the frame parts have to be actually available. The kite needs to handle well, it can't be too floppy, and it mustn't be too twitchy. The new parts for the 2nd frame are made from the same carbon used in the Clipper and OC345. (One owner thought his was less stable with this frame, which indicates that the wing spars are a bit too stiff, and a 5mm carbon rod frame is ready for testing.)
Using the stock spreader conveniently introduces the possibility of an R series kite with two frames covering a wide range of wind conditions from quite light on up. A short sleeve of heatshrink tubing on the spars at the spreader pocket ensures that the wing spars fit sleeves made for the standard ¼" fiberglass.
So, why use the heavier frame at all? The answer is that, firstly, the "heavier" frame is not too heavy. In fact it's just right for a normal kite, giving just the right balance, handling and stability for a smooth-flying all-rounder. Secondly, although quick and snappy in flight, carbon frames can have unexpected behaviors in certain situations, such as a lack of control in lulls. That's why testing in a wide variety of wind conditions is necessary.
How light is light?
The original standard frame weighs 193.9 grams (Frame A, below). The new lightweight frame weighs 119.6 grams (Frame B, below). The 8mm pull-wound carbon fiber spreader used with both configurations weighs 39.8 grams. I choose spreaders based on raw strength and weight giving good overall handling plus balance in lulls. With its stock frame this kite is close to perfection as an all-rounder.
How does it fly?
So far so good. The wind was variable on the first Frame B test day, causing the old 50lb nylon to sing every now and then - not ideal for a light wind test. But it was light enough to require a long launch to get above the turbulence, and we had no problems with handling or stability. Testing in calmer weather and the odd thermal will have to wait (better conditions rare in this neck of the woods).
The second test flight with Frame B was a long flight in changing wind conditions, and was very pleasant at all times, including the landing (right to the hand).
Frame C in the list is altogether lighter, and has now also been test-flown. Ideally it would be used in kites made using lighter fabric than normal, and could also have a fin re-design to maximize pull. This frame is very light, but also thin and relatively fragile (especially the spreader) - it's strictly for light winds and thermals.
There was a perfect light wind for the flight with Frame C, and the R7's flying behavior was impeccable. It was also the first time we'd tried our new 80lb TUF-Line XP, which no doubt helped (note: 300 yards was not enough).
With no discernible wind at ground level, long launches were required, but applying a little low wind flying skill meant all the line was soon out. After bringing the kite back down through the light but fickle breeze (it was changing direction every few feet) and then sending it back up again, the kite was so well-behaved it could take off within 6 inches of the ground, and even when we caught it for re-launches, it never once touched the ground. There was barely a cloud in the sky, and all in all it was a glorious day of trouble-free, high angle flying.
|A) (Stock frame) 6.35mm PT fiberglass tube||6.35mm PT fiberglass tube||8mm Exel PW carbon tube||193.9 grams (6.8oz)|
|B) 5.5mm thickwall PT carbon tube*||5.5mm thickwall PT carbon tube|
To test: 5.5mm PT fiberglass tube
|8mm PW carbon tube||119.6 grams (4.2oz)|
|C) 5mm PW carbon tube*||5mm PW (Exel Cruise)||6x4mm PT carbon tube (for 1st tests only)|
Slightly stronger 6mm PW carbon tube (future builds)
|85.2 grams (3.0oz)|
|D) 5mm PT rod*||5.5mm PT fiberglass tube initially|
6mm PT fiberglass rod
|8mm PW carbon tube or|
6mm PT carbon rod
|Not made yet|
|* these wing spars have heat shrink spacers at the spreader pocket gap, which was made to fit standard ¼ inch wing spars.|
|Fabric: Bainbridge AirX700n|
Frame D has not been made yet, but will be the next one on trial. It will retain the stock spreader for initial tests.
Standard fiberglass wing spars no longer in production
The switch to new wing spars will be the biggest major change to the original Whirlwind since the very beginning in 1980. Until something better turns up, the next standard wing spars will probably be 5mm carbon rod, already proven in the Carbon Whirlwind prototype. Initially the spine will remain as 5.5mm PT fiberglass tubing. Test spreaders will be 8mm carbon tubing (two weights available) and 6mm carbon rod. They will be compared in flight, looking for the best fore-to-aft balance. The 6.35mm PT carbon tube previously used on an experimental lightweight Wildcard has been discontinued, but we may test it for reference.
We will be testing different spines.
Standard Whirlwind spreaders (old notes)
We tested a Whirlwind with a frame that mimics the original wood fame by using 5.5mm pultruded fiberglass tubing for the spine, and tested two spreaders on it. One was the current standard pull-wound 8mm, the other the previously used, and heavier, 8mm carbon tube pultrusion. Flying it with the latter pleasantly reminded me of early Whirlwinds - the flying qualities of which I like very much. However, it's impossible not to marvel at the performance with the lighter pull-wound spreader. It was snappy where the other was smooth. I would be happy with either, but I suspect customers would prefer the snappier version, so I'll continue making them that way for the time being. I had suspected that the one with the heavier spreader might handle strong winds better, but, although the winds were terrible on the day of the test, I couldn't see it. I guess I like them both. Unfortunately, I don't have my own Whirlwind prototype to use with both spreaders over a long period. Every time I make one, someone buys it. (That explains the odd bits of dried grass occasionally found rolled up in a new kite.)
5.5mm pultruded fiberglass tubing is a perfect substitute for 5/16" (8mm) hardwood dowels as center spines. It's the same weight as the lightest 5/16" dowels (which varies a lot), but it's not quite as stiff. Like lighter, thinner dowels, it gives center lines on kites a nice curvature (called camber) which improves handling and pitch stability. Because they are more flexible, they are also good for gusts and strong winds. So for the time being, 5.5mm fiberglass tubing will be used for the center spines in the Whirlwind, Wildcard, R5, and, maybe the R6. We've test flown an R5 with one, and like it coupled with a light and stiff spreader. Two of our R6 prototypes will have their wood dowel spines replaced with 5.5mm fiberglass on 27 July 2009.
New 5.5mm carbon tube (replaced with 5mm carbon rod)
Further down on this page is a report on the manufacturer ceasing production of the thin-wall 5.5mm carbon tubing formerly used on the Light Whirlwind. Recently we got samples of a new precision-made 5.5mm pull-wound carbon tubing by WFC.
