Photo Credit: Martin Pilko
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Wingspan:
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124"
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Wing area:
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1054 sq. in.
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Weight:
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Primary = 80.9 oz, Backup = 81.1 oz
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Wing Loading:
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11 oz/sq.ft
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RX Battery:
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5 cell, 1100mah Ni-Cad
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Servos:
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Volz Wing-Maxx (ailerons), Volz Micro-Maxx (ruddervators, flaps)
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Radio:
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Multiplex Profi 3030, Hitec SuperSlim RX
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Available From:
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Icare Sailplanes
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Introduction
When I found out that the 2004 F3J World Championships were going to be held very closet to
my home town of Calgary, Canada, I knew that I had to try out for the Canadian team (they're in
Red Deer, an hour or so north of Calgary).
I've always been the type to keep a few different models around, but in an attempt to maximize
the effectiveness of my practice time, I decided that I was going to have to concentrate on one
design. I chose the Eraser 2000 (El Camino F3B in North America) for my main weapon for the team
trials, since it combines great ranging ability with strong overall performance.
Produced by Lubos Pazderka in the Czech Republic (http://www.f3j.cz/english.htm), the Eraser is a fully-modern
hollow molded composite model with thin balsa skins and a healthy carbon spar. The model comes
in a few versions and layups (including an extended span F3J version), but as a backup model I
chose to stick with what I knew - the F3B flat wing and carbon d-box layup. Two years of
experience with my primary model showed me that the wing was more than capable of taking gorilla
launches, and I didn't want to change a system that was already working very well for me.
That said, I shot an order off to Etienne Dorig at Icare Sailplanes, and had a backup model
in my hands exactly one week later.
Kit Contents
Although the Eraser arrives with all the structural components pre-finished, there are
still about 12-16 hours of work that are required before the model is flyable.
All the components arrive wrapped in bubble wrap.
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Icare includes a nice hardware package and a set of instructions with the Erasers.
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Wing
The main wing of the Eraser is made up of three panels, joined to each other by solid
angled rectangular carbon joiners, and to the fuselage using three metric steel bolts. I've
always liked the three-panel arrangement, since it doesn't require a joiner at the center of the
wing where launch stresses are the greatest.
The center panel has three quarters of a degree of dihedral built into it, and the tip
panels add a further three and a half degrees with the carbon joiners. The stability imparted by
that much effective dihedral allows the model to be reasonably stable when flown at distance,
but avoids the crosswind hassles of a RES (rudder/elevator/spoiler) or other high dihedral
model.
Since the Eraser is a full-house sailplane, it requires four servos in the wing. The
ailerons are top-hinged and bottom actuated, and the flaps are bottom hinged and top actuated. A
full 90 degrees of flap travel is available for those that require it, making the model a viable
choice for AMA TD (Thermal Duration) contests.
Here's a shot of the left tip panel.
The finish on these models is extremely nice.
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The newest Erasers come with carbon patches to reinforce the servo wells. My
original model did not have these, though they are a welcome addition.
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The v-tail comes as a single-piece, molded unit.
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Fuselage
The fuselage of the F3B Eraser is a gellcoated composite structure of fibreglass and carbon
fibre, and uses a removable nosecone for access to the flight gear. There are two fibreglass
ballast tubes accessible from the underside of the nosecone, and these allow the model to be
useable in a wide variety of contest conditions. The F3B version uses strong carbon tubes to
actuate the v-tail control surfaces, which allows for slop-free operation.
The F3B fuselage uses two internally mounted fibreglass ballast tubes.
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Ballast slugs are loaded from slots under the nosecone.
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All versions of the Eraser feature an externally adjustable towhook. Adjustments
require the use of an allen key.
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Hardware Package
The hardware package is very complete, and should provide most items that are required to
complete the model. It includes a nice set of angled rectangular carbon wing joiners, a set of
gell-coated fibreglass servo covers, a computer plug for the wing/fuselage wiring harness,
threaded brass control horns for the flight control surfaces, three metric wing bolts, allen
keys for said bolts, and some interesting plastic/brass-combination clevises. My only complaint
is that I don't like how the carbon wing joiners are shipped in the same bag as the metal bits,
since carbon is notoriously intolerant of nicks. Still, everything emerged unscathed, which was
nice to see.
Icare includes a hardware package and instruction manual.
