Maxford USA Neptune Boatplane ARF Twin User manual

Copyright Maxford USA 2017 Page 1 of 12 S171201
GLOW/ELECTRIC 60-INCH WINGSPAN
N
NE EP PT TU UN NE E
B
BO OA AT T
P
PL LA AN NE E
A
AR RF F
T
TW WI IN N
INSTRUCTION MANUAL
This Neptune Boat Plane ARF Twin is the twin-engine version of our earlier single-engine Neptune.
The engine pods sit atop carbon-fiber tubes large enough for any wires you may need to install between
the engine pods and the fuselage. The supplied three-piece engine pods may be used for 40-class glow
engines, throttle servos and fuel tanks or for electric motors.
Both aileron servos are located safely inside the fuselage near the center of the wing. The wing rod is a
lightweight composite material. The nose compartment is the perfect location if you decide to add an
onboard glow-plug driver, for an electric power system’s ESCs and flight batteries, or to add any weight
to fine-tune the center of gravity. (The hatch arrives out-of-the-box covered
over. To access this compartment, simply cut the covering material around
the edges of the hatch.)
You could also enjoy this airplane on land with the optional landing-
gear and tail skid set as pictured at the right. Its color scheme is bright
and visible both in the air and on the water.
We invite you to enjoy the pride of ownership and the joy of flying this
high quality balsa, carbon-fiber, fiberglass and light-ply almost-ready-to-fly aircraft.
Table of Contents:
I. Specifications
...................................................
2 VI. Safety precautions & assembly tips
..................................
4
II. Parts list
.............................................................
2 VII. Limited warranty, liability waiver & return policy ...... 5
III. Special features
................................................
3 VIII. Photo instructions and assembly notes ......................... 6
IV. Important things customers must know
........
3 IX. Initial setup, adjustments and preflight checks ............. 11
V. Storage, field setup & preflight checks
........
3

Copyright Maxford USA 2017 Page 2 of 12 S171201
I. SPECIFICATIONS*
•Wingspan ..................................................................................................................................................................... 60 inches
•Length ........................................................................................................................................................................... 55 inches
•Wing area ................................................................................................................................................... 713 square inches
•ARF-only weight .................................................................................................................................... 6 pounds 6 ounces
•Flying weight ........................ Approx. 9 pounds 4 ounces (depending on your power and radio systems)
•Center of gravity (CG) ....................................................................... 3¾-inches to 4½-inches (approx. 102 mm)
back from the leading edge of the wing
•Radio system (not included) ................................... Minimum of 4 channels with four standard servos and
two mini servos with internal combustion engines,
or four standard servos if electric powered
•Recommended power .................. Twin 40-class 2C glow engines or equivalent-powered electric motor
systems (such as a pair of Maxford USA 35425 motors and 60A ESCs)
•Propeller .................................................................................. 10- to 11-inch diameter by 6- to 7-inch pitch or as
recommended by the maker of your power system
*(Dimensions and weights are approximate.)
II. PARTS LIST
1. Included items
•Precovered fuselage, wing panels, ailerons,
empennage with elevator and rudder.
•
Twin pods with cowls
for engines or motors.
•Two sets of 40-
class glow-engine
mounts.
*
•
Composite mounting
pedestals for engine
or motor mounting pods.
•
Wing-tip floats and tail-bracing struts.
•
CA hinges and precut slots.
•Composite wing joiner, control horns and
related hardware (except items normally
supplied with servos, engines and motors).
•
Aileron, rudder and elevator pushrods and
related linkages.
•
This illustrated instruction manual.
•
Fuel tanks, complete with metal tubing, clunks and fuel lines.*
*(NOTE: engine mounts and fuel tanks can be ordered with this boatplane at no charge.)
2. Items you must supply to complete this ARF
•Cyanoacrylate (CA) and epoxy adhesives and optional threadlock compound.
•Common household shop tools (screwdriver, pliers, etc.).
•Two 40-class 2-cycle glow engines or an equivalent electric power (EP) system.
•A pair of 10- or 11-inch dameter by 6- or 7-inch pitch propellers or as recommended by the maker of
your power system. (Propellers may both rotate in the same direction, as done during all test flights.)
•A four- (or more) channel radio system.
•Four standard servos (such as Hitec HS311) plus two mini servos (such as Hitec HS55) when using an
internal combustion engine, or four standard servos (Hitec HS311) if using an electric power system.
•Using either twin glow engines or an electric power system: two 10-inch extensions and a Y-harness
(depending on customer’s choice of engine or motor setup).
