Peel 3.5m²
Change from cross bridle
PEEL REEFING
To add the reefing system to existing Peels, the cross bridles must be
separated into two groups on each side, one set from each alternate
primary bridle starting from the wing tip set, the others for the
remainder. This will require some cutting and re-tying. A loop is made at
the confluence of the wing tip set of cross bridles on each side and to
this a 1.5m line is attached, to the other end of which the flying lines
are attached and from which point 1.25m of "stretchy" returns through
the loop to the remaining cross bridle set on that side. Confused? I am;
then have a look at an existing reefing Peel.
Convert to 4 line
Any Peel can be rigged for 4 line flying. There are many different ways.
I usually attach (sew) four loops of light braided line, to each side of
the kite, the eight attachment points being evenly spaced along the
trailing edge. The extra flying lines on each side are attached to these
loops by other loops. All knots are left to float so that the control line
pulls evenly on the kite's trailing edge. At Fano in 1992 someone from
Switzerland who's name I should remember showed me his Peel rigged for 4
line flying in a manner similar to this, but without floating knots, this
had required the addition of a restraining line between the attachment
points of the 3rd and 4th lines to improve control. Rather than
attaching the extra lines via loops to the trailing edge the loops can be
just tied onto the rearmost primary bridles on each side. This is O.K. for
flying but not so effective for reverse re-launching.
For larger kites, 4 line control of this type runs up against the limits of
wrist-twist movement. At a certain scale there is just not sufficient
movement available to effect satisfactory control. The 5m and 6.4m
Peels are large enough to have this problem to a minor extent, but it can
be alleviated by adding a "displacement doubler" at the handles or at the
kite in a manner akin to that used for the new 2 line quick turning system
as described later.
PEEL SAFETY
Peels are large strong pulling kites quite capable of injuring the flier
or bystanders if used injudiciously. If you are not experienced in the
flying of this type of kite you MUST take special care.
* Choose light or moderate winds.
* Fly in large unobstructed areas clear of people, cars and power
lines.
* Ensure a clear recovery area downwind of where you are flying in
case you need to release the kite.
* Don't go further into the air than you are happy to fall - kite
jumping, except perhaps over water, is not a safe activity. Broken
ankles and worse are not uncommon.
* Don't fix yourself to the kites without a "deadman" release system.
* Tethered Flying. Flying kites while suspended off the ground
between kite and anchor is not safe and has resulted in fatalities.
Kites are absolutely not safe when used in this way. DON'T DO IT!
PEEL DATA
From June 1992 four models of Peels are available 3.6m (2.5sq.m.), 5.1m
(5sq.m.), 5.1m (5sq.m.) reefing and 6.4m (7.5sq.m) reefing. The reefing
models can be flown with the reefing system engaged or (by attaching the
flying lines differently) as non reefing kites. The reefing system (filed
for patent June 1992) works by causing the Peel canopy to assume a
"corrugated" form as pull increases thereby reducing effective span.
Working to reduce maximum pull by about 25% (currently), this system allows
the use of a bigger kite with its greater pull at the edge. All models of
Peels can be retrofitted with the reefing system.
Peels can be tuned for different performance characteristics. We use a
table of differences - see Table 1 to set up our Peels for racing.
Differences are listed for the four bridles on each cell as first minus
second third minus second and fourth minus third. Generally, first-
second is the critical dimension. If this is too low the kite will exhibit
worse luffing characteristics. Because the second bridle takes the
greatest load, after extensive strong wind flying this bridle will
stretch more than the others causing a gradual deterioration of flying
characteristics. "Blue Printing" the bridles back to the table of
differences will restore the lost performance. Also, because of
unavoidable small differences in knot tying when the Peels are first
bridled even "Blue Printing" a new Peel may improve its performance, but
do some flying first to "settle the bridles in". Increasing third minus
second and fourth minus third will assist high wind buggying/kitesailing
but light wind buggying/kitesailing performance will suffer. This may
seem to be the reverse of how it should be but is all to do with the
previously mentioned "its no use having a kite that will go along way
around the edge if when it gets there it hasn't enough pull left to get
you moving!"
Moving the bridle point back increases the apparent wind speed at which
the onset of stall will occur. It also makes the kite much less pleasant
to fly. Winning is what matters though and back bridling definitely
improves light wind buggying performance. This situation poses a
problem for buggy racing rule writing as the better answer to improved
light wind performance is to use a bigger kite but there is a strong
temptation to set kite area limits on buggy racing classes.