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Instructions
As much as I like kit, I wasn't wild about the instruction manual. While Etienne at Icare
has to be applauded for adding his own instruction set to the kit (it usually doesn't come with
one), you really need to be an experienced builder to put this model together. I guess the
feeling is that if you're experienced enough to be flying a model like this one, you should have
developed your understanding of model building to the point where you can assemble the kit
without help. The manual is really only intended to provide vague recommendations for
equipment selection and for initial control throws and balance, so don't expect a step-by-step
explanation of how things are supposed to be assembled. Luckily, that's why I'm here!
Assembly
The following sections will deal with how I chose to assemble my Eraser. These guidelines
simply represent one person's opinion on how the job should be done, and I'm sure there are
other methods that will work equally well (or better).
Gear Location
The first thing that I did was to plan out my gear placement in the nosecone. I wanted to
use a set of Volz Micro-Maxx servos due to their extreme precision and quality, but these servos
are just too wide to permit side-by-side mounting. If you choose to use a micro servo instead of
a mini (Hitec HS85 or JR341, for example), you can use a setup similar to the one that is shown
below.
Here's an alternate gear placement from the manufacturer's website. Remember to
put a wrap of tape around that battery and receiver in case you lose your
nosecone in flight!
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The problem with choosing to use a mini servo is that the ballast tubes on the underside get in
the way of two servos placed in-line. After a bit of head scratching, I decided to mount the
servo at a 45 degree angle, which would also permit the use of a longer servo arm should extra
servo travel be required.
First, remove the carbon pushrods to avoid nicking them with the grinder. Next, mark the
locations of the servo and switch cutouts on masking tape - I find that pen is too prone to
smudging if applied directly to the gellcoated surface. I opened the entire area ahead of the
tape for the battery and receiver. Also, speaking from experience, you'll find that you have to
grind away a significant portion of angled surface ahead of the radio gear mounting plate (the
angled area about 2" from the nose pin) to allow the addition of nose weight.
I used a fibreglass cutoff disc for most of the cuts, and finished with a drum sander to avoid
having any 90 degree corners (cracks will tend to start there). Please be sure to grab your
respirator, since fibreglass dust isn't particularly good for your lungs. This is by far the
most mentally stressful part of the build, since it requires you to cut into a pristine model!
Just make sure to measure a couple of times before making the first cut.
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All the components needed to mark the gear locations
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Make sure to use a respirator when grinding composites.
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Onboard Battery
After blowing out all the dust that you created carving holes in your new pride and joy, make a
decision about what kind of radio battery you're going to use. I chose to make up a 5-cell pack
using Sanyo 1100 AA cells, with 2 sticks of two cells on the bottom and a fifth on top. I was
out of shrink-wrap at the time, so I just wrapped the pack in electrical tape. While batteries
are still on your mind, put the pack on a cycler a few times to make sure that the cells are
good - it's hard to wait for a pack to cycle after the model is complete!
Fuselage Servo Installation
Remembering that the rear ruddervator servo has to be installed at an angle to clear the ballast
tubes, I made up a couple of angled shims out of 1/4" aircraft plywood. These angles get glued
to the fuselage with medium CA, and stabilize the servo to prevent it from rocking. Be careful
when drilling pilot holes in these shims, since you're drilling along the plies in the wood. Use
screws that are long enough to bite into the fibreglass tray to avoid relying on the wood for
strength. I was tempted to use wooden backing plates under the tray, but the servo screws that I
used seemed to get a good bite into the fibreglass on their own.
Finish this step by screwing the servos and switch into place.
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Here are the materials required to install the rear ruddervator servo.
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Fuselage Pushrods
Next, check to see that the ball-socket fittings on the end of the pushrods are secure. They
come fitted from the factory, but be sure to double check everything just to make sure. Ever
since I pulled the end off of a pushrod supplied with a brand new Hera with only light pressure
(different manufacturer), I've been paranoid about checking factory joints thoroughly.
Next, slide the pushrods back into their holes - you'll be able to feel when they align properly
with a support bulkhead in the tailboom. Align the cupped fittings with the openings in the
tail, and tape the pushrods so that they don't slide all over the place.
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Tape your pushrods to prevent them from sliding around. Note that your servos will
likely be mounted at this point - this photo shows how the fuselage comes out of
the box.
