Zactly F3P - 2009/03

THE COOL THING about flat-foam models is that almost
anything you can think up that has wing area and a correctly
located CG will fly. My biplane design came about just that way;
it’s exactly what I wanted.
For the last three years, the original Zactly has been available from
Midwest Products as a free full-size plans download. At the time of its
release, it was a great-flying foamie for outdoors or indoors. With
more than 400 square inches of area, you could build it from blue
foam at 16 ounces or 5mm Cellfoam 88 at 12 ounces.
The Zactly is a blast to fly and is exceptionally good at
Harrier, hover, and constant rolling maneuvers; the RC pilot
can do a Rolling Circle without losing an inch of altitude, just
by his or her holding in right aileron (no elevator or rudder
corrections required) and roughly half throttle.
The lightest model built had the 5mm wings and
stabilizer exchanged for 3mm Cellfoam 88, and
carbon-fiber crossbracing rods were substituted
for full-length wing spars. That version’s
flying weight was 10 ounces; the Zactly
just kept getting
better.
Conversations with friends who had built the original
Zactly brought up the question of how well it would perform
F3P-style aerobatics. All the rage in Europe and spreading
quickly in the US, F3P is essentially flying precision RC
Aerobatics within an indoor envelope.
The flying space is more confined in F3P, but
patterns have been developed, taking into
consideration the foamie airplanes’ seemingly effortless
maneuverability, that adapt traditional forms of precision
to the habitat and still keep an audience from falling asleep.
The result is sequences that are performed quickly and show off
the foamies’ modern abilities. The “Sources” list at the end of this
article includes the address of a Web site that explains F3P and shares
downloads of the three skill-level maneuver schedules.
The Zactly’s original shape conforms to how I thought an F3A
RC Aerobatics (Pattern) biplane should look. It was also an
experiment in surface-area ratios and wing-stagger variations.
However, it was a fat pig compared to the current models flown in
F3P, and it had coupling issues that I thought needed to be designed
out of the airframe before it could be an honest contender.
Besides flying the model on my own, I learned a lot from
studying experienced designers such as Jason Noll, David Payne,
and Quique Somenzini. Their ideas about airplane dimensions,
thrustlines, and incidences, plus the addition of drag devices,
changed the Zactly in subtle ways, but enough each time to easily
see what the model liked or didn’t like.
That was all because I was simply asking it to roll axially, pull
straight corners, and do every maneuver at 5-10 mph of airspeed.
Sheesh, we RC pilots just want the model to fly itself, don’t we?
The slower the airplane could fly, the less intense an adjustment
needed to be for it to fly the desired way. That was a timeconsuming
lesson. Something as simple as locating the 300 mAh 2S
Li-Poly battery on top of the fuselage instead of the bottom made
one of the most dramatic improvements; almost all the pitch
coupling went away in knife edge with that fluke change.
One might call the Zactly F3P “the new and improved Zactly.”
It’s 93% of the original’s size and has a bit less than 360 square
inches of area. Made entirely from 3mm Cellfoam 88, the F3P
incorporates a large amount of 0.02-inch carbon-fiber rod for
structural rigidity. It has a 6-ounce flying
weight, which is still relatively heavy by
some F3P standards; 5 ounces is the goal.
With the right motor choice and routing
out, the Cellfoam 88 would produce an
airframe that is in the optimal weight zone.
Depron is slightly lighter and less dense,
so building the Zactly F3P from that
material would surely trim this model up.
Prototypes have been built that weighed 8
ounces, and there’s nothing wrong with the
thrill factor those models offered.
Power-system choices vary, depending
on the builder’s taste. Maxx Products motors
are some of the best built and dependable.
I’ve done all my testing with the Himax
2805-1430 outrunner, which is essentially a
275-class motor. I run only a two-cell pack;
Type: RC indoor aerobatics
Skill level: Beginner builder, intermediate pilot
Wingspan: 28.5 inches
Flying weight: 5.5-7.0 ounces
Wing area: 358 square inches
Length: 34.25 inches
Power system: 250-class outrunner; GWS 0843 propeller;
300 mAh, two-cell Li-Poly battery;
Thunderbird-6 ESC
Construction: 2mm-3mm flat foam,
0.02-0.03 carbon-fiber rod
Finish: Sharpie marker, airbrush, or decals
Other: Three microservos, four-channel
microreceiver, hinge tape, thin foam-safe cyanoacrylate
the new Thunder Power V2 300 mAh has
spoiled me.
Almost any micro radio system will
work in the Zactly for sport-flying, but
micro digital servos such as the Futaba
S3153 (and newer) and the JR DS185 are
optimal for F3P performance. Choose a
receiver that weighs 3-5 grams.
The ESC that has worked best for me is
the Castle Creations Thunderbird-6. I
discard the motor connectors and solder the
motor wires directly to the board of the
ESC. Hey, every gram saved counts. (The
modification certainly voids the warranty.)
CONSTRUCTION
Built exactly … : No matter what material
you choose to build the Zactly F3P, follow
the plans’ guidelines regarding template
usage. I like to make the parts’ outside
dimensions slightly larger for safety, so I
cut to the outside of the heavy outline.
In regards to making cutouts for the
horizontal fuselage, wing, and stabilizer, as
well as the slots in the wings for the struts,
the openings are made on the hairline or just
on the inside, so they are a tight fit, or you
can easily adjust them with a light scuff
with an emery board. Material is easier to
remove than to add.
There is absolutely no way a builder is
going to make this model’s target weight if
he or she uses adhesives such as hot glue
and/or epoxy. I’ve found that thin, foam-
safe cyanoacrylate is the best and lightest
option for this aircraft. I even get more
anal retentive and wipe the excess glue
with a Q-tip before spraying accelerator.
