Dynamic Spreader Spar for Variable Wind Conditions



  • Al,
    Your implementation looks very clean, nice job with this. I really like the idea of fabricating a longer piece and cutting it into small sections to distribute across the length of the spars. The green heat shrink adds a nice touch.

  • edited April 2014
    The adventure continues. I look forward to hearing how a single, floating center sleeve works when coupled with the tracking bridle. I have a feeling that this new approach will work very well.

    You may not need to use arrow nocks on outer spar ends to attach the tracking bridle. For recent builds, I ended up just drilling a small hole near the end of each spar to route the line through and knot it. I figured that the holes are far enough toward the outer ends of the spars to not impact the strength. Either way should work fine. The tracking bridle outer spar attachment point is shown in the photos below. The holes on this one are farther in from the ends because I wanted to make it collapsible for airline travel. The outer ~4'' is a removable spar piece that is ferruled to the main piece.

    DS - Tracking Bridle

    DS Breakdown

    After building a few of these, I think I can relate to the sense of satisfaction a Jedi Knight must have felt when completing his own Lightsaber. We shall use them to overcome the dark side of the wind! (sorry, couldn't resist that)
  • edited April 2014

    Love that light sabre analogy, however much you charge for these it's not enough! The nice thing about the 'floating guide' idea is that it strips down into handy sized parts for transport.

    The last throw of the dice today was to use a clip to fix the elastic centre to the sleeve offset to balance the 2 bands. Finding the elastic centre has to be done on the kite as the bands can vary in tension accrding to twist, having a finger tightenable clip was a boon.


    This worked remarkably well. The only problem with this is a small load off the centreline which can't help things but I was pleasantly surprised at how well this worked. I'll keep playing with this till I get the nocks I need for the tracking bridle (should be a couple of days) I will not take a drill anywhere near the 6mm carbon: I think it’s too short as it is and the scope for error is tight!

    I'm getting close to trusting this with a camera again, I did a swap for a rigid spar on test and the DSBV is far smoother on the lne.
  • edited April 2014
    I am now the proud owner of the1st working example of the tracking bridle on a 'floating sleeve' DS! More tedious video action here:


  • Nice job Bill. You may be able to loosen the bridle tension a little if the friction feels too high. Looking forward to hearing how it flies for you.
  • edited May 2015
    After a lot of tinkering I abandoned my attempt to make one. I got close but found the spar would 'stick' and knock the kite out of balance far to easily in gust- the spar needs to react really fast and stay perfectly balanced to work.

    Thanks to this remarkable international network I am now the proud owner of a Mike Le Duc original and it works really well: the Levitation is working in the lower end of Bft 5 nicely and lifting 600g happily.


    I'm going to see if I can pitch the DS Levi against the DL Trooper and the PFK Nighthawk next time we have clear skies and BFT 5.

    Watch this space: arch.ced.berkeley.edu/kap/discuss/index.php?p=/discussion/2656/trooper-vs-nighthawk-which-to-buy#latest

  • Mike: it appears that you have further simplified the tracking bridle. It is now a single string device attached to the two ends that move. Am I seeing this right? I have just finished the two string version in advance of a trip to the beach in a week; I have been slow to keep my version of your design up to date.

    Bob Llewellyn
  • Bill, Welcome to the Dynamic Spreader club! Mike LeDuc does excellent work.

  • edited May 2015
    Bill, Glad to hear that you received your DS and that it's working for you. I'm looking forward to your results comparing the different kites in higher winds. Keep up the great work on your blog!!

    Bob, the latest tracking bridle still uses two strings so you should be good for your trip to the beach if that's the configuration you currently have (let me know how it works for you). Where did you see the single string design? (maybe I have some old photos floating around that need to be removed).

    Jim, Thank you for the compliment. I still need to refine the construction techniques to make it more easily producible. Building one is a bit tedious but well worth it...

  • Mike: I think your response is exactly right. I was checking to refresh my memory on the tracking bridle. I found images in your FLICKR account dated 15 September 2013 with what I took to be the simplified tracking bridle. There was a sequence of 6 or so images showing a one string version, simply attached to the arrow nocks on the ends of the two spars.

    Will press on with the two string version!

    Bob Llewellyn
  • Hi Mike
    I've been using the dynamic spreader again. I think the elastic must have weakened because the kite has lost power and won't carry the 700g rig even at f4.:-(( I think it might be because I've left the elastic fitted under tension all the time for ease of use.
    Could you tell me how long/ how strong the normal white elastic is please?
    Next outing I'll use the blue elastic and see how that flies.

    Fly High


    P.S. Tim has lost his blue elastic. I wonder if you could let us have some new elastic when I go to KAPiCa - I think you said you were going.

  • edited March 2016
    Hi Sue,
    It sounds like your elastic cord has lost some strength due to storing it under load. The white cord I'm using is 3/16 inch diameter elastic shock cord. It is available in most hardware stores here in the US but I'm not sure of its availability in the UK. You can make a new one by starting with a piece about 16 inches long and making two overhand knots about 12 to 13 inches apart. You can experiment with different knot distances to see what works for you. You can also substitute standard pieces of sewing elastic or large rubber bands. Depending on what type of elastic you use you may need to use multiple pieces in parallel to get sufficient tension. Here's a link that shows how to "calibrate" the elastic cord that I've found works well for flying in ~15 - 30 MPH winds with a 400g rig.

    Dynamic Spreader Spar Calibration (2/9/15 Updates)

    Note that the calibration forces shown are provided as general guidelines to give a rough idea of how much force to set your DS to. There's room for experimenting and trying different tensions so have fun with it and see what works for you in the various wind conditions in which you fly your kites.

    Since you're using a 700g rig, you might want to use even stiffer settings to maintain enough lift especially in lower winds.

    Hope this helps.

    Unfortunately I won't be able to attend KAPiCa this year but can send a bunch of cord to someone there to distribute. I can also send some to you in the UK.

  • Thanks for that Mike
    I made a knot to make it an inch or so shorter and thatThat carried the 700g rig better yesterday till the wind died too much. . I'll have a look for the shock cord here.
    I'm sorry you can't make KAPiCa as I would have liked to have met you in person.
    I'm going out tomorrow with Eyesonly - Dave to have lunch and KAP a canal.

    Fly High

  • I spent the weekend honing my Jedi skills and now have a Dynamic Spreader of my own.

    Dynamic Spreader
  • Looking good Dave. Welcome to the DS club.

  • I just returned from a quick, lunchtime test flight. It seems to work great! The kite flew nicely and I could see the spreader adjusting itself constantly. Unfortunately there wasn't time to set up the camera.
  • edited June 2017
    Nice job Dave. The build quality looks really good, not surprising. Powerful you have become!
  • Excellent work Dave - and I like the sewing machine edging its nose into the picture!
  • Thanks, guys. I'm planning to start sewing a Dan Leigh R8 delta as my next project. And build a new DS for it, too, of course.

    I used 3mm (1/8") model aircraft plywood to hand-make the little sliders. That was a huge pain! It took hours to cut, drill and sand those little things into shape. So for the next iteration I ordered a set of them from a laser cutting service. I'll post some pics of the construction process when I build the next one.
  • edited June 2017
    That would be a lot of work to fabricate the sliders from plywood. I've been working on an improved construction technique and am planning to start another small "production run" this summer and may have an easier design to implement.
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