Pete O Shea
May 01, 1996, 01:00 AM
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<head>
<title>A Review of Astro Flight's Porterfield Collegiate</title>
</head>
<body bgcolor="#FFFFFF">
<pre>Overview
The Astro Flight Porterfield Collegiate is a 1/6 scale kit of a 1930's light-
weight two-person high-wing trainer airplane, somewhat similar in outline
to a Piper Cub. The plane is available in two versions, the basic version is
the kit only, and the deluxe version is the kit and an Astro cobalt 25 geared
motor. The plane, built per plans, is a good trainer-type airplane with rela-
tively light wing loading and good performance. With some modifications,
it can perform moderate aerobatics.
At the time of writing of this review, Astro Flight has discontinued produc-
tion of the Porterfield Collegiate kit. It is rumored that another company
has bought the kit rights and production will continue in the future. Right
now (5/96), there are still unsold kits that may be found.
The first thing that must be mentioned about this kit is its structure: the
fuselage and tail surfaces are all built up out of 1/4" square balsa sticks.
This results in a very strong and lightweight structure, but it is somewhat
difficult and time-consuming to build. This kit is therefore not recom-
mended for beginners with no building experience. On the other hand, it is
very repairable: twice I've crunched the entire forward section of the fuse-
lage (large-scale pilot error each time). Each time I built a new forward
fuselage from the wing trailing edge forward, and grafted the new forward
fuse to the old rear section with tail. Both repairs were straight, light, and
successful. The fuselage is large enough to accommodate just about any-
thing you would want to put in it (8mm camcorder, anyone?).
Data
Span: 69.5" (176.5 cm)
Chord: 10.0" (25.4 cm)
Area: 675 sq. in. (4355 sq. cm)
Fuselage length: 45.0" (114.3 cm)
Equipment used: Fiberglass Master aftermarket fiberglass cowl, Williams
Bros. 1/6 scale plastic sportsman pilot figure, Astro cobalt 25 geared motor,
APC 12x7 prop, Astro 205 speed controller, World Engines 7 channel
radio, 4 cell 500 mAh receiver battery, Airtronics 94831 servos (1 rudder, 1
elevator, 1 ailerons), 14 1700SCRC Sanyo cells, Sermos connectors, arm-
ing switch, 25A mini-ATO automotive fuse soldered in electrical center of
motor battery.
Weight: Wing 15.8 oz (446 g), fuse 51.7 oz (1463 g), motor pack 28.7 oz
(812 g), total 96.1 oz (2721 g)
Wing loading: 20.5 oz/sq. in. (6.25 kg/sq. m)
Watts/pound: 62
Kit Quality and Construction
The quality of the wood and accessory components is average. Before you
start, it's a good idea to sort out the 1/4" balsa, using the densest and
straightest for the fuselage longerons, the next densest for the supporting
structure for the wing, and the lightest for the tail surfaces. The fuselage is
built up one side at a time over the plans, then the two sides are brought
vertical and the cross-members are added. This is more time-consuming
than building the fuse out of, say, slabs of lite-ply, but the fuse is very
strong and very light. The tail surfaces are built flat out of 1/4" balsa. The
wing is built in a conventional way, with spruce top and bottom spars with
shear webbing, a D-tube structure, and cap strips from the spar back to the
trailing edge.
The directions provided with the kit are fair, not as complete as you would
find in a beginner's kit such as the Electra, but photos are provided to show
important stages in the process. If you have the modeling skills to build the
Porterfield, the directions will be sufficient.
Modifications I've made
I've made some changes to the kit to make it a bit more to my liking, sum-
marized below:
1. Add ailerons according to the scale outline on the plans. The process is
pretty easy:
a. build the wing sections according to the plan.
b. cut out the ailerons following the scale outline on the plan</pre>
<pre> (right in the middle of the ribs, etc.).
c. add a sub-spar to the trailing edge of the wing cutout, and</pre>
<pre> a leading edge to the aileron, and half-ribs at the ends</pre>
<pre> of the ailerons.
d. add your favorite hinge type.
I use an Airtronics 831 mid-size servo in the wing center to control both
ailerons, and have found that birch dowel pushrods (1/8" diameter, sup-
ported each rib by a bushing made with plastic pushrod outer tubing) and
90 degree bellcranks work the best. The plastic tube-in-tube pushrods gave
me much grief with thermal expansion problems. With temperature
changes, the pushrods changed length, and both ailerons would either
droop down or raise up. The plastic pushrods, curved around 90 degrees in
the wing, also required more force to operate than straight pushrods with
bellcranks.
