Hieronder een overzicht van toom-maten van diverse c-quads afkomstig van eigen nieuw aangeschafte vliegers.
Hieronder een overzicht van toom-maten van diverse c-quads afkomstig vanaf internet (o.a. www.kiterider.info).
Hieronder een overzicht van de orginele toom-maten, zoals opgegeven door Peter Lynn.
Tot slot een beschrijving opgesteld door Pete Lynn (de zoon van Peter Lynn), omtrent zijn mening over het tunen van c-quads.
CQuad Bridle Tuning - Pete's Opinion
In order for a CQuad, or any traction kite for that matter to perform to its full potential it must be individually tuned to
the specific handling characteristics preferred by the user. For a CQuad this tuning is primarily
achieved by bridle adjustments at the skin of the kite. The initial bridle setting of a CQuad are set to a
"happy average" but with use this may deteriorate as different bridles stretch by different amounts in relation
to bridle weight and type, individual loading, and exposure to water. The kite bridles will also "stretch in" when
the kite is first flown with significant power, this is taken into account in the initial bridle setting. Large kites are also
far more sensitive to bridle adjustment than are thumb kites, this is due primarily to increased size and sensitivity to apparent
wind, structures which are necessarily proportionally lighter, and increased bridle numbers of lighter weight.
Firstly it is important to note that like most kites the CQuad can fly badly
in the presence of water. When a CQuad is dropped in the water and then relaunched and flown under power while the bridles are
still wet the bridles may stretch beyond there usual limit seriously effecting the handling of the CQuad. This bridle stretch
can be reversed by again wetting the bridles and then allowing them to dry in the absencse of load. Under these conditions
the bridles will return to their original prestretched length. This is a rather strange characteristic of various braided lines
and is not just restricted to dynema. This stretch problem in the presense of water was first discovered with paragliders where
not suprisingly it was quite problematic. Paragliders however, do not have quite the same affinity
for water that CQuads being used for kitesurfing do, especially if they are still learning how to fly and prone to a little
swimming.
The preferred flying characteristics are often related to such things as the
experience of the user, their weight, their finesse, the strength and steadiness of the wind, the depth and wildness of the water
, waves, board, whether one is cruising or jumping, how long the swim, etc. The flying characteristics that one will specifically
tune for are anti-luffing, power, lift to drag ratio (which translates to speed and upwind performance) and the ability to depower.
The bridles of a CQuad can loosely be categorised into primaries, secondary cross bridle and brake bridles. The CQuad is
comparatively insensitive to adjustment of the secondary cross bridle and the brake bridles and it is very unlikely that these will
ever want adjusting beyond original setting. If they are ever broken it is only necessary to return them to their original length,
it is often useful to use the opposite bridle on the other side of the kite as a reference. Primary bridles are further divided
into spine bridles and check bridles, spine bridles are designated as A, B, C, D or E from leading edge to trailing edge, number
dependent on spine and kite size, the A bridles are on the leading edge at each spine end. The check bridles are on the leading
edge in between the A bridles, of the three wing tip leading edge bridles the bridle closest to outer spine can largely be assumed
to be a check bridle while the outer two bridles function more like spine bridles.
Check bridles are adjusted to be slightly loose, around 20mm is a good starting point,
with reference to the primary bridle setting. When the CQuad is flying without power the check bridles should be sagging slightly,
as soon as the power comes on they should pull tight. If a check bridle is too tight the leading edge will be inclined to distort
and buckle inwards causing the CQuad to luff, alternatively if the check bridle is too loose the leading edge will sit too far back,
back bridling the CQuad when the power comes on, which powers it up further just when you do not want it. Loose check bridles make
the CQuad far more prone to stalling and greatly reduces the capacity of the CQuad to depower when the brakes are let off. Loose
check bridles can initially reduce luffing slightly, especially if the rest of the primary bridle is out of adjustment, however if
taken to extremes the spring back of the leading edge in response to an abrupt decrease in power can actually precipitate a luff.
Generally a less experienced flier will want the check bridles slightly looser, increasing the luff resistance slightly, while a
more experienced flier will want the check bridles slightly tighter, on the verge of distorting the leading edge inwards, allowing
greater depower and penetration through the gusts. A CQuad properly tuned in this fashion will actually be very luff resistance
and give ample warning of an incipiant luff, allowing an experienced user to actually "ride the luff", a very useful
depowering trick which enables the flier to use a larger CQuad than otherwise possible under given conditions. This is especially
useful in circumstances requiring the mitigation of aparent wind build up, it helps one avoid being dragged off down wind at high
speed.
The stronger the leading edge the less sensitive the CQuad will be to check bridle
adjustment, but a heavier leading edge is no substitute for propper bridle adjustment. Any additional weight on a CQuad invaribly
makes it fly worse and additional weight at the leading edge is to be avoided at all costs because it has the greatest effect in
moving the centre of gravity forward increasing the susceptability of the CQuad to luffing. Poor adjustment of check bridles is
the first and foremost cause of poor handling in CQuads. Part of the reason for this is that because the check bridles are
significantly less heavily loaded than the rest of the primary bridles they tend to stretch out less. This means that the check
bridles tend to become tight as the bridles stretch out and often require retuning. This stretching out of bridles only appears
to be significant on larger CQuads, the 8.3 and 10.5 specifically although thumber sizes can usually benefit from fine tuning.