The table of differences listed in Table 1 is our current best
compromise. For those Peel fliers who have had unfortunate accidents
(usually involving other people's Kevlar lines) which have cut their
bridle lines, Tables 1 and 2 can be used to reconstruct all primary and
cross bridles.
The technique we usually use to fix a few cut bridles is to first match up
the cut ends and mark back 75mm each way, tie in a 100mm length of similar
diameter line and adjust the knots until the two marks are 150mm apart.
From the beginning of 1992 Vlieger Op of Holland began manufacturing and
distributing the 3.6 and 5.1m Peels under a sole franchise contract for
Europe. All 6.4m Peels and the remainder of the world are supplied from
New Zealand.
LAUNCHING
Basic launching techniques are assumed to be understood but
we have developed a (relatively) safe strong wind launching system:
Launch the kite at the edge of the wind facing outwards not upwards.
Although this requires some experience from the launcher it does get the
kite up safely without that arm wrenching rush as the kite heads for the top
from a downwind launch. For launching by yourself from sand or grass surfaces,
attach a short (say 100mm) peg permanently to each main line attachment
point. Fix rubber bands to these pegs so that they are normally held up
parallel to the mainline loops. For launching in all except very strong
winds just stand the kite on its trailing edge restrained against the
wind by these two pegs stuck into the ground. Pulling on the line handles
will now release the pegs from the ground, launching the kite. This
system was developed by Phillip McConnachie, Ashburton New Zealand.
BRIDLE UNTANGLING
It's a matter of experience and is surprisingly easy.
I'm very sloppy about packing so generally have to untangle every time I
bring a kite out. Lay the Peel out on the ground, hold one line tie loop in
each hand and just do what looks logical. It always works. When packing
away I don't braid the bridles, but some do, doesn't matter either way but
the key is to avoid letting either line tie loop pass through any bridle
lines - fold the kite up towards the face but separate the loops and
settle them on the back (top skin of the kite).
POROSITY
Peels are not very sensitive to fabric porosity. I fly one 5m
Peel which I can comfortably breathe through! Its performance is not
noticeably different to impermeable kites. Paradoxically, as the skins
become softer and perhaps more porous with use the fabric also becomes
stronger.
PEEL HISTORY
One day in 1988 I sat down and listed the ideal features for a traction
kite, attempting to anticipate in advance what the traction kites of 2015
will look like. Some of the listed features, in addition to the
fundamentals of good Lift to Drag Ratio and satisfactory M.M.R. (maximum
pull/minimum full ratio - see later explanations) were: Ability to scale
up to large sizes without deterioration of the weight/area ratio, full
options for airfoil profile; robustness in crashes (especially when being
swilled around in the surf) and at least a potential for automatic
reefing (some way of making the kite smaller automatically as apparent
wind increases). Ease of packing and "soft is safe" were bonus features
after I had already decided to attempt a soft stunter. The direct
lineage of the Peel design was an evolution from the old 20sq.m. two line
parafoil I had been given by John Waters while at Lincoln City in 1987.
The problems faced were to dramatically improve L.D.R. and control
without causing a luffing problem. Soft kites also have the inherent
problems of necessary bridle complexity and a tendency to collapse when
flown into wind pockets (their form holds only when there is positive air
pressure available from relative motion). After thirty three prototypes
and numerous frustrating re-cuts and re-rigs the first satisfactory
Peels were coming through intermittently during 1990 and I started using
them at festivals during that year.
Chasing those essential characteristics for traction kites L.D.R. and
M.M.R., I tried every possible airfoil
profile from a wedge to a Flexifoil clone. At first I could find no window
between poor tracking (the ability of the kite to hold a horizontal
traverse, without "mushing out" especially in light winds - kites that
fail by this measure will gradually require to be pointed more and more
upwards even while maintaining a horizontal course) and luffing (tendency
of the kite to collapse catastrophically when the angle of attack
becomes negative). I differentiate two forms of luffing. One occurs when
or if air flow ever sets up a "couple" with one force lifting the trailing
edge while another force pushes the leading edge down. This form of
luffing is inherent to the profiles used and to the bridling setup and can
occur even during steady flight in smooth wind. It is absolutely
unacceptable. I call this form of luffing Centre of Pressure migration
luffing, C.P. luffing for short. The other form of luffing occurs when the
kite experiences negative angle of attack. This can easily occur when
flying in turbulent winds or even just when high speed/momentum carries
the kite out passed that point at the edge of the wind where it is, in the
limit, able to hold steady state flight. This is a huge problem for
kitesailing because unless you can walk on water there's not much you
can do to stop it once it starts happening. When flying statically (i.e.
