After Mongolia Guangdong, Weifang, Shenzhen. 20 Oct to 1 Nov 2015.

After Mongolia Guangdong, Weifang, Shenzhen. 20 Oct to 1 Nov 2015.

Octopus and Serpent: The Serpent currently has much more curve-down on each side; more sled like than the Octopus (Blue ex Kaixuan). The Octopus also has less camber in the mid-top body area. Flown alone, the Octopus has more inclination to falling-off to one side in light conditions- making launching in light winds difficult. At none of these events, did it show any tail tangling tendency- and quite strong winds at Shenzhen, almost more than I could pull down- 3sq.m 1Skin Pilot. 

 

SSSL Octopus with inflated leading edge at Shenzhen 2015

At Weifang; added a crescent shaped ram-air inflated leading edge element to the Octopus (360mm wide x 200mm deep, independent of the top skin) and the Serpent (320mm wide, 200mm deep using the leading edge and top skins as 2 of the 4 sides). 

The Octopus flew well straight away, had none of the leading edge collapse in stronger winds it had previously had. In a Wiefang test - strong wind very wind-shadowed area- it fly by itself very well, at least as reliably as the 1Skins, more reliable than Craig's 8sq.m pilot. It also flew well for very many hours with a 1Skin pilot at Shenzhen (light lifting to strong on shore). Craig thought it was volatile unstable, but I doubt this, did see some sashaying when the wind was light but this had no tendency to increase as the wind built- could be either a light wind (falling-off) effect or a pilot effect. It did seem to have less pull than before the ram air element was added.

 

SSSL Serpent with inflated leading edge at Shenzhen 2015

The Serpent would not initially inflate- the extended leading edge caused flow across the inflation gauzes rather than blowing into it. This may have been largely because the centre leading edge where the gauzes are is quite set back on the Serpent relative to the Octopus. After taping off the leading edge extension it did inflate OK- though still rather depressed in the centre and too far forward in the shoulders. It then flew all day reliably- no volatility- under a 3sq.m 1Skin. Didn't try it by itself. Need to cut-off or sew down the extended leading edge (will this cost some light end?) and set the centre LE forward relative to the shoulders and test again. Perhaps the tail panels could overlap for the same functional effect as the current longitudinal gaps- but for better visuals. The eyes need to be closer together.

For the Octopus, clearly the Serpent style leading edge cavity is lighter and simpler- but will it work as well? 320mm width is sufficient. Need to adjust the Octopus bridling to a bit more like the Serpent to stop the light wind falling off, and test how far forward the bridling can be pulled before leading edge collapse again becomes a problem. 

1Skins;

Both the latest 3sqm (yellow) and the 6 sq.m (orange) ex Kaixuan were excellent- did good service at Guangdong and Shenzhen (though not used when the wind was very strong and gusty offshore on the second day at Shenzhen). Ron Spaulding and Andreas Agren both said the 6sq.m dived-off, twice, tangling them in the tight formation flying during the first day at Shenzhen. I didn't see this, but it's possible- or could have been

interference from another kite or just a patch of turbulence and a slow recovery. At Weifang on the 29th- strong turbulent wind, both these kites were much more useful and reliable than Craig's red 8 sq.m. pilot- which was collapsing badly.

While at Kaixuan on the 29th, had a prototype 3sq.m. (blue, no number) with tubular ram-air inflated leading edge built. At Shenzhen this showed no sign of leading edge indentation (the presumed cause of diving-off) at all, and adds less than 5% by weight and cost. This kite did not have tuning lines and was progressively left wing so wasn't tested in the strongest winds, but is looking promising. Add tuning, test again- and try pulling the bridling forward to see if this kite will now accept a lower angle of attack.

And what if the indentation that presumably causes diving-off is asymmetric because once the kite starts diving off to one side the flow centre/stagnation point is displaced from centre towards that side?

To test for this, try a 1Skins with inflation at 1st rib each side and with no connection to the opposite side.

