SSSL Ray

History:

Ray 1 June 2015, purple, AR 1.4 uncontrollable diving over. Used rope tail.  Held shape OK, but would not fly for even 10 seconds.

Ray 2, Pink, Jan 2020, AR 1, with cut back rear.  With ribbon tails, did fly, but exhibited uncontrollable falling off wing tip collapse except sometimes in strong winds.

Ray 2 Blue/blue/black,  Feb 2020, AR 1.0 with cut back rear.  Flies relatively well but with falling off/tip collapse in lighter winds and weaving instability in strong winds.  Was better after a 500mm wide by 17m tapered tail was fitted.  Looks more like an Indian Fighter than a Ray

Ray 4. Yellow/orange/red/black, 16 Feb 2020, aspect ratio 1.23.  Severe falling off/tip collapse with original bridling (flat).  Flew satisfactorily in stronger winds with less WI than Ray 3 (because of higher AR), especially after 500mm wide x 17m heavy fabric tail was fitted in January 2022.    

January 15 2021: Ray 4 was re-rigged with 200mm of anhedral.  This improved recovery at edges dramatically and has reduced weaving in stronger winds.  

Further development:

 On 8m line, light sea wind, rhythmic weaving about 30 degrees either way.  Weaving amplitude stayed about the same as line length was increased, (hence angular  deviation decreased).  With single point tail attachment, no noticeable difference (tail width at root 500mm).

 In mid-range wind (10 to 20kg line pull), weaving reduced and became inconsistent- more a falling off to either side, with recovery occurring as the underside tip collapsed a bit. This is a form of blink stability

 Check behaviour in stronger winds.

Ray 4 with anhedral Is sensitive to bridle lateral symmetry but not particularly to other bridle changes except centre leading edge.

Biggest challenge now is in to reduce and if possible eliminate falling off induced wingtip collapse (especially in light winds when it causes the kite to fall to one side or the other), and to do this without cost to performance.

Questions:

1. What is optimal anhedral?

2. Should it be an angle or a curve or just pulled down tips?

3. Why has anhedral caused more collapsing of centre leading edge, requiring bridle let outs? Should be opposite.

4.  Increasing AR could be used to reduce weaving instability (WI) if this increases in stronger winds, but can this be done without exacerbating falling off? 27 Jan strong wind test Ray 4 : No weaving, surprising stability (better than current SSP's, much better than Stinger, 30m Serpents would not have flown).  Minor wingtip collapses (not detrimental) and some upper centre concertina- how to fix this? Maybe wait until there is a second identical Ray.

Ray 3, same wind, weaving but not quite looping, broke line- 4mm soft Chinese Dyneema, same as broke with Octopus and Serpent in Satoon (2017?).   

5.  Many dynamic bridles were tried on Ray 4:  The most sophisticated was by rigging outer bridles through a pulley so that more pressure on one side released that side marginally while at the same time shortening the outer TE bridles on that side to steer the kite back to centre.  None of the iterations tried had useful effects but there could still be benefit in dynamic lateral bridling (there is in dynamic chordwise bridling) if a precise right arrangement can be found-

6.  Try moving wingtips forward- unfortunately this requires a complete new kite- 3 days work?

7.  28 Jan '22 Stiff easterly at Wakanui, close to being unable to pull Ray 4 down; tends to hang a little left then a little right- seems to be tips LE's folding a little, let out 25mm?

8. Reverse steers (in strong at least) : pull in tip TE left a lot (came off knot) , goes right (but stayed up). 

9. Light mid range wind at Wakanui, 29th Jan '22.  Let out 3 LE wingtip bridles each side by 30mm.  Flew perfectly, slight sideways movements (not weaving) but no significant tip collapses except when line length was short during pull down.  Centre line bridles towards LE are loose- tension is taken by next sets out.

10. Panels could be made with curved-in corners to create diamond pocketing with this design- templates changed for this, Ray 5.  

Wakanui kite day 30 Jan '22, quite strong easterly by 4pm:

Ray 4 is astonishingly good- was flying when SSP 14 and 15 were still struggling in earlier light wind, then unmoving in the sky as a pilot for 2/30m Serpents. At take down, line tension for this train was very high- 3 people could not pull in enough to get a loop (used gripper).  Tied to van a rapid upwind move caused the Ray to dive over to the right- presumably tip collapse (2 TE tip bridles had slipped).  Wing tips were still tending to fold under a little in the strongest winds.