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V-Tail Mounting
The v-tail assembly is held onto the fuselage with two metal bolts, which are supplied with the
kit. While the paranoid among us might feel tempted to add a blob of silicone to make sure that
the tail stays anchored, I haven't found the stock system to be a problem. Just remember to
check the tightness of the bolts every couple of outings, and you shouldn't find yourself with a
flying wing.
Getting the metal balls into the plastic cups on the pushrods was my least favorite task in
building my Erasers, and I'll show you how I did it. I attached the tail to the fuselage, and
taped the ruddervators to prevent them from moving. Next, I grabbed a pair of medical forceps to
grip the elevator linkage shank, and patiently wiggled the socket onto the ball by supporting
the pushrod with the flat side of a jeweler's screwdriver. My first tail took me about 40 mins
of fighting, and the second took about 5 mins. I guess it's just a matter of practice. I
recently bought myself a neat set of helicopter ball-link pliers, which should make this task a
snap in the future (forgive the pun).
I wouldn't recommend that you remove the tail for transport unless you really have to,
since that will quickly wear out the plastic pushrod ball sockets.
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Here are the materials required to attach the tail. Cover over the hole in the
tail with a blob of tape to avoid getting dirt and grass in the opening.
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The ruddervators are actuated by bent wires, with neat brass ball fittings
pre-soldered to the wires.
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Leaving the ruddervators taped in place to prevent them from moving, thread a clevis midway onto
the ends of each of the two supplied brass pushrod end fittings. I chose to replace the supplied
plastic/brass clevises with black metal Dubro versions, since most plastics don't take kindly to
Canadian sub -30C winter temperatures. I would also worry about the pins in the clevises working
themselves loose, as there is no way to slide a keeper over them.
Attach an arm to each of the servos, and make sure that you are still able to slide the nosecone
onto the fuselage (*important*). Mark and cut the pushrods to length, either using a wrap of
tape and a fine saw or using a cutoff wheel. Make SURE to use a respirator when grinding carbon
fibre, and avoid having contact between the carbon dust and your skin. Adhere the brass fitting
to the pushrod using medium c/a and leave the joints to cure fully, avoiding any kickers or
catalysts. If you're patient, I've been assured by an adhesives engineer that the resulting bond
is very secure. Remove the tape from the control surfaces, and check for any binding in the
system - a servo tester like the ones sold by Astroflight or Multiplex is handy here.
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A shot of the completed servo installation. The battery is just loosely in place
at this point.
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Fuselage Wiring Harness
The next task in assembling the model is to construct the wiring harness for the wing and
fuselage. Those who aren't handy with a soldering iron are encouraged to either seek the help of
a sympathetic club member, or to purchase a commercially available system. I seem to remember
that Tom Hoopes (USA) creates pre-wired harnesses, as does Simon van Leeuwen (Canada) . They
should save at least 3-4 hours of construction time, but the solder work isn't hard for those
who wish to try.
The first thing that you'll require is a good soldering iron, either an adjustable soldering
station or a decent 15-20W pen. Next, arrange for some electrical-grade solder and some
electronic flux (I like the paste variety). Resist the urge to use that tin of plumber's flux
that we all have squirreled away somewhere, or your harness will slowly corrode on you over
time.
I dip each wire in liquefied flux, but I tend not to pre-tin my wires. I find that by
mechanically wrapping the joints together beforehand, it's a little easier to get solid
connections without the danger of a cold joint. A handy device to have here is a fishing
fly-tiers vice, which should be available at any sporting goods store. When I join two pieces of
3-strand wire, I individually shrink wrap each joint, then add a wrap of larger-gauge
shrink tubing around the whole joint. It seems redundant, but I feel that it's more secure. I
have a friend who gets good results by staggering the wire joints, then using one piece
of tubing to go over the whole area. To each their own. With a good quality shrink wrap, you can
either use a Monokote heat gun or the shank of your soldering iron to tighten the wrap.
A quick note about wire gauge/style is probably appropriate here. I tend to use heavy (I
believe 20 gauge), 3-conductor, multi-stranded wire for most of my longer runs (wing and
fuselage harness), and use standard servo wire for short runs (ruddervator leads). While the
currents aren't very high from the servos, I like to avoid the excessive voltage drop that comes
with undersized wiring. If you don't have easy access to braided wire, try to twist your wire at
least once per 1" run to avoid induced interference problems. Try to keep all wiring runs as
short as possible, but leave enough length so that the wire is not under any tension.