Bridle stretch seems to stablize after the first couple of weeks of use after which time there is little more need for bridle
tuning. When viewed from the front the leading edge of the CQuad should smoothly camber back around 20mm (dependent on CQuad size)
between spines, more or less than this and the check bridle should be adjusted. All bridle adjustments are made at the kite, usually
this involves untying the attachment knot and retying at a shorter length although if the bridle is to be extended it may be necessary
to add in a short length of line to achieve this.
The adjustment of the primary spine bridles is quite simple, in theory, the bridles must
be adjusted such that the spine is straight. In practice these spine bridles are adjusted to provide a slight convex, or reflexive
camber. The reason for this is that a spine with concave camber is extremely prone to catastrophic luffing creating a very unpleasant
flying CQuad. A CQuad which is suffering from this will be quite powerful, prone to stalling and continually on the verge of
catastophic luffing, it will have virtually no capacity for depower and require extreme vigilence and excessive use of the brakes
merely to keep it in the air. Such a CQuad can not be relied upon even by an experienced user and desperately needs to be tuned. This
bad behaviour can be quite a common occurrence with larger CQuads, especially if they have been subject to high loads. When a large
CQuad is subject to high loads the middle spine bridles, B and C bridles, and D bridles on larger CQuad sizes preferentially take more
of the load and hence stretch more creating the concave and luff prone spine profile which causes such unpleasant flying characteristics.
This is the reason for pulling in the B, C and D bridles to create a slightly convex profile. This adjustment usually has to be made
on the larger CQuads after they have stretched in, because of their size, number of bridles and slower response to apparent wind change,
they are very sensitive to the spine profile. If B,C and D bridles are pulled in to far the CQuad becomes stall prone and the
capacity for depower is decreased. This adjustment also acts to flatten the camber of the CQuad, decreasing the power which the CQuad
develops. The A bridle is let back such that the spine leading edge sits up slightly, significantly improving luff resistance at the
cost of a slight increase in stall speed. If the CQuad is layed out on a flat surface with the spine held straight and the primary
bridle held up the A bridle should have around 10 to 20mm of slack.
The adjustment of the primary spine bridles also sets the angle of attack of the spine,
whether it is forward or back bridled. If a spine is back bridled it will develop higher power, be less inclined to luff, but
be more prone to stalling. The more forward bridled the spine is the lower the stall speed and better the depower, but at the expence
of luffing. Generally it is better to have the CQuad more forward bridled and use the brakes to back bridle the CQuad as required,
this extends the flight envelope giving the flier greater control and capacity for depower, however greater attention is required by
the flier. If the CQuad is to be bridled for maximum depower then the CQuad should be progressively more forward bridled towards the
wingtips. This allows the wingtips to luff and feather when the brakes are released which also acts to reduce the spanwise tension
along the trailing edge forward bridling the centre cells, achiving maximum depower. The centre cells determine whether the CQuad luffs
or not and the centre spines should be sufficiently back bridled so as not to luff even when the wingtips are allowed to flutter.
Alternatively the wigtips can be back bridled, providing greater power at the expense of the capacity for depower and general
handling.
There are two basic configurations that a CQuad can be tuned to, and an infinite number
of incremental variations between, depending on the experience and preferences of the flier and the conditions and applications
for which it is used. Solid power and reliability at one end with maximum capacity for depower, breadth of flight envelope and smooth
handling at the other end. For example, with respect to kite surfing and jumping with a thumb board where higher speed apparent wind
build up is not a major issue, reliable power is the overriding concern. To achieve this CQuad should be back bridled, especially at
the wingtips and both A bridles and the check bridles let out slightly.
Tuning for maximum depower is somewhat more challenging, the middle spines should be
slightly back bridled so that the centre cells provide significant power and are antiluffing. The CQuad should be progressively
forward bridled toward the wingtips with the wingtip leading edge so forward bridled that when the brakes are released the wingtips
luff and flutter while the centre cells still resist luffing, this is full depower mode. A bridles should be pulled in until the
spines are almost straight and the check bridles pulled in until just before the point at which they start distorting the leading edge.
This is a time consuming bridle configuration to achieve as it requires considerable precision and fine tuning, but it is also very
rewarding as it can greatly improve your control and ability to handle overpower.
Skin shape primarily determines the inclination of the spines and leading edge to distort
from the straight or curve that they should desirably assume. Obviously skin shape also determines the section of the wing profile,
while this bares some relation to the top skin of a parafoil it is, not a parafoil. There are some rather interesting three dimensional
feedback relationships going on, some of which are good, some of which are not so good. Fortunately the fine tuning of the skin profile
is primarily achieved through bridle adjustment and it is quite unnecessary to alter the skin shapes of a CQuad, unless of course you
really want to. For those intent on playing with the camber of a CQuad, a flatter section with the point of maximum camber closer to
the front will be faster and more luff resistant, but will have significantly less power. Flatter CQuads are easier to get right but
are very apparent wind sensitive and generally less pleasant to fly, standard CQuads are designed with a high degree of camber so that
they give better power and improved useability.
There are many other little tricks and theories that can aid in improving the performance
of CQuads which for the sake of brevity I have not gone into here. CQuads are still a very young kite and our understanding is far from
complete, I am quite sure that there are many significant advances yet to be made.