Lightweight wing spar tests
We made a test Whirlwind using lightweight AirX600n fabric and the new WFC pull-wound 5.5mm tubing for both wing spars and spine, and flew it during a lull on a day spent testing fresh breeze kites. It was a quick, short flight, but it showed the frame had promise.
This frame is very light, and the kite handles well. The spreader is 6.35 carbon tube, which seems to have a good heft (so far) and is as stiff as 6mm pull-wound Exel carbon tube. That first prototype was sold, and I haven't got any more of the 5.5mm pull/wound tubing long enough to make the 50" long wing spars. Instead of buying a small number of extra-long (1.5m) stock lengths, our current Carbon Whirlwinds use 5mm carbon rod. It's very durable, and because it's slightly more flexible the kite is easier to handle in the air. But it may be a little bit too flexible, less able to ride out gusts. Our next step is a return to WFC 5.5 carbon tubing, and try to find a combination of spine and spreader that gives good balance in pitch. The spreader is proving elusive on the Wildcard, and may be so for the Whirlwind, as well. We may need to get some 8mm Exel from The Continent, since it's about 1.5 grams/meter lighter, and closer to the weight of the discontinued 6.35mm.
The new 5.5mm tube has been used for spars and spine in an OC345 which seems to be a very good flyer. Unfortunately, its 6mm Exel Pro spreader (very stiff) is the last one, so there is an on-going search for a substitute.
A Clipper GPX has been test flown using 5mm Exel wing spars, a 5.5mm pultruded thick-wall carbon tube spine, and a 6mm Exel spreader. Questionable whether or not this kite should have a stronger spreader. I expect it would encourage people to fly it in too much wind.
Meanwhile, Little Bear center spines are being changed back to 4mm f/g rod from 5.5mm f/g tubing. This switch will save 8.5 grams. We're keeping an open mind. Since weight is the overriding factor, carbon won't be under consideration (at this point in time at least) - suitable carbon spines would have to be made from long lengths of large diameter, expensive stock.
6.35 fiberglass spar replacements
Since RBJ is no longer producing my favorite wing spars, their 6.35" diameter PT fiberglass tube, I have to find replacements for all the kites that used them. They were in the original Trooper in the 1970s, and the first Whirlwind in 1980. The Whirlwind and Wildcard will probably use 5mm carbon rod, as in the light versions. The same may work for the R7, as long as they don't flex too much. But the Trooper, whose spars need a bit of heft, presents a bit of a conundrum. We intend try everything remotely suitable, though most will be too bendy. Then there is 5.5mm PT carbon tube, which is almost the right stiffness, but could be too light. An experimental setup is ready for testing using 5.5 thickwall PT carbon tube wing spars and two spines: 5.5mm and 6mm PT fiberglass tube and 6mm PT carbon rod. The final alternative is 6mm PT fiberglass rod, which may be too bendy as well as too heavy. The very first kite that eventually evolved into the Trooper used 6.35mm PT fiberglass rod wing spars, so a scaled-down version of that kite may well be on the cards.
There is also the 6mm PT carbon spreader (below) in addition to the stock spreader.
In addition to the wing spar problem, it also looks like the spreaders may go out of production, since they've been substituting WFC pull-wound carbon tube, the lightweight stuff. I have a solution for these, though it adds a few extra steps in the making.
Standard spine: 6.35mm p/t fiberglass - standard spreader: 8mm p/t carbon tube
|EXPERIMENTAL SPREADER STRUTS|
|8mm p/t carbon tube||6mm p/t carbon rod||8mm p/w carbon tube||6.35mm p/t carbon tube|
|42.3 grams||40.8 grams||30.5 grams||28.7 grams|
|Standoff 1: 4 inches||Standoff 1: 3 3/8- inches||Standoff 1: 3 5/8 inches||Standoff 1: 3 1/2+ inches|
|Standoff 2: 4 inches||Standoff 2: 4 inches||n/a||n/a|
First test session - the unexpected!
Wind: very gusty; max gust 27mph at ground level while flying (normally I'd pack up and go home)
Line: 220lb utility-grade braid on a big plastic spool - this is a two-handed job (with gloves)
As reported elsewhere on this page, the R series kites flew best using the lightest and strongest spreaders, and I expected the light and rigid 8mm pull-wound spreader to be the best of the bunch, but the exact opposite happened. The kite was all over the sky, threatening disaster at any second. It was wild and hairy, and I was lucky to get down without crashing. I thought it was just too rough up there for anything to fly. We couldn't strap the wind meter to a tree - there were no suitable branches. Trees in violent motion all over the place. The highest gust measured was nothing compared to some that nearly blew me over, and the wind was a lot stronger higher up, above the trees. So, rather than pack up and go, I tried another spreader, anticipating a quick, short test. I wasn't prepared for what happened next.
Fitted with the 6mm pultruded rod, the 1991 Trooper flew like the wind had suddenly dropped. But it hadn't. It flew as if I'd put on a tail. I hadn't. During that flight the meter registered 27mph at ground level on its little pocket tripod.
So, what's going on? My guess is that weight isn't the only factor at work here. I think the 6mm pultruded carbon rod has a little "give," so it bends a little. Now I need to test fly the kite with a stock spreader for comparison. It's more or less rigid at almost the same weight. That should show if the 6mm rod's extra flexibility is the key stabilizing factor. (I couldn't test one today, because the kite never had one; it only had a pair of wood spreaders; plus, I thought the pull-wound 8mm carbon one was going to be best.)
Third test session
Line: Braid with unknown breaking strain on an 8" plastic spool - possibly 120lb nylon
The wind dropped for the second set of tests, so all we could do was have a short flight and lunch. The third set had swirling breezes with a few decent gusts, but the kite flew equally well with either of the two test spreaders. No gusts were strong enough to reveal any differences between them. The kite was well balanced, however, and this is the best the kite has ever behaved during landings.
The last change to the test spreaders has been to re-cut the 6mm rod spreader so it fits the kite with the same dihedral as the 8mm tube spreader, which had been cut to fit a bit looser than previous spreaders have been on this particular kite. The aim is better strong wind flying; one by-product will be spreaders that are easier to put in.
We flew the Trooper out as far as it would go using our old 8" hoop spool with its old, non-descript medium-heavy nylon braid (about 1.4mm in diameter), 6mm carbon rod and 8mm p/t carbon tube spreaders, both re-cut for a 4" Standoff (with kite hung upside down), giving plenty of dihedral. I can't say why, but I still preferred the 8mm tube. Maybe this kite just likes the weight of it. So, current Troopers will be framed this way.