Could this also be a problem/solution for the ST Ray? 
Wuhan 7th 8th November 2015

Octopus and Serpent; The Serpent bridling at the leading edge was mis-rigged in various ways from hasty re-attachments after the active part of the leading edge was sewn down at Weifang after Shenzhen. After correcting this to some extent, and reducing the amount of spanwise arch- which seemed excessive- the bridling was too low- would barely launch, even with a 1Skin pilot in the light winds. Looked good when it was up though. Leading edge still does not inflate well- better than at Shenzhen, but not now nearly as good as the Octopus (which has an inflation cavity independent of the top skin). Maybe shortening the centre front bridles will fix the Serpent's inflation and stalling; need to fly it beside the Octopus at Wakanui. Maybe there will be a useful advantage from adding an inflated central keel as well- for the Octopus also. The Octopus looked and flew exceptionally well and at a high angle using a 6sq.m 1Skin- wraps only happened when the top kite fell back and the Octopus overflew the top kite line. The tentacles never tangled if they started fairly clear. Sashaying does appear to be caused by having a top kite at a lower flying angle. There are definite hopes for these kites in stronger winds now. 

For bridling; all the secondary's should be identical length, variations only in the primary's- which should all be cut to the same length and tied centrally- and 500mm x 2 longer to allow for length variation requirements. 

1Skins: 

These kites are currently excellent in their window, but that window still isn't wide enough at either end of the wind range for them to supplant conventional pilots. Their advantages are higher flying angle, huge pull and much easier launching and active flying. In the light to nothing winds at Wuhan, a 6sq.m 1Skin could immediately lift either a max Trilobite or Ray up to flying altitude uninflated -the only maxi kites that did get up enough to fly (briefly) on the second day. 

What can be done to improve their light end? This is worth maximum effort as an even 10% improvement will likely make them the best of all pilot kites when the wind is alternating from nothing to very little- the usual conditions at China events- and not uncommon elsewhere.

Is there any way to make a reactive bridle that responds to stalling by reducing the kite's bridled A of A for just long enough to get the kite moving up again? Problem is that this is exactly what will also cause luffing - because the centre of pressure moves rearward in luffs and in stalls. Such a mechanism is possible if it's active- like a human pilot, but can it be done passively with levers, pulleys, springs and dampers? Theory suggests not because to prevent luffing the rear bridles must be shortened - which requires energy input. The active leading edge does seem to helping quite a bit to reduce stalling- if it's extended, will it help more without causing other issues? It is compatible with inflated element leading edges. Try this. 


 

Weifang, 21st to 23rd July 2015:

Test flew 1Skins; K1 1.5sq.m, K1 6sq.m, K25 3 sq.m. (all with adaptive leading edges).

Main civic square in Weifang; almost no wind, then strong wind and heavy rain, then rain and no wind.

K25 3sq.m yellow and K1 1.5sq.m yellow appear to be satisfactory- didn't try during the brief windy period, but their responses were as they should be. This 1.5sq.m (the first one) was very volatile until it had some line pull- then straightened up and was stable, as expected for a smaller kite. It will be interesting to see what upper range this kite has- if it will fly reliably in stronger winds than the 3sq.m"s, as I suspect, this implies that fabric stiffness is probably a significant factor at the upper end.

K1 6sq.m orange (the first 6sq.m), was flown straight-off without checking on a long line during the squalls to lift an ST Ray. In the strongest gusts it would eventually dive inexorable to either side (shoulder collapse)- and didn't seem that keen to stay central except in very light winds. Is this a scaling effect (fabric stiffness as above?) or is there some scaling error or other influence. A bridle check showed the shoulder bridles to be all 60mm shorter than they should be proportional to the current 3sq.m"s- and this would definitely cause diving-off. Lengthen these and re-test. It"s also possible that its behavior was just very bad inner city wind- the square is surrounded on all sides by sky-scrapers- though none closer than about 200m .

SS show kites:

The first sample 20m SS Octopus (blue) from Kaixuan looked generally OK but was terminally inclined to "diving off". Visually the bridling appeared to be significantly different to O2 yellow, but I didn't have time to find the actual differences and correct them. They have also used bridling and cording line that is far too heavy - the bridles alone probably added a kg (to a kite that should weigh less than 3kg total). Easily fixed; and perhaps in future the bridles should be all individual rather than cascaded like for O2, S1 and this sample. This would be quicker to do and have many less possibilities for errors. Suggest cutting all bridles to the longest length, then marking in bands back to the shortest. This would allow the person bridling to quickly tie every line without further measurement- just by counting back the bands for each position. Left-over ends could then be cut off (the longest "tail" will be less than 500mm). Should some capacity to change the relative overall lengths, leading edge to trailing edge, be retained by keeping, say four secondaries at the line attachment point? Maybe there will eventually be "strong wind" and "light wind" settings, but I don"t have useable ways to do this yet for the Octo or the Serpent because far too many changes are required. The goal for now is; one bridle for all conditions- though at present, without changing anything for different winds, they're a long way from this with less than the best achievable light wind performance (still amazing though) and leading edge collapse from about 15km up for the Octopus, maybe 25 for the Serpent (at probably some cost to its light end).