I’ve built several Zactly models, so
saying that nothing is simpler to put
together is subjective. The fact that it’s a
profile, by nature, reduces the parts count
significantly, so that in itself makes the
project a candidate for a Geico
commercial. (I act like a caveman at
times.)
If you have never built from scratch,
the plans alone should suffice in getting a
relatively well-built model together, so I
won’t insult the detailed plans by being
redundant.
This will sound odd, since the topic of
this article is to scratch build, but the best
learning exercise I can suggest for a
would-be first-time foamie builder is to
buy and assemble a foamie kit from the
likes of Horizon Hobby or Great Planes.
The Zactly isn’t all that much different
from those offerings and many, I’m told,
from Fancy Foam Models, 3D Foamy, and
others. I’ve learned a lot from building
models from other designers, and you will
too.
Begin by cutting the templates away
from the plans. The top view and head-on
view (cross-section A) are for reference
only. I run the blade of an X-Acto knife
along the outside edge. Leave the control
surfaces attached; you will cut them away
from the foam later.
Instead of holding the paper template
around the outside edges with tape, make
tape holes. Use a sharpened brass tube or a
cool, new FoamWerks drill tool from
Midwest to make openings at key points.
Cover the holes with tape so that the paper
templates can be temporarily attached
while keeping the edges free for a knife or
pen to follow.
The templates should be located on the
foam sheets so that minimal waste is
produced. The templates last longer and
are less likely to distort if the cutouts and
key mounting points are referenced with a
pinhole rather than a complete opening in
the template. Use the point of a T-pin to
reference alignment points and cutout
slots.
A sharp X-Acto knife does quick work
of cutting through the foam; multiple
shallow passes are more accurate. Once the
outer shape of the part is complete, remove
the template and set it aside but close by.
Use a fine-point marker to locate
reference points, hinge lines, and cutouts.
This is a good time to reference where the
carbon-fiber bracing will attach.
The wing template is for both the top
and bottom; stacking the foam so that two
are cut out at the same time assures that the
strut locations are identical. Note that the
center-strut and cockpit-relief cutouts are
on the top wing only.
Stacking blank material is a great way
to save time. A few tiny strips of doublestick
clear tape can hold layers of material
together very well and is easy to separate
later.
A good time to decorate the parts is
before the control surfaces are cut away. I
use Sharpie markers, which add no weight
whatsoever, to add color to the model. Light
coats of spray paint or details with an
airbrush are extremely light as well. Kits
from Fancy Foam Models are decorated with
vibrant computer-generated schemes that are
ink-jet-printed directly on the foam sheet
material. Pretty sweet!
All of the control surfaces are top
hinged—even the rudder, which is typically
hinged on the port side. (I’m not sure if it
matters.) Optimally, a double bevel produces
the desired control throw. Save the rudder
hinge for last, since the stabilizer needs to be
mounted prior.
Assemble the fuselage by slipping the
horizontal fuselage into the vertical fuselage.
Using any means on hand, glue the two parts
at the seams so that they are perpendicular.
Add the gussets to the bottom and side of the
fuselage front assembly, which should feel
surprisingly stiff even at this point.
Slide the assembled horizontal stabilizer
into the fuselage, align, and tack-glue in
place; yes, just tack it for now. Lay the
fuselage assembly on the work surface so
that the area below the horizontal section
overhangs the edge and the vertical fin is flat
against the table. Weight the assembly down
and hinge the rudder to the fuselage.
Cover the work surface with plastic and
lay the lower wing, face-side up, on it.
Position the fuselage on the wing; working
with the nose pointing away has worked
best. Shim the tail as needed while the wing
remains flat, and confirm its alignment often.
Temporarily rig the airframe as necessary to
keep everything square.
Add the struts and, finally, the top wing.
At this point, the Zactly is dry-fitted except
for the stabilizer.
When all looks square, squeeze thin
cyanoacrylate into the joints. Wipe away the
excess, as I mentioned earlier. Kicker is not
required until you are totally satisfied with
the alignment of the boneless (no carbonfiber
stiffening) airframe.
Now you must complete the arduous task
of installing the carbon-fiber stiffening
material. Bear in mind that the use of the
word “arduous” is relative to the effort
through which a foamie is assembled.
Wiping the steamed milk foam from one’s
lip is an arduous task when describing the
enjoyment of a delicious latte.
You can use the plans to rough-cut these
carbon-fiber pieces. Crisscrossing the
bracing adds significantly to the structural
integrity.
Sharpen each rod like a pinpoint for
easier mounting. Tack the pieces as the
process continues, confirming alignment of
the airframe along the way. You can untack
parts if necessary.
The wing and fuselage stiffeners work
together so that this ultra-light model doesn’t
wiggle violently like a fish out of water when
the RC pilot’s intention is to do a single roll
or snap. The Zactly F3P snaps really well
too, because the finished airframe is so stiff.
The points where the landing-gear
struts pass through the wing and into the
fuselage are reinforced with cyanoacrylate
hinge material that is cut down neatly into
3/4-inch disks. Save two of these for the
wheel pants.
Notice the plans for conventional wheel
or landing-skid options. The tail wheel is
basically just a skid and can be attached to
the fuselage or rudder.
The airframe is completed with the
addition of LE and TE drag strips. Save
the air brake installation as the final step.
If the need for these creates some headscratching,
finish the model and fly it
without them.
While flying, note especially the speed
on the backsides of loops and down-lines
from stall turns. Add the rudder drag strips
first and observe the speed change, and
then add them to the elevator and finally to
the wing LE. The air brakes alone slow the
model well, and tripling the horizontal and
vertical cross-sections does wonders; little
changes had the biggest effect.