The new design has now been test flown (several times). At times the wind was pretty horrendous. This one is about 8% bigger than the original scaled-up Wildcard of some years ago. It has a slightly deeper scallop and a different frame. The wing spars are longer and both the spine and spreader are carbon. The spine is solid rod, and the spreader is 10mm tube. It's a heavy pultruded carbon tube, not the lightweight pull-wound stuff I use for the R8.
It weighs a hair under 17 ounces with a wing loading of 0.91 oz/ft². It flies, luckily; in fact, this one's definitely a keeper.
It hasn't got a name yet, but the drawing is number 9 - it's the ninth version on paper, but the second ever actually built. I could have filled a waste paper basket with rejected designs, so the fact that this one flew is quite a relief.
Span is nominally 9¼ foot. Wing area is 18.7 ft². This one's built a little heavy with extra reinforcements, heavier tapes and so forth. Unfortunately, because of those extra reinforcements plus the way the fabric fits the layout, or rather doesn't fit, this one's not going be economical to build for sale.
The 8mm carbon rod spreader weighs 89.2 grams. The 10mm carbon tube spreader is 81.7 grams. I have yet to test it with the 8mm rod; more weight might improve it in strong winds, or it could just prevent the nose from turning upwards if it dives to one side. With the current spreader the kite is nice and responsive. It handles well. The kite's neither too quick nor too slow to correct itself, so, so far, there's been little incentive to change it.
There is a tail loop, but a tail has not been tested. Jump to earlier note
This is a follow-on to the R6 project. What was learned there might be applied to this kite. The new frame parts need to be tried and tested to zero in on the best all-round combination.
Wing spars are the original 8mm fiberglass tube.
|Test Frame||Spines||Spreaders||Field Notes|
|Original||7/16" wood||1/2" wood|
|1st test frame||8mm fiberglass tube||10mm thinwall carbon tube||10mm thickwall carbon||All motions are perfectly damped. Flying behavior is dignified, as if in slow motion. With this combination the kite is well-mannered and imperturbable. It's easy to control and there's none of the "oh my gawd what's it going to do now!" you sometimes get with experimental kites.|
|2nd test frame||8mm carbon tube||10mm thinwall carbon tube||10mm thickwall carbon||Being lighter, this spine makes the kite more efficient, but it is also more a case of pull hard/not pull/pull hard/not pull; climb a bit, drop back, turn right, turn left, drop, climb, and so on. I greatly preferred flying it with the heavier spine.|
|3rd test frame||8mm carbon rod||10mm thinwall carbon tube||10mm thickwall carbon||The rod for this spine is too heavy and too expensive; Frame 1 is so good there is no need to try this one.|
Frame 1 gets the nod, but one or two other combinations will be tried as parts come available.
This is one of my oldest designs, but also one of the most highly refined. Upgrading it to carbon meant designing a new fin (similar to the one on the CC345). The frame options are very limited. The wing spars and spine are suitably flexible 5.5mm carbon tubing and there is only one possible spreader, an imported thick-walled 6mm tube. Because there will be no Flex-Stop, the spreader needs to be both light and stiff.
The prototype has wings of Icarex P-31. The fin is Icarex P-38. Since Icarex is no longer available, the next one will be something like Seaspeed SS060 wings with a fin of Bainbridge Airx 600n.
The wing loading is a mere 0.556 oz/ft².
On the day of the first test flight the wind was so light the new experimental Aztec wouldn't fly on my old 50lb twisted nylon. Bev gave me a long launch and the OC345 shot right overhead and stayed there. I let it drop, turned it, brought it down, let it drift back, let it dive to see it turn on a penny. It turns around its tail. In short, I cannot remember ever flying a better flyer.
When we went out, I wasn't at all sure this kite would fly properly and was half expecting to be trying to figure out how to fix it if it didn't, so after the tests I wasn't just relieved, I was totally elated. I thought at the time that this could be the most perfect delta I've ever made. There is one spreader blank left; I have been hunting for similar spreader stock without, as yet, success.
The Aztec gave some flights that refuse to fade from memory, so a new prototype is planned with hemmed trailing edges, fiberglass or carbon center spine, and a carbon spreader. A series of test flights similar to the ongoing R5 testing will follow, though there are far fewer options for an Aztec frame.
A design can seem perfect after quite a few flights, yet a day can come along that sends it back to the drawing boards.
True in this case. The XFS center spine proved too light in the Aztec. This one has been shelved.
R5 & lightweight Little Bear.
It's time to revise the framing of the R5, the first R-series kite and the "winner" of the contest between four different prototypes with wide wind range as the objective. The original had a very heavy frame, and was very good in strong breezes. Ideally, the new carbon version should be equally as good, which means the new frame should probably be quite heavy. Carbon is light, though, and, as the R6 proved, it is possible to retain the strong breeze performance and extend the wind range downward to include lighter winds as well.
There are many options. We tested some of them in light winds first, and if we get caught in stronger breezes, so much the better, for that will tell us which frame ultimately wins out.
|Test Frame||Spines||Spreaders||Combined Mass (approximate)|
|0 (original)||5/16" wood||5/16" wood||56+ grams (varies)|
|1 (2nd frame on original)||1/4" wood||5/16" wood||46+ grams (varies)|
|2 (lightweight version - out)||fiberglass rod||6mm carbon tube||40 grams|
|3 (good)||5mm fiberglass rod||5mm carbon rod||57 grams|
|4 (good)||5mm fiberglass rod||5.5mm thickwall carbon tube||~54 grams|
|5 (best - 1st place this set)||5mm carbon rod||5.5mm thickwall carbon tube||47 grams (spreader can flex in strong gusts)|
|6 (very good)||5mm carbon rod||5mm carbon rod||50 grams|
|7 (very good)||5mm carbon rod||6mm carbon tube||46 grams|
|8 (good - 3rd place)||5.5mm thickwall carbon tube||5.5mm thickwall carbon tube||~43 grams (spreader can flex in strong gusts)|
|9 (close 2nd)||6.35mm carbon||6.35mm carbon||48.4 grams (unstable on short line, i.e. landings. This 6.35mm carbon tube is no longer made)|
These being R-series kites, they all fly well in every wind we've tried them in, ranging from very light (needing long launches) to breezy. We've used my old 50lb twisted nylon line and also 50lb Kevlar. They're all very stable. There have been slight differences in balance when drifting downwind (taking out line), or a slight tendency to sway or dance about, or more or less stability coming in for landings. Two combinations have proven to be the favorites so far. A couple were just so-so, and the rest are all very close to the best, so close it's been hard to tell if it was a change in the wind or not, which meant frequent re-tests.