3. Optional items you may choose to add
•Servo extension safety clips.
•Landing-gear set for land-based flight operations.

Copyright Maxford USA 2017 Page 3 of 12 S171201
III. SPECIAL FEATURES
•Classic balsa and plywood construction.
•All required openings are predrilled and/or precut.
•Each aileron is separately operated by its own servo, giving customers the option of flaperons (if
permitted by customer’s radio system) and both aileron servos are safely located within the fuselage.
•The wing is easily removed for transport to and from the lake for storage.
•All major assemblies are preassembled and either precovered in Mylar or prepainted.
•Designed for glow engines, but may be easily converted for electric power.
•A supplied removable hatch gives customers a wide range of choices for using space inside the nose.
IV. IMPORTANT THINGS CUSTOMERS MUST KNOW BEFORE ASSEMBLING THIS ARF
Please read and follow all instructions carefully, even if you are an experienced builder. Any assembling,
testing or flying of this airplane is done entirely at your own risk. If you use a receiver battery to power
your radio system and you are using an electric power system, do not attempt to combine the output of
your radio’s battery with any battery-eliminator circuit.
V. STORAGE, FIELD SETUP & PREFLIGHT CHECKS
1. Check the Mylar covering material’s joints and surfaces. If necessary, carefully use an iron on medium
heat to secure the edges and to tighten any loosened areas. Recheck and retighten from time to time; be
careful to not apply too much heat as you secure edges or tighten the Mylar. If any trim becomes
loosened, press it down and/or apply clear tape. Never apply heat to any trim or plastic part.
2. Ensure the propellers are securely attached to your engines or motors and that they remain undamaged
and correctly balanced.
3. To remove the wing:
a. Remove the bolts securing the wing to the fuselage near the trailing edge of the wing.
b. Slide the wing a few inches toward the tail, disconnect the servo extensions and glow-plug driver
wires if used, or motor wires if using an electric power system, then lift the wing fully away from the
fuselage. If desired for transport or storage, the wing panels may also be separated and the wing rod
may also be removed. Be careful to retain the removed wing attachment bolts, any optional Maxford
USA servo-extension safety clips you may have installed, and the wing rod if removed from the wing
panels.
4. To reinstall the wing, reverse the above procedure:
a. If the wing panels were separated, slide the wing panels onto the wing rod. Position the wing above
the fuselage and reconnect the servo extensions, optional Maxford USA servo-extension safety clips
and any other optional wiring (or motor wires if using an electric power system).
b. Slide the wing forward and insert the carbon fiber ‘pins’ in the leading edge of the wing into the
former at the front of the wing saddle, then use the wing attachment bolts to firmly secure the wing
to the fuselage.
5. Preflight checks:
a. If any weight was added in the nose or tail to adjust the CG, ensure it remains secure.
b. Double-check the condition and secure attachment of your propellers and batteries.
c. Make certain all screws, clevises and other mechanical and electrical connections are secure.
(Do not attempt to fly with any damaged or frayed electrical or mechanical connection.)
d. Double-check all control directions and the amounts of control throws.
e. As with all radio-controlled model airplanes, this model must pass the radio range ground check
recommended by your radio’s manufacturer or you may not fly safely.
f. Make it a habit to set your transmitter’s throttle control safely to minimum before turning ON your
transmitter and receiver and starting your engines or connecting your Lipo flight batteries.
g. Setup and operate your radio-control and power systems according to their manufacturer’s
instructions and follow the guidelines offered by the Academy of Model Aeronautics, your local R/C
club, and concerned manufacturers, who all wish to help ensure your safe enjoyment of this hobby.

Copyright Maxford USA 2017 Page 4 of 12 S171201
VI. SAFETY PRECAUTIONS & ASSEMBLY TIPS
(IMPORTANT – READ THIS SECTION CAREFULLY BEFORE YOU BEGIN ASSEMBLY)
1. This product should not be considered a toy, but rather a sophisticated, working model that functions
much like a full-scale airplane. Because of its performance capabilities, this product, if not assembled and
operated correctly, could cause injury to you or to spectators and damage to property. Maxford USA
provides you with a high-quality, thoroughly tested model airplane kit and written/photo assembly
instructions. However, the quality and capabilities of your finished model airplane depend on how you
assemble it, and your safety depends on how you use and fly it. Any testing or flying of this model airplane
is done entirely at your own risk.
