Mini-Circoflex Variant - Plan and Notes

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WARNING: This plan is still in development. A section on problems and tweaking the kite is still to be added, though much has been said in the Circoflex Hints and Tips.

I generally add to plans in response to email I receive, which is why my plans are generally very verbose, with lots of options. As such if you email me your questions and suggestions, and not only will I reply but add the answer to the plan itself.

Contents

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Introduction
Main Ring Sail
Trailing Edge and Leech Line
Leading Edge Spar Pocket
Bridling
Ballast Weight
Folding for Transport
...to expand...
Flying in Trains (dosen't work)
Responses about this plan (separate page)

Introduction

I am now building these ``Mini-'' Circoflexi, all under 5 meters (circumference) in size, not only for my own use, but also as a special item for swaps or personal gifts to fellow flyers ;-)

These are great little kites, easy to transport, you can just fold them up and then throw into the air (like a pop-tent), attach the line and launch.

Note that this plan will get more detailed with time. I like verbose plans, so don't let its size put you off! Also the more questions people email me the more detailed it will become.

Main Ring Sail

[photo] The material is ripstop (.75oz/m^2) sewn into strips 32 cm wide (1 foot and 1 inch), which allows for a 1 cm (1/2 inch) fold on each edge for leach line and the 2mm fibreglass spar). When creating the strips I do not worry about the exact length of the strip just ensure it is 32cm wide and will fit together straight.

[photo] I then sewn the pieces together until the ripstop strip is roughly somewhere between 3.5 to 4.5 meters (yards) long. At that point I measure the completed ring to get the size of this mini-circoflex's circumference.
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Yes the size varies. This way I do not have to worry about the amount of material absorbed by sewing the pieces together. I also don't waste the material as I would if I was trying to building to an exact size.
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The only time I sew to an exact size, is when the ring is part of a larger construction (See my Olympic Logo). Or the pieces fit together to form a pattern. If it doesn't matter, don't worry about it, just use the material you have at hand.

The same goes for the width, you do NOT have to make the pieces 32 cm wide, they just should be all the same width. Hmm.. anyone like to try building a mini-circoflex of varying widths, say thick at the top and thin at the bottom?

I measure out a leech line to the rings circumference, adding a extra 20cm or so extra line on each end, beyond the length marks. The extra line prevents you looseing the end of the line as you do the next step, and makes it easier to adjust when test flying.

It is also a good idea at this point, to measure and mark 8 equally spaced points around what will be the leading edge, for the bridle point placements. One of these points should be noted as being the bottom, 6 o'clock, or lowest point of the kite. This is where the bridle line ends will protrude on the trailing edge, and close to which a gap for the spar in the leading edge will be made (see below)

Aside: It may also be a good idea to write the circumference of the kite onto the kite itself, prehaps somewhere near the 6'0 clock point, for future reference. :-) Signing your work and adding the date is also a good idea :-)

Trailing Edge and Leech Line

[photo] I fold the trailing edge over by 1 cm (1/2 inch for the Americans out there) and sew the leach line into the trailing edge hem as I go. Note, I do not bother to do a full rolled hem on the mini's. I have never seen the edges fry and there is not enough material to catch the wind, which would not matter if it did.

I sew continuously all the way around the ring leaving the smallest gap between the start and end lock stitches, at the 6 o'clock mark, where the end of the leech line comes out. You may find taping one end of the leech line to the kite at the 6 o'clock mark just before you start a big help, during sewing. [photo]

To help set the trailing edge I then pull both ends of the leach line as much as possible! That is, I gather and compress the ripstop into the smallest possible length of the leech line. This initial gather seems to improve the initial flying characteristics of the circoflex.

I tie the leach line 2 cm shorter that the marked length on the leech line, but leave the rest of the line attached until after the initial test flies. I then spread out the gathered fabric completely, reforming the normal ring.

Actually I find that a leech line in a mini-circoflex becomes nearly a non-requirement, as the gather also reduces the trailing edge size of the ring by an appropriate amount. But I leave it in place as it allows some adjustment and better wear with age.

Caution, do not shorten the leech line too much, something which is VERY easy to do. Reducing it too much leech line is much worse than too little. First it is harder to correct, and second produces too much drag, preventing the kite from flying as high as it should. The leech line should be practically non-existent.

