A Kite Building Challenge...

by Tony Sangster
(Adelaide, SA, Australia)

Nose detail.

Nose detail.

...A delta-style kite without a horizontal spreader spar.

From playing around with some kite designs in folded A4 paper and use of straws for spars I tried out a design in plastic and dowels, undertaking to Tim that I would provide some photos. However the trials were not successful and I am still trying to get there (hopefully with a serious attempt and success this long weekend)

However you budding designers may wish to come up with your own version in plastic/dowel or similar materials. I am attempting to make a Delta-style kite without a horizontal spreader spar. A spar could however be used in some other fashion or orientation. Originally I was trying to save weight in the construction but have decided to get the design right first.

Have fun and happy flying!

(NOTE - Tony has since posted further comments, plus the photos up there. Check out all the details on this interesting kite design! T.P.)

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Sprung series
by: Tony Sangster

Sprung 2 was a challenge because the the bendy spreader on the upper side of the kites when positioned upright tends to push down more on the front end of the leading edge spars and affects the airflow over the kite and thus affecting its stability. A long tail was needed in most winds.

Sprung 2
by: Tony Sangster

Over the last weekend I made Sprung 2 as an intermediary step to Sprung 3. Unfortunately 20 knot plus winds on Sunday in Adelaide at the beach prevented me trialling Sprung 2 - but with a suitable tail Sprung 2 after several crashes flew magnificently.

Construction: dowel 6 mm (in cm length)- central 49.5, leading edge 50.5, 5 mm dowel spreader 32 each joined as in Sprung one with the bendy bit of a tooth brush - skin of oven bag plastic.

Overall dimensions: leading edge 72.5, base 102, no keel but two point bridle attached 14 cm from nose, 10 from back. Spreader attached via PVC tubing internal diameter 6 mm situated 37 cm from rear end of LE spars - a classic delta configuration as per Dan Leigh.

The bent spreader was held with elastic and string attached from nose to bendy bit to rear bridle attachment, elastic allows some give but in the gusty conditions the string held the bendy spreader.

Please see photos - fellow kite flier Steve ably assisted me in the gusty conditions and offered helpful insights from his kite and sailing knowledge.

Further comments on Sprung 1
by: Tony Sangster

When I first tried to fly this kite it would rise a little then flattened out and nose-dive. I figured the weight of the nose assembly and lack of a horizontal spar in the middle area of the kite to balance the kite would cause the nose dive. I ended up tensioning the leading edges back with the strings on the upper side in order to move some weight backward and since this didn't work well enough I also added the loop tail which pulls the back of the kite down a bit.

The rest is history. Once I retrieve the flight shots you can believe that it really does fly.
Now for Sprung 2!

The evidence
by: Tony Sangster

Finally I have got photos of a Delta kite without horizontal spreader - called Sprung (version 1)

The skin is from oven-proof plastic which is light and strong but I did reinforce the edges with tape.

  1. 6mm dowel two lengths 50 cm each, one length 36 cm. Take a bendy tooth brush, cut and shave it to give symmetry and glue/wind polyester thread around it; attach sections of 50cm spars each end.

  2. Attach to bendy bit some tubing with hole to accomodate 36cm spar end. (see photo)

  3. Cut out skin, taping as needed, 4 sided figure two adjacent sides 60cm, and two 44cm, symmetrical centre 40cm.

  4. Crease skin in half along shorter symmetrical centre, fold back wings each side zero at 60cm end (nose) and at 22cm along centre a depth of a keel of 10cm crease so that a keel is formed all the way along. Open inside of the keel a little and tape inside at centre crease a bamboo skewer (24cm long) from nose begin about 3.5cm from end of skin.

  5. Tape sections of the keel top edges from nose backward symmetrically, leave a gap at 20cm along on the same plane as the wings.

  6. Three legged spar is held in shape by a string tied near ends of and tensioning the 60cm lengths (see photo) and placed on skin.

  7. Wrap skin evenly over 60cm (leading edge) spars and tape firmly in place so that the skin is taut, similarly tape over the centre spar leading gap at 20cm. Trim excess skin and remove the spar tensioning string carefully as you tape in spar assembly.

  8. Place 2 bamboo skewers (24cm long each - no sharp ends) each side of centre spar at 20cm from nose and tape and tie one set of ends (swivel it to side and ensure enough gap in the skin to then swing the tied ends with extra tape also attached to stick the ends to the bamboo skewer earlier situated inside at the bottom of the keel at 18.5 cm from nose along keel skewer and tilted back to 200cm and taped either side of the centre spar, then together at the top, giving a tilted-back mast. 90 cm of double skewer mast is in keel section.

  9. Attach a line from about 40cm back from nose of each leading edge and run it and secure across mast top mast, a similar line underneath around the bamboo skewer keel. Tensioning of these lines produces and maintains dihedral shape.

  10. Tape from back end of skewer keel to end of centre spar, trim off excess keel.

  11. Keel tow point from nose - 15cm or use bridle line to better adjust the tow point.

  12. Vital point... Attach a looped tail from wing tip to wing tip approx 150cm long, 2cm wide. The kite will not fly properly without it!

    In degrees: nose angle ends up about 97, dihedral 120.

    Go fly !

The Challenge joined and met
by: Tony Sangster

A successful kite fly in ideal weather yesterday (Monday) I am sorting the photos out with details of construction of the delta without horizontal spreader. I have named to version "Sprung 1" - reasons will become clear once you se the photos.

The main leson is that deltas with horizontal spars are a superb design and trying to do without the horizontal spreader does certinly lead to compromises - but also increases interest and can lead to further interesting ideas.

by: Tim Parish

I think the only way around something functioning as a spreader is to make the kite from a rigid material. That is, a flat plate with some shape (compound curves?) bent into it to provide stability. Or else construct a special Sled that looks Delta-like from a distance. Come to think of it, parafoils do exist which have a roughly Delta planform.

But I think a spreader is pretty fundamental to any delta concept. Something has to keep those leading edges from folding together under air loads. The spreader's position can vary a lot, and perhaps it doesn't even have to be rigidly attached at each end (thinking of a spreader that is part of a bridle!). But something somewhere has to function as a spreader. Those are my thoughts :-)

Another thought - could a horizontal ram-air tube function as a spreader? A long shot....

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