2. Assemble this model airplane according to these written/photo instructions. Do not alter or modify the
model beyond any assembly and/or power-system options covered in these instructions; doing so may
result in an unsafe or unworkable model. If the instructions differ from the photos, the written
instructions should be considered correct. If you have any question or concern about the instructions,
before you proceed with assembly of this product, contact your dealer or speak to a Maxford USA
customer service representative at 562-529-3988 (Monday through Friday, except national holidays,
9 AM to 5 PM Pacific Time).
3. While this kit has been flight-tested to meet or exceed our rigid performance and reliability standards in
normal use, if you elect to attempt any high-stress flying, such as racing or aerobatics, or if you install a
larger power system than specified, you (the buyer or user of this product) are solely responsible for
taking any and all necessary steps to reinforce the high-stress points and/or substitute hardware that is
more suitable for such increased stresses.
4. Throughout the lifetime of this model, use only the Maxford USA-recommended power system and a new
or well-maintained radio-control system with fully charged batteries.
5. Before you begin assembly of this model airplane, study the instructions and test-fit each part to ensure
you fully understand the instructions and that no parts are missing, damaged or unsatisfactory. Some
parts may differ slightly from those pictured in this manual. Due to temperature and/or humidity
differences between the factory, our warehouse and your home or workshop, there may be some need for
slight adjustments to these instructions and/or to some mounting surfaces to ensure proper installation
and alignment. We recommend you contact us before attempting any such adjustment.
6. It is your responsibility to install the receiver and to connect the R/C components in such a way that this
model passes all applicable safety/range tests and that the power system and controls operate correctly.
7. Recheck the operation of this model before every flight to ensure all equipment is still operating correctly
and that the model remains structurally sound; also check all electrical, control and structural connections.
Do not fly without replacing any that you find damaged or worn.
8. To help ensure the security of your servo connections, we recommend using optional
Maxford USA servo-extension safety clips as pictured at the right. (For information
about safety clips see http://www.maxfordusa.com/servoextensionsafetyclip.aspx.)
9. Assemble any included or optionally installed
EZ-Link connectors as shown at the right.
When applying threadlock compound, do NOT
glue the EZ-Link connector to the control arm
or mounting tab, and be careful to not let any
pushrods bind against any nearby surfaces.
10. Use your radio system or a servo tester to center your servos before installation. (You may be interested
to learn more about servo testers at http://www.maxfordusa.com/servo.aspx.)
11. String may be supplied to pull your servo’s leads and/or servo
extensions or other wiring through the wing or fuselage; however,
you may find it easier to use masking tape to temporarily attach
the end of the wire to a length of coat-hanger wire, then use the
wire to pull the lead through the airframe as pictured at the right.
12. After you determine each wood-screw’s location, drill a small guide
hole then apply thin CA adhesive to harden and strengthen the wood where the screws are to be installed.
Clamping bolt
Connector body
Control arm (or tab)
Washer
Mounting nut

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13. If Mylar hides a CA hinge’s slot, find and open the slot by carefully pressing with a fingernail or sharp
hobby knife.
14. If you are not an experienced ARF assembler or R/C pilot, we strongly urge you to get assistance from an
experienced R/C assembler and pilot.
15. Apply threadlock compound or CA adhesive to secure hardware from vibration.
16. Use epoxy to permanently attach, protect and reinforce critical airframe assemblies.
17. If you have concern about the security of any factory-fabrication procedure(s), you may apply extra epoxy
adhesive around the perimeter of such part(s) as a safety precaution.
18. Production details such as included hardware and/or Mylar, trim, or paint colors may vary.
19. After adjusting any clevis, secure the clevis to its threaded rod with
threadlock compound, epoxy, or CA adhesive.
For additional safety, you may hold the clevis closed by adding a
small piece of tubing (not supplied) as shown at the right.
(NOTE: if included with this model, clevises may be made of plastic or metal.)
20. Use crimp tubes to secure any included wing wires to anchor points and/or to attach pull-pull cables to
threaded rods and clevises as pictured at the right:
a. Slide the crimp tube onto the cable. Guide the
end of the cable through the anchor point or
hole in the end of the threaded rod.
b. Direct the end of the cable back into and all
the way through the crimp tube.
c. Adjust the cable’s tension, then use pliers to firmly squeeze several places along
the length of the crimp tube to securely crimp the tube onto the cable.
(NOTE: for your safety, after squeezing any crimp tube or adjusting any clevis
on its pushrod or threaded rod, apply epoxy or thin CA adhesive to permanently
secure each crimp tube or clevis in position. Be careful to not leave any strands
of wire poking out from the end of any crimp tube; exposed small steel strands
can be sharp enough to cut or abrade skin!)
