2m^2 Sands Quad4m^2 Sands Quad6,5m^2 Sands Quad
The contents of this page is copyrighted 1995 - 2001 by Bernhard Malle. The stuff may not be reproduced in any non-electronical form without my written permission!
This page is not intended to give in-depth information about the design parameters of a modern traction foil. This page is more about how changes of these parameters had some practical influence and also to give some examples of the limits in which you can change them and still get some good results out of it.
If you want to in-depth information you should read:
If you want to get additional tech tips about (mostly dual line) traction foils, please visit Gene Matochas new page about HIGH AR.
All observation are very subjective and only represent MY personal view. If I am talking about enormous pull, e.g. Andrew might judge different compared to his 13m^2 Chevron.
Since beginning of 1996 I am a passionate buggy rider. I own a Libre buggy (commercially sold in Germany for about $400). Since that time I have also built several traction kites, 2 liners and quadline kites, with different experiences which I would like to share. During that time I have exchanged many ideas and thoughts with Robert Pudlo, Andrew Beattie, Emiel Stroeve, Ben Mulder and Matthew Hurrell. Thanks to all of them.
I have built the following traction foils:
| Sputnik-4-type | |
|---|---|
| 5m^2 Sputnik | 8m^2 Sputnik |
| 3m^2 Sputnik | 2m^2 Sputnik |
| Quadrifoil-type | |
| 3m^2 Quattrofoil | 2m^2 Sands Quad |
| 3m^2 Sands Quad | 4m^2 Sands Quad |
| 4m^2 Sands Quad with DRips | 6,5m^2 Sands Quad |
I am a lazy person. If you look at my "built-" page, you might get a different impression, but whenever building a kite, I try to minimise the effort which is needed. That's why after reading the SKII book and realising how much work was needed to sew the famous v-lines onto each profile where a bridle will b attached, I decided that this could be done in a different way.
Therefore I am not sewing a v-line to the profiles. I reinforce the place, where the bridle primariy line will be attached to the skin with a thick line, that runs from the front of the kite (air inlet) til the trailing edge. It is sewn onto the seam allowance of those profiles. The process of attaching the bridle line is identical. Different to the assumption of Andrew, I have not yet a single failure of this attachment method, and I claim that sewing a line on the profile my way is much faster and less complicated.
The kite has a surface of around 3m^2, profile length of xxcm and an aspect ratio of xx. The bridle is an ordinary two point bridle which results in awful distortion of the whole kite when turning.
Because of tuning problems with my next traction foil, the 5m^2 Spuntik, this was my ideal traction foil in the '96 buggy season. When comparing it to another kite, built after the same plan, we discovered that one of the disadvantages of this kite can be managed by using very short lines: If the wind blows rather strong, using this kite is very straining. If you use lines which are only 3m long, the kite will not pull that strong.
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The Sputniks are generally 2-line kites. At the beginning, neither Robert nor I had enough experience to tune the kite sufficiently. Therefore we decided to add brake lines and to change it to a quadline kite. For Robert this was his perfect buggy-kite in '95 and most of '96. I experienced some difficulties with the setting-up of the kite. I therefore changed back to a regular two liner. After Robert had changed the bridle attachment of his 5m^2 Sputnik, he also changed the bridle and is now using a modified "Andrew Hawken cross bridle" with very good results.
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Some time end of may '96, Robert surprised me with the gift of a 2m^2 Sputnik. The kite is a standard Sputnik 4 type with tapered tips and an arch bridle. The kite is very nice. Although I could use it only for very short time at fanoe, Robert made his best and longest speed run on Fanoe with a similar kite: When the wind was very strong and going upwind was difficult, we decided to buggy from the middle of Fanoe beach down to the south end of the isle. Robert was using the buggy and I followed in Roberts car. We were always driving above 40km/h and most of the time even faster than 50km/h. This was truely AoxomoxoA...
With this kite we have also experienced our first failures. After a crashing the kite at nearly full speed onto the beach (and afterwards I repeated this with the other tip) I noticed that several profiles were broken. When examining the failures a little bit closer, we could see, that three profiles at the tip of the kite were cut exactly in the middle (the three outer cells are closed...). Even the v-line on the profiles could not help against this damage.
Additional comment June '97
I have now finally made this kite unusefull. On a rather gusty day at
Fanoe I did not pay attention for a very short moment and directly
afterwards my wonderful sputnik crashed with full speed on the beach.
First I thought, "ok the this is the usual two-profiles-at-each-side-
ripped-in-the-middle-failure", but later on at home it turned out that
I had successfully crashed ALL profiles right in the middle. Sigghh.
Now the kite is debridled and is used as decoration in my working
room at home.
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Shortly before the Fanoe festival '96 Robert and I felt that the 5m^2 Sputnik would leave us underpowered in case of low winds at Fanoe. We therefore decided to build a larger traction foil. For the 1st time, we changed the profile of the kite. After some discussions with Andrew and Emiel we decided to use an asymetrical profile. This profile was built by ploting a 21% profile and a 11% profile to generate an asymetrical 16% profile.
We also decided to use a cross bridle on this kite to compensate for the large wing span. Apart from these changes, the kite is a traditional Sputnik 4 type with tapered tips.
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After coming back from a short three days trip to the danish islands of Romo, I decided I would need another traction foil slightly larger than the 2m^2, that I had got from Robert.