Since Volz servos are supplied with their own style of connector, my first task was to make
short Volz-to-Universal/JR adaptors for my fuselage servos. Even though the white Volz
connectors aren't great electrically, I like to keep them in place to facilitate easy servo
servicing. Also note that Volz service centers will usually charge an extra fee for servicing
servos that have these connectors removed.
If you aren't using Volz servos, it's largely up to you as to whether you want to leave the
original leads in place, or to solder the servos into the wiring harness permanently. Other than
with Volz, I always clip and solder all my servos, though this does mean that swapping out a
servo in the field is more difficult. Leaving the stock connectors in place also means that
you're usually left with a lot of excess wire in the wing or in the fuselage, and requires that
you buy 6 female servo plugs so that you can plug the servos into the harness that you'll
eventually make. If you can solder well (and have the patience to do the extra joints), I
recommend that you clip and solder.
After making up the adaptors, tighten a band of shrink wrap around the white Volz connector to
avoid having them accidentally come apart.
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Here are all the parts required to make the short fuselage-servo adaptors. Note
the small pieces of shrink wrap that are used to insulate the joint.
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A finished ruddervator servo ready to be reinstalled in the fuselage.
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Next, make up the wiring harness that will lead from the receiver to the fuselage computer
connector. Since there are 9 pins on the connector, the easiest (and safest) way to use the pins
is to run four signal wires, two positive wires, and two negative wires. Make sure that each
wing uses its own set of positive and negative wires, so that a break in one wire will still
leave at least one aileron and flap active. Be very careful when soldering into the computer
connector, as it's easy to burn the insulation of adjacent wires since the clearances are so
tight. Draw a diagram of the connector wiring code that you choose, so you can easily reference
which wire does what in the case of a problem.
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Completed fuselage wiring harness. Be sure to twist your wires before installing
the harness.
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Auto-Aligning Wing Connector
The next sequence is largely optional, but makes the installation a little more slick. It
involves making an auto-aligning wing-to-fuselage connector, which avoids having to dig around
inside the fuselage for a lost connector. It also avoids having to handle the fuselage
connector, and the wire fatigue that goes along with that.
First of all, make a wooden tray to sit the connector on, with two vertical posts that are
spaced as far apart as the extremes of the opening in the fuselage will allow. Next, screw the
connector to the mounting plate. Mate the wing connector with the fuselage connector, and trial
fit the assembly in the fuselage hole.
Making sure that the connector will sit flush with the top of the wing saddle, mark the vertical
posts with the correct length. Cut off the excess. After protecting the wing saddle area with
masking tape and triple-checking the fit of the fuselage and wing connectors, use c/a or epoxy
to bond the vertical posts in place.
Sand the area flush, and admire your handiwork. If you nick the gellcoat, modeling paints can be
used to touch up the finish.
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Make a connector mounting assembly with two vertical posts. 1/4 x1/8" spruce is
used here.
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Mate the wing and fuselage computer connectors, and check to see that the assembly
will fit with the wing connector flush with the wing saddle.
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Cut off the excess post height, protect the area with masking tape, and bond the
connector in place.
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Center Panel Wiring Harness
Next, it's time to make up the wiring harness for the center panel. Some people choose to keep
the wiring runs for the aileron and flap servos completely separate, but I don't care for the
extra weight. Additionally, since the servos share positive and negative wires in the fuselage,
there really isn't much point in not doing the same inside the wing. If you take a look at the
following photo, you'll see that there are three components to each half of the center panel
harness. A run of wire goes from the tip to the servo well, a second goes from the well to the
wing connector, and a third from the well to the servo itself. There should actually be a fourth
wiring component shown in the photo, since you'll need to run a single white wire to bring the
signal from the DB-9 connector to the flap servo.
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Here are the three wiring lengths that make up each half of the center panel
harness. Missing is a single white signal wire that would run from the servo well
to the center.
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Begin by wiring your tip-panel-to-center-panel connector in place on the outboard end of the
long wiring run. As usual, there are a couple of ways of doing this. The simplest is to use a
set of male/female servo connectors, where the female is permanently anchored in the tip and the
male lead extends freely from a hole in the end of the center panel (or vice versa). The
connector gets plugged in by hand as the wing sections are joined. While this works well, you
can sometimes lose the male lead back inside of the center panel, which then becomes a pain to
fish back out. With this system it's prudent save the tape that you use to join the wing panels,
and use it to tape the male lead to the surface of the wing - this prevents it from
disappearing.