Ray 3 was WU in the stronger winds, would not stay up, even on a longer line.

Ray 5, 1 Feb '22 has 74 bridles.  Are all the centre line bridles necessary- at least 4, possibly 6, are probably not?  Are one pair of tip bridles redundant?   2 days to completion- 4 hours of this were making Ray 4 bridle chart and 4 hours making all new templates- but tail was taken from Ray 3, as were bridles (no saving).  

2nd Feb '22 gusty NW, kiefactory paddock.  Ray 5 did all the right things- appears to fly well, amazing recovery. At Lake Hood 3 Feb, strongish southerly, does have good recovery but is WU in stronger winds- stabilises and recovers when it dips down into lower winds,  Wakanui, 3 Feb strongish southerly 5 is WU, 4 is stable.  Tried shortening rear centres- maybe better but not entirely sure.  Tried letting off tip TE's 25mm, did seem improved, but wild sashaying on launch, looping, more stable when it did get to apex. Biggest effect was from letting off the front 3 centre line bridles- back to the same as 4-  seemed to be dramatic improvement, launched straight up, very little sashaying.  This needs more checking as the wind was variable.   5 has more notching and creases than 4- which calls into question the curved edge panels but may be to do with different bridle pairings.  5's primaries are 1.45m, secondaries 2.45m, same as 4's.

Ray series to try:

1. Releasing rear centre bridles- will centre LE buckle? Front centre cell buckling seems to be best reduced by letting out their bridles- 4 inadvertently had longer bridles there. 16 Feb '22, let 4 rear centre bridles by max available- no discernible effect on flying.

2. Effect and refinement of LE adjustment- if significant, fit auto adjuster. Centre LE bridle pair are loose, have no effect, need to make centre LE panel wider. Does require auto adjuster, get range of by light and heavy wind flying first. On light wind setting, before adding fabric to centre three LE panels, would fold nose and collapse in mid-range winds, now (16 Feb '22) is quite resistant to this even in stronger gusts but does still show some chordwise compression in centre front area.  Need to now tune for strong winds then fit auto adjuster. LE centre panel let out to 270mm as sewn and adjacent panels to 285mm as sewn appears to be about the best dimensions for the centre leading edge.  Main 4 leading edge panels let out to 260mm as sewn (were 235mm) appears about right for outer LE.  No change required to tips. From strongish wind test 17 Feb '22, 5 is currently not weaving unstable in stronger winds, did lean over a little (right) but this was corrected by de-cambering the left wing tip by 30mm on one centre panel bridle. Conventional TE adjustments were ineffectual- as was leading edge pull in. Releasing centre tip bridles may have reduced weaving.  Releasing rear centre bridles didn't seem deleterious, but in stronger wind there is still some chordwise compression of centre panels- but this has largely disappeared towards the LE.      

3. Removing all centre line bridles. Causes creasing, may be possible at rear? Was(16 Feb '22)

4. Removing central tip bridle pair. Did this 16 Feb, still seems to fly fine, maybe with improved stability in stronger winds see 7. .

5. 7 x 7 cell version to reduce bridles, cost, and to check scaling.

6. Narrower tail, shorter tail.

7. Variations in dihedral:  More? Less? Tips only? 20 Feb '22, Wakanui, upper mid-range: 5 with 50mm auto bridle, 50m line, very steady, nose flap folded back,  20kG pull.  4 was OK but weaving a bit (25m line).  Let out rear centre bridles, WI less or unchanged. Centre 5 rows of bridles were then made the same length, except for the TE which were left longer and the towards the front which was left with the same relative bump. This left anhedral only on outer wings: No noticeable change in flying but noticeably flatter centre.  Suggests anhedral stability effect is from tips only.

