Richard Sutherland
May 01, 1996, 01:00 AM
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<title>The Mini-Viper Pylon Racer</title>
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<pre>The mini-Viper is a small speed 400 powered pylon racer. It has a span of
770mm (30") and an area of 8.4 dm2 (130"2). It uses a shoulder wing layout
and its most distinctive feature is its swept forward wings.
THE KIT
I normally prefer to scratch build and this is the first kit that I have
built in about ten years. The kit arrives in a fairly small box about 550mm
(22") long, included are diecut parts, hardware (for linkages and wing hold
down) and a sheet of brightly coloured graphics. The wood selection is OK -
maybe not exactly what I would have chosen, but the only wood that had to be
replaced was the wing sheeting (heavy and badly warped). The cutting was
mostly pretty clean although the stabiliser and fin were badly "die
crushed". In some ways the kit was overly complicated ie three pieces glued
together when one piece would have done. For example the fuselage sides and
bottom are all made of two pieces glued together - maybe so they will fit in
the small box?
CONSTRUCTION
The kit goes together without problems, parts fit is good and the
instructions and plans provide ample information. To get the nicely rounded
fuselage and also light weight liberal use should be made of the sanding block.
CHANGES
1) I changed the single aileron to the right wing panel as I believe this is
where it should be since any adverse yaw keeps the nose up in a pylon turn.
2) The aileron linkage shown is pretty awful, so I decided to place a micro
servo on its side in the wing panel and drive the aileron with a straight
piece of music wire. The wing is pretty thin and the servo does stick out
the bottom of the wing about 1.5mm (1/16") for about 12mm (1/2") of span but
the linkage shown on the plan has the torgue rod sticking up a similiar
amount for about 35mm (1 1/2") of span. This change saves weight, drag and
gives a tighter linkage.
3) I turfed the supplied outer pushrod (heavy) and used the inner pushrod
with a piece of music wire and ran this straight out the rear of the
fuselage, again lighter and less drag.
WEIGHTS
completed wing: 80g (2.8oz)
completed fuselage: 70g (2.5oz)
RX and 2 servos: 84g (3.0oz)
speed 400 motor: 73g (2.6oz)
ESC & wiring: 27g (1.0oz)
GR6x3 folding prop: 10g (0.4oz)
7 x 500AR battery: 140g (4.9oz)
total: 484g (17.1oz)
As you can see the finished airframe weighed 150g (5.3oz). The Viper was
covered in flourescent orange film which was a bit of a mistake as it
accounts for 27g (1.0oz) of the finished weight, using a lighter film would
probably save at least 15g (0.5oz). If you are not used to building light it
would be very easy for the airframe to end up 50-75g (1.8-2.6oz) heavier.
MOTOR
The motor used was the Graupner speed 400 6v, the timing was advanced by
rotating the backplate 5mm anticlockwise. Initially the Graupner 6x3 folder
was used.
SETUP
I was doing final assembly/checks when I plugged a freshly charged battery
in to my brand new Simprop RS400 ESC to check that the BEC operated the
servos etc and the ESC fried!! I have no idea why? - polarity was correct,
the motor wasn't blocked etc. Anyway suffice to say this impressed me no end!
So this meant swapping to my only other ESC with BEC a "Simprop S90". This
is a 30amp softstart so the weights given earlier need to be increased by
15g (0.5oz).
The CG was set as shown on the plans and this required a little stand with
two prongs to balance it correctly (being 2mm out is the same as being 10mm
out on a larger model).
FLYING
The first flight almost ended in disaster when the guy launching the Viper
caught his finger on the aileron linkage (I guess thats a minus for my
linkage mod) causing the model to be launched down at about 40 degrees. The
Viper hit the ground pretty hard and bounced into the air still flying so I
kept the throttle open and after a few anxious moments it was away. The
aileron was pretty sensitive (set to the sugested + -7.5mm) but after
hitting the low rate switch things settled down. I would recommend reducing
the throw to about + - 5mm for the first flight or use a bit of exponential.
The next flight was much more civilised with a straight climb away from a
good launch. Even with the 6x3 prop the Viper is pretty quick and gets small
in a hurry - not the sort of plane you can take your eyes off! The bright
flourescent orange wasn't a bad idea after all! I was pleasantly surprised
with the power off glide and handling - much tamer than I had imagined!
Flight times were about 3 minutes which equates to a average current draw of
about 10 amps in the air.
All in all I am very pleased with the mini - Viper, now I just need someone
to race against.
