Mountain Models ParkJet Manual

ParkJet Builder’s

Manual

Thank you for purchasing the ParkJet. The ParkJet is a profile ducted fan airplane that can be flown in a

larger park. The ParkJet was initially designed by Scott Stoops and modified for laser kitting by

Mountain Models.

March 19, 2003

Last revised April 13, 2003

www.mountainmodels.com

(719) 592-1387

(719) 528-6125 fax

Specifications:

Wingspan: 33.75”

Wing Area: 200 sq. in.

Weight with 8x600AE batteries: 17 ounces

Required Equipment

To build:

! Xacto with #11 blades

! Thin and Thick CA – Cyanoacrylate glue (Super Glue)

! White Glue

! Sanding block with 200 grit sandpaper

! Smooth, flat work table

! Wax paper to protect plans

! Needle nose pliers

! Wire cutters

! Hobby Iron for applying covering – also called a sealing iron

To fly:

! Three channel radio (The Berg5*dsp is highly recommended, second is the GWS-R4P micro

receiver. Two micro servos: Hitec HS50s, HS55s, or GWS Pico servos recommended

! GWS EDF-75

! Motor Speed Control: 15 amp rated

! Battery pack: 8 cell 600AE or Kan 950.

Parts List

1 ea – 1/8” laser cut balsa sheet

2 ea – 3/32” laser cut balsa sheet

1 ea – 1/16” laser cut balsa rib sheet

2 ea – 1/64” laser cut plywood sheet

1 ea – 1/16” laser cut plywood sheet

1 ea – 1/8"round x 19” hard wood leading edge

1 ea – 1/8"round x 17” hard wood leading edge

2 ea – .032” music wire pushrods

1 ea – 8” plastic pushrod tube

1 ea – .200” x 14.5” carbon fiber tube

1 ea – .200” x 6” carbon fiber tube

1 ea – 6” Heat shrink tubing for pushrods

1 ea – Velcro strip for mounting the battery

1 ea – 1/8” x 1/2” long aluminum tube elevator bushing

2 ea – 3/32” x 2” music wire elevator attachment rods

2 ea – micro pushrod adjusters

1 ea – Roll of covering material

Notes and Hints

• The ParkJet has been designed with weight in mind. Parts and reinforcements were chosen so as

to keep the plane light. Special care must be taken when making glue joints to ensure that the

ParkJet can survive rough landings.

• There is very little that is critical when building the ParkJet. The only thing that requires special

attention is to make sure the wings are not twisted. If the wings are straight, the ParkJet should fly

hands-off without any trim.

• Heat shrink can be heated with a soldering iron or, if you dare, with a lighter. Pay close attention

to what is near the heat shrink when you are heating it.

• You really need the sealing iron (Also called a hobby iron). You will find putting on the covering

so much easier. They are reasonably inexpensive and invaluable.

• The parts are held into the sheets by retaining gaps. When you break a part loose, you should

lightly sand the nubs left by the gaps down.

Assembling the Tail

1. Lay down some wax paper on a flat work area.

2. Remove the tail parts from the 3/32” balsa sheets.

3. Carefully holding the pieces together so that you don’t glue yourself to the model, flow some thin

CA into the joints.

4. Glue the 1/64” plywood doublers to the rudder and elevator halves using thin CA

5. Flow some thin CA into the elevator joiner rod openings to harden the elevator in that area.

6. Sand the tail surfaces smooth and round the edges.

7. Cover the tail surfaces with the supplied Doculam or a lightweight covering such as Solite. See

the wing covering section for covering tips.

Wing Assembly

Note: It is very easy to make two wings of one side, i.e., two right wings. This is a bad thing.

! Tape a sheet of wax paper over the plans to protect the plans and to prevent glue from sticking to

them.

! Remove the two vertical spars from the 1/16” balsa sheet. You will note that they fit together with

a V joint to form the center wing. Be very careful to make a left and a right wing. It doesn’t

matter which vertical spar forms the left or right side.

! Slide the ribs into the vertical spars. The largest rib goes next to the V. Do not glue yet.

! The four spar caps are identical except for the Vs in the center. Take special care to use two of the

same type (V pointing out) on the same side of the wing.

! Position the upper and lower spar caps so that they line up with the notches in the ribs. Ensure

that the end of the spar with the V shape is towards the center of the wing, that everything is tight,

that the ribs fit fully into the spars and that the vertical spar is touching the cap spars. Once

everything is aligned, flow some thin CA into all the joints.

! Position the 1/8” trailing edge so that it is flush with the bottom of the ribs and that it is pushed as

far forward as possible. The end that is shaped like a V goes towards the center of the wing. Glue

with thin CA.