From a durability point of view the 6mm thin-wall carbon tube used in Combinations 2 & 7 is rather fragile. It's not ultimately practical. We used Combination 2 on a day when there was no wind, but I didn't like the balance in pitch. Combination 7 was very good in a strong breeze, but exhibited a slight tendency to dance about. So it's safe to eliminate both these combinations from contention.
From a continuity point of view I'd have liked a combination that used the same material for both parts, but we are not choosing on that basis alone. (The original one used the same wood dowel for both spine and spreader, but I carried a ¼" dowel spine for light wind.)
From a cost point of view, fiberglass parts would be better, but if the combination isn't good, we'll go with whatever works best. (As it happens, certain customers have preferred frames different from the ones we picked here.)
Combination 4 has a low, rearward center of gravity, which should theoretically have made it a better flyer, but though okay, it wasn't a favorite.
Combination 5 was Bev's overall favorite in strong breezes. Combination 9 came in a close second, being stable, solid, dead steady on drifting back, but due to the greater momentum of the heavy frame, it was significantly less stable on landings. The priority here is good flying across the widest wind range with the emphasis on the upper end, and if landings are the only difference between two combinations, they'll have to be taken into account. (Again, certain customers preferred a stronger frame in spite of landings.)
Combination 6 is good, but a trifle nose heavy. It's probably just too heavy overall.
Combination 8, while responsive, wasn't quite as well balanced when dropping back, but it's not out yet, because it needs testing in lighter winds. The spine may be a little too light, but if the kite has a wider wind range because of its better light wind performance, it'll be worth testing further.
Nice balance isn't absolutely necessary, but it makes a kite nice to fly. Combinations 5 through 9 are so close to each other that the choices have been down to very small differences in just one or another aspect of handling in a particular set of conditions.
So far the two mid-weight combinations are the best in strong breezes, but we still need further testing in light winds. Also, we need to test Combination 5 in a kite made from our current fabric. The old prototype's fabric is softer and more stretchy. Combination 9 is in a new kite, and the difference in landing may be due to the difference in fabrics.
After the eliminations we are left with:
|Test Frame||Spines||Spreaders||Combined Mass (approximate)|
|A||5mm carbon rod||5.5mm thickwall carbon tube||48.4 grams (1.7 grams of which is for two ferrules)|
|B||6.35mm carbon tube*||6.35mm carbon tube*||48.4 grams|
|C||5.5mm thickwall carbon tube||5.5mm thickwall carbon tube||~43 grams|
|D||6.35mm carbon tube*||5.5mm thickwall carbon tube||~47.3* grams (our favorite in this set, but see notes 5 and 8 above)|
Frame D here is new. It was meant to have the balance of Frame A with the stiffness of Frame B, but it isn't as stiff as Frame B. One might be better in some conditions than the other, but Frame D is the current favorite as far as flying in normal winds is concerned. For stronger winds, see Update, below.
Light winds: under 4mph (nothing at ground level) to about 6mph, 50lb kevlar line. The favorite from previous tests was not the favorite this time. The longest and highest flight came from Frame B. But conditions were not constant and Frame D almost equalled it in both height and duration.
After more light wind flights Frame D is the current favorite (but see Update, below). It's the most constantly level flyer, if that makes any sense, I can remember ever flying. That balance extends to recovering from upsets quickly. It turns on a point, too, and isn't too hard to land. If it's good in strong breezes, it'll be the #1 choice. But light wind tests like these are not conclusive, and more testing will follow as conditions and time permit.
A customer who tested his own kite using both 6.35 and 5.5mm spreaders said the 5.5mm spreader flexed too much in strong winds and I should go back to using a 6.35mm spreader. That noted, we'll next be testing a pull-wound 6mm spreader with the stiffness of the thicker tube combined with the lighter weight of a thin one.
|Test Frame||Spines||Spreaders||Combined Mass|
|E||6.35mm carbon tube (no longer made)||6.0mm pullbraided carbon tube||45.9 grams*|
|F||5.5mm fiberglass tube||6.35mm pultruded carbon tube (no longer made)||51.2 grams|
|G||5mm carbon rod||6.0mm pullbraided carbon tube||47.1 grams|
|H||5.5mm fiberglass tube||6.0mm pullbraided carbon tube||48.7 grams|
Since 5.5mm fiberglass tube spines are so close to the original wood in weight, and have a bit of flex, I like them in combination with a 6mm pull-wound carbon tube spreader. Cost-wise, fiberglass spines are less expensive, while pull-wound spreaders are the most expensive.
With performance as close as this has been, wind conditions at testing time can tilt the balance one way or the other on any given day. The goal is a cost effective kite, good in a wide range of winds, and possessing the balance and handling qualities of the prototype with its wood dowel spine and spreader. Fortunately the R5 is versatile and forgiving, and there are lots of parts available to choose from (some quite a bit more expensive than others).
The tests were instructive. For instance, we had a good, high flight with Frame E, but when the wind dropped to almost nothing the unexpected happened. With the heaviest center spine on test the kite caught what little wind there was regardless of flying angle, and pulled the line taut. The way it hung in the sky with the tail hanging down was reminiscent of an old flat kite with a tail - it didn't level out or turn downwind in lulls. On the other hand, it didn't handle well at all and was ultimately rejected.
XFS testing went on for a full year. There were no frame changes, but there were major changes to the fin. During that entire period I flew nothing else. After a somewhat shorter period it looks like we're about finished testing the R5, a kite we both enjoy flying.
The lightest delta isn't always the best flyer. The best flyers have enough weight to drop downwind and handle properly. Their weight distribution balances them like a tightrope walker's long balance pole, helping to turn the nose up when they get tipped over sideways. As my son put it, when he was about 11 years old, the R-series kites 'do what you want them to do, and don't do anything you don't want them to.' That's still the goal.
The original R5 was heavier than all but one of these test configurations. R-series kites are unusual (for my deltas) in that they fly with heavy frames. Usually heavy frame parts on deltas make them less stable, prone to diving (or worse), and hard to land. Conversely, very light deltas can tend to float about randomly like falling leaves when you let out line, refusing to respond to control inputs, even after taking up the slack, and then won't level out when you want them to. This next kite was like that.