21. This model may include plastic, fiberglass and/or carbon-fiber-reinforced parts. If you ever drill, grind or
sand any such part, wear safety goggles, a particle mask and rubber gloves to guard yourself from eye,
skin and respiratory-tract irritation; never blow into such a part as the dust may blow back into your face.
22. If you use an electric power system, read “IMPORTANT THINGS TO CONSIDER WHEN INSTALLING AND
OPERATING YOUR MODEL AIRPLANE’S ELECTRIC POWER SYSTEM” on the Maxford USA Website
at http://www.maxfordusa.com/brushlessmotorandcontroller.aspx.Also read any instructions that may
be included with your motors, electronic speed controls, batteries and charger. Failure to consider and
follow such instructions could result in permanent damage to your model airplane, its electric power
system, their surroundings, and possible bodily harm! If you crash this model airplane, carefully check for
any battery damage. Do NOT attempt to use or recharge a damaged battery.
VII. LIMITED WARRANTY, LIABILITY WAIVER & RETURN POLICY
Maxford USA guarantees this ARF kit to be free from defects in material and workmanship at the time of
purchase. Our products have been inspected in our factory and are checked again when shipped from our
warehouse. However, Maxford USA cannot directly control the materials you may use or your final
assembly process. Therefore, Maxford USA cannot in any way guarantee the performance of your finished
model airplane. Furthermore, in purchasing this product, you (the buyer or user of this product) exempt,
waive, and relieve Maxford USA from all current or future liability for any personal injury, property
damage, or wrongful death, and if you (the buyer or user of this product) are involved in any claim or suit,
you will not sue Maxford USA or any of its representatives.
If you do not fully accept the above liability and waiver, you may request a return-merchandise
authorization number (RMA#) as explained on the following page in item 2. If you think there is a missing,
damaged or unsatisfactory part, please read the following after-sales service and return policy and
instructions.

Copyright Maxford USA 2017 Page 6 of 12 S171201
After-sales service and return policy and instructions:
1. Inspect your order upon delivery for any missing, damaged or unsatisfactory part(s). If you believe
there is a problem, you must call us at 562-529-3988 (Monday through Friday except holidays,
between the hours of 9 AM and 5 PM Pacific time) before you begin assembly and within 10 days from
receipt of your purchase. During this telephone conversation, and with your support, we will
determine how to resolve your concern.
2. To request a return-merchandise authorization number (RMA#), call 562-529-3988 (Monday through
Friday except holidays, between the hours of 9 AM and 5 PM Pacific Time). If we elect to issue you an
RMA#, you must clearly mark this RMA# on the outside of the package. (No return or exchange will be
authorized after 10 days from the date of your receipt of the product; any package delivered to us
without a Maxford USA RMA# is subject to being returned to the sender, as received, with return
postage payable upon delivery.) Returned merchandise must be in its original condition as received
from Maxford USA, with no assembly or modification, in the product’s original packing materials,
complete with any included printed materials, manuals and accessories. Return shipping and
insurance charges must be prepaid by you, the buyer.
3. Returned merchandise that is accepted by Maxford USA for credit is subject to a 10% to 20%
restocking fee (the final amount will be determined by Maxford USA upon receipt and examination of
the returned merchandise).
Return address:
Maxford USA
15939 Illinois Avenue, #B-C
Paramount, CA 90723
IMPORTANT: Print the RMA# issued by Maxford USA
on your package near our address.
VIII. PHOTO INSTRUCTIONS AND ASSEMBLY NOTES
If you use glow engines, use the following instructions to install both engines:
Secure the servo-type connector of a throttle-servo extension to this
end of the string preinstalled in the wing panels.
NOTE: if using an optional onboard glow-plug driver, also secure its
wires to this string.
Use the string to pull the wires from the opening in the top of the wing
toward the root rib, then guide the wire(s) down and out through the
oval-shaped opening pictured below.
NOTE: if Mylar covers
any needed opening,
use a sharp hobby knife
to cut and remove the
Mylar near that
opening’s edges. We
recommend using a
Y-harness to simply
control both throttle
servos from your transmitter’s throttle channel; however, if you are a twin-engine pilot who likes to
setup your transmitter with differential steering, you may use a separate servo extension to connect
and control each throttle servo from its own transmitter channel.
With the notched end of the pedestal facing down, test-fit an engine-mounting pod onto a composite
mounting pedestal as pictured at the top of the following page.