Finally a tip from Rec.Kites newsgroup... Lock stitch the leech line in place at the 12 o'clock point (on the oppisite side of the ring to where the leech line come out of the hem)! This allows you to adjust the two sides of the kite separatally, allowing you to fix any `loop in strong wind gust' problems which may otherwise be impossible to fix. I myself don't like this especially on larger full sized circoflexi, as it makes spreading the "gather" by hand on the field more difficult.

Leading Edge Spar Pocket

The leading edge spar pocket also folded over by 1cm (1/2 inch) is just sewn empty, to form a spar pocket. A larger 3-4 cm gap left between the start and stop of the stitch, is left to allow a 2mm fibreglass spar to be inserted and feruled into place. A gap this small does NOT need to be closed, so you can, if you need to, remove the spar again later.

This gap should be close to the 6 o'clock mark, just to one side. If you put it at exactly the lowest point, the bridle line loop will end up in the middle of that gap, making it harder to insert, and join the spar together.

I get the fibreglass in 6 meter stock lengths directly from the factory, allowing me to often use a single piece for the spar. But I also sometimes piece 2 or 3 smaller pieces to produce the required length. So whatever lengths you can get it in will be fine.

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Cut or join the fibreglass, to form a single spar 2 to 3 cm LONGER that the measured circumference of the ring. The ripstop stretches a bit, particularly if damp, so the extra length ensures that the spar end will remain pushed together in the ferule.

To join the spar ends together I use a thin brass tube as a ferule, 1.5cm (1/2 inch) long, with an exact 2mm inner diameter (the size of the fiberglass spar). The brass tubing is from the local hobby shop and is used for model aircraft, so is very strong. It is also available in both imperial and metric measures with exact measurements for internal and external diameters and wall widths.

I super glue the brass tubing halfway on one end of each rod and then (when dry) just push the other end into the tube to form the ring -- do NOT glue the second end into the tube! This allows you to remove the spar later during tests, repairs or upgrading to a thicker spar (I have never needed a thicker spar, only replacing due to breaks).

At one point I used to slightly crush the ferule onto the fibreglass but it is far to easy to over do it and crush the rod itself. If you do this the spar will weaken and is likely to snap or break just short of the ferule in a spot which is difficult to repair. I had a high failure rate in my first run mini-circoflexi kites due to this. Superglue is better.

Bridling

After inserting the spar in the circoflex. I sew the 8 bridle loops equally spaced around the circoflex. Did you remember to mark these points when measuring?.

The loops are created using a thin strip of ripstop folded three times (sew a fully rolled hem on a piece of scrap ripstop the appropriate color, and then cut it off the scrap!). This is then folded over and around the edge of the kite (both sides) sewn in place, behind the 2mm spar inside the hem. A zipper foot on the sewing machine with a straight stitch sewn back and forth a couple of times does the job nicely.

The bridling however is different to the larger circoflexi. For reasons why see Mini-Circoflexi Bridling in Circoflex Hints and Tips page.

First I am using a 8 line bridle (instead of 12 on the large `normal' circoflex), and position the bridle point 3/4 of the distance from the center to edge (instead of the usual 1/2 way) so that the bridle point is lower down, with the bridle point remaining 25 cm out from the plane of the leading edge ring.

The actual bridle line lengths (5 of them) is basic mathematics (Pythagoras's Theorem) using the above bridle point position above the plane the spar in located in. The Bridle Line Calculator in the hints and tips page, makes this calculation very, very easy, listing the lengths in a nicely formated table. Or use the Online Java Script Calculator.

I use bridle pigtail attachments method to measure out and attach the lines to small loops of line larks headed to the bridle loops (loop knot away from the kite).

Essentually I tie a loop with a "stopper knot" to the bridle loops. Another loop is then tied to the end of the line comming from the roll, and this is lark headed to the stopper knot of the loop attached to the sewn loop. The line can be then measured out from the kite, plus about 1cm extra (as the line will shorten slightly due to the next knot). From this point the line is folded over and a nother loop created with an simple overhand knot. The completed bridle line is then cut from the roll.

The completed bridle line can then be detached from the bridle loop, the line larks headed to the bridle ring, and the other end re-attachedto the bridle loop.