Very light deltas are wonderful for flying in the lightest of winds, but, because they can also be quirky, they are somewhat specialized. An experimental Little Bear in Icarex P-31 (31 grams per square meter) with a very light frame including a super-light 4mm carbon tube center spine. The kite was as light as possible, but it was stubborn. It would turn downwind like any delta, but unfortunately would refuse to turn back around when the line was tugged! It would just drift off on its own, nose down, until it felt like turning or, more accurately, coincidentally got turned by a chance ground wind.
The spreader is already as light as practicable. There are but few options. The cure is to increase the weight of the center spine without impinging on its light wind credentials. It now responds, though somewhat reluctantly, to control inputs. The only remaining alternative would be to put a regular Little Bear spine in.
We have recently compared the XFS's flying qualities with fiberglass and carbon tube center spines (they used to be wood dowel). These are probably the first XFS Deltas we've flown since 1992 or 1993.
Thin fiberglass rod is very bendy compared to carbon tube of the same diameter and quite a bit heavier, although in the air the difference between them is less pronounced. In terms of flying, in light to medium breezes there's maybe a subjective 10% in it between the two. Thin fiberglass rod spines are just too bendy for this design, though. When the spine is a proper fit (not too loose), the front of the kite is just too flexible and the tail end bends down at the rear making the trailing edge of the fin go floppy.
The light carbon tube makes the kite perfect in the winds I've tested it in. When the kite was up high, my 50lb line was occasionally singing, even though lower down there was next to nothing. With the thin carbon tube spine the handling seemed to me to be flawless, the balance perfect. They fly so well with the tubing, from now on XFS Deltas will have 4mm tube, only reverting to 4mm carbon rod should the supply falter. Carbon rod may be less prone to splitting or being crushed on the ground (where most fractures occur) than thin carbon tubing, but it costs more.
I'm sticking with the carbon tube for now; the kite flies so beautifully with it. I'll test some thin carbon rod sometime, when I happen to have an XFS handy. It's only marginally heavier, but should be a more durable alternative to thin tube.
One would think this would be an obvious upgrade on a Little Bear, but when I tried one with an all-carbon, lightweight frame, it was less than controllable. It seems to need a bit more weight or else it just floats off on its own merry way and was wont to respond to line control. I'll be trying a solid carbon spine on that one in the near future, and if that isn't heavy enough, I'll stick with fiberglass.
(Some years ago) Had a series of good, high altitude test flights with the old Wildcard #1 with a new spreader, thinner and lighter than previously. This is with 5mm carbon wing spars, and the original 8mm wood spine. Highly promising. But is it practical?
Next: a lighter spine to go with it. (March 2006) On a new Wildcard used 5mm carbon rod spine and wing spars, and 6.35mm carbon tube spreader (28g). It weighs just under 230 grams. This is a wonderful combination for a kite flying enthusiast (I love it - I flew hardly anything other than experimental Wildcards for two years).
Note: those spreaders aren't available any more.
It's finally time to make the change from wood spines to fiberglass or carbon.
8mm hardwood dowels vary in density, hence Whirlwind and Wildcard spines have always varied in weight. The heavier ones weighed about as much as a 5mm fiberglass rod, while the lighter ones weighed about the same as 5mm carbon.
We've been testing a standard Wildcard (heavy fiberglass wing spars, solid rod spreader) with A) a 5mm fiberglass rod spine, and B) a 5mm carbon rod spine. So far it's inconclusive - there isn't a lot of difference in the air, not even with fore-and-aft balance.
We've tested both spines on a std. Whirlwind, too. Fiberglass spines are bendier, which may help* in gusts, but it's heavier by a few grams. That usually helps stability, but hampers light wind performance. With the fiberglass spines, both kites seemed "smooth flying," while with 5mm carbon spines they may have been slightly more efficient (in lightish breezes) and perhaps more stable on landings. In the air there was really no detectable difference between the kites with fiberglass spines versus carbon spines on our two test days - but we have not pushed the upper limits of wind speeds. Fiberglass spines might be better near the upper end of the wind speed range, if there isn't too much spine flexing.
These days, kite fabrics are made with an eye toward inflatables, so it's soft and fairly stretchy. Stretchy fabric allows more bowing of the spine, and when the centerline is cut on the fabric's bias, that bowing is exaggerated (which is one reason I prefer non-stretchy fabric). Conversely, with a low-stretch fabric, cut so the grain's in line with the centerline, spines can't flex as much as they can when the centerline is on the fabric's bias. In other words, a fiberglass spine combined with a stretchy fabric cut on the bias will bend the most in the air, while a carbon spine combined with non-stretchy material cut on the straight will flex the least. As these kites have non-stretchy fabric cut on the bias, I believe I'll go with carbon spines; they are lighter and, because they flex the same as the original wood, flying characteristics will be most like the original kites. There will still be some more testing. Some flexing is not a bad thing.
* In the mid 1970s John Loy designed a delta with a bent tube ferrule in the spine just at the front end of the fin, bent upwards 7°. I tried it, but found it somewhat impractical (I like to be able to roll kites up neatly). However, one afternoon at the Round Pond I crashed a kite and broke the spine at precisely that spot. To our surprise, it still flew, and not only still flew, it was also not bad in the strong breeze that caused the crash in the first place. That nose end bobbled up and down in the wind, yet did not try to flip up and over backwards. Fiberglass spines on deltas may be advantageous in gusty conditions by allowing the nose end of the spine to flex upward.
Bev has been testing the carbon-sparred X-100C, and declares it docile, well-behaved and an excellent flyer in light wind. It's "totally perfect," Bev says. In lulls it doesn't drop its nose or swoop; it just hangs in the air. In gusts it pulled so hard it burned her hands, but it didn't get bent out of shape. Landings: she can bring it down to her hand every time. I've decided to drop the old heavy original version from the catalog.
Since the thin-walled unidirectional carbon tubing used for light wind wing spars on several of my kites, including the Light Carbon Whirlwind, isn't being made anymore, I cannot make the optional light wind frame for Whirlwinds.
In early September 2003 I began weighing up some different Whirlwind frame combinations based on solid carbon rod wing spars with flexibility almost the same as the original fiberglass, plus two spreaders - one rod and one tubular, both thinner than the Standard Whirlwind's 8mm.