Aileron-servo opening Oval-shaped opening

Copyright Maxford USA 2017 Page 7 of 12 S171201
Guide the throttle-servo extension from the opening in the
top of of the wing into the notched end of the pedestal and
bring out approx. 1- to 2-inches inside the pod.
Test-fit the notched end of the pedestal down into the round
opening in the top of of the wing panel – all the way to the
‘floor’ at the base of each of these round openings.
When satisfied with the position of the pedestal, throttle
extension, and any wires for your onboard glow-plug driver
if used, permanently secure the pedestal into the wing with
epoxy. (Do NOT glue the pod to the pedestal at this time.)
Decide how you will position your engine, then test-fit it to the front of the pod. NOTE: since a glow
engine that is mounted inverted or on its right side may have problems with hydro lock or fouling of
the glow plug, we advise positioning the engines with their cylinders pointing straight up.
Once you have decided how you will position your engines, test-fit engine mounts, engine, throttle
servo, throttle pushrod and cowl. Mark and drill the necessary holes in the pod, then mount the engine
to the firewall, install your throttle servo, and connect a throttle pushrod. Install the fuel tanks with
their vent and clunk lines as pictured at the right.
NOTE: to maximize the fuel tank’s usable capacity, install the vent line
as near as possible to the top-center of the tank, then install the fuel tank
inside the engine mounting pod. If using the the supplied almost
11-ounce fuel tanks, position them on their sides to fit inside each pod’s
fuel tank compartment; if necessary, trim wood around the tanks to
ensure each fuel tank fits fully down inside the allotted fuel tank space
and to ensure the pod’s hatches are able to fully close.
Test-fit to determine where the supplied fuel-tank’s clunk and pressure
lines need to be routed to your engine and muffler. Mark and drill the
necessary holes in the front of the pod. Connect the tank’s ‘clunk’ line to
the carburetor and the ‘vent’ line to the muffler.
Mount your propeller onto the engine, then position the pod on its pedestal so the pod’s lower surface
is approx. 1/4-inch above the wing. If necessary, gently twist the pod on its pedestal to give the
propeller blades zero-degrees of left/right offset relative to the leading edge of the wing.
When you are satisfied with the position and alignment of the pod, use epoxy to secure the pod to the
pedestal and to provide an extra measure of fuel-proofing. (NOTE: you may also wish to fuelproof and
waterproof at the pedestal’s round opening in the wing by filling any gap with epoxy, Shoe Goo or ZAP
GOO adhesive/sealant.)
Remove your propellers and perform a final test-fitting of the cowl, then cut or trim the cowl as
necessary to fit your engine, muffler, throttle linkage and the tank’s fuel and/or pressure lines.
Attach the pod to the cowl with your choice of screws, glue and/or tape.
If you use an electric power system, your Lipo flight-power battery and ESC may be able to fit
inside the pods. If so, follow the process for installing servo leads outlined in the preceding glow-engine
instructions, using the preinstalled strings to guide the servo-like lead from each ESC through the wing.
If your ESC and Lipo battery will not fit inside the pods, you may mount your battery and ESCs down
inside the fuselage.
NOTE: any electric power system needing longer wires between its Lipo flight battery and motor
should be given that additional length only by extending the three wires between the ESC and the
motor. NEVER lengthen the wires between your battery and ESC unless recommended or approved by
the maker of your motor and ESC.We recommend using a Y-harness to control both ESCs from your
transmitter’s throttle channel; however, if you are a twin-engine pilot who likes to setup your
transmitter with differential steering, if necessary, use separate servo extensions to connect and
control each ESC from its own transmitter channel.
Extension from
top of wing panel
(and glow-plug
driver’s wires
if used)

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To mount your battery and ESCs down inside the fuselage, install three additional wires between your
motors and ESCs using the same process described for installing throttle-servo leads. NOTE: the
benefit of mounting your batteries in the fuselage is that they may be connected in parallel, preventing
any unwanted yaw due to a weak battery. The
nose-compartment’s hatch may be large enough to
allow battery and ESC installation in the nose and
to recharge your batteries between flights.
To install your rudder and elevator servos,
test-fit and if necessary adjust the servo tray’s
openings to fit your servos, harden the servo tray’s
wood with thin CA adhesive where the screws will
be inserted, then mount your elevator and rudder
servos using the hardware provided with the
servos.