The 1/16 plywood firewall is minimally
sized, to suit the Himax, but it should work
for all 250-size outrunners. The firewall
butt-glues to the nose and keys into the
notches in the fuselage. It’s more than
strong enough for the 10-14 ounces of
thrust it must endure. Add the
reinforcements to the nose once the
firewall is mounted.
The servo, receiver, and battery
placement is based on the CG requirement.
The plans reference estimated locations.
Pull-pull control systems for the rudder
and elevator are the lightest option, but I
like the ease of carbon fiber as pushrods. I
use a mix of homemade hardware and that
from Du-Bro.
The aileron interlink shown on the
plans is made from 0.03-inch carbon-fiber
rod, Kevlar thread, and heat-shrink tubing.
It’s the lightest setup I’ve been able to
make, and it seems to hold up well under
F3P conditions and the irregular midair.
Flies exactly … : Set the control throws as
noted on the plans. Dual rate is used for
flying most F3P schedules, so set those to
approximately half of full deflection and
half the recommended exponential.
Although the Zactly F3P is fully loaded
with all the drag devices, it should cruise
with no trim adjustments at roughly 60%
throttle. Should elevator trim be required,
try to move the battery until as much trim as
possible can be removed.
The Zactly is a kite, and if you’re forced
to fly in a tight area such as a school gym or
an airplane hangar, sport-flying will be
comfortable. This model cruises at a pace
that is close to a fast walk.
One of my favorite points about this flatfoam
model is that it’s pitch neutral in
inverted or upright flight. The CG location
has a lot to do with it, but this trim condition
is a pleasing characteristic of the Zactly. I
hate it when foamies need up-elevator to
keep from climbing while inverted.
The Zactly flies like an airplane with
airfoil-shaped wings, because the LE drag
strips trick the air into thinking that there’s
an actual airfoil. The trick works on
foamies, so I’m not knocking it. The model
should need no obscure mix for up- and
down-lines; mine flies straight up and down.
What did take some getting used to was
the throttle application timing. I’m not
accustomed to adding power in the downlines.
Because of the air brakes, the speed
literally falls off the airplane at the bottom
of a loop or dive recovery; pull to
horizontal and, bam, the airplane stops.
Keeping the airspeed constant is the trick
to flying F3P, so teaching habits that
include adding power before the pull/push
to level are required.
Also, while performing a roll, snap, or
any maneuver really, prepare to include a
bit of extra throttle with the control
combination so that the airspeed is there to
maintain the line or heading at the end of
the maneuver.
A 2S 300 mAh battery has enough
power for roughly three minutes of flying,
which is plenty since F3P sequences and
Artistic Aerobatics routines are scheduled
for approximately two minutes.
I use a GWS 0843 propeller, because
the APC equivalent (my favorite) is much
heavier. Consider binding the propeller
with fishing line instead of the typical
rubber O-ring; input from the tail surfaces
can cause the propeller to flex and bounce
on the motor hub.
The Zactly F3P, as can the original
Zactly, can make the RC pilot look good
doing the right Rolling Circle to the left.
How fast it rolls depends on entry speed
and throttle setting. It is possible to ascend
and descend, because the model will
repeat the circle as long as there’s battery
power and space between it and the
ground.
Despite the long tail moment, the
Zactly is great at performing 3-D as well.
It hardly wags at all through the Harrier,
and it can hover almost as if it were
second nature. Outside Waterfalls are
surprisingly tight, but the long tail
moment probably doesn’t help it with the
Tail Slide. I’ve never been happy
performing those, but who flies backward
in FAI? That’s a joke.
Advancements in this interest are
happening constantly; as is the hover,
backward flight will surely become
commonplace. And I’m all for it.
Have fun! MA
Michael Ramsey
[email protected]
Sources:
Midwest Products
(800) 348-3497
www.midwestproducts.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Castle Creations
(913) 390-6939
www.castlecreations.com
Du-Bro
(800) 848-9411
www.dubro.com
F3P Aerobatics
www.f3p-uk.org.uk

THE COOL THING about flat-foam models is that almost
anything you can think up that has wing area and a correctly
located CG will fly. My biplane design came about just that way;
it’s exactly what I wanted.
For the last three years, the original Zactly has been available from
Midwest Products as a free full-size plans download. At the time of its
release, it was a great-flying foamie for outdoors or indoors. With
more than 400 square inches of area, you could build it from blue
foam at 16 ounces or 5mm Cellfoam 88 at 12 ounces.
The Zactly is a blast to fly and is exceptionally good at
Harrier, hover, and constant rolling maneuvers; the RC pilot
can do a Rolling Circle without losing an inch of altitude, just
by his or her holding in right aileron (no elevator or rudder
corrections required) and roughly half throttle.
The lightest model built had the 5mm wings and
stabilizer exchanged for 3mm Cellfoam 88, and
carbon-fiber crossbracing rods were substituted
for full-length wing spars. That version’s
flying weight was 10 ounces; the Zactly
just kept getting
better.
Conversations with friends who had built the original
Zactly brought up the question of how well it would perform
F3P-style aerobatics. All the rage in Europe and spreading
quickly in the US, F3P is essentially flying precision RC
Aerobatics within an indoor envelope.
The flying space is more confined in F3P, but
patterns have been developed, taking into
consideration the foamie airplanes’ seemingly effortless
maneuverability, that adapt traditional forms of precision
to the habitat and still keep an audience from falling asleep.
The result is sequences that are performed quickly and show off
the foamies’ modern abilities. The “Sources” list at the end of this
article includes the address of a Web site that explains F3P and shares
downloads of the three skill-level maneuver schedules.
The Zactly’s original shape conforms to how I thought an F3A
RC Aerobatics (Pattern) biplane should look. It was also an
experiment in surface-area ratios and wing-stagger variations.
However, it was a fat pig compared to the current models flown in
F3P, and it had coupling issues that I thought needed to be designed
out of the airframe before it could be an honest contender.