The next-to-lightest light wind frame (after the one that's no longer available) uses thin carbon rods slightly heavier than the original thin-walled carbon tube. This rod performs so well in the R6 it seemed certain that it would suit the Whirlwind, and in fact that has proven to be the case. It is also as durable as the old unidirectional thin-wall tubing was fragile.
The most recent test flight was in a steady, very light wind that increased after the kite went into cloud at about 1000ft. The line - 50lb Kevlar - started to sing. The kite was surprisingly well-balanced. It sat level in lulls, and straightened itself out quickly if upset by a cross-wind. The spreader was the relatively heavy 6mm solid carbon rod used on Wildcards; the spine was the then-standard 5/16"/8mm dowel.
Previously this kite had been test flown with a 6mm (¼") dowel spine and the tubular carbon spreader from the original light wind frame option, a classic delta frame setup for light winds. In that strictly light wind testing the kite was an efficient flyer. However, this latest version seems to handle and balance as well as a Wildcard.
The old experimental versions described below laid the groundwork for the next generation of Wildcards using alternative wing spars. They will almost certainly use 5mm carbon rod for the wing spars, and either that or the current 5.5mm fiberglass tube for spines. The big question mark is the spreader, but there aren't many possibilities to choose from. The aim is not to make lightweight Wildcards for light winds, but to have an all-rounder as good as the original if at all possible. The best-case scenario is that it will be better. There may be several versions over the latter half of 2015, and cost considerations have to come into it, too.
After but a single session of attempting to test fly a new adjustable fin idea, I put a standard stock fin on the test Wildcard, which became the test bed for some new frame combinations. The plan was to eliminate combinations that were clearly no good. This kite has now been flown on four consecutive weekends using combinations of two pairs of fiberglass wing spars, three carbon spreaders, and two wood spines, in winds ranging from very light to pretty blowy (80lb line singing).
No combination proved to be a bad flyer.
The kite was flown on 80lb line, with 6mm dowel spines (19.5g) for light winds and 8mm (30.0g) for strong breezes, complementing the different wing spars.
Each combination has its own particular character, but none stood out as significantly better. With lighter frames the kite pulled a bit harder, and felt more lively; it moved in response to small cross winds more and recovered from dives more quickly. Heavier combinations tended to be smoother overall flyers. The kite didn't react to every little cross wind, took a little longer to recover from dives, and was less stable on landings, but it stayed level in lulls, instead of dropping the tail or nose (a characteristic I want to keep if at all possible). Being heavier, the kite pulled less hard in strong breezes, and the smooth flying is very nice once it's up there. One surprise was the degree of improvement in light winds with a lighter center spine, regardless of what wing spars & spreader were used.
Each combination has a different center of gravity, so each setup has a different balance. Heavy wing spars with a lightweight spreader puts the C of G further aft, while light spars with a heavy spreader shift it forward, which accounts for the different pulls and different responses to upsets. There were times when one or another combination felt better, but as conditions vary, so too do assessments of flying quality.
One question was whether a light framed Wildcard would ultimately prove to be a good all-rounder, better in light winds yet nearly as good (or even better) in the stronger, upper limits of the wind speed envelope. With a light frame it seems to manage - up to a point at least. It hasn't been pushed in really strong breezes yet. The standard fiberglass wing spars are far more durable than thin-wall carbon, so, based on intended use, it would make sense to concentrate on these in consideration of long-term reliability. At this point I hadn't considered carbon rod yet (see below).
One recent test-flying day began with the kite fitted with lightweight carbon wing spars, a thin wood spine, and a 6mm solid carbon rod spreader compared with a slightly stiffer 6.35mm carbon tube spreader. These same two spreaders were tried with the standard fiberglass wing spars, and the final flight of the day was with a heavier spine as well. Unfortunately the wind had died by then.
Though the Wildcard's wood spreader is a millimeter thinner than the Whirlwind's, both kites came with 8mm carbon spreaders as optional extras (that was back when the originals were wood). At 53 grams the 8mm carbon spreader is 3 grams heavier than the original. Wood spreaders are a great deal easier to make and fit, but out of any bundle there are fewer and fewer dowels good enough for spreaders these days, so the 6mm carbon rod, at 48 grams, looks like an excellent choice, since it maintains the ideal balance of the original Wildcard. It remains to be determined if the 34 gram 6.35mm carbon tube, giving a slightly different balance, would be better (or not) with the standard fiberglass spars (I preferred it to 6mm rod on the R6, below).
Ironically, 6mm carbon rod costs more than 8mm carbon tube (by about 13%), so I want to make absolutely certain, over a period of time (to cover a range of conditions), that I arrive at the best combination. After a succession of test flights it is beginning to look as if the solid rod will be best in Wildcards, while the ¼" tube will be best in the new R6.
The initial test was very successful using a lighter (6.35mm p/t carbon tube) spreader. That's an understatement - I loved this kite and have had several magnificent test flights with it. In spite of its light weight, it seemed as good in fresh breezes as it was with its stock heavy frame. More spreader tests are required, including the light and strong 8.0mm used on the Whirlwind.
|Spar Material||Spar Weight - grams per piece|
|5.5x3.2mm carbon tube||21.7|
|5.0mm carbon rod||31.25|
|6.0x4.0mm Exel fiberglass tube||29.9|
|Stock 6.35 p/t fiberglass tube||48.8|
The success of the 5mm rod wing spars in the Wildcard led on to trying a Whirlwind with 5mm rod wing spars.
The 5.5mm thin-wall tubing I used on the original Light Carbon Whirlwind is fragile; it can split on a bad landing or if it's stepped on. Tubes often arrive with one end crushed in the deliveries. The weight difference between the 5mm rod and the 5.5mm thin-wall tube is about 10 grams per spar - 25 grams vs. 35 grams - for a total of 20 grams per kite. That's almost ¾ of an ounce heavier, but that difference seems less significant compared with a standard fiberglass spar at 58 grams per spar.
The first test flight was nonetheless rather fine in spite of the extra 20 grams (with 6.35mm spreader). It's an obvious trade-off - ultimate lightness versus durability. More testing should determine which the combination has the better handling, regardless of whether it's the lightest in weight or not. (This question is now redundant; the manufacturer has informed me that their original unidirectional 5.5mm thin-wall carbon tubing will no longer be available.)
This is another kite whose original drawing was lost when we temporarily moved out of the house, along with some of the other R-series kites.