NOTE: some flying-boat owners like to reinforce their airplanes against long-term vibration, water and
hard landings by applying extra 30-minute epoxy to all accessible points of contact between the
fuselage formers and the fuselage’s bottom and sides; if you choose this option, now is a good time to
add some epoxy.
Using EZ-Link connectors or Z-bends, attach the rudder and elevator pushrods to their servos’ arms.
To install the ailerons, test-fit the
ailerons, CA hinges, and the projecting
ends of the metal aileron control rods.
Apply a small dab of epoxy to the
projecting end of one of the metal
aileron control rods and insert the
control rod into the predrilled hole in
its aileron.
Before the epoxy has time to thicken, insert the CA hinges into their precut openings in the aileron and
in the trailing edge of the wing panel. (Make sure the inner end of the aileron does not bind against the
cutout in its mating wing panel; also, leave enough clearance between the trailing edge of the wing
panel and its aileron so full UP and DOWN aileron travel is not restricted.)
Apply a few drops of thin CA to permanently secure each aileron hinge
into its wing panel and into its aileron as pictured at the right.
As the epoxy cures, hold the aileron control rod and aileron so the free
end of each aileron control rod (the end nearest the center of the wing)
is at or near a 90-degree angle to its aileron.
Attach the remaining aileron to the other wing panel as described above. Carefully hold this second
aileron while epoxy cures so its aileron control rod’s free end is at the same at or near 90-degree angle
as the first aileron.
If you wish to permanently join the left and right wing panels, cut away any excess Mylar
covering material from each wing panel’s root rib to maximize the gluing surfaces, then apply epoxy to
one end of the wing rod and insert the wing rod midway into the right wing panel. Apply epoxy to
the projecting end of the wing rod and
to both wing panel’s root ribs. Keeping
the wing rod centered, slide the root
ribs of the two wing panels together.
Carefully line up the leading and
trailing edges of the wing panels.
NOTE: permanently joining the wing panels is optional. Do NOT attach the tip floats at this time.
Carbon-fiber ‘pin’
Wing rod
Aileron servo
Oval opening
Tip float

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Apply masking tape to hold both wing panel’s leading and trailing edges in alignment. Test-fit the two
carbon-fiber ‘pins’ into the leading edge of the wing to their openings in the former at the front of the
wing saddle. Secure the pins with 5-minute epoxy, then set the wing assembly aside to allow the epoxy
at least 3 hours to cure fully.
To install your aileron servos, connect your aileron servos to a servo tester or to a Y-harness and
the Y-harness to your radio’s aileron channel, power ON the servo tester or radio, and ‘center’ the
aileron servos. Disconnect the aileron servos and set aside your servo tester or radio system.
NOTE: if you use a Y-harness, we recommend using optional
servo extension safety clips at these connections as pictured at
the right.
Test-fit and, if necessary, adjust the aileron servos’
openings to fit your aileron servos. Guide the
servos’ leads through the precut oval-shaped
openings in the wing. Position each aileron servo in
its opening and use your servo manufacturer’s
hardware to mount each servo as pictured at the
right.
Attach an EZ-Link connector to each of the servo
arms. Secure the quick-connectors onto the servo arms with a dab of thick
CA adhesive on the exposed threads at the bottom of each nut. Use the
hardware supplied with your servos to attach the aileron servo arms to the aileron servos.
Twist a supplied nylon horn bracket onto the threads at the the end of each aileron control rod.
Position and temporarily hold
the ailerons in a ‘neutral’
position by applying a small
piece of masking tape between
each aileron and the adjacent
trailing edge of its wing.
Twist a clevis onto one end of
an aileron pushrod.
Insert the pushrod’s other end into the opening on the EZ-Link connector, then attach each
aileron pushrod’s clevis to its nylon horn bracket as pictured above.
Use the EZ-Link connectors to secure the aileron pushrods to the servo’s output arm. Make a small
bend in the pushrods to minimize the possibility of binding, then cut off and discard the excess length
from each aileron pushrod and remove the masking tape.
NOTE: some flying-boat fans choose to add some aileron differential by setting up their computer
radio with separate servos and channels for each aileron; others choose to use a Y-harness and set up
each aileron control rod with some forward-offset.
Attach the tip floats to the bottom of the wing near to and parallel with the tip ribs.
NOTE: adhesive-backed hook-and-loop materials are generally most popular, but some flying-boat
fans report they prefer to permanently attach their tip floats with double-sided tape, epoxy, Shoe Goo
or ZAP GOO adhesive/sealant.