Besides flying the model on my own, I learned a lot from
studying experienced designers such as Jason Noll, David Payne,
and Quique Somenzini. Their ideas about airplane dimensions,
thrustlines, and incidences, plus the addition of drag devices,
changed the Zactly in subtle ways, but enough each time to easily
see what the model liked or didn’t like.
That was all because I was simply asking it to roll axially, pull
straight corners, and do every maneuver at 5-10 mph of airspeed.
Sheesh, we RC pilots just want the model to fly itself, don’t we?
The slower the airplane could fly, the less intense an adjustment
needed to be for it to fly the desired way. That was a timeconsuming
lesson. Something as simple as locating the 300 mAh 2S
Li-Poly battery on top of the fuselage instead of the bottom made
one of the most dramatic improvements; almost all the pitch
coupling went away in knife edge with that fluke change.
One might call the Zactly F3P “the new and improved Zactly.”
It’s 93% of the original’s size and has a bit less than 360 square
inches of area. Made entirely from 3mm Cellfoam 88, the F3P
incorporates a large amount of 0.02-inch carbon-fiber rod for
structural rigidity. It has a 6-ounce flying
weight, which is still relatively heavy by
some F3P standards; 5 ounces is the goal.
With the right motor choice and routing
out, the Cellfoam 88 would produce an
airframe that is in the optimal weight zone.
Depron is slightly lighter and less dense,
so building the Zactly F3P from that
material would surely trim this model up.
Prototypes have been built that weighed 8
ounces, and there’s nothing wrong with the
thrill factor those models offered.
Power-system choices vary, depending
on the builder’s taste. Maxx Products motors
are some of the best built and dependable.
I’ve done all my testing with the Himax
2805-1430 outrunner, which is essentially a
275-class motor. I run only a two-cell pack;
Type: RC indoor aerobatics
Skill level: Beginner builder, intermediate pilot
Wingspan: 28.5 inches
Flying weight: 5.5-7.0 ounces
Wing area: 358 square inches
Length: 34.25 inches
Power system: 250-class outrunner; GWS 0843 propeller;
300 mAh, two-cell Li-Poly battery;
Thunderbird-6 ESC
Construction: 2mm-3mm flat foam,
0.02-0.03 carbon-fiber rod
Finish: Sharpie marker, airbrush, or decals
Other: Three microservos, four-channel
microreceiver, hinge tape, thin foam-safe cyanoacrylate
the new Thunder Power V2 300 mAh has
spoiled me.
Almost any micro radio system will
work in the Zactly for sport-flying, but
micro digital servos such as the Futaba
S3153 (and newer) and the JR DS185 are
optimal for F3P performance. Choose a
receiver that weighs 3-5 grams.
The ESC that has worked best for me is
the Castle Creations Thunderbird-6. I
discard the motor connectors and solder the
motor wires directly to the board of the
ESC. Hey, every gram saved counts. (The
modification certainly voids the warranty.)
CONSTRUCTION
Built exactly … : No matter what material
you choose to build the Zactly F3P, follow
the plans’ guidelines regarding template
usage. I like to make the parts’ outside
dimensions slightly larger for safety, so I
cut to the outside of the heavy outline.
In regards to making cutouts for the
horizontal fuselage, wing, and stabilizer, as
well as the slots in the wings for the struts,
the openings are made on the hairline or just
on the inside, so they are a tight fit, or you
can easily adjust them with a light scuff
with an emery board. Material is easier to
remove than to add.
There is absolutely no way a builder is
going to make this model’s target weight if
he or she uses adhesives such as hot glue
and/or epoxy. I’ve found that thin, foam-
safe cyanoacrylate is the best and lightest
option for this aircraft. I even get more
anal retentive and wipe the excess glue
with a Q-tip before spraying accelerator.
I’ve built several Zactly models, so
saying that nothing is simpler to put
together is subjective. The fact that it’s a
profile, by nature, reduces the parts count
significantly, so that in itself makes the
project a candidate for a Geico
commercial. (I act like a caveman at
times.)
If you have never built from scratch,
the plans alone should suffice in getting a
relatively well-built model together, so I
won’t insult the detailed plans by being
redundant.
This will sound odd, since the topic of
this article is to scratch build, but the best
learning exercise I can suggest for a
would-be first-time foamie builder is to
buy and assemble a foamie kit from the
likes of Horizon Hobby or Great Planes.
The Zactly isn’t all that much different
from those offerings and many, I’m told,
from Fancy Foam Models, 3D Foamy, and
others. I’ve learned a lot from building
models from other designers, and you will
too.
Begin by cutting the templates away
from the plans. The top view and head-on
view (cross-section A) are for reference
only. I run the blade of an X-Acto knife
along the outside edge. Leave the control
surfaces attached; you will cut them away
from the foam later.
Instead of holding the paper template
around the outside edges with tape, make
tape holes. Use a sharpened brass tube or a
cool, new FoamWerks drill tool from
Midwest to make openings at key points.
Cover the holes with tape so that the paper
templates can be temporarily attached
while keeping the edges free for a knife or
pen to follow.
The templates should be located on the
foam sheets so that minimal waste is
produced. The templates last longer and
are less likely to distort if the cutouts and
key mounting points are referenced with a
pinhole rather than a complete opening in
the template. Use the point of a T-pin to
reference alignment points and cutout
slots.
A sharp X-Acto knife does quick work
of cutting through the foam; multiple
shallow passes are more accurate. Once the
outer shape of the part is complete, remove
the template and set it aside but close by.
Use a fine-point marker to locate
reference points, hinge lines, and cutouts.
This is a good time to reference where the
carbon-fiber bracing will attach.