Richard Sutherland
34 Hopkinson Way
Wilson 6107
Western Australia
</pre>
</body>
</html>
<head>
<title>The Mini-Viper Pylon Racer</title>
</head>
<body bgcolor="#FFFFFF">
<pre>The mini-Viper is a small speed 400 powered pylon racer. It has a span of
770mm (30") and an area of 8.4 dm2 (130"2). It uses a shoulder wing layout
and its most distinctive feature is its swept forward wings.
THE KIT
I normally prefer to scratch build and this is the first kit that I have
built in about ten years. The kit arrives in a fairly small box about 550mm
(22") long, included are diecut parts, hardware (for linkages and wing hold
down) and a sheet of brightly coloured graphics. The wood selection is OK -
maybe not exactly what I would have chosen, but the only wood that had to be
replaced was the wing sheeting (heavy and badly warped). The cutting was
mostly pretty clean although the stabiliser and fin were badly "die
crushed". In some ways the kit was overly complicated ie three pieces glued
together when one piece would have done. For example the fuselage sides and
bottom are all made of two pieces glued together - maybe so they will fit in
the small box?
CONSTRUCTION
The kit goes together without problems, parts fit is good and the
instructions and plans provide ample information. To get the nicely rounded
fuselage and also light weight liberal use should be made of the sanding block.
CHANGES
1) I changed the single aileron to the right wing panel as I believe this is
where it should be since any adverse yaw keeps the nose up in a pylon turn.
2) The aileron linkage shown is pretty awful, so I decided to place a micro
servo on its side in the wing panel and drive the aileron with a straight
piece of music wire. The wing is pretty thin and the servo does stick out
the bottom of the wing about 1.5mm (1/16") for about 12mm (1/2") of span but
the linkage shown on the plan has the torgue rod sticking up a similiar
amount for about 35mm (1 1/2") of span. This change saves weight, drag and
gives a tighter linkage.
3) I turfed the supplied outer pushrod (heavy) and used the inner pushrod
with a piece of music wire and ran this straight out the rear of the
fuselage, again lighter and less drag.
WEIGHTS
completed wing: 80g (2.8oz)
completed fuselage: 70g (2.5oz)
RX and 2 servos: 84g (3.0oz)
speed 400 motor: 73g (2.6oz)
ESC & wiring: 27g (1.0oz)
GR6x3 folding prop: 10g (0.4oz)
7 x 500AR battery: 140g (4.9oz)
total: 484g (17.1oz)
As you can see the finished airframe weighed 150g (5.3oz). The Viper was
covered in flourescent orange film which was a bit of a mistake as it
accounts for 27g (1.0oz) of the finished weight, using a lighter film would
probably save at least 15g (0.5oz). If you are not used to building light it
would be very easy for the airframe to end up 50-75g (1.8-2.6oz) heavier.
MOTOR
The motor used was the Graupner speed 400 6v, the timing was advanced by
rotating the backplate 5mm anticlockwise. Initially the Graupner 6x3 folder
was used.
SETUP
I was doing final assembly/checks when I plugged a freshly charged battery
in to my brand new Simprop RS400 ESC to check that the BEC operated the
servos etc and the ESC fried!! I have no idea why? - polarity was correct,
the motor wasn't blocked etc. Anyway suffice to say this impressed me no end!
So this meant swapping to my only other ESC with BEC a "Simprop S90". This
is a 30amp softstart so the weights given earlier need to be increased by
15g (0.5oz).
The CG was set as shown on the plans and this required a little stand with
two prongs to balance it correctly (being 2mm out is the same as being 10mm
out on a larger model).
FLYING
The first flight almost ended in disaster when the guy launching the Viper
caught his finger on the aileron linkage (I guess thats a minus for my
linkage mod) causing the model to be launched down at about 40 degrees. The
Viper hit the ground pretty hard and bounced into the air still flying so I
kept the throttle open and after a few anxious moments it was away. The
aileron was pretty sensitive (set to the sugested + -7.5mm) but after
hitting the low rate switch things settled down. I would recommend reducing
the throw to about + - 5mm for the first flight or use a bit of exponential.
The next flight was much more civilised with a straight climb away from a
good launch. Even with the 6x3 prop the Viper is pretty quick and gets small
in a hurry - not the sort of plane you can take your eyes off! The bright
flourescent orange wasn't a bad idea after all! I was pleasantly surprised
with the power off glide and handling - much tamer than I had imagined!
Flight times were about 3 minutes which equates to a average current draw of
about 10 amps in the air.
All in all I am very pleased with the mini - Viper, now I just need someone
to race against.
Richard Sutherland
34 Hopkinson Way
Wilson 6107
Western Australia
</pre>
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