As I had just testflown the Quadrifoil C2 and had have the necessity to repair the small Sputnik, I decided that a Sputnik without gaze as air-inlet might have some advantages. But not only repairs, but also the setting up and bridling of the kite should be easier, as one could always access the inner part of the kite.
Another item that I changed was the thickness of the kite. As I was moving towards a rather high aspect ratio, I tried to compensate for a possible banana-effect through the fact, that the tip profiles are thinner and should thereby fly faster.
As 3m^2 is rather small, I did not try to fiddle with the little bit more complex cross bridle, but used the arch bridle calculated from the plot-software. later on it turned out, that the apart from adjusting the a-lines, the kite flew out of the box with good results and performance.
I also used the Competition-type of tips: no profiles, but bottom and top skin are directly sewn together.
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When I was planning the Sputnition kite, I wanted to know in
advance, whether I could really use the Icarex type 2nd quality ripstop,
that I had bought. I therefore decided to build an extra small
quadrifoil-type of traction kite, to be used in the very high end
winds. As I had just gotten the plans for the Sands fourliners, I
decided to go for the 2m^2 Sands quad.
The instructions in the plan were very clear and easy to follow.
Nevertheless, I decided to skip the keels and also use a cross bridle
instead of the ordinary two point bridle. As the outline of the kite
is a simple rectangle, this decision made the bridling very simple
(Only three different lengths for the primary bridle, identical
secondary bridle). The cross-bridle was build using a rigg of nails,
hammered in the floor of our house (at a place where hopefully noone
will see the small holes...). Laying out the rigg, applying the
Spectra bridle and attaching it to the secondary bridle was done
within half an hour! Building the kite actually took me less than a
week (without having worked each day).
I have not yet flown the kite in real high wind, but from what I
have seen right now, it seems that the kite flies ok, and might just
need some fine tuning.
I have now had the time to test fly the new Sands Quad in different
wind conditions. The cross bridle works fine, just the brake lines
need some adjustments. When I first flew the kite, wind was rather low
and if I had built the kite from Carrington (as I have always done it
before) the kite might not have flown at all. But by using ICAREX type
of ripstop, the kite flew quite nicely. However I noticed that the
cross bridle migth be to narrow. Whenever I was pulling one one side
too much, this side of the kite was behaving like a accordion and the
profiles shrinked together. Some days later, when I tested the kite
again in higher winds, this effect had nearly disappeared, and I
expect the kite to behave well, once the wind is strong enough to use
the kite for real buggying.
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Shortly before the Fanoe '99 festival I decided I need another buggy
engine. As I had all the different plans of Chris Sands I decided to build
the 4 m^2 quadri. This model has flaps at the trailing edge, but apart from
this, it's a just a standard quadri. Building is very easy and straight
forward as all Sands kites.
At Fanoe, I got a lot of time of actually flying this kite and I was
really impressed. Very good upwind performance, no the least tendency to
luff and overall very easy to control. If you want to get an extra push,
just pull the brake lines and experience the additional power.
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| Built: June 1998 |
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This is another of the really simple to built and equally simple to fly four-liners based on the plan of Chris Sands. All his kites feature a rather high AR of nearly 4, compared to something like 2 of the standard Quadrifoil kites and the corresponding rip-offs. Nothing special with this kite; I added flaps - will see on Fanoe whether it makes any difference to the version without flaps.
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| Built: January 1999 |
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In September '98 I heard in rec.kites that Chris Sands had developed a
new generation of fourline kites for buggy racing. When I got him on the
phone, Chris told me that since his son was using the new foils, he had
never again lost in a buggy race. This convinced that I immediately ordered
the new plans (15 pound per size).
The new kites differ in the following:
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| Built: December 1998 |
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In early January 1999 we decided that we could go together to the 1999
Fanoe festival, my wife and me. As this will be the first time that we will
be at Fanoe without children, I thought that this might be ideal for Anja to
learn buggying. That's why I am currently building a second line of traction
kites for Anja.
At the same time I discovered the interesting pages of Gene
Matocha about
High AR.
On one of his pages, he describes a new technique how to build diagonal rips (DRips)
into traction kites to reduce the number of bridle lines. Using DRips
enables to reduce the number of bridled profiles to every third. The 4m^2 Sands
Quad has got 20 cells, so I enlarged it by one cell and have now got a kite
which is effectively bridled only every thrid cell.
This also meant that I could only use the primary bridles from the plan and had to "invent" a new secondary bridle. As of now, the bridle is a standard two point bridle, but I consider to add some cross bridles. At the winglets,
the kite (basically all Sands Quads) has got small triangles instead of
bridle lines. The reduced number of bridle lines also means that the stress
on each bridle point increases. For the first time since a long time, I have
used a different method to attach the bridle lines. Instead of sewing a
reinforcement line to the seam allowance of the profiles, I have attached
reinforced strips of ripstop nylon (8-fold!).
As of writing (February
1999), I have only tested it as two-liner and it flew excellent; new
secondary bridle needs some fine tuning. Flaps and brake lines added, but
not yet tested.
Additional comment July 1999: I have now had the chance to test the x-foil.
The power is at least the same as with the conventional Sands Quad. However when Anja crashed the kite into
another buggier, one bridle attachment point was ripped off the kite to my surprise.
But after ten minutes of sewing, the kite was ready for buggying again. I have now also added
two cross bridles on each side, which makes the kite more powerfull during turns.
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| Built: January 1999 |
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