The wing template is for both the top
and bottom; stacking the foam so that two
are cut out at the same time assures that the
strut locations are identical. Note that the
center-strut and cockpit-relief cutouts are
on the top wing only.
Stacking blank material is a great way
to save time. A few tiny strips of doublestick
clear tape can hold layers of material
together very well and is easy to separate
later.
A good time to decorate the parts is
before the control surfaces are cut away. I
use Sharpie markers, which add no weight
whatsoever, to add color to the model. Light
coats of spray paint or details with an
airbrush are extremely light as well. Kits
from Fancy Foam Models are decorated with
vibrant computer-generated schemes that are
ink-jet-printed directly on the foam sheet
material. Pretty sweet!
All of the control surfaces are top
hinged—even the rudder, which is typically
hinged on the port side. (I’m not sure if it
matters.) Optimally, a double bevel produces
the desired control throw. Save the rudder
hinge for last, since the stabilizer needs to be
mounted prior.
Assemble the fuselage by slipping the
horizontal fuselage into the vertical fuselage.
Using any means on hand, glue the two parts
at the seams so that they are perpendicular.
Add the gussets to the bottom and side of the
fuselage front assembly, which should feel
surprisingly stiff even at this point.
Slide the assembled horizontal stabilizer
into the fuselage, align, and tack-glue in
place; yes, just tack it for now. Lay the
fuselage assembly on the work surface so
that the area below the horizontal section
overhangs the edge and the vertical fin is flat
against the table. Weight the assembly down
and hinge the rudder to the fuselage.
Cover the work surface with plastic and
lay the lower wing, face-side up, on it.
Position the fuselage on the wing; working
with the nose pointing away has worked
best. Shim the tail as needed while the wing
remains flat, and confirm its alignment often.
Temporarily rig the airframe as necessary to
keep everything square.
Add the struts and, finally, the top wing.
At this point, the Zactly is dry-fitted except
for the stabilizer.
When all looks square, squeeze thin
cyanoacrylate into the joints. Wipe away the
excess, as I mentioned earlier. Kicker is not
required until you are totally satisfied with
the alignment of the boneless (no carbonfiber
stiffening) airframe.
Now you must complete the arduous task
of installing the carbon-fiber stiffening
material. Bear in mind that the use of the
word “arduous” is relative to the effort
through which a foamie is assembled.
Wiping the steamed milk foam from one’s
lip is an arduous task when describing the
enjoyment of a delicious latte.
You can use the plans to rough-cut these
carbon-fiber pieces. Crisscrossing the
bracing adds significantly to the structural
integrity.
Sharpen each rod like a pinpoint for
easier mounting. Tack the pieces as the
process continues, confirming alignment of
the airframe along the way. You can untack
parts if necessary.
The wing and fuselage stiffeners work
together so that this ultra-light model doesn’t
wiggle violently like a fish out of water when
the RC pilot’s intention is to do a single roll
or snap. The Zactly F3P snaps really well
too, because the finished airframe is so stiff.
The points where the landing-gear
struts pass through the wing and into the
fuselage are reinforced with cyanoacrylate
hinge material that is cut down neatly into
3/4-inch disks. Save two of these for the
wheel pants.
Notice the plans for conventional wheel
or landing-skid options. The tail wheel is
basically just a skid and can be attached to
the fuselage or rudder.
The airframe is completed with the
addition of LE and TE drag strips. Save
the air brake installation as the final step.
If the need for these creates some headscratching,
finish the model and fly it
without them.
While flying, note especially the speed
on the backsides of loops and down-lines
from stall turns. Add the rudder drag strips
first and observe the speed change, and
then add them to the elevator and finally to
the wing LE. The air brakes alone slow the
model well, and tripling the horizontal and
vertical cross-sections does wonders; little
changes had the biggest effect.
The 1/16 plywood firewall is minimally
sized, to suit the Himax, but it should work
for all 250-size outrunners. The firewall
butt-glues to the nose and keys into the
notches in the fuselage. It’s more than
strong enough for the 10-14 ounces of
thrust it must endure. Add the
reinforcements to the nose once the
firewall is mounted.
The servo, receiver, and battery
placement is based on the CG requirement.
The plans reference estimated locations.
Pull-pull control systems for the rudder
and elevator are the lightest option, but I
like the ease of carbon fiber as pushrods. I
use a mix of homemade hardware and that
from Du-Bro.
The aileron interlink shown on the
plans is made from 0.03-inch carbon-fiber
rod, Kevlar thread, and heat-shrink tubing.
It’s the lightest setup I’ve been able to
make, and it seems to hold up well under
F3P conditions and the irregular midair.
Flies exactly … : Set the control throws as
noted on the plans. Dual rate is used for
flying most F3P schedules, so set those to
approximately half of full deflection and
half the recommended exponential.
Although the Zactly F3P is fully loaded
with all the drag devices, it should cruise
with no trim adjustments at roughly 60%
throttle. Should elevator trim be required,
try to move the battery until as much trim as
possible can be removed.
The Zactly is a kite, and if you’re forced
to fly in a tight area such as a school gym or
an airplane hangar, sport-flying will be
comfortable. This model cruises at a pace
that is close to a fast walk.
One of my favorite points about this flatfoam
model is that it’s pitch neutral in
inverted or upright flight. The CG location
has a lot to do with it, but this trim condition
is a pleasing characteristic of the Zactly. I
hate it when foamies need up-elevator to
keep from climbing while inverted.
The Zactly flies like an airplane with
airfoil-shaped wings, because the LE drag
strips trick the air into thinking that there’s
an actual airfoil. The trick works on
foamies, so I’m not knocking it. The model
should need no obscure mix for up- and
down-lines; mine flies straight up and down.
What did take some getting used to was
the throttle application timing. I’m not
accustomed to adding power in the downlines.