Originally framed with robust ¼ inch fiberglass wing spars, the plan form is geometrically similar to a light wind kite (such as the old Carbon Flyer). It (eventually) occurred to me to try some lightweight frame combinations in an R6. I tried thin-wall 5.5mm carbon wing spars a few years earlier, but they turned out to be too stiff - it flew, but was too twitchy to handle. Having two of those earlier kites to play with, I put 5mm fiberglass rod in one and 4mm carbon into another, and had an assortment of different spreaders. At that time I didn't have any suitable lengths of 5mm carbon rod to try. Since the smaller R5 Rustler also uses 5mm fiberglass, I thought the bigger R6 would actually be too bendy in anything but very light winds, so I waited for a calm day.
By the time we arrived on the hill, however, it was plenty breezy. I tried a test flight anyway, and - wouldn't you know - the one with 5mm fiberglass wing spars flew amazingly well in the strong breeze despite being seriously bendy. This was on 80lb line, which was singing a good deal of the time. It had a ¼" wood (light wind) spine, too, which I changed to 5/16. The 4mm carbon configuration wasn't too bad, either, with thin spine and ¼" carbon spreader, but it wasn't quite as smooth as the one with 5mm fiberglass.
This was beginning to look like a new combination of lightweight frame with breezy-weather towing point. The towing point is slightly forward of the optimum position, almost the same as the XFS (another light wind frame). Originally I thought the drag from the extra trailing edge fabric would cause excessive wing spar bending, but it wasn't too bad and the kite actually climbed into gusts.
Enter 5mm carbon rod
The two test kites now seem about right with 5mm carbon rod wing spars, ¼" carbon tube spreaders, and 5/16" wood spines. It's beginning to feel like a final version, and testing will continue with the two spreaders, one 6mm carbon rod, the other ¼" carbon tube. We're looking for the combination that's better balanced.
I definitely prefer this kite with the 6.35mm carbon tube spreader. The options for center spines are wood, fiberglass, and carbonfiber. I no longer keep wood here, leaving 5.5mm fiberglass tubing and 5mm carbonfiber rod (by weight), with no firm commitment either way. The closest in weight to the original wood (which varies a lot), is the 5.5 fiberglass, while the carbon rod is lighter by 2.7 grams, but stiffer. The weights of just a small sample of wood dowels showed a weight variation of more than 6 grams.
Fiberglass takes a better curve without stretching the sleeve too much, giving the centerline a nice camber without trying to poke through the ends of the sleeves. It can also flex in strong gusts and self-adjust in turbulence. The carbonfiber rod, on the other hand, gives a slight edge in the lightest breezes and perhaps a snappier feel, though discussion of responsiveness in an R-series design with its flapping trailing edges might seem out of place. I currently have 5.5mm fiberglass spines in my two R6 test kites. If I change, then the production kites will change as well, though the price will have to reflect that change.
Superficially these kites are similar to the first deltas I ever saw in the mid-1970s. But more so than those early deltas with thin dowels the R6 approaches the ideal of a delta that flies in light winds as well as quite strong breezes without zooming all over the place and threatening to crash-dive. I'd been trying for years to achieve this. Those cloth 7 foot deltas from the early 1970s used very light frames with 48" long, ¼" diameter dowel wing spars, ¼" dowel spines, and 5/16" wood spreaders.
Finding a blend of towing point and frame that does it all is almost unattainable, without sacrificing performance altogether. The R6 project is like picking up where I left off in the mid-1970s when I started scalloping trailing edges. What goes around came around.
I never got the chance to fly this, my latest "experimental" kite, and so must rely on its new owner's own enthusiastic reports. He has a better wind meter than I do, and the brief was to make a new version of the Clipper that would improve on the standard Clipper's minimum wind speed of around 2mph.
So this isn't a new design geometrically. It's made from 0.5oz spinnaker cloth, framed with thin-walled carbon wing spars and a 6.35mm spreader. I left off the anti-stretch sleeve reinforcements and the fin gussets at the towing point for a simpler construction and to reduce weight. The center spine was utilitarian 8mm dowel (but could have been lighter).
On relatively heavy 88lb braided dacron line the kite lifted a 6oz falconry lure virtually overhead in a measured 0-1mph wind at ground level! (This exceeded expectations.)
What with the double move, first out then back in, followed by building and decorating, there hasn't been a free weekend since before Christmas. In any case, foot-and-mouth restrictions has meant my flying site has been closed off.
What's worse, and there's no way to over-state this, somehow during the move I lost a whole pack of working drawings - most of the R-series, including the R4 Ranger, R5 Rustler, R6, R8, plus the R3 Snippet and all the successive Wildcards. Fortunately, I have patterns and prototypes of the small ones, but the scaled-up Wildcard project will have to be started again from scratch, when I've caught up with orders and have some time for playing. So, rather than testing, the latest design work has all been on paper.
I have a new set of dimensions worked out for a scaled-up Wildcard, but there is a problem with the carbon spreader. All the other parts are available in the scaled-up sizes. The wing spars are crucial, the spine is okay, but there isn't a stock size readily available (that I know of) for the spreader. Jump to earlier note
I've been testing two frames on the X-100. One is standard, with 8mm fiberglass wing spars and a wood spreader. The other is a fancier one with 1/4 inch carbon wing spars and an 8mm carbon spreader. So far I prefer flying it with the standard frame, but that's because it's been so breezy. The kite is a very nice flyer with the standard frame; the handling is smooth and stability is solid. With the carbon frame in the same winds it's got a tendency to go down to one side if the gusts are too much for it. It's another candidate for a 10mm carbon spreader (but I don't have any 10mm carbon yet).
In light winds, however, the carbon frame is almost essential. Bev managed a better flight in light wind than I did with a CC345 one day, both on 80lb line.
The original scaled-up Wildcard has to be replaced, since it's in California, fitted with a new frame using materials not available here.
The smoothness of the wing fabric is visible in this photo by Kevin Flynn. Back to newest note at top
This kite had been packed away in the corner of the workroom for several years, after I lost interest in its flight behavior. I had forgotten about the experimental fin on it until recently when I re-discovered the original drawing. A couple weeks ago I made a new fin for it, based on the original Trooper, and test flights in rough breezes have been very good ever since.
This is another kite which needs to be made again, next time using a lighter fabric.
It has been flown both with and without the tail, which is there to help stabilize the kite in blustery turbulence - not to rescue a faulty flyer.