8. Variations in A of A between tips and centre.

9. Less cell pocketing- reduce panel edge curvature to 10mm?

10.  Graphic effects; eyes, mouth, gills

11.  Find better bridle pairing. As from 16 Feb '22, appears to need 68 bridles only.

12.  Primaries need to be longer.

13. Moving tips forward.

14. Try cutting LE centre back- eliminating one bridle (can be matched by releasing one more centre rear bridle).  Did this 17 Feb., (2 centre bridles by 120mm); found that it does seem to stop the nose buckling in strong apparent wind, but also found that the remaining flap, which extends in lighter winds and at low angles of attack, does seem to help light wind flying.  This is a reprise of the flap LE's tried on early SS Octopus's, which didn't seem to be useful.  Need to try the Ray 5 flap system in very strong winds: Did this 19 Feb '22 in strong gusty southerly.  With a 70mm flap covering the front 2 bridles.  Ray 5 is much more resistant to nose pushing in than it was with the same bridle lengths, no flap.  120mm flap not yet tried.  Flew quite well with middle bridle setting but eventually crashed with slightly folded nose (50m line and behind trees).  Let out to longest front bridle setting (+25mm), had no consistent nose pushing in and only occasional tip fluttering.  Did hang mainly right though (try more left wing centre panel pull in?). Quite impossible to pull down, soon broke line (4mm soft China Dyneema).  Wasn't entirely steady but no sign of weaving, need to try longer line to check behaviour in less turbulent wind. Nose is quite pointy, could usefully be cut back a bit for better appearance.

Stability effects at 23 Feb '22

Both 5 and 4 seem to fall over and dive over to a lesser extent when bridles in the centre front area are let out (not the LE bridles). This also decreased visible chordwise compression in the centre span for 5, but not so noticeable for 4.

Releasing the rear centre bridles, 4 and 5, has not had any deleterious effects and should both reduce total lift (hence decrease WI) and move the C's of P forward, which should assist recovery and reduce falling over and diving over- but has it?  That 5 is not WU through to quite strong wind is evidence that it has?  But 4 is still a little WU- which could be an anhedral effect or even just that overall drag is still less than for 5.

5's dihedral is a uniform angle from centre to tips, 4 has been flattened in the centre, increased at the tips, for roughly the same total amount.  4 became much less WU when more tip anhedral was applied.  Is this a lateral area effect?

Releasing tip centre bridles did seem to reduce WI for 5 (completely loose) but doesn't seem to reduce WI for 4.  Is this because having these tight creates tips with less lift, or more specifically with lower L/D than letting them off?  Weaving instability should be able to be countered by adding drag to the tips.

Wi does seem to reduce when the LE is pulled in as much as possible- is this a C of P effect or from the extra drag that having the LE folding under a bit creates?

5 and 4's remining tendency for weaving instability at the top end seems to be damped by wing tip collapse at the edges. Blink stability.

Both 4 and 5 tend to climb fairly straight (5 especially) but WI starts appearing as 4 gets to apex in stronger winds- an angle of attack effect?

Adding a 12m pink tail to each tip made 4 steadier- but also possibly increased diving over.  Shifting the same tails to the centre also steadied the kite but without extra diving over. Would higher aspect ratio be similar to the two wingtip tip tails or by moving both lift and drag outwards, would it decreases weaving without increasing diving over?

Higher aspect ratio (1.31)  Ray 5 5sq.m green is noticeably steadier than Ray 3 (AR 1.21) 5sq.m red with same bridle. 3 becomes weaving unstable in stronger winds (compared to Ray 4 5 sq.m AR 1.21 blue which has angular rather than curved anhedral) whereas 5 appears to be as steady as Ray 6 10m sq.m (AR 1.21) red in stronger winds.  5 green did perhaps show falling over to one side in light winds (because of higher AR?).  6 red is probably steadier because of a scale effect- like for SS Serpents- but what is this scale effect?

Rear 4 bridles appear to be redundant on 5 and 6.  Removing these and making each wingtip a triple would reduce the secondaries to 32, or to 33 to accommodate the 2 rear centre bridles (tips back to pairs).

March 11'22 strong Norwest (but not crazy strong):

 5 green 5sq.m flies very well, quite steady, no weaving, no nose folding, occasional not too serious hanging over.  Has auto bridle, flapped nose and 66 bridles (rear 8 removed). Excellent angle, had to use van to pull it down. Still has worrying falling over in very light winds

3 red 5 sq.m was quite unstable - looping, even after letting front bridles out past main bridles by 25mm.  With rear 8 bridles released was no better- possibly worse (or more wind?).

6 red 10sq.m was reasonably stable, maybe slight weaving tendency, no hanging over (though maybe a bit right wing) .  Was showing some nose folding- need to fit flap.