standing on the ground) fliers instinctively, unconsciously take a quick
step backwards to hook the kite back into some movement relative to the
air - the prerequisite for continuing kite inflation. I call this form of
luffing Apparent Wind luffing. A.W. Luffing for short. For a while I
despaired of usable solutions and went back to developing delta form
rigid frame stunt kites. For reasons explained later this kite style has
fundamentally good M.M.R. a feature that I am sure is well understood by
Don Tabor from San Diego to whom the kite world owes a hugh debt for the
development and popularising of this kite style. Building larger and
larger delta form kites (up to 5.5m windspan) I was eventually defeated
by a scale effect problem. Lift increases as the square of span but
strength requirements increase as the cube of span. Big rigid kites
suffer terminal handling problems because they must be too heavy for
their area. For all this, large rigid structure kites (carbon) could yet
become the dominant traction kites as their shortcomings are
circumvented or if the alternatives prove to have worse failings.
Likewise for stacks of smaller rigid frame delta form kites which I have,
at least temporarily, given up on because of launching problems and
their tangle susceptibility when crashed - especially in rolling surf.
Also tube breakages can be a nuisance. Returning to soft stunter
development I decided to just put up with poor tracking and bridle the
kites back to eliminate C.P. luffing while I concentrated on
control/steering development for a time. By October 1990 I had tried a
large number of systems starting with just separate bridles to each
side of the canopy as for the original John Waters parafoil and the
Paraflex. This caused a loss of performance through canopy distortion.
The next attempt was to use a semiflexible bar spaced out along which
were bridles to the individual cells and below which were various criss-
cross or linked "Y" bridles connecting to the flying lines. This worked
very well but was "impure"-use of a rigid member in a soft kite. Next
came the caternary bridle; the flying lines are set up as a continuous
loop with individual cell bridles attached to it at various spacings. With
this I could not get tight turning without unacceptable canopy
distortion and large arm movement. But I have since seen this type of
bridle used entirely successfully by Nop Velthuizen in Holland even on
5m2 soft stunters. Next I tried a complicated cascading pulley system
which worked satisfactorily but then hit on the current (and copyright
protected) cross bridle system which is simple, causes minor if any
canopy distortion and allows tight turning without excessive arm
movement even for 7.5m wingspan kites.
In early 1991, researching airfoil profiles I was told of the profile forms
used on flying wing airplanes to prevent basically the same C.P. luffing
Peels were suffering from. This quickly led to the (copyright protected)
humped trailing edge profile we now use that opened the window to good
tracking and the elimination of C.P. luffing. I now believe that it is
possible to use a profile without a trailing edge hump and not have
serious C.P. luffing but there are currently other reasons for not doing
so; the assumed M.M.R. benefit from the hump and also a simple but poorly
understood limitation of "skins and ribs" soft kite construction. The
average kite airfoil profile is not the rib profile but is always deeper
particularly at points where the cell width is much greater than the rib
depth. I am always much amused by the mega precision and mega computer
optimisation that is claimed for some soft kite rib profile airfoils. The
rib profile applies for less than 1% of the kite! To accomplish a perfect
wedge shaped trailing edge, an infinite number of ribs would be required.
Practicable rib spacings always cause "coal sack" type distortions along
the trailing edge, seriously disturbing airflow exit and placing a
limitation on attainable L.D.R. of maybe only 15 or so (good sailplanes
manage a wing L.D.R. of 100+!) the humped trailing edge may cause less
form drag than conventional trailing edge forms - think of the wedge
shaped low drag shapes currently fashionable in car design. Using the
humped trailing edge the window has opened very wide. I can now bridle
Peels far forward of the position where the lift coefficient drops out of
the useful range without C.P. luffing becoming a problem.