Both O2 yellow 20m Octopus and the S1 green 35m Serpent flew very well when conditions were suitable- their ease of launching is phenomenal - quite unexpected- just let wind into any part of the leading edge and they "inflate" and launch themselves- provided they're pointing approximately upwards. In light winds, pulling or running doesn't help much, unless there is more wind at altitude- they either fly or they don't. The Octopus was more susceptible to leading edge collapse than the Serpent, but seemed to require (very) slightly less wind- need to check this though, might have been because it was flying higher where the wind was stronger. The Octopus was also slightly inclined to diving over when the wind was zero- would slide off inexorably to one side or the other as it came down in the lulls. The Serpent didn't seem to do this to the same extent- a function of its slightly greater spanwise camber? Developing the Octopus and Serpent bridling completely independently has been an excellent approach- it is clearly identifying the effect of differences.

Changes for the Octopus:

Individual bridles as per above, taper tentacle ends and don't have a cross hem (to reduce tangling), try increasing the active proportion of the leading edge for less leading edge collapse in stronger winds, and try one with Serpent bridling.

The Serpent had less leading-edge collapse in stronger winds but did appear to be on the verge of volatile instability at about when its leading edge begun to push in. The lengthwise slots in the tail (to allow some airflow through so that the rear upper side of the tail does not become a big low pressure zone) have very successfully stopped the tail from folding over- and without the visuals being too detrimentally effected; a triumph for theory! Appearance is generally good- plenty of fliers wanting to buy- but sharper colour contrasts will be better. The eyes are too wide apart- one eye is partially obscured when looking from the side.

Changes for the Serpent:

Individual bridles as for the octopus above, move the eyes closer together, try increasing the "active" proportion of the leading edge for better light and strong wind flying.

Generally both these new designs are a very good beginning- will find market niches I expect, but the challenge is to increase wind range without adding adjustment complexities that fliers will simply not accept.

Using a 1Skin pilot above the Octopus did help its upper range a bit (was excellent in Kelantan), but in the briefly much stronger and gustier Mongolian conditions it was not sufficient- its leading edge collapsed so extensively that the Octopus would wrap itself around the pilot line when recovering. I didn't try a pilot above the Serpent at this event because it was generally OK- only came down twice in strong winds. Need to try it with a pilot, and also with a drogue. Best will be if a combination of active leading-edge changes and bridling can push the wind range up without, at the least, costing lower end. They're pretty good for such radical new designs already though, and will get better.

For the next style of SS show kite, to consider is that the Boomers, 1Skins, Octopus's and Serpents all have approximately semi circular leading edges- is this contributing to these successes by comparison to the SS Ray and SS Flag which don't (yet?) fly satisfactorily? Also, currently the SS show kites (Octopus and Serpent) are both upper range wind limited (though I haven't yet tried a pilot with the Serpent or a drogue with either). The Boomers and 1Skins have better top ends but are not as good as the Octopus or Serpent at the light end (except if they're actively flown). How to get more wind range? It seems that having lateral area stability (Boomers and 1Skins) helps the upper end (both the Octopus and Serpent appear to be volatile unstable in stronger winds- if their leading edges don't collapse first). And possibly, tails help the lower end by preventing overflying and LE collapse when more forward bridling is used- though it"s more likely that the Boomers and 1Skins would fly in much less wind with more forward bridling, but would lose their upper end (which is barely good enough now). The Octopus and Serpent's lack of upper range could be corrected by bridling back (which would prevent leading edge collapse), but unless taken to an extreme, they may then become volatile unstable without either longer tails or a drogue. Except that I did try a rearward bridling for the 20m yellow Octopus at Kelantan, and this did enable it to fly in much stronger winds (lost the light end though). And, the 10m pink O1 did fly in VERY strong winds in Vietnam, so perhaps it is just that the current bridling arrangements do not have wide enough ranges rather than there being any fundamental upper range limiting factor with these designs. Too much pull is also a consideration. More rearward bridling will increase pull- and they all have more than enough now.

For the next design, is there a show kite style that has some lateral area as well as some tail drag?

A caterpillar maybe (legs could provide lateral area)?