Because of the air brakes, the speed
literally falls off the airplane at the bottom
of a loop or dive recovery; pull to
horizontal and, bam, the airplane stops.
Keeping the airspeed constant is the trick
to flying F3P, so teaching habits that
include adding power before the pull/push
to level are required.
Also, while performing a roll, snap, or
any maneuver really, prepare to include a
bit of extra throttle with the control
combination so that the airspeed is there to
maintain the line or heading at the end of
the maneuver.
A 2S 300 mAh battery has enough
power for roughly three minutes of flying,
which is plenty since F3P sequences and
Artistic Aerobatics routines are scheduled
for approximately two minutes.
I use a GWS 0843 propeller, because
the APC equivalent (my favorite) is much
heavier. Consider binding the propeller
with fishing line instead of the typical
rubber O-ring; input from the tail surfaces
can cause the propeller to flex and bounce
on the motor hub.
The Zactly F3P, as can the original
Zactly, can make the RC pilot look good
doing the right Rolling Circle to the left.
How fast it rolls depends on entry speed
and throttle setting. It is possible to ascend
and descend, because the model will
repeat the circle as long as there’s battery
power and space between it and the
ground.
Despite the long tail moment, the
Zactly is great at performing 3-D as well.
It hardly wags at all through the Harrier,
and it can hover almost as if it were
second nature. Outside Waterfalls are
surprisingly tight, but the long tail
moment probably doesn’t help it with the
Tail Slide. I’ve never been happy
performing those, but who flies backward
in FAI? That’s a joke.
Advancements in this interest are
happening constantly; as is the hover,
backward flight will surely become
commonplace. And I’m all for it.
Have fun! MA
Michael Ramsey
[email protected]
Sources:
Midwest Products
(800) 348-3497
www.midwestproducts.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Castle Creations
(913) 390-6939
www.castlecreations.com
Du-Bro
(800) 848-9411
www.dubro.com
F3P Aerobatics
www.f3p-uk.org.uk

THE COOL THING about flat-foam models is that almost
anything you can think up that has wing area and a correctly
located CG will fly. My biplane design came about just that way;
it’s exactly what I wanted.
For the last three years, the original Zactly has been available from
Midwest Products as a free full-size plans download. At the time of its
release, it was a great-flying foamie for outdoors or indoors. With
more than 400 square inches of area, you could build it from blue
foam at 16 ounces or 5mm Cellfoam 88 at 12 ounces.
The Zactly is a blast to fly and is exceptionally good at
Harrier, hover, and constant rolling maneuvers; the RC pilot
can do a Rolling Circle without losing an inch of altitude, just
by his or her holding in right aileron (no elevator or rudder
corrections required) and roughly half throttle.
The lightest model built had the 5mm wings and
stabilizer exchanged for 3mm Cellfoam 88, and
carbon-fiber crossbracing rods were substituted
for full-length wing spars. That version’s
flying weight was 10 ounces; the Zactly
just kept getting
better.
Conversations with friends who had built the original
Zactly brought up the question of how well it would perform
F3P-style aerobatics. All the rage in Europe and spreading
quickly in the US, F3P is essentially flying precision RC
Aerobatics within an indoor envelope.
The flying space is more confined in F3P, but
patterns have been developed, taking into
consideration the foamie airplanes’ seemingly effortless
maneuverability, that adapt traditional forms of precision
to the habitat and still keep an audience from falling asleep.
The result is sequences that are performed quickly and show off
the foamies’ modern abilities. The “Sources” list at the end of this
article includes the address of a Web site that explains F3P and shares
downloads of the three skill-level maneuver schedules.
The Zactly’s original shape conforms to how I thought an F3A
RC Aerobatics (Pattern) biplane should look. It was also an
experiment in surface-area ratios and wing-stagger variations.
However, it was a fat pig compared to the current models flown in
F3P, and it had coupling issues that I thought needed to be designed
out of the airframe before it could be an honest contender.
Besides flying the model on my own, I learned a lot from
studying experienced designers such as Jason Noll, David Payne,
and Quique Somenzini. Their ideas about airplane dimensions,
thrustlines, and incidences, plus the addition of drag devices,
changed the Zactly in subtle ways, but enough each time to easily
see what the model liked or didn’t like.
That was all because I was simply asking it to roll axially, pull
straight corners, and do every maneuver at 5-10 mph of airspeed.
Sheesh, we RC pilots just want the model to fly itself, don’t we?
The slower the airplane could fly, the less intense an adjustment
needed to be for it to fly the desired way. That was a timeconsuming
lesson. Something as simple as locating the 300 mAh 2S
Li-Poly battery on top of the fuselage instead of the bottom made
one of the most dramatic improvements; almost all the pitch
coupling went away in knife edge with that fluke change.
One might call the Zactly F3P “the new and improved Zactly.”
It’s 93% of the original’s size and has a bit less than 360 square
inches of area. Made entirely from 3mm Cellfoam 88, the F3P
incorporates a large amount of 0.02-inch carbon-fiber rod for
structural rigidity. It has a 6-ounce flying
weight, which is still relatively heavy by
some F3P standards; 5 ounces is the goal.
With the right motor choice and routing
out, the Cellfoam 88 would produce an
airframe that is in the optimal weight zone.
Depron is slightly lighter and less dense,
so building the Zactly F3P from that
material would surely trim this model up.
Prototypes have been built that weighed 8
ounces, and there’s nothing wrong with the
thrill factor those models offered.
Power-system choices vary, depending
on the builder’s taste. Maxx Products motors
are some of the best built and dependable.