There was always a solution to the C.P. luffing problem. The "Paraflex"
design from Wolfgang Schimmelpfennig and Wolkensturmer uses bridles
only in the forward 25% of its chord and an airfoil which seems to be
evolving towards the "Flexifoil" profile. This is an excellent vice free
and exciting kite to fly but does not seem to have a satisfactory
combination of L.D.R. and lift coefficient to allow satisfactory upwind
performance for kite traction application. As for Flexifoil though, it
could be quite suitable for speed record use where sufficient "runup" is
available for apparent wind to build. A basic explanation of this
limitation may well be to think of only the forward 30% (the bridle
supported portion) of the Paraflex as being the effective lift creating
area with the remaining 70% just along for the ride, for visual effect (as
used in the very effective "Snoopy" and "Big Boss" etc type decorative
kites) and to act as a sort of anti luffing "whales tail".
To complete the Peel history requires introduction to the final member
of the Peel innovation troika: Cross Bridle, Humped trailing edge and, as
from the patent filing date of June 1992, the Reefing Bridles. First must
come a thorough explanation of how the characteristics of L.D.R. and
M.M.R. can be combined to make a good traction kite.
Accepting that as buggy/boat speed reaches true wind speed and above
(see Kite Traction), all courses tend to be upwind courses from the kites
perspective. It is essential that the kite has good L.D.R. and as much
pull as possible when it is "at the edge" (see definitions). L.D.R. is a
measure of how far around
the "edge" is for a given kite and apparent wind. 80 degrees,
representing L.D.R. of 5.7 is currently very good L.D.R. for a kite. If a
second kite can only manage 70 degrees at which "edge" it has the same
pull as the first kite at 80 degrees then, quite accurately, a buggy/boat
powered by the first kite will be able to maintain the same velocity to
windward as the second kite but on a 10 degree higher course. This is a
huge difference and would probably result in the second buggy/boat being
lapped after 3 laps of a typical circuit. Of course, if the second kite
had more pull but still at only 70 degrees (L.D.R. 2.75) It's buggy/boat
won't be able to go as high as its rival but it will go faster and may well
prevail. This compromise is the essence of traction kite optimisation.
Kite L.D.R. is largely a matter of basic design and is often limited by the
imperatives of retaining good control (steering) avoiding all C.P.M.
luffing and most A.W. luffing. The biggest factor effecting kite pull at
the edge is kite size, in general bigger kites generate more pull. Simple
answer then: use a bigger kite! Unfortunately kite size is limited by its
maximum pull (see M.M.R. definition) not by its pull at the edge (minimum
pull). Too much pull and you capsize (boat) slide sideways (buggy), or fly
into the air (boat and buggy), all of which are highly detrimental to
progress! To allow the use of a bigger kite for superior performance
upwind we need to also have a kite with low M.M.R. Of course, for
buggying/boating off the wind (apparent wind hitting your back) high M.M.R.
is no great disadvantage, but in most buggying and much kitesailing this
rarely occurs. There are many ways of improving M.M.R. The ideal system
would retain constant high L.D.R. while holding pull constant at its
maximum usable value for all significant wind speeds. There are no
available systems on any available kite types which even get close to
this ideal.
Now back to Peel development history. In its standard 1991 form Peels
have good L.D.R. quite satisfactory M.M.R., no C.P. luffing and can, with
experienced fliers, avoid A.W. luffing at least as well as other available
traction kites. I have tried very hard for some years to improve the
Peel M.M.R. still further. It is now possible on 1992 peels to use spring
bridling that moves the bridle point automatically forward as pull
increases thereby decreasing theoretical maximum pull by at least 25%
without causing C.P. luffing. This seems like an ideal solution to better
M.M.R. but it has an (expected) side effect. Bridling forward increases
the speed of the kite through the air which increases the pull
proportionally, offsetting much of the pull reduction accomplished by
forward bridling in the first place. Accordingly the best solution seems
to be to make the kite smaller as pull increases - a reefing system. My
diaries from 1988 onwards are peppered with unsuccessful attempts at
Peel reefing. I developed what I thought was a clever, organised search
system just for the purpose of finding a usable peel reefing system but
after four years of rigorous application I had exhausted all
possibilities. The next night a solution just occurred to me in the middle
of the night! It does cause a deterioration of L.D.R. as reefing
progresses but so does every available system on other kite styles
(except, I suspect that wing tip twist off as used on delta style stunt
kites probably helps control tip vortex losses at the same time as
reducing pull) and it works! Currently achieving about 25% pull reduction
over non reefing layouts it has the potential of achieving 50% reduction
or more. It also appears to have the bonus of reducing the occurrence
of A.W. luffing. I surmise that as the kite's momentum carries it into a
lower apparent wind zone, the kite responds by increasing its effective
lift area, allowing the kite to climb out through the danger zone.
