I have had a bit of a love-hate relationship to Roks - I love the
simple, elegant form and it is a great canvas for appliquing; but it took
me a lot longer than expected to figure out the details required to
make it a well-behaved flier.
The Rok's simplicity is misleading: there are enough
variables to adjust to make it hard to isolate cause and effect. Small
alterations can make all the difference between a stable flyer and a
manic looping kite.
Here's a list of my current preferences:
- 6-point bridle
The 6-point bridle makes bridle-tuning
quite a chore, but it has advantages over the 4-point bridle. It gives you more control over the
Rok's shape under wind pressure - not so relevant for static flying but
very important for fighter-Roks. 50% more bridle points also help to
distribute the pressure more evenly - you can get away with lighter
rods than would be required for a 4-point setup.
- bowing of upper and lower spreader
The standard rule is to bow the lower more than the upper spreader.
Don't be too timid, you really do need a pronounced bow. The most convenient
set-up for me is to put split caps on the spreaders which go into spar pockets.
This gives you a nice clean shape without any spars jutting out. Also it
avoids any unneccessary straining or distortion of the sail which can easily
result if the bow line is attached to the sail.
I'm still not quite satisfied with the tensioning mechanism. I've tried
various kinds of sliding tensioners and none seemed really reliable. Fixed
tensioning points, on the other hand, can't easily be adjusted to match the
prevailing wind conditions or desired flight characteristics. Now I'll try
a back-to-the-basics sliding knot ... let me know what has worked for you.
- sail billow
This is, in my experience, the least critical point. The proper billow
develops automatically as a result of the frame construction and bowing. I
was cautioned not to make too heavy a seam, because it would not stretch
as much as the sail and would hamper the formation of the proper billowed
shape. In practise I have found this is not really a problem: I use a standard
I find Roks to be quite sensitive to minor adjustments of the flight angle:
tow point too far up and they start swinging and looping; too far down and
they're sluggish and won't rise.
Initially, I had all-carbon frames. Recently I replaced the spreaders with fibre glass tubing, using carbon only for the spine. The increased flexibility puts less strain on the sail, makes the kite more resilient to changing wind conditions and overall just more stable. For small Roks solid carbon could be an alternative - but I doubt whether it would be much of a gain in terms of weight or durability.
- aspect ratio
So far, I have always used a 3-4-5 aspect ratio. This is the true Rok,
as far as I am concerned. I suppose a 4-5-6 ratio or an enlarged lower triangle
would result in a more stable kite, but I haven't yet tried either.
I have built large static Roks according to
Simo Salanne and
They are each about 1.5m by 1.2m, Carrington and carbon/fibre-glass frame.
I don't usually use Carrington, since it has more stretch and absorbs more
water than Icarex does. It is nice, though, for "show kites": it
doesn't crinkle at all during sewing and has a nice silky look from up close.
Charlie's design: This kite was built as a wedding present (kind of obvious :-)
Simo's design: Another wedding kite (not so obvious). The glyph is the chinese
symbol for Chi, loosely translatable as "life energy". The
blue and red areas symbolize the elemental forces of fire and air.
This one is really small, with a 75cm spine. It is primarily meant to be a fighter Rok. I haven't yet participated in a real Rok battle, but I do like
to zoom around a fighter kite every now and again (check out my
fighter kite page to find out about other types
The spine is 4mm carbon, the
spreaders are 2mm fibreglass. I initially used 3mm spreaders but these
proved to be too stiff: the kite did not respond properly. Of course,
if you're just flying it as a static kite 3mm is fine.
The sail is Icarex applique. The Navajo design was a result of my '98 trip
to the south-western states of the US.
Last Updated: Mar 15, 2003