At Margam Park Kite festival several years ago, this is the kite I flew for most of the day - the gusts were too much for everything else until late afternoon when the wind finally dropped. I even allowed it to fly tethered from lunchtime onwards. I don't normally do this, but the sky wasn't crowded enough to worry about tangles with other flyers.
The tail is visible here. It's perhaps 45 feet long, double-thick ripstop strips sewn together and snipped along the full length.
The fringe keeps the tail from whipping, and the two layers give it the right heft. Tails help prevent meandering in gusty conditions, and help on landings in tight quarters.
This kite has a new spine and spreader. The original parts are ramin hardwood. The new spine is the same 8mm fiberglass as the wing spars, and the new spreader is 10mm carbon tube. The new spine weighs about 26½ grams more than the old spine, and the new spreader is about 17½ grams heavier than the original, but this is as close as it's possible to get to a scaled-up version of the current Trooper. It is a heavy kite, but it nevertheless flies pretty well in winds gusting to over 12mph at eye level, and easily double that aloft. (My first day out with the new wind meter.)
Although this initial version is as close to a scaled-up Trooper RS as it's possible to get, I want to try some lighter spine and spreader combinations. On the Trooper RS the spine and wing spars are the same material, and the chosen spreader is the heaviest of those tested during development.
The PullTruded fiberglass used for this kite's wing spars are a given - they cannot be changed. So that's the logical first choice for the center spine.
In line with the regular Trooper, the logical choice for the spreader would appear to be the heavier of the two in the table below, but that one is so much heavier than the original wood spreader that the lighter one could ultimately be chosen instead.
There are two alternatives for the 8mm PT fiberglass spine: 8mm PullWound fiberglass, and 8mm PT carbon tube. Weightwise, the PW fiberglass is closest to the original wood. But, as noted, the regular Trooper RS has a heavy spine, so all three in the table will be tested. Hopefully the elimination process will go quickly.
We have a new special order stock part for another spreader, 8mm PT thick-wall carbon tube, with a 1.5mm thick wall section.
Early Troopers were nose-heavy, because their wing spars went almost all the way to the nose. They were solid in high flight, but those long spars were restricted in their ability to self-steer as they pivoted up and down about the spreader attachment point - noticeable especially during landings. It is possible that heavy spreaders have a similar effect on the current Trooper's balance.
|8mm PT fiberglass tube||86.8 grams||10mm PT carbon tube||79.3 grams|
|8mm PT carbon tube||66.6 grams||10mm PW carbon tube||48.9 grams|
|8mm PW fiberglass tube||60.2 grams||8mm PT thick carbon tube||about 55 grams|
|Original 3/8" Ramin hardwood||57.6 grams||Original 7/16" Ramin hardwood||59.4 grams|
There's an old rule for deltas: heavier spines add stability (up to a point). I don't use heavy spines for stability in light wind deltas, because it defeats the object. These kites, however, are not for light winds. Previous Trooper test kites have never worked if I tried to change them; I'm hoping this one will be relatively free from unpleasant surprises and that testing will proceed swiftly. Time will tell.
The tail was added because when I brought the kite down, local turbulence made a controlled landing almost impossible. When a heavy kite like this turns sharply in swirling turbulence, its momentum makes it want to carry on turning, which effectively then becomes almost a spin. On a short line it can go wild. Besides the skill of the flyer, the only corrective forces available to curb that tendency are aerodynamic. At times there is just too much momentum for the aerodynamic forces available, so you add some. That's where the tail comes in. It effectively counteracts the tendency of the kite to spin while coming in for landings, in addition to keeping the kite on an even keel at altitude.
Tails like this are able to slip across and over kitelines - there is nothing to catch or snag.
Nothing conclusive to report. There was hardly any wind - an average of 1.7mph, ranging from 0.0 to a single gust of 7.8mph (at 6 feet from the ground). That's not to say it was a washout. In fact we had an unexpectedly nice flight - a surprisingly good flight for any kite, let alone a Trooper. It was rock steady, with hardly any pull in spite of my old hefty, rough, industrial 240lb nylon braided cord (neither of us likes a lot of pull anyway).
Because of the light wind, we began with the lightest spine and the lighter of the two spreaders, and had a fantastic flight. Next, I put the heaviest of the three spines in, sticking with the light spreader, and it wasn't all that different. It was only after I put in the heavy spreader that it wouldn't stay up at all. That may mean, of course, that that will be the best strong wind combibation.
The way it goes is that in any given wind there is going to be one set of frame parts that works perfectly in just that given set of circumstances, but here we are looking for one for the worst set of conditions. Today was not the worst, but it was bad enough for us. We'd rather not get involved with winds that can do damage, where the fun is replaced by a job of serious work.
I had no place to mount the wind gauge, so a few quick readings were all we had to go on. The maximum gust measured was 15mph, but there were some stronger than that. The kite was not easily brought down. Bev could only hang on to the spool with both gloved hands.
|Five seconds of a landing in turbulence - the kite is actually further away in the last photo |
(test frame 1 with the heavy spreader)
The sweet spot ? (test frame 2)
The first combination took line out in perfect balance, and was solid at altitude, but it was also very difficult to land (being prone to excessive inertia). The second gave a little more pull, but it wasn't unmanageable. It was the best of the day and, I think, hard to beat. It reacted to gusts with more agility and was a bit easier to land, too. The last test tried out the intermediate center spine, and rather than being the happy medium, it turned out (in today's conditions at least) to be neither fish nor fowl. Just that bit too light, the winds seemed to bat the kite around too much for a Trooper or Tempest. It needed the tail, really, but that wasn't the point of today's testing. There was no point in trying the lightest spine today, either. It'll be kept in the bag for light winds, though, along with the heavy spreader, which hasn't been eliminated from contention just yet because of that unknown 10%.
This gentle giant was given an outing in winds just too strong for comfort, yet it behaved impeccably (to my great relief). It's currently sparred with 8mm carbon tube in the wings and I flew it with the heavy wood spreader on 120lb line. It can't remain upright if the wind is too strong, however. The R10 was better for such conditions.
This is the kite I flew recently for my first session of falcon training, when falconer Roger James couldn't get his Wildcard up in the light winds of the day.
Click here for a few photos of a nice kite I had the opportunity to build several years ago. It has 8mm carbon wing spars, and sometime I hope to get an experimental (10-12mm) carbon spreader.