Building the Voltij
(See also Kevin Newton’s web site for a review and building hints
<http://www.knewt.com/planes/aerobatic/voltij.htm>
The Voltij is a revolutionary moulded glider intended for aerobatic
soaring. It has a symmetrical profile designed to use four-axis control. This
means it is as responsive inverted as upright. The controls easily permit rapid
gain of altitude to facilitate aerobatic flying. When building, great care must
be taken in assembling the controls since there must be no play to affect the
precision needed for aerobatic flying. The controls have to be virtually rigid
as indicated in the instructions.
The paintwork is a type of acrylic that does not react well to
solvents. Alcohol & other solvents must be avoided; soapy water is best.
Estimated building time: 15-20 hours.
Technical
specifications
Span 2020
mm
Cords 250,
110 mm
Surface 36
dm2
Profile MG
05 to 9%
Length 1250 mm
Empty Weight 1600 g
Ballast 200 g
Wing loading 44,50
g/dm2
Radio 4
good quality standard servos
1
battery 4 or 5 cells, 1400 mAH
1.1.
The ailerons
Aileron width is 7.5 cm (30%
of the cord) at the center and 3.3 cm at the tip. The ailerons are full span
and go to the tip.
.
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|
Scrape the foam out of the leading edge of the aileron to allow it to
slide into the wing |
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Remove the foam from the aileron leading edge then fill the leading
edge with resin and micro balloons to make it less flexible. (A 4 to 1 mix of micro balloons to resin is about right). |
|
|
Tape the aileron leaving only half a mm of play and check the
clearance of aileron sliding into the inner part of the wing. If necessary,
adjust until the aileron moves freely. |
|
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With the aileron folded to 90° on the outer edge, apply silicone glue
to the hinge (about I mm diameter bead) then let the aileron dry in a neutral
position. |
.
1.2.
Installation of Aileron ball links
We recommend ball links to
make assembly in the field easy, and to leave no play.
For the ailerons, install a
horn of 10 mm high placed at 20mm from the center of the wing and level with
the hinge to avoid introducing an undesirable mechanical differential.
1.3.
Installation of aileron servos
We recommend installation of
both servos in the wing fairings. This part of the assembly is described in
detail in the fuselage instructions.
1.4.
Wing attachment
The wings can be secured
during flight by using tape on the wing fairings, but it would look better to
use two hooks and an elastic band.
2.
The stabilizer
Can have separate elevators
or be fully flying. The latter is easier, but some people prefer the linearity
of elevators.
2.1.
Separating the elevators (option for elevator stab)
For this, use the same
method as for the ailerons, using the following dimensions
Install horns before
sticking with tape or silicone.
2.2.
Installation of elevator ball links (for stab with
elevators only)
Use piano wire 2mm in
diameter.
First cut two pieces of wire
6 cm long, bend at 90° at 1.2 cms. Press a ball link onto the bent end and glue
or solder it. Bend the other end so that the horn goes into the elevator. Glue
that end into the elevator with quick setting epoxy using a temporary hinge of
tape.
Stabilizer control now looks
like this:
3.
The rudder.
3.1.
Capping the base of the rudder
Cut a piece of 6mm balsa to
the following dimensions,
and glue with cyano in
the rudder, level with the base.
3.2.
Installation of rudder ball link
The rudder horn should be
glued in relation to the control you planned in the fuselage: to do this, make
a small hole in the rudder, remove some foam and glue the horn with epoxy,
completely filling the hole.
3.3.
Rudder Attachment
The rudder is attached by
tape on the right hand side of the fin. You can also put a line of silicone on
the joint to reduce play.
4.
The fuselage
4.1.
Installation of elevator linkage (only for stab /
elevator option)
Make a hardwood block 50 mm
x 16mm x 15mm
Glue it inside the rudder,
level with the stab and clamp while setting to form a solid joint
Drill 2 holes of 3mm,
through the rudder and the wood, at the places indicated on the left side of
the rudder, being careful to keep it perpendicular to the plane of the rudder.
If necessary use a drill press and hold the fuselage horizontally.
Cut two tubes from 3mm brass
to the required length and glue these into the rudder with cyano.
4.2.
Clearance for control horns
If you want to insert the
stabs when out in the field, you need to mill a passage sufficiently large to
attach the horns from the outside.
4.3.
Installation of stab linkage (for all-flying tail plane)
Make two small hardwood
blocks 15mm x 15mm x 5 mm. Drill a 3mm hole through the center. Assemble the 2
pieces and the bell crank on a 3mm brass tube 18mm long. The tube should
protrude 1mm on each side of the fin.
Make the 3mm holes at right
angles through the rudder level at the mark on the left side. Scrape the
interior of the rudder at the level of the stab so that the glue holds. Use
epoxy to glue the little pieces of wood onto the bell crank.
Next mill a circular passage
so the 2mm stab joiner can move freely.
4.4.
Installation of rudder spar
Cut from 6mm balsa to the
following dimensions
Using coarse glass paper,
sand the inside of the rudder and glue the spar with cyano into the fixed part
of the rudder 8mm back from the left edge once the bell crank, rods etc have
been finished and installed.
4.5.
Installation of wing joiners
This is tricky because the
two wings must fit perfectly into the fairings of the fuselage. Glue both
aluminium joiners inside the fairings in the following manner:
Draw the outline of the root
of the wing by pressing it hard into a piece of A4 paper. This shows the
outline and the joiner holes. The use the outline of the left wing on the right
hand fairing and vice versa. Your paper will fit perfectly onto the fairing
allowing you to mark the center of the joiner holes through the paper with a
sharp point. Centering the paper on the fairing is easy enough on the vertical
but be very careful that horizontally the holes are perfectly opposed.
