P15462
Manufacturing Process
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Foam Cutter:
1. Generating Point .dat Files
a. If you have a series of x,y points in excel (as we often did) Make sure that all the points
are 5 characters long (negative signs count as a character). Save as a space delimited
text file with 5 spaces between the columns.
b. Change your computer settings so that file extensions are not hidden and change the
file extension from .txt to .dat
2. Converting .dat file to .dxf to g-code
a. Open up foam works and generate a .dxf file from your .dat file.
b. Generate G-code and upload your .dxf files. For a taper you will upload two different
files, otherwise you will upload the same file twice.
c. Saving your g-code will save two files. The .tap file is the one used while running the
foam cutter.
3. Practice cut
a. Practice cuts expose unsuspecting errors in your points or dimensions. The following
details specific adjustments we have had to make in our processes (see cut
wings/tail/fuselage).
4. Cut Wings
a. The wing is broken into three sections. Root, Middle, Tip.
b. Root: The root has no taper and is only 3.5 inches long. This part is made so that the
glued plane isn’t also the shear plane at the edge of the fuselage structure. The root
cord length is 10 inches however after measuring a practice cut to find the true length
to be approximately 9.5 inches we have changed to cutting a 10.5 inch cord for a true 10
inch length. The amperage used is around 2.62 amps and the feed rate was 6.
i. To begin the cut the wire is zeroed half an inch past the reference wire mark.
ii. [Note: for all purposes the reference origin for each cut is the right edge of the
cutting platform and the front wire burn mark on the platform.]
iii. Make this point your X zero. Raise each wire mount to be 4.375 inches from the
red base of the tower. This is the Y zero.
iv. Back the wire out horizontally to place your foam, heat the wire, and load your
g-code.
v. Once the wire is heated, click go to zero and the wire will cut into half an inch of
the foam.
vi. Run the g code. Note your airfoil will be cut upside down.
c. Middle: The middle section of the wire is the first section from the root with a taper.
The cutting process will be much like that of the root but with a tapered zero starting
point. This is due to the fact that the foam cutter starts at the trailing edge and our
particular plane has a tapered trailing edge and an even leading edge. The length of this
section is 12.25 inches.
i. The new zero has the right tower only half an inch past the burn mark but the
left tower (t2) must be 3.42 inches deep from the wire burn.
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Manufacturing Process
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ii. Back out the wire once it has been re- zeroed and prep your station much like
you did in the root cut.
iii. For this cut we used 2.75 amps and we increased the feed rate as the cut was
finishing near the trailing edge to 7.9, this is to avoid burning through the very
thin trailing edge of the wing.
d. Tip: The tip of the plane concludes the taper and follows all the instructions that the
Middle section does. The only difference is that for this case the second tower needs to
be 3.94 inches deep. The length of this section is 12.25 inches.
e. Cutting the spar hole: -> currently an unrefined process.
5. Cut Tail
a. The tail cut is much simpler than the wing section because it is not tapered. However,
since the tail is 26 inches long and the foam cutter cannot cut anything longer than 18 x
18 inches the cut will be in two parts. Follow the initial zeroing process like the root cut
of the wing. After the tail has been cut and glued together, cut a notch in the center for
the boom to meet the tail spar.
b. The most challenging part of the rudder is generating the points so that the profile is
half an airfoil. After this step the cut is straightforward. Note this piece does not need a
hole cut into it via foam cutter, the hole will be cut using a drill.
6. Cut Control Surfaces
a. Cut control surfaces with an exact-o-knife. Trace the profile beforehand. Note, for our
plane the control surfaces were cut perpendicular to the taper because the taper is on
the trailing edge.
7. Cut fuselage
a. It was discovered that the foam cutting software cuts circles towards the user rather
than away, like airfoils. As a result the zero point had to be much further into working
plane. A similar half inch zero into the foam was used. The foam is provided in sheets of
2 inch thick foam. Since the fuselage is 4 inches in diameter the foam is made from
gluing two sections together and letting it cure before the cut.
b. Note: Because the zero point is in the foam, after the cut the user must manually back
out the wire from the material.
c. The rounded end caps were generated by cutting a semicircle and rotating the part
every 45 degrees to make a total of four cuts. The material between the cuts is sanded
down to make a flusher surface.
d. The fuselage is cut into three sections, nose, mid, and tail which have the lengths 5
inches, 6 inches, and 5 inches respectively. The middle section will be hollowed out by
cutting a smaller circle inside. This will be the housing for the electronics.
e. Cut a section of foam out in the nose to house the battery, this is to add weight to the
nose and keep the center of gravity near the aerodynamic center.
f. After all the fuselage cuts are made, glue back the three sections of the fuselage.
P15462
Manufacturing Process
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Manufacture Electronic Chassis:
1. Solder wire extension to motor. The stock wires off the motor are quite short. Ours were 18 awg
wires and Dr. Gomes had stock wire to extend another foot.
2. Solder male battery connection to the speed controller. Buying parts separately is cheaper
however it makes the connections on the parts nonexistent to be more universal. We purchased
the male version of the connector the battery required and soldered it in place. That being said
the speed controller had female banana plugs for the motor mount.
3. Solder male banana plugs to end of wire extensions of the motor. Be careful when sizing the
banana plugs, a label on the speed controller led us to purchase the wrong sized motor, we
suggest measuring the inner diameter of the female connector directly.
4. Thread motor shaft for prop components. The gentlemen in the machine shop are more likely
than not to be better skilled for this job. The trick is holding the motor in proper place to tap the
shaft. Since we pulled the propeller from the bought plane we wanted the tread pitch and
diameter to match that motor.
5. Attach prop components. All the prop components were pulled from the purchased plane and
so assembly was easy. However our motor was oriented differently than the old motor and as a
result we had to use two nuts to pinch the prop in place (if left un-pinched the prop would be
tightened against the fixed surface of the motor and would not rotate).
6. The servos are shipped pre wired. See photo for proper wiring connections.
7. Check to see all of your electronics communicate properly with the controller. Each time the
controller is turned on and the battery is plugged in to the electronics the speed controller must
be “armed”. This is done by adjusting the throttle in a specific order so that the throttle control
has the same range and the speed controller. The speed controller should come with an
instruction manual to guide the arming process. However, the purchased plane did not come
with such instructions and only after we searched the internet forums for the part number were
we able to properly arm the system.
Drill and Cut Frame:
1. Cut carbon fiber tubes to model length using a dremel tool
2. Drill a hole through the rod near the tips for end clips.
3. Fuse the wing spars by gluing a drill bit blank halfway into one of the wing spars. After cure, glue
the surface of the exposed blank and place that into the other spar. This has effectively
extended the length of the wing spar.
Make Control Surfaces and Push Rods:
1. Cut piano wire into desired lengths.
2. Straighten wire:
a. Drill a hole slightly larger than the diameter of the piano wire into a wooden block that
can be held in one hand.
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Manufacturing Process
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b. Put one end of the piano wire into a drill chuck. Stick the rest of the wire through the
hole in the wooden block until the drill is touching the wood.
c. Pull the trigger and as the wire spins draw the wire through the hole at an angle of
about 30-45 degrees. Make the angle more exaggerated the father the drill is from the
block of wood. Move quickly to get better results.
3. Fix the push rods to the servo motors and control surface horns.