rokkaku tipping and diving

edited April 2010 in Kites
I know that there have been numerous discussions on rok tuning, but they seem to focus on angle of attack, kites taking of or no, etc., so I hsitated to post this, but I think my problem is slightly different than other situations explaned.

I have a different problem: I tune my kite, it takes of and flies well, but when the wind picks up or becomes gusty, it tends to keel over and fly to the right, sometimes hangs fully horizontally, or starts to dive down. I avoid catastrophes by letting out line or even running towards the kite, but I get tired after a while ;-)

How should I troubleshoot this? I use the 2 secondary bridles-1 primary bridle system, as described in the wonderfull pdf of Larry Green (http://essexkites.studio1.net/Images/rok_bridle_info/Rok Bridle Guide.pdf), so the bridles are about 1 3/4 the height of my 2 meters tall rok. Larry writes to solve yaw by moving the connections of primary to secondary, but does not tell me how. Should I just experiment. Does this all sound familiar to any of you?

all the best,

Jasja

Comments

  • A question:

    Does the kite fly well and vertically in moderate wind, but leans when the wind picks up and gusts? If so, this sounds to me like the kite is overpowered by the wind in those conditions and you can make some improvement, but every kite has it's upper limit in terms of wind range.

    There are 3 things you can try if this is the case:

    1. Increase the amount of bow introduced by your bow lines on the back of the kite so that the kite spills more wind when the wind does pick up.
    2. Lower the angle of attack by moving the tow ring on the primary bridle closer to the upper/secondary bridle. Loosen the prussik knot on the tow ring and slide the ring a little bit (try 1/2" increments maximum) then re-tighten the prussik knot.
    3. Adjust the attachment of the primary to secondary as described. What you want to do is loosen the prussik where the primary attaches to the secondary, then move the knot *away* from the side that the kite is leaning to. So, if your kite is leaning to the right, you will want to move the knot to the left. Loosen the prussik and then just slide the secondary line through the the prussik about 1/2 inch and re-tighten. For this, do it on the LOWER or BOTTOM secondary bridle.

    The final adjustment may be a combination of all three things, but try one thing at a time.

    If your kite is leaning to the right in general (even in moderate, "normal" wind) do what is described in item (3) above, but do it on the UPPER or TOP secondary bridle line.

    Make small adjustments and do one kind at a time, then test fly. If your adjustment made an improvement (but not enough), take the kite back down and make another similar adjustment (take another 1/2" movement, for example.) If there was no improvement, try one of the other suggested adjustments (AOA, bow depth of the spreaders, or bridle balance.)

    Make sense?
  • Makes perfect sense! It starts to lean when the wind becomes "gusty".

    Thank you for your advice, sounds like I have a nice fun sessions of troubleshooting ahead.
  • edited April 2010
    Jasja,

    I use to fly my Rokkaku with a fiberglass spreader (the lower spreader, that is) when the wind might pick up. They simply bow more than carbon spars in gusts. And use more bow on the lower spars, always. Never failed me ever since. And never changed the bridle, by the way... But most of the time I fly with carbon spar (10mm) and spreaders (both 8mm) as this is my light wind kite.

    This was my story on the diving Rok
  • What a bizarre coincidence. My Rok was playing up in a very similar way today. Once I got above the trees the wind was stronger and I had several dips, to the left in my case, and even one 360. I brought the kite down and increased the bow on the lower spar and actually decreased it slightly on the upper. It worked a treat and the kite was much more stable. This is the first time that I have really noticed the effect of changing the bow in a dramatic way but it was very effective.

    Martin
  • Thanks Ramon for the spreader tip, might try that too. Meerstone, I guess the same winds that blew over the Netherlands yesterday now reached you. Glad to hear the solution was so simple, gives me hope ;-)
  • No mention of Rok size or wind strength so far..... could it be that the wind is just a bit too strong for the kite?

    I'm sure the tuning tips are spot on but there must be a point when flying a Rok in a certain strength of wind will become tiring very quickly!
  • Properly tuned, as I recall, my late lamented rok would simply fly at a lower angle as it became overpowered. In 30 mph plus, it would fly almost straight out.
  • Quite right Jasja the wind was from the east, so it was probably yours yesterday.

    Kev in my case the wind was within the range for the kite. Probably gusting to 10-15mph once above the trees. My issues were just down to tuning and easily fixed. Think of the bow adjustments as like changing gear in a car. Sometimes you need a lower gear, sometimes a higher one. I fly my 80in Rok from as little as 3mph (ground wind speed) up to about the speed I had today although it is rated up to 18mph. It was pulling quite enough today. The amount of bow I need to get it off the ground in lower winds is very different. So today was a bit like deciding which gear to use to drive up a hill once you see how the car is responding.

    Martin
  • Kev, my kite is 2 meters tall, and the wind cannot have been over 4 bft, the national metereological institutes reports 6 ms (13.5 MPH) for my region that day. I think the rok should be able to handle that, if properly tuned of course...
  • Jasja, totally agree, 13mph for your Rok doesn't sound too hardcore! (I was enjoying Bft 6-7 today with my PFK)

    Me and my 7' Rok still have a love/hate relationship.
  • Kev, thanks, that was what I was hoping!

    And the love-hate relation: same here!. It is a nice kite, and was easy to make, but can be a bit fiddly. But messing around with tuning is part of the fun, although I cringed when I saw the kite diving with the rig attached. I think I will waitbefore upgrading my Canon A470 until I have a bit more control of the kite...
  • Hi Jasja,
    Roks are my favourite Kites, what is yours sparrred with only sometimes if it flys to one side try taking out the top spar and turning it round then fly again, if it flys the other way then you know its the spar thats the problem.

    Len.Kent Kite Flyers UK
  • Hi Jasja and all others,

    I been flying and making ROKs for more than 20 years now and the greatest failure I have seen on the commercial ROKs is that the spine is stretched by a piece of rubber band. What will happen if the wind pick up is that the sail is not taught anymore. The rubber band stretched. The same problem happens with the spreaders. After a couple of hours flying the sail is stretched a little and the spars are to short than. The sail of a ROK must be taught.
    So to get everything again in a good condition is to look of the spars must be changed and remove the elastic band and replaced this for a piece of line to secure and stretch the sail on the spine.
    Wen you adjust your bridling and the ROK fly fine in a lower wind never ever readjust the bridling for higher wind. The only thing you must do than wen there is more wind bend the spars to give them more bow.
    The lower spar must be bend more than the top spar.
    In lower wind I bend the top spar of my 2 mtr. ROK about 15 centimeter and the lower about 25 centimeter. Wen I fly them in higher wind, say about 4-5 BF I bend them about 35 cm for the top and 55 for the bottom spar. For the spars I use 6 mm glas.
    A common problem with a ROK is when you flying in strong winds the flying angel is lower than in low winds.
    Hope this will help you a litle.

    Bas

    Rember: Kite flying is always plaingwiththewind.nl
  • Hi.
    one thing i think isn't mentioned here: make sure to use non-stretching line for the bridle.
    Due to different streching lines the kite might loose balance. The top lines get more force on the than the lower bridle lines, therefore the angle of attack will increase when the kite get into stronger wind, because of the increased AOA it will pull even harder until the balance is lost. IMO the best line is Dyneema/Spectra.
    Good luck
  • Hello bas,

    thank you for your advice. I've only seen them now! With the rubber band, you mean the way the spreaders and spars are attached to the sail?
    I am replacing my lower carbon spar with a fiberglass one!
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