I’ve done all my testing with the Himax
2805-1430 outrunner, which is essentially a
275-class motor. I run only a two-cell pack;
Type: RC indoor aerobatics
Skill level: Beginner builder, intermediate pilot
Wingspan: 28.5 inches
Flying weight: 5.5-7.0 ounces
Wing area: 358 square inches
Length: 34.25 inches
Power system: 250-class outrunner; GWS 0843 propeller;
300 mAh, two-cell Li-Poly battery;
Thunderbird-6 ESC
Construction: 2mm-3mm flat foam,
0.02-0.03 carbon-fiber rod
Finish: Sharpie marker, airbrush, or decals
Other: Three microservos, four-channel
microreceiver, hinge tape, thin foam-safe cyanoacrylate
the new Thunder Power V2 300 mAh has
spoiled me.
Almost any micro radio system will
work in the Zactly for sport-flying, but
micro digital servos such as the Futaba
S3153 (and newer) and the JR DS185 are
optimal for F3P performance. Choose a
receiver that weighs 3-5 grams.
The ESC that has worked best for me is
the Castle Creations Thunderbird-6. I
discard the motor connectors and solder the
motor wires directly to the board of the
ESC. Hey, every gram saved counts. (The
modification certainly voids the warranty.)
CONSTRUCTION
Built exactly … : No matter what material
you choose to build the Zactly F3P, follow
the plans’ guidelines regarding template
usage. I like to make the parts’ outside
dimensions slightly larger for safety, so I
cut to the outside of the heavy outline.
In regards to making cutouts for the
horizontal fuselage, wing, and stabilizer, as
well as the slots in the wings for the struts,
the openings are made on the hairline or just
on the inside, so they are a tight fit, or you
can easily adjust them with a light scuff
with an emery board. Material is easier to
remove than to add.
There is absolutely no way a builder is
going to make this model’s target weight if
he or she uses adhesives such as hot glue
and/or epoxy. I’ve found that thin, foam-
safe cyanoacrylate is the best and lightest
option for this aircraft. I even get more
anal retentive and wipe the excess glue
with a Q-tip before spraying accelerator.
I’ve built several Zactly models, so
saying that nothing is simpler to put
together is subjective. The fact that it’s a
profile, by nature, reduces the parts count
significantly, so that in itself makes the
project a candidate for a Geico
commercial. (I act like a caveman at
times.)
If you have never built from scratch,
the plans alone should suffice in getting a
relatively well-built model together, so I
won’t insult the detailed plans by being
redundant.
This will sound odd, since the topic of
this article is to scratch build, but the best
learning exercise I can suggest for a
would-be first-time foamie builder is to
buy and assemble a foamie kit from the
likes of Horizon Hobby or Great Planes.
The Zactly isn’t all that much different
from those offerings and many, I’m told,
from Fancy Foam Models, 3D Foamy, and
others. I’ve learned a lot from building
models from other designers, and you will
too.
Begin by cutting the templates away
from the plans. The top view and head-on
view (cross-section A) are for reference
only. I run the blade of an X-Acto knife
along the outside edge. Leave the control
surfaces attached; you will cut them away
from the foam later.
Instead of holding the paper template
around the outside edges with tape, make
tape holes. Use a sharpened brass tube or a
cool, new FoamWerks drill tool from
Midwest to make openings at key points.
Cover the holes with tape so that the paper
templates can be temporarily attached
while keeping the edges free for a knife or
pen to follow.
The templates should be located on the
foam sheets so that minimal waste is
produced. The templates last longer and
are less likely to distort if the cutouts and
key mounting points are referenced with a
pinhole rather than a complete opening in
the template. Use the point of a T-pin to
reference alignment points and cutout
slots.
A sharp X-Acto knife does quick work
of cutting through the foam; multiple
shallow passes are more accurate. Once the
outer shape of the part is complete, remove
the template and set it aside but close by.
Use a fine-point marker to locate
reference points, hinge lines, and cutouts.
This is a good time to reference where the
carbon-fiber bracing will attach.
The wing template is for both the top
and bottom; stacking the foam so that two
are cut out at the same time assures that the
strut locations are identical. Note that the
center-strut and cockpit-relief cutouts are
on the top wing only.
Stacking blank material is a great way
to save time. A few tiny strips of doublestick
clear tape can hold layers of material
together very well and is easy to separate
later.
A good time to decorate the parts is
before the control surfaces are cut away. I
use Sharpie markers, which add no weight
whatsoever, to add color to the model. Light
coats of spray paint or details with an
airbrush are extremely light as well. Kits
from Fancy Foam Models are decorated with
vibrant computer-generated schemes that are
ink-jet-printed directly on the foam sheet
material. Pretty sweet!
All of the control surfaces are top
hinged—even the rudder, which is typically
hinged on the port side. (I’m not sure if it
matters.) Optimally, a double bevel produces
the desired control throw. Save the rudder
hinge for last, since the stabilizer needs to be
mounted prior.
Assemble the fuselage by slipping the
horizontal fuselage into the vertical fuselage.
Using any means on hand, glue the two parts
at the seams so that they are perpendicular.
Add the gussets to the bottom and side of the
fuselage front assembly, which should feel
surprisingly stiff even at this point.
Slide the assembled horizontal stabilizer
into the fuselage, align, and tack-glue in
place; yes, just tack it for now. Lay the
fuselage assembly on the work surface so
that the area below the horizontal section
overhangs the edge and the vertical fin is flat
against the table. Weight the assembly down
and hinge the rudder to the fuselage.
Cover the work surface with plastic and
lay the lower wing, face-side up, on it.
Position the fuselage on the wing; working
with the nose pointing away has worked
best. Shim the tail as needed while the wing
remains flat, and confirm its alignment often.
Temporarily rig the airframe as necessary to
keep everything square.
Add the struts and, finally, the top wing.
At this point, the Zactly is dry-fitted except
for the stabilizer.