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The male servo lead extends freely from the center panel...
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...while the female is anchored securely in the tip panel.
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While you can see that I used this simpler system in my primary model, I don't really like it
very much. Instead, a friend recently introduced me to these fine little connectors, which I
purchased at a local electronics store (I don't have the part # I'm afraid). In addition to
being much cheaper than servo plugs, they have enough gluing surface on the connectors to allow
a plug-and-fly system similar to the one used in the wing-to-fuselage joint.
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Components required for Auto-Plugs
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So, as I mentioned before, the first step is to solder the male connector to the outboard end of
the long wiring run in the center panel harness. After adding 1 twist per inch of wire, solder
together the positive wires from the long wiring run, the short well-to-center run, and the
well-to-servo run. Repeat for the negative wires. Next, solder the white signal wire from the
long run to the white wire from the well-to-center run - this is the signal wire for the aileron
servo. Finally, solder the lone white signal wire to the signal wire from the servo connector -
this is the signal wire for the flap servo.
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Here are the completed wiring harness halves prior to final assembly.
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Cut a small hole in the end of the center panel to fit the outside diameter of the male
connector. Feed a length of fishing/retriever etc. line through the hole, and pull the male
connector through the hole (you'll obviously need just a little clearance in the hole to do
this). Remove the fishing line, and glue the connector into the wing panel with epoxy or
c/a. Please make sure to avoid getting glue on the tines of the connector, since that's a
phenomenal way of ruining your day. Repeat these steps for the other side of the center panel.
Aligning the center panel computer connector is easy since there is a molded recess for the
plug, so after cutting a hole in the wing to clear the wires and the base of the connector,
check to see that you can screw it into place. After removing the plug, drop a trace string to
bring the eight wires through the hole. After consulting your connector wiring diagram (you did
make one before didn't you - your other plug is screwed into the fuselage!), complete all the
solder joints. Be careful to protect the wing surface with tape or cardboard to prevent stray
drops of solder from marring the surface.
Gently push the wires back into the wing, and secure the connector with the supplied screws.
Gluing it into place isn't advised in case you ever have wiring problems in the future.
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The male connector glued into place on the tip panel.
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The center panel computer plug screwed into place. Note the pieces of red tape
that denote the c/g range for the model.
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Tip Panel Wiring Harness
Compared to the center panel, completing the tips is easy. First of all, cut a length of
3-strand wire that will be long enough to reach from the aileron servo well to the root of the
tip panel. Solder a female connector to the end of this wire, and set the harness aside.
Next, grab your center panel, and one of the carbon wing joiners that are supplied with the
model. Slide the angled joiner home in the center panel, and gently slide the tip panel until
there is just enough clearance that the male connector in the center doesn't get squished.
Remember that Erasers are built with extremely small manufacturing tolerances, so even if a
little force is needed to slide the joiners into the panels, don't get overzealous - that
connector is in the way!
With the minimum clearance distance established, scribe the horizontal and vertical outlines of
the male connector onto the tip panel with an exacto blade or a screwdriver. This measurement is
obviously much more critical with the auto-locking method, as the connectors must align
properly. Remove the tip panel, and check to see if your scribe marks are visible. If not,
repeat the process until you have a clear outline of the material that must be removed to clear
the female connector.
After making the cutout for the female connector, drop the wire into the tip panel and tack the
connector in place with a drop of c/a. Using the center panel again, check to see if the male
and female connectors will mate properly without binding the joint, and enlarge the hole in the
tip as necessary until they do. After you're happy with the fit, fill in the gap with thickened
epoxy or medium c/a and kicker, and sand the panel smooth. You'll never have to fish for another
wire again!
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Here's a photo of the completed tip panel. Note the extra gap on the underside of
the connector to clear the locking pin on the male connector.
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Wing Servo Installation
Now that the wiring harness is complete, the worst is over with. Installing the wing servos is
the next step, and there are a variety of ways to accomplish this task. My favorite method is
one of the simplest - I don't always do things the hard way! It involves wrapping the servo with
masking tape or shrink wrap, and epoxying it to the upper wing skin in the servo well.