2. Reduce the wing dihedral to the scale amount.
3. Leave out the wing struts. This makes the plane less scale, but it assem-
bles faster at the field and flies with less drag. To keep the wing from
departing from the fuselage at the wrong time, beef up the wing attachment
with two dowel hold-downs in the front, and two nylon 1/4-20 bolts in the
rear. Double up the 1/4" square structure in the cabin area to take the addi-
tional stress.
4. Add a battery hatch to the bottom of the fuselage. This is a hinged door
wide enough for the 14-cell pack, and long enough to insert and remove the
pack at an angle. The pack is constrained by two top plates, styrofoam
blocks on the sides, and the pack rests on the bottom of the fuselage. All of
these surfaces are padded with 1/4" thick compressible foam. Closing the
bottom hatch door compresses the pack between bottom and top supports,
keeping it firmly in place. An adjustable velcro tape is the front battery
constraint, and this adjustability lets me move the battery forwards or rear-
wards to get the CG at the proper position. The hinged battery door lets me
change packs easily between flights, and is something I do on all my
planes. Since I have multiple packs for the Porterfield, I can rotate them
between flying, cooling, and charging and get more flying time per (all too
short) time at the field.
Performance
On my Porterfield, I've set up dual rates on the ailerons and elevator. Low
rates (5/8" aileron, 1" elevator) are completely sufficient for normal, scale-
like flying, and are recommended for takeoffs and landings. Higher rates
(1" aileron, 1 3/4" elevator) enable the Porterfield to perform snap rolls,
somewhat axial rolls (with coordinated elevator input), spins, etc. I've set
the rudder throw to about 2 1/2" to allow effective ground steering.
Being a taildragger, the Porterfield can be tricky to fly off an asphalt run-
way for those used to tricycle-gear airplanes. Holding the plane on-track
with the rudder is best practiced with lots of taxiing passes at varying
speeds. Off a grass runway, the plane tracks much easier. The Porterfield
becomes airborne fairly quickly and climbs with ease, although it's wise
not to try to climb too fast until you're familiar with the airplane.
Overall, the Porterfield is my favorite plane. It averages 9 to 10 minutes
per flight of touch-and-goes, loops, rolls, spins, and low slow flybys. I've
flown it for 17 minutes in thermal air. I've brought it to KRC a bunch of
times, and while it's not the most scale example (being without wing
struts), there's always a few people coming up to me after a flight and ask-
ing "what've you got inside there?"
Peter O'Shea
Reading, MA peter.oshea(at)analog.com
Permission is given to reproduce this article in print or electronically.
</pre>
</body>
</html>
<head>
<title>A Review of Astro Flight's Porterfield Collegiate</title>
</head>
<body bgcolor="#FFFFFF">
<pre>Overview
The Astro Flight Porterfield Collegiate is a 1/6 scale kit of a 1930's light-
weight two-person high-wing trainer airplane, somewhat similar in outline
to a Piper Cub. The plane is available in two versions, the basic version is
the kit only, and the deluxe version is the kit and an Astro cobalt 25 geared
motor. The plane, built per plans, is a good trainer-type airplane with rela-
tively light wing loading and good performance. With some modifications,
it can perform moderate aerobatics.
At the time of writing of this review, Astro Flight has discontinued produc-
tion of the Porterfield Collegiate kit. It is rumored that another company
has bought the kit rights and production will continue in the future. Right
now (5/96), there are still unsold kits that may be found.
The first thing that must be mentioned about this kit is its structure: the
fuselage and tail surfaces are all built up out of 1/4" square balsa sticks.
This results in a very strong and lightweight structure, but it is somewhat
difficult and time-consuming to build. This kit is therefore not recom-
mended for beginners with no building experience. On the other hand, it is
very repairable: twice I've crunched the entire forward section of the fuse-
lage (large-scale pilot error each time). Each time I built a new forward
fuselage from the wing trailing edge forward, and grafted the new forward
fuse to the old rear section with tail. Both repairs were straight, light, and
successful. The fuselage is large enough to accommodate just about any-
thing you would want to put in it (8mm camcorder, anyone?).
Data
Span: 69.5" (176.5 cm)
Chord: 10.0" (25.4 cm)
Area: 675 sq. in. (4355 sq. cm)
Fuselage length: 45.0" (114.3 cm)
Equipment used: Fiberglass Master aftermarket fiberglass cowl, Williams
Bros. 1/6 scale plastic sportsman pilot figure, Astro cobalt 25 geared motor,
APC 12x7 prop, Astro 205 speed controller, World Engines 7 channel
radio, 4 cell 500 mAh receiver battery, Airtronics 94831 servos (1 rudder, 1
elevator, 1 ailerons), 14 1700SCRC Sanyo cells, Sermos connectors, arm-
ing switch, 25A mini-ATO automotive fuse soldered in electrical center of
motor battery.