When all looks square, squeeze thin
cyanoacrylate into the joints. Wipe away the
excess, as I mentioned earlier. Kicker is not
required until you are totally satisfied with
the alignment of the boneless (no carbonfiber
stiffening) airframe.
Now you must complete the arduous task
of installing the carbon-fiber stiffening
material. Bear in mind that the use of the
word “arduous” is relative to the effort
through which a foamie is assembled.
Wiping the steamed milk foam from one’s
lip is an arduous task when describing the
enjoyment of a delicious latte.
You can use the plans to rough-cut these
carbon-fiber pieces. Crisscrossing the
bracing adds significantly to the structural
integrity.
Sharpen each rod like a pinpoint for
easier mounting. Tack the pieces as the
process continues, confirming alignment of
the airframe along the way. You can untack
parts if necessary.
The wing and fuselage stiffeners work
together so that this ultra-light model doesn’t
wiggle violently like a fish out of water when
the RC pilot’s intention is to do a single roll
or snap. The Zactly F3P snaps really well
too, because the finished airframe is so stiff.
The points where the landing-gear
struts pass through the wing and into the
fuselage are reinforced with cyanoacrylate
hinge material that is cut down neatly into
3/4-inch disks. Save two of these for the
wheel pants.
Notice the plans for conventional wheel
or landing-skid options. The tail wheel is
basically just a skid and can be attached to
the fuselage or rudder.
The airframe is completed with the
addition of LE and TE drag strips. Save
the air brake installation as the final step.
If the need for these creates some headscratching,
finish the model and fly it
without them.
While flying, note especially the speed
on the backsides of loops and down-lines
from stall turns. Add the rudder drag strips
first and observe the speed change, and
then add them to the elevator and finally to
the wing LE. The air brakes alone slow the
model well, and tripling the horizontal and
vertical cross-sections does wonders; little
changes had the biggest effect.
The 1/16 plywood firewall is minimally
sized, to suit the Himax, but it should work
for all 250-size outrunners. The firewall
butt-glues to the nose and keys into the
notches in the fuselage. It’s more than
strong enough for the 10-14 ounces of
thrust it must endure. Add the
reinforcements to the nose once the
firewall is mounted.
The servo, receiver, and battery
placement is based on the CG requirement.
The plans reference estimated locations.
Pull-pull control systems for the rudder
and elevator are the lightest option, but I
like the ease of carbon fiber as pushrods. I
use a mix of homemade hardware and that
from Du-Bro.
The aileron interlink shown on the
plans is made from 0.03-inch carbon-fiber
rod, Kevlar thread, and heat-shrink tubing.
It’s the lightest setup I’ve been able to
make, and it seems to hold up well under
F3P conditions and the irregular midair.
Flies exactly … : Set the control throws as
noted on the plans. Dual rate is used for
flying most F3P schedules, so set those to
approximately half of full deflection and
half the recommended exponential.
Although the Zactly F3P is fully loaded
with all the drag devices, it should cruise
with no trim adjustments at roughly 60%
throttle. Should elevator trim be required,
try to move the battery until as much trim as
possible can be removed.
The Zactly is a kite, and if you’re forced
to fly in a tight area such as a school gym or
an airplane hangar, sport-flying will be
comfortable. This model cruises at a pace
that is close to a fast walk.
One of my favorite points about this flatfoam
model is that it’s pitch neutral in
inverted or upright flight. The CG location
has a lot to do with it, but this trim condition
is a pleasing characteristic of the Zactly. I
hate it when foamies need up-elevator to
keep from climbing while inverted.
The Zactly flies like an airplane with
airfoil-shaped wings, because the LE drag
strips trick the air into thinking that there’s
an actual airfoil. The trick works on
foamies, so I’m not knocking it. The model
should need no obscure mix for up- and
down-lines; mine flies straight up and down.
What did take some getting used to was
the throttle application timing. I’m not
accustomed to adding power in the downlines.
Because of the air brakes, the speed
literally falls off the airplane at the bottom
of a loop or dive recovery; pull to
horizontal and, bam, the airplane stops.
Keeping the airspeed constant is the trick
to flying F3P, so teaching habits that
include adding power before the pull/push
to level are required.
Also, while performing a roll, snap, or
any maneuver really, prepare to include a
bit of extra throttle with the control
combination so that the airspeed is there to
maintain the line or heading at the end of
the maneuver.
A 2S 300 mAh battery has enough
power for roughly three minutes of flying,
which is plenty since F3P sequences and
Artistic Aerobatics routines are scheduled
for approximately two minutes.
I use a GWS 0843 propeller, because
the APC equivalent (my favorite) is much
heavier. Consider binding the propeller
with fishing line instead of the typical
rubber O-ring; input from the tail surfaces
can cause the propeller to flex and bounce
on the motor hub.
The Zactly F3P, as can the original
Zactly, can make the RC pilot look good
doing the right Rolling Circle to the left.
How fast it rolls depends on entry speed
and throttle setting. It is possible to ascend
and descend, because the model will
repeat the circle as long as there’s battery
power and space between it and the
ground.
Despite the long tail moment, the
Zactly is great at performing 3-D as well.
It hardly wags at all through the Harrier,
and it can hover almost as if it were
second nature. Outside Waterfalls are
surprisingly tight, but the long tail
moment probably doesn’t help it with the
Tail Slide. I’ve never been happy
performing those, but who flies backward
in FAI? That’s a joke.
Advancements in this interest are
happening constantly; as is the hover,
backward flight will surely become
commonplace. And I’m all for it.
Have fun! MA
Michael Ramsey
[email protected]
Sources:
Midwest Products
(800) 348-3497
www.midwestproducts.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Castle Creations
(913) 390-6939
www.castlecreations.com
Du-Bro
(800) 848-9411
www.dubro.com
F3P Aerobatics
www.f3p-uk.org.uk