To install the tail section, firmly grasp the elevator’s pushrod housing at its opening in the top-aft
portion of the fuselage to gently stretch it through the fuselage, then route it into and through the base
of the vertical stabilizer. Test-fit the vertical stabilizer (wide end down) onto the top-aft portion of the
fuselage, being careful to leave enough of the elevator’s pushrod and housing projecting above the top
of the vertical stabilizer for connection to the elevator.
Use the tip of a hot soldering iron to burn (or carefully cut) and remove covering material as necessary
to obtain good wood-to-wood gluing surfaces between the vertical stabilizer and its mounting surface
at the top-aft portion of the fuselage.

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With the elevator’s pushrod housing ‘stretched’ through the fuselage, confirm the aft-end of the
elevator’s pushrod will be able to reach to where the elevator and its control horn must be attached
behind the top of the vertical stabilizer. Using epoxy, permanently attach the vertical stabilizer to the
top-aft portion of the fuselage. Before the vertical stabilizer’s epoxy has noticeably thickened, make
certain the vertical stabilizer is aligned along the length of the fuselage and vertically to the bottom of
the fuselage and wing-saddle, then apply masking tape to securely hold the vertical stabilizer in
position. Set the fuselage and vertical stabilizer assembly aside and allow the epoxy to cure fully.
Test-fit the horizontal stabilizer to the top of the vertical stabilizer. Use the tip of a hot soldering iron
to burn (or carefully cut) and remove covering material as necessary to obtain good wood-to-wood
gluing surfaces between the top of the vertical stabilizer and the bottom-center of the horizontal
stabilizer.
Using epoxy, permanently attach the horizontal stabilizer to the top of the vertical stabilizer. Before the
horizontal stabilizer’s epoxy has noticeably thickened, make certain the horizontal stabilizer is aligned
parallel to the bottom of the fuselage and to the wing-saddle, then apply masking tape to securely hold
the vertical stabilizer in position. Set the fuselage with its vertical stabilizer and horizontal stabilizer
aside and allow the epoxy to cure fully.
Using the bottom of the supplied elevator pushrod fairing
as your guide, use the tip of a hot soldering iron to burn (or
carefully cut) and remove enough covering material from the
bottom of the elevator pushrod fairing and the top-center of
the horizontal stabilizer to obtain good wood-to-wood gluing
surfaces.
Slide the elevator pushrod fairing over the elevator pushrod’s
housing and use epoxy to permanently attach the elevator
pushrod fairing to the top of the horizontal stabilizer.
Attach the elevator to the horizontal stabilizer using the
supplied CA hinges, the precut hinge slots, and CA adhesive.
Using a Z-bend in the end of the elevator’s pushrod, attach the
elevator’s control horn to its pushrod, then attach the control
horn to the elevator in line with and directly behind the
elevator pushrod fairing and elevator pushrod.
Use epoxy to permanently secure the small triangular-
shaped fin to the bottom of the fuselage in line with the
aft-end of the vertical fin. (NOTE: some customers choose
not to install this small fin to better enjoy ‘drifting’ through
turns on the water.)
If necessary, cut the covering material to open the rudder’s
precut CA hinge slots. Then permanently attach the rudder
to the vertical stabilizer, fuselage and bottom fin using CA
hinges and CA adhesive.
Using a Z-bend in the end of the rudder’s pushrod, attach the
rudder’s control horn to its pushrod, then attach the control
horn to the rudder in line with and directly behind where the
rudder pushrod exits the fuselage.
Test-fit then attach one end of the tail-section struts to the
sides of the fuselage. Or, if you prefer, attach them to each side
of the vertical stabilizer as pictured on page 1 of this manual.
Attach the upper ends of the tail-section struts to the wooden
‘hardpoints’ in the horizontal stabilizer as shown at the right.
Triangular-
shaped fin
Tail-
section
strut
Horizontal
stab.
Vertical
stab.

Copyright Maxford USA 2017 Page 11 of 12 S171201
Installing the optional landing gear and tail skid set:
To fly this airplane from the land, test-fit the landing gear at approx.
5-inches in front of the step of bottom, then mark where to drill holes
for the bolts and blind nuts included with the landing gear kit.
Glue some
scrap ply-
wood (not
included)
inside the
bottom of
the fuselage
where the bolt holes will be drilled. After the glue is fully cured, drill the holes and install the blind nuts
as pictured above. Attach and reinforce the landing gear using the bolts, supplied steel cables and crimp
tubes as pictured at the right.