The Erasers have a carbon patch around the servo well, but if you ever have a model without this
handy feature, be sure to reinforce the skin. If you don't, movement of the servo can sometimes
buckle the wing surface, which isn't great for controllability or the long-term health of the
skin. I've used carbon cloth or 1/64" plywood in the past, just remember to use slow-setting
epoxy to avoid heat-induced warping in the skin.
If you're using Volz servos or female servo plugs, plug the servos in and shrink-wrap the
connection to prevent them from coming loose. If you're soldering the servos in, go ahead and
solder away. Before you actually wrap and glue your servos, drag out that radio or servo tester,
and make sure that everything is working properly. Better yet, if you want to be sure that your
harness is good before risking a servo, a voltmeter set to check continuity is a good option.
Next, locate the threaded brass connectors that are supplied with the kit, and check to see that
they engage the threads in the wing surfaces properly. You can either leave them long, or cut
them down with a cutoff wheel so that no threads are exposed - I did the latter. Thread
these into the wing surfaces, and check to make sure that whatever clevis you choose to use will
fit with the hole in the horn. I needed to shave a sliver of material out of the hole in order
to use the black Dubro clevises.
Make your pushrods out of 2-56 threaded wire. If you use standard partially-threaded pushrod
material, use a solder clevis on one end and use a threaded clevis on the other. I like to use
2-56 all-thread material, since that way I never run out of threads on the rod if I misjudge its
length and need to shorten it. With all-thread, you can simply lock one clevis in place with
c/a.
The Great Eraser Flap Quandry
In that the Eraser uses bottom-hinged flaps that are actuated from the top of the wing surface,
it can be difficult to get the full 90 degree flap travel that seems to be a requirement for AMA
TD. In fact, the usual message to the Radio Control Soaring Exchange goes something like this:
"When I installed flap servos into my Eraser open class plane, the flaps will not
hinge all the way to 90 degrees ... more like 45 degrees. What can I do to get more
travel?"
It's actually not hard to get the full flap travel, but it does require a bit of pre-planning.
For all methods, be sure that the servo is as close to the spar as the servo arm will allow.
That way you can get the greatest travel possible without binding. Before I show you the one
that I ultimately used, here are a couple taken directly from the RCSE:
Method #1: "Adjust your radio (using subtrims, etc.) for maximum throw with the control
arm facing about 15 degrees forward with flaps aligned at neutral. At full flap, the
servo arm should be pointing almost straight back. You'll have to grind away the wiper
and the top skin (recessed) up to the balsa subspar in the wing. Once you see the balsa
subspar, take a piece of 1/4 brass tubing and "drill" at a shallow angle following the
pushrod such that you remove about another 1/8" of top skin. The top skin should be
intact at the LE of the balsa subspar. When you're done, you'll have removed most of
the subspar material but it's okay. If you have the servo properly mounted, you'll have
no binding at all. " -Various sources
Method #2. Cheat, and mount the control horn on the bottom of the flap. (Author - Boo!!)
Various sources
Method #3: "Layout of the linkage is simple but difficult to explain. Start with a full
size drawing of the airfoil with correct servo and flap location. Draw a circle over the
servo with the radius equal to the distance from the servo shaft to the hole in the arm.
Draw a circle centered on the flap hinge point with radius of the flap horn. Draw a
straight line tangent to the two circles. The tangent point on each circle should be the
mid point of travel for both the servo and flap. In this case, the flap should be at 45
degrees while the servo is at zero. Adjust the servo arm and flap horn to give this setup.
Like I said, it's much easier to do than to explain. I knew that course in kinematics and
linkages I took 50 years ago would be useful someday. :-)" -Chuck Anderson
The route I chose to go with is closest to Method #1, though I didn't choose to cut into the
wing skin. I did cut into the flap wiper, however, and ultimately have about 70 degrees of flap
travel. I don't like to have short arms on my flap servos since it reduces their resolution, and
hence my ability to precisely use camber and reflex. I also don't personally feel that 90
degree flaps are a requirement anyway, since if you're using that much flap on landing, you've
probably blown your score anyway. What ended up doing was making a "bulged" servo cover out of
vacuum bagged carbon cloth (2 layers of 4.7 c/f cloth), so that I can continue to use the longer
arms without penalty.