Pre-drill 4 x 5mm holes and
slip the rods in to check that they are parallel and perpendicular in all axes.
Then slide tubes of 8mm outside diameter and 5mm interior diameter onto the
rods and check they move easily within the joiners. Then enlarge the holes with
a 9mm drill if they are nicely centered, or with a round file if there is some
unevenness. The aluminium joiners must now be pushed in hard. Check the
parallelism, perpendicularity and movement again with the wings mounted on
their joiners.
Now glue the joiners with
cyano to render them immobile. Then reinforce them with a mixture of chopped
fiberglass and resin. Do this in two steps. Scratch the inside of the fairing
with coarse glass paper so that the resin sticks, tape the exterior of the
right hand fairing to prevent the resin from running, reinforce and leave to dry
lying on the right hand side of the fuselage. Then do the same thing with the
left hand fairing.
4.6.
Attachment of Canopy
Use your preferred method,
or a good way is to glue two small pieces of piano wire 2mm x 80mm fore and aft
with epoxy. Sand for grip and fold the wires in a zigzag for better hold.
In this way the wire will
protrude 2-3 mm being held under the edge of the fuselage and allowing the
canopy to slide.
5.
Installation of radio
The fuselage holds the 4
standard servos for the stab, rudder, ailerons, receiver and the 4 or 5 cell
battery (1400mAh). By placing the battery well forward in the nose, you should
get the expected center of gravity with the addition of very little lead (less
than 50 g).
5.1.
Installation of servo tray
Make a servo tray from ply
to the following dimensions:
Scrape the inside of the fus
so that resin epoxy glue adheres and holds the tray at the place indicated in
the drawing. It is best to install the radio tray at the same level as the wing
for better balance.
5.2.
Installation of Aileron servos
The two servos are fitted in
the fairings. The moulding is thick enough between the two joiners to allow
direct screwing of a standard servo. Just ream the fairing and make four small
holes in the moulding for the screws.
The tops of the servos stick
out from the fairing into the wing panel, which must also be hollowed out to
match. The inside skin must also be cut in a T to allow the horn to pass during
assembly of the wing and during flight. The advantage of this type of installation
is that it does not weaken the wing, avoids the need for a supplementary joiner
and keeps the inertia in the center, which is important for flight. During
mounting and dismounting of wings on the field the ball links may be easily
attached or removed.
5.3.
Control linkages
The links are simple
threaded rods cut to the right length. Screwing and unscrewing the links will
do fine-tuning.
The two links for elevator
and rudder are made of carbon tubing 6mm diameter with rods glued to each end
with epoxy. In the case of separate elevators, you must insert two threaded
rods of the same length with two ball joints on the side of the stab to form a
Y and thus control the two elevators simultaneously.
6mm dia carbon rods will be
sufficiently stiff. If you like to fiddle, you can install a brace with 2 holes
of 7 mm above the wing joiner of the back wing to guide the rods.
6.
Centre of gravity.
Neutral is at 105 mm from
the leading edge. With a 1400 mAh battery practically no lead is needed. For
the first few flights, one can bring the center forward by 5mm, i.e. put
another 30 g into the nose.
7.
Control movement and mixes
Positive movements are
downwards and are measured at the root of the control surface in question. As
the glider is symmetrical, there must be equal up and down movements.
The controls given here
create a very agile glider on all axes. We strongly advise you not to use these
controls without a lot of exponential (30-40%) to allow the necessary precision
for a clean flight.
Use the flaps for 4 axis flying,
i.e. the flap control is on a transmitter control stick, which you can modify
by removing the return spring and making a detent to mark the center position
The Volij is specifically
designed to use flaps so an elevator to flap mix should be used to get best
results.
Stab with elevator: +7 mm /-7
mm
All flying tail: +14
mm /-14 mm
Rudder +35
mm / -35 mm
Ailerons: +30
mm / -30 mm no differential
Camber : +6
mm
Inverted camber: -6 mm
Snap flaps +20
mm / -20 mm
Elevator to flap: +15
mm / -15 mm
Air brakes: -30
mm
Elevator compensation with
air brake: +50%
8.
Flying
8.1.
First flight
The first flight should be
made without ballast, with all controls in neutral, center of gravity a 95mm
from the leading edge. The wings are fixed to the fus by tape or elastic bands
along the joint. We advise you also to do the first few flights with 50% Dual
Rate on all 4 axes to accustom yourself progressively to the astonishing
agility of this glider.
Because this glider is symmetrical
it will tend to be sensitive in pitch in both upright and inverted flight. In
either mode use the flaps to give a little camber for smooth flying.
8.2.
Thereafter
Bring the center of gravity
back by 100mm from the leading edge according to your feelings. A reasonable
back limit is 105mm. Familiarise yourself with the glider before increasing the
movement to the suggested values.
8.3.
Ballast
Not terribly important in
the Voltij. That’s why no ballast tube has been provided for. Nevertheless in a
strong wind the carbon wing joiners can be replaced by 8 mm steel rods, which
corresponds to +/- 200g of ballast. This makes the glider fly more rapidly and
the maneuvers become smoother and more ballistic.
Thanks to John Godwin for
this english version.