Invented in 1977
by Peter Waldron of
Worcestorshire, England, the Waldof Box kite is a spectacular sight in
the sky
and and the envy of onlookers. Whilst certainly not a beginners kite to
build,
with a little time and care, neither is it very difficult. This model
is 1.8m
in diameter (6ft in round numbers) as this gives simple dimensions for
the
parts, but it can be easily scaled up or down, adjusting spar
thicknesses
accordingly.
The
prototype which I made (shown in the photo at the end) is half the
length from
front to back of these plans. Only later, on careful study of some
plans
someone kindly sent me, photocopied from an Italian book, did I realise
the
true proportions of Peter Waldron's kite.
My kite is not as stable as
I would like. With the proper dimensions it should be much better and
should
fly in less wind. Exactly the same construction method can be used but
you may
have to experiment with the bridle. One day I'll have to build another.
The sail is
made up of four parts:
For each
part, the second dimension is the dimension in the front to back
direction. Dimensions
are finished dimensions, excluding hems and seams.
Colours refer to the
picture and the diagrams; you can of course choose any colours you
like.
There are different grades
of ripstop nylon. Be sure to use the crinkley sort, which makes a noise
if you
screw it up in your gand, not the softer sort with a rubbery feel,
sometimes
sold as "balloon fabric", and used for soft kites. This has little
resistance to shearing and so is unlikely to be successful.
In addition, there are:
Start by
cutting out all the panels. For those panel edges that are to be sewn
into
other panels, add 6mm seam allowance per edge. For other edges, cut to
size and
edge-bind according to Peter de Jong's
method (or your own). Rectangular
panels must, of course, have the grain parallel to the edges. The wings
can
have the grain parallel to the base, but the other two edges must
then
be edge-bound, not hemmed. However, if I was making another, I'd make
each wing
out of two pieces, each with its grain parallel to one of the two
shorter
edges. But I'd still edge-bind it.
Start by edge-binding all
the edges of panels that are not going to be sewn into hems.
Next, construct
the inner boxes with the spokes
sewn between the box
sections, as shown in Fig 2. Having added a 6mm seam allowance, for
each seam,
you can temporarily stick the panels together with seamstick tape, then
sew 6mm
from the combined edge. For the last seam, turn the box inside out.
Make sure
the seamstick tape is clear of where you are going to sew, not only so
you can
remove it afterwards, but also so that it doesn't gum up your needle.
The outer box and wings are
then attached to the spokes in a similar manner, as shown in Fig 3.
(Ignore the
blue loop underneath for the moment.)
At the centre of the base
of each wing, sew a strip of ripstop to form a loop through which a
radial spar
can pass. A piece of ripstop 4x7cm folded into 3 to make a strip
5x1.3cm will
do. Sew it to the wing, but allowing it to rise up in the centre, so
allowing a
spar to pass through.
Two tunnels
must now be sewn to the opposite
side of the long edge of
each wing, as also shown in Fig 3 (the blue loop underneath, actually,
a tunnel
seen in cross-section), to house the longerons. Each can be made from a
piece
of ripstop 16cm x 4cm, which allows for a 6mm hem on all edges before
attaching
it to the wing. Position them so their ends overlap the sewing of the
loop for
the radial spar on the other side. This gives extra strength to this
edge
against stretching where it isn't sewn into the outer box.
The 6
radial spars meet in the centre of the kite in a hexagonal boss. You
will need
to consider carefully what materials you have available for this.
Unreinforced
wood will simply split as soon as a gust strikes (I know from
experience). I
finally used 2cm acrylic (perspex) sheet - actually, two 1cm pieces
bolted
together. This is very strong and light.
Cut a hexagon, 4.5cm across
the flats. In the centre of each of the 6 sides, drill a 12mm hole to a
depth
of 15mm.
If you have no alternative
to wood, you may be able to strengthen it with a large steel washer on
each
side and a bolt through the middle.