Weight: Wing 15.8 oz (446 g), fuse 51.7 oz (1463 g), motor pack 28.7 oz
(812 g), total 96.1 oz (2721 g)
Wing loading: 20.5 oz/sq. in. (6.25 kg/sq. m)
Watts/pound: 62
Kit Quality and Construction
The quality of the wood and accessory components is average. Before you
start, it's a good idea to sort out the 1/4" balsa, using the densest and
straightest for the fuselage longerons, the next densest for the supporting
structure for the wing, and the lightest for the tail surfaces. The fuselage is
built up one side at a time over the plans, then the two sides are brought
vertical and the cross-members are added. This is more time-consuming
than building the fuse out of, say, slabs of lite-ply, but the fuse is very
strong and very light. The tail surfaces are built flat out of 1/4" balsa. The
wing is built in a conventional way, with spruce top and bottom spars with
shear webbing, a D-tube structure, and cap strips from the spar back to the
trailing edge.
The directions provided with the kit are fair, not as complete as you would
find in a beginner's kit such as the Electra, but photos are provided to show
important stages in the process. If you have the modeling skills to build the
Porterfield, the directions will be sufficient.
Modifications I've made
I've made some changes to the kit to make it a bit more to my liking, sum-
marized below:
1. Add ailerons according to the scale outline on the plans. The process is
pretty easy:
a. build the wing sections according to the plan.
b. cut out the ailerons following the scale outline on the plan</pre>
<pre> (right in the middle of the ribs, etc.).
c. add a sub-spar to the trailing edge of the wing cutout, and</pre>
<pre> a leading edge to the aileron, and half-ribs at the ends</pre>
<pre> of the ailerons.
d. add your favorite hinge type.
I use an Airtronics 831 mid-size servo in the wing center to control both
ailerons, and have found that birch dowel pushrods (1/8" diameter, sup-
ported each rib by a bushing made with plastic pushrod outer tubing) and
90 degree bellcranks work the best. The plastic tube-in-tube pushrods gave
me much grief with thermal expansion problems. With temperature
changes, the pushrods changed length, and both ailerons would either
droop down or raise up. The plastic pushrods, curved around 90 degrees in
the wing, also required more force to operate than straight pushrods with
bellcranks.
2. Reduce the wing dihedral to the scale amount.
3. Leave out the wing struts. This makes the plane less scale, but it assem-
bles faster at the field and flies with less drag. To keep the wing from
departing from the fuselage at the wrong time, beef up the wing attachment
with two dowel hold-downs in the front, and two nylon 1/4-20 bolts in the
rear. Double up the 1/4" square structure in the cabin area to take the addi-
tional stress.
4. Add a battery hatch to the bottom of the fuselage. This is a hinged door
wide enough for the 14-cell pack, and long enough to insert and remove the
pack at an angle. The pack is constrained by two top plates, styrofoam
blocks on the sides, and the pack rests on the bottom of the fuselage. All of
these surfaces are padded with 1/4" thick compressible foam. Closing the
bottom hatch door compresses the pack between bottom and top supports,
keeping it firmly in place. An adjustable velcro tape is the front battery
constraint, and this adjustability lets me move the battery forwards or rear-
wards to get the CG at the proper position. The hinged battery door lets me
change packs easily between flights, and is something I do on all my
planes. Since I have multiple packs for the Porterfield, I can rotate them
between flying, cooling, and charging and get more flying time per (all too
short) time at the field.
Performance
On my Porterfield, I've set up dual rates on the ailerons and elevator. Low
rates (5/8" aileron, 1" elevator) are completely sufficient for normal, scale-
like flying, and are recommended for takeoffs and landings. Higher rates
(1" aileron, 1 3/4" elevator) enable the Porterfield to perform snap rolls,
somewhat axial rolls (with coordinated elevator input), spins, etc. I've set
the rudder throw to about 2 1/2" to allow effective ground steering.
Being a taildragger, the Porterfield can be tricky to fly off an asphalt run-
way for those used to tricycle-gear airplanes. Holding the plane on-track
with the rudder is best practiced with lots of taxiing passes at varying
speeds. Off a grass runway, the plane tracks much easier. The Porterfield
becomes airborne fairly quickly and climbs with ease, although it's wise
not to try to climb too fast until you're familiar with the airplane.
Overall, the Porterfield is my favorite plane. It averages 9 to 10 minutes
per flight of touch-and-goes, loops, rolls, spins, and low slow flybys. I've
flown it for 17 minutes in thermal air. I've brought it to KRC a bunch of
times, and while it's not the most scale example (being without wing
struts), there's always a few people coming up to me after a flight and ask-
ing "what've you got inside there?"
Peter O'Shea
Reading, MA peter.oshea(at)analog.com
Permission is given to reproduce this article in print or electronically.
</pre>
</body>
</html>