The bridle ring is a small solid (no gaps) brass or plastic ring, and the lines are added to the ring using the single ring bridle arrangement to keep the bridle lines neat, rather than the 3 ring arrangement I use on the larger circoflexi.

In summery, the lines are attached in an alternating left side then right side order so the ring will want to sit vertically, allowing a neat arrangement for the bridle lines and the flying line when clipped to the bridle ring.

Ballast

For the ballast weight I use steel bolt washers, 3/4 inch diameter. 3 to 4 for a 3 meter mini-circo, 4 to 5 to for 4 meter, and so on. 6 to 7 is about right for a 5 meter, though a thicker spar will also be needed for that variation.

The weight will be placed along a line about 1/4 of the rings width away from the trailing edge, on the inside to the ripstop fabric. When the leech line in the trailing edge is pulled in slighly, this position forms a natural pocket in the sail, that hides the weight from the ground. The weight is spread out along this line evenly on both sides of the 6 o'clock mark, (say between the 5 and 7 o'clock marks). If you have a lot of small weights, you can incrase the amount off weight near the 6 o'clock position and thin out the weights as it approaches the 5 to 7 o'clock positions.

To attach washers to ripstop I cut a square of ripstop of the appropriate colour, about 1/2 inch (12mm) larger than the washer. I then edge that square with double sided tape and a small diagonal piece in the middle. I remove the paper backing of the tape, stick the washer to the square and add another diagonal piece of double sided tape to other side of the washer. Removing that extra pieces paper backing I then stick the ripstop square with the washer to the inside of the ring in the appropriate place, and press together well.

Only once has this method failed, with the washer coming loose, and that was on a kite three years old, and which was used on a mud flat, where the slit gummed up the double sided tape. That is better performance then the previous methods I have used, using clear all weather tape, which seems to come loose in sand, grass or after just a few months.

This looks neat on both sides, and with a darker shade of ripstop becomes completely invisible. Of corse with a lighter shade, light shining through the ripstop will show up the presence of the washers, but you will only really notice them if you look for them.

Other methods are given in the circoflex hints and tips pages on ballast weights

Folding for Transport

As mentioned above the kite easily folds into small bundle for transport, without removing any spars.

To folded the kite:- Stand in front of the kite and grab the two sides. You may like to put your foot on the bottom of the kite in windy conditions. Now push the two sides together and continue past each other so as to form a sort of triple figure 8. Then fold the top `loop' of the figure 8 down onto the middle `loop', and the fold that bundle over the lower `loop' being held lightly by your foot.

The circoflex is now folded in to a disk about a 60 cm in diameter which can be squeezed into a suitcase or behind the back seat of the car. To unfold you can generally just throw it into the air and attach the flying line. Though you may have to make some slight adjustments to unwrap a bridle line or two.

Simple and easy.

One final point about transport. Do not leave fibreglass in a hot car. The resin which holds the fibres in place is heat sensitive and weakens. Leaving a folded mini-circoflex in a hot car (like we often get here, down under) and you will find the bent spars broken into lots of sharp angles, instead of a smooth curve! Circoflexi with even a small kink in the spar, tends not to fly very well.

Flying?

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(See the circoflex hints and tips page for now)

Flying in Trains (not very good)

Like their normal sized cousins, these mini-circoflexi can also be linked in a train. Unfortunatly they have problems due to a lower bridle point.

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Basically what happens is that the line from one mini-circoflex to the next catches the lower part of the sail, if the kite decided to do a loop (particularly during launch). This causes one or two mini-circoflex kites to tip upside down, resting on the line leading up to the next kite in the train. This is where the kite settles, pulling the rest of the train down.

Unless you have a set of very well behaved mini-circoflexi, I do NOT recommend flying this variant in a train. However flying a mini just behind or inside the ring of a normal sized circoflex looks great.

Responses

For more information about peoples experience with building a kite with this plan, and what results they have achieved, I suggest you look at the various Responses I have received. Many thanks to all who have replied.

If like this plan, and/or build one, please mail and let me know what you think. Including any ideas, suggestions or other experiences. That way I can add them to the above so others can read and benifit from your results. :-) Photos especially welcome!


Created: 12 March 1999
Updated: 30 October 2001
Author: Anthony Thyssen, <Anthony.Thyssen@gmail.com>
WWW URL: http://www.cit.gu.edu.au/~anthony/kites/circoflex/minicirco/