Apply threadlock compound or
CA adhesive to ensure the
wheels remain securely
attached to the landing gear
strut. Attach the tail skid to the
bottom of the the small
triangular-shaped fin at the bottom of the fuselage using glue and/or screws as pictured above.
(NOTE: to maintain optimal water-based operation, remove landing gear bolts add rubber washers,
then screw bolts back. Using a steerable tail wheel is not recommended.)
To install your radio receiver and perform final setup, connect the aileron, elevator and
rudder servos, glow-plug wires if used, or ESC-to-motor wires if used, and your throttle servos or
ESCs to your radio receiver.
Align and slide the wing’s leading-edge pins into their corresponding holes in the fuselage, then snugly
attach (but do not over tighten) the wing-retaining screws in the blind nuts in their wing-saddle
mounting blocks. NOTE: some flying boat fans like to create an improved water seal at the wing
saddle by adding weather stripping such as M-D Building Products’ white ‘Rubber Weatherseal,’
available at hardware stores.
Setup your radio as instructed by the maker of your radio system, carefully making any necessary
adjustments to servo directions and control throws.
Setup your power system as instructed by the maker of your engines or motors.
NOTE: you may install pieces of triangular-shaped material as strakes. If you prefer to not enjoy
‘drifting’ on the water during high-speed turns, you may use epoxy to attach a strake at the center of
the fuselage immediately in front of the step and/or immediately behind the step.
Use the preinstalled rare-earth magnets to install the pod’s hatches, and add any optional (not
included) decorative markings and/or trim stickers you may desire.
CONGRATULATIONS! ASSEMBLY IS FINISHED!
IX. INITIAL SETUP, ADJUSTMENTS AND PREFLIGHT CHECKS
1. The Neptune’s center of gravity (CG) must fall within 3¾-inches to 4½-inches (approx. 102 mm) back
from the leading edge of the wing. If necessary, move batteries and/or add weight to the nose or tail to
ensure the CG is correct.
2. Check the heat-shrink covering material’s joints and surfaces; if necessary, carefully use a dedicated
covering-material iron to secure the edges and to tighten any loosened areas. Recheck and retighten
from time to time, being especially careful to keep the edges well sealed to prevent water leakage.
Approx. 5 inches
Step
N
o
s
e

Copyright Maxford USA 2017 Page 12 of 12 S171201
3. Check/adjust servo centering, direction and end-point adjustments. If you fly mode 2, when you pull the
right stick toward you, the elevator should deflect upwards; push the right stick to the right and the right
aileron should deflect upwards and the left aileron should deflect downwards; push the left stick left and
the rudder should deflect to the left as viewed from the rear of the fuselage. Review your radio’s
instruction manual if you require assistance with any radio-related installation or servo-adjustment
questions.
4. Recommended initial deflections: Initial control surface throws for your first flights:
Low rates
Ailerons .......................................... +20 degrees (+3/8 inch) .............................. +35 degrees (+1/2 inch)
Elevator .......................................... +25 degrees (+1/2 inch) .............................. +30 degrees (+5/8 inch)
Rudder ............................................ +25 degrees (+1 3/4 inches) ...................... +30 degrees (+2 1/8 inches)
High rates
(NOTE: if you mix rudder with your ailerons, begin with an aileron-to-rudder mix of 35 to 45%.)
5. Double-check the security of the engine/motor pods and make certain that all screws, clevises and other
connections throughout the airframe are secure.
6. Double-check the control directions of the throttle, ailerons, elevator and rudder.
7. As with all radio-controlled model airplanes, this model must pass the radio range ground check
recommended by your radio’s manufacturer, or you may not safely fly.
8. Get into the habit of moving your transmitter’s throttle to minimum before turning ON your radio system,
and carefully break-in and operate your engine or electric power system according to the manufacturer’s
instructions.
Reminder …
•This product is NOT a toy.
•The quality and capabilities of your finished model airplane depend on how you assemble it.
•Your safety depends on how you use and fly it.
•Any testing, flying and use of this model airplane is done entirely at your own risk.
PLEASE ENJOY YOUR HOBBY AND FLY SAFELY!
Manufactured by:
Maxford USA RC Model Mfg, Inc.
Distributed by:
Maxford USA RC Model Distribution, Inc.
15939 Illinois Avenue, #B-C Telephone (voice) ......................... [phone]
Paramount, CA 90723 Website ............................. www.maxfordusa.com
Order replacement parts, optional accessories, servos, brushless motors,
electronic speed controls, and a wide variety of other high-quality
RC hobby items online at www.maxfordusa.com.