Another idea would be to
fabricate it from glass fibre, using one of those kits sold in car
accessory
shops for filling dents and rust holes in cars. Wrap the ends of the 6
radial
spars (or 6 short pieces of 12mm dowel) with greaseproof paper, then
clamp them
in position. You can then build up the fibreglass around them. Pull out
the 6
spars just before the fibreglass sets solid. When it has done so, you
can pull
out the greaseproof paper and trim the completed boss with a file
and/or
hacksaw.
The sail is
tensioned by short pieces of line attached to the sail, running over
the ends
of the spars, and secured with a short piece of plastic tubing fitting
snugly
over the spar end, as in Fig 4 above.
Left is a
picture of a wingtip. (This is the
prototype - your wingtip
should have an angle of 90 degrees.) Sew a piece of line 10cm long to
the wing,
with 5cm sewn down each edge from the tip, but not sewn actually at the
tip. (Hopefully,
your sewing machine has a special foot with a groove in it, allowing
you to sew
the line to the sail, with the needle passing through the line. See Fig
The method of
attachment of the longerons,
shown right, is not dissimilar though drilling holes in 6mm dowel would
weaken
it too much. Sew a piece of line to the sail along the seam depicted in
Fig 3. The
line is passed through a groove in the end of the spar and secured with
plastic
tubing as before.
In each end of each
longeron and in one end of each radial spar, cut a groove. Also drill
two small
holes through the spar near the end and at right angles to each other.
A piece
of flying line attached to the sail can then be passed through the two
holes in
turn and then over the groove. A small length of PVC tubing fitting
snuggly
over the end of the spar will now secure the line very firmly.
To tension the lines over
the ends of the spars, tie a knot in the end of each. (The holes in the
radial
spars must be big enough for the knot to pass through.) You can now
make up a
simple tensioning tool as follows. Take another piece of line and tie a
loop in
each end. Larks-head one loop to a piece of broomhandle or similar, to
act as a
convenient handle. Larks-head the other loop to the line to be
tensioned. The
knot at the end of it will stop the larks head from slipping off. You
can now
pull the line as tight as you like, and easily remove the tensioning
tool when
you have secured the line with the plastic tubing.
On first
trial assembly you will probably find that either the inner or the
outer box is
slack. Pinch out a fold in one panel and adjust its size until that box
is
taught but the other hasn't started to go slack. Measure the length of
the fold
(double the length of the pinch) to get the amount by which the
circumference
of the box must be reduced. Divide this by six, giving an amount x cm,
say. Now
at each seam as shown in Fig 2 or Fig 3, sew another line of stitching
x/3 mm
from the first in the case of the inner box, or x mm in the case of the
outer. If
x is a mm or less, you can divide the fold by 2 or 3 instead of 6, and
apply
the correction to only 2 or 3 seams. On reassembly, both boxes should
now be
taught. If either box is noticeable irregular, or one edge is tighter
than the
other, you can improve or correct this in a similar way.
The bridle
is not critical, but needs to be reasonably long for stable flight.
Three loops
are sewn to the sail at the front ends of three non-adjacent longerons
at the
2, 6 and 10 o'clock positions. The upper segment of the bridle is 260cm
long,
attached to the 2 and 10 o'clock loops, and with a loop tied in it
exactly at
the middle. The lower segment is 230cm long and tied to the 6 o'clock
loop and
the loop at the centre of the upper segment. Larks-head a metal ring to
the
lower segment at about 24cm from where it is attached to the upper
segment.
Hold the kite up to the
wind with your finger around the lower bridle segment near the ring.
Try
various positions around the ring to find one where the kite best wants
to fly,
and move the ring to that position. You can now try a test flight. When
you're
satisfied, you can prevent the ring from moving on the bridle by
converting the
larks head into a prussic knot.
All that
remains is to enjoy it, and to bask in
the admiration of
onlookers!