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This photo shows how much material I removed from the wiper
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After deciding which way you want to go, shrink wrap or tape your servos, and drop them into the
wells to see where they should lie. The arm of the servo should line up with the horn, without
needing any bends in the pushrod. After installing the pushrods and checking for full and free
movement of the linkages, go ahead and glue your servos into place. If using shrink-wrap, make
sure to scuff up the plastic beforehand.
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This is about how you flap servo installation should look before it gets glued in,
with the servo pressed up close against the spar.
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This is an aileron servo loosely fitted in place. Note that there is no point in
ultimately using the bracket around a Volz WingMaxx servo, as you cannot get at
the lower setscrew to install it!
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Wing Final Assembly
In order to finish off the wing, the last step is to install the servo covers over the servo
wells, and over the upper flap linkages. Before the aileron bay is sealed, however, install the
wing on the fuselage, and balance the model laterally (side-to-side). If your wings are wildly
out of balance for some reason, add weight to the lighter tip. You can add weight easily under
the cover, or you can add proportionally less weight by drilling a small hole in the very tip of
the wing. My model was close enough that I didn't need to add any weight.
The easiest way to do install the covers is to simply use coloured tape, and this method has the
advantage of being easily serviceable in the field. A cleaner way to do this is to use a very
thin layer of silicone or Goop - thin enough that you're not likely to have to squeeze the tube
to get the Goop out. If you need access to the servos in the field, you can tape the covers back
on temporarily. Make sure to tape the covers on as the Goop cures, and any leakage can be rubbed
off with your finger after the Goop has cured fully.
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A finished stock flap servo cover...
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...and its counterpart on the upper wing surface.
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A finished aileron cover. I'm not sure why the red looks so dark here, but the
entire underside of the model is a uniform red colour.
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My home-made carbon flap covers.
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Fuselage Final Assembly
To finish off the fuselage, drill a small hole in the side (or bottom) of the fuselage in the
vicinity of the wing connector opening. Thread your antenna wire through this hole, and tape the
wire along the fuselage. The fuselage construction uses a lot of carbon fibre, which is a known
hazard to radio reception, so this is more of a preventative measure. You can try to do a range
check with your antenna inside if the thought of an external antenna bothers you, but I didn't
want to take the chance.
Install your receiver and battery, check that all the servos still work, and bolt the assembled
wing to the fuselage. Make sure to rescue your charging lead before it gets accidentally sealed
under the tape. Add weight to the nose in order to bring the model into longitudinal balance
(fore-and-aft, or "traditional balance"), and cover the battery and receiver openings with a
couple of wraps of tape (remember that the nosecone should be installed when you check the
balance). This way, if you happen to lose your nosecone, your battery won't follow suit.
Depending on the weight of the cells that you chose, you'll likely have to add a fair amount of
lead. I used scraps cut from a sheet of very malleable 1/8" roofing lead, which can be cut with
a pair of scissors.
That's it - following a range check at the field, you're ready to fly. If you haven't done so
already, be sure to cycle your onboard battery a couple of times before your first flight, and
check it periodically over the day with a loaded voltmeter.
Flying
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Calgary's Team Eraser! From left to right: Martin Pilko (F3B), Jozef Pilko
(Xtreme), Adam Till (F3B)
Photo Credit: Ryan van Beurden
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This is the fun part, and good for you to those who skipped here directly! I'm going to start by
saying right up front that I really like the way that this model flies - otherwise I wouldn't
have bought two. I'm firmly convinced that the Eraser represents a nice blend of strength,
flight performance and price, which goes to explain its growing popularity on the competition
circuit.
To give you an idea of where your author is coming from, I've owned 5 molded sailplanes so far
in my flying career: a Genesis, an Emerald, a Hera, and now two Erasers. In addition, I've flown
various Victories, Sapphires, Storks, and Edges for people in my club, and compete in club
contests against a field that is predominantly Artemis's at the moment (with the odd Icon or
Cobra thrown in to keep things interesting). As such, I'll try to draw comparisons between the
Eraser and some of the more popular models at our club, just so that everyone has a common frame
of reference.
The F3B version of the Eraser (the only one that I've flown) has absolutely no bad habits
whatsoever. It launches very well, and when balanced properly the model will not sn
Sep 09, 2004, 03:22 PM
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