Experience seems to be confirming the result at least if not the
hypothesis.
As things stand I believe that effective reefing is one of the two great
breakthroughs that are required if kitesailing is ever to become a
viable recreational activity. After 3 months use I believe this Peel
reefing system is at least the beginnings of that breakthrough. (The
other required innovation is an on-the-water launching and retrieval
system which I believe is also close to being achieved.)
PEEL OPTIMISATION CHARTS
Recently I have spent some time optimising the cross bridle setup.
Relative to 1991 models it is possible to greatly improve turning radius
and simultaneously shorten the lines, reducing bridle drag. It's
fascinating; turning can be improved to the point where the inside tip is
effectively moving backwards through the air and consequently collapses
from lack of inflation pressure in light winds! I'm uncertain whether to
bridle Peels for the tightest possible turns - leaving it to operator
skill to avoid collapses or to back off to an "idiot proof" compromise.
The Table 2 cross bridle dimensions for 5m reefing Peels and 6.4m reefing
Peels do allow over steering in some conditions.
Table 1: Peel Bridle Differences
3.6m Peel 1st -2nd 3rd - 2nd 4th - 3rd
mm's mm's mm's
Tip 0 4 30
2 5 12 70
3 8 22 100
4 10 35 90
5 13 35 90
6 13 35 90
Centre 13 35 90
2nd bridles are all approx. 730mm long, knot to knot
5.1m Peel Tip 0 6 37
2 0 13 100
3 15 40 130
4 25 45 125
5 25 50 125
6 25 50 125
Centre 25 50 125
2nd bridles are all approx. 1010mm long, knot to knot
6.4m Peel Tip 5 12 50
2 10 20 115
3 25 50 150
4 35 60 150
5 40 65 150
6 40 65 150
Centre 40 65 150
2nd bridles are all approx. 1220mm long, knot to knot
Table 2 Cross Bridles, In Metres
3.6m Peel 5.1m Peel 5.1m Peel 6.4m Peel
(Reefing) (Reefing)
Tip 1.11 2.42 1.60 2.00
2 1.10 2.47 1.58 1.98
3 1.11 2.53 1.60 2.00
4 1.15 2.60 1.66 2.07
5 1.21 2.68 1.74 2.17
6 1.29 2.76 1.86 2.31
7 1.39 2.85 2.00 2.47
8 1.51 2.95 2.16 2.66
9 1.63 3.06 2.34 2.87
10 1.76 3.18 2.53 3.09
11 1.90 3.31 2.72 3.32
12 2.05 3.44 2.92 3.56
These are our best choices as at June 1992 (and I'm still not that happy
with the primary bridling on cells 1, 2 and 3, all models). When
improvements are introduced new optimisation charts will be published. I
have no especial monopoly on knowing what the best bridle dimensions are
so don't be afraid to experiment for yourself. For example, my
impression is that 6.4m Peel primary bridles are maybe a little too
forward. I hope that those who discover improvements will share their
knowledge with others as I am committed to doing.
The simplest and best way to "power up" a Peel is to shorten (at the skin)
the No 3 bridles by 5mm (3.6m Peel), 7.5mm (5.1m Peel) and 10mm (6.4m Peel).
Usually we do this only on the central rib and the 2 or 3 bridle sets each
side of centre and will sometimes re-rig or de-rig this change even
between races to match changing wind conditions. This modification is
also the most effective cure for persistent luffing.
REPAIRS
Peels can be split in heavy nose-first landings, especially if
onto water because this closes the gauze leaving the internal pressure
nowhere to go except out by bursting rib seams on the top skin. It's not
easy to do, I've only split 3 kites in 3 years, always in wild, high wind,
out of control water crashes. Don't despair, permanent and effective
repair is easy, at home, by most kite retailers or, in the limit, at one of
our factories. The steps are: unpick the trailing edge seam where
necessary for access and also unpick the split seams, - repair splits in
ribs and skin using ripstop tape (white tape applied on the inside shows
least on all colours) - sew the ribs back to the skin, and finally, close
the trailing edge after incidents like this it pays to re "blue-print"
the bridles.