! We will now glue the two wing halves together. Position the spars and the trailing edge carefully

together and glue with thin CA.

! Glue the two 1/8” rib reinforcements to the inside of the outermost ribs as shown.

! Measure and cut the 1/8” hardwood leading edge dowel so that it is flush with the outer edge of

the outermost rib and only goes halfway through the gap created between the innermost ribs. Glue

in place with thin CA. Sand the front of the dowels where they join together. You will have a

small length of dowel left over. Hang on to it. It will be used as a finger rest for throwing the

plane.

! Glue the 1/64” plywood strips to the centermost ribs. Take special care to ensure that the

plywood is well bonded to the spars.

! Verify that the top and bottom spars are glued to the vertical spar completely and that there are no

gaps in the glue joints.

! Lightly sand the wing to remove any bumps and glue

Covering the Wing

The ParkJet kit comes with a clear, paintable covering called Doculam which is actually a laminating

film. The frosted side has a heat activated adhesive. Unlike most coverings, Doculam does not have a

backing sheet. Compared to SoLite (Solarfilm Lite – another excellent choice for the ParkJet),

Doculam is stronger, heavier, and needs a higher temperature to adhere and to shrink. It should also

be painted which will add weight. We will cover one half of the wing at a time.

! Lay the wing on the table and cut a piece of covering so that it starts at the inner rib of the opposite

wing and overlaps the wingtip and the leading and trailing edges by ~2”.

! Tack one corner of the trailing edge then the other corner of the trailing edge with a covering iron,

ensuring that the covering is tight.

! Pull the covering tight and straight then tack the two corners of the leading edge.

! Tack down the entire leading and trailing edge. Wrap the covering around the back of the trailing

edge and tack it down across the back of the trailing edge.

! Pull the covering tight across the high point of the wingtip and tack.

! Tack down the covering to the inner rib.

! Trim the covering so that there is a 1/8”- 1/4” overlap around the inner rib. Tack down the overlap

to prevent the covering from pulling away when you shrink it.

! Cover the other side. This side should overlap the other sides covering by at least ¼” to ensure a

good bond.

! Once both sides of the wing are covered, shrink the covering with a covering iron or heat gun. If

you are using the supplied clear covering, you will need a fair amount of heat to shrink the

covering but too much heat will result in a hole.

! You can paint the supplied Doculam covering with Testors Pactra Racing Finish car body paint,

which has been specifically designed for lexan car bodies. Krylon spray paint will also work.

Fuselage Assembly

! Lay the 3/32” balsa fuselage on a flat surface.

! Lightly spread white glue completely over one side of the fuselage and position one of the 1/64”

plywood fuselage sides over the balsa fuselage. To help with alignment, you may wish to insert a

short section of 1/8” dowel in the 1/8” hole in the bottom rear of the fuselage.

! Once the 1/64” ply is properly aligned, weigh it down with something like a large book till the

glue sets up. You may wish to protect your weight with a sheet of wax paper.

! Glue the other 1/64” fuselage side as you did the first side.

! There are three 1/64” ply reinforcement pieces per side. Glue them in place with thin CA.

! Lightly sand the longer carbon fiber rod and glue it to the top of the fuselage with thick CA.

! Glue the shorter carbon fiber rod to the bottom of the fuselage.

! Glue the vertical stabilizer to the end of the carbon fiber rod as shown.

! Glue the short remaining piece of 1/8” dowel in the hole in the rear of the fuselage as a finger rest

for when you throw the plane.

! Glue the 1/16” plywood battery mount to the bottom of the battery opening. Attach some Velcro

to the mount.

Final Assembly

! Carefully measure the exact center of the wing and remove a 3/32” strip of covering from the

center section of the wing. This is to ensure a good glue bond between the wing and the fuselage.

! Slide the wing into the fuselage. You may need to lightly sand the fuselage wing cutout to get the

wing to fit. Glue in place with thin CA.

! Sand a 30-degree bevel in the leading edge of the ailerons.

! Sand the entire ailerons lightly and paint or cover them.

! Attach the ailerons to the wing with a 1” wide strip of packing tape. Ensure that the ailerons move

freely.

! Center the short 1/8” aluminum tube in the vertical stabilizer. Slide one of the 2” x 3/32” metal

rods into the tube to help with alignment. Ensure it is square to the vertical stabilizer. Remove the

metal rod and glue the tube with thin CA.

! Slide the two 2” x 3/32” metal rods into one of the elevator halves.

! Slide the forward rod through the aluminum tube and the rear through the opening in the vertical

stabilizer then press on the other elevator half.

! Glue the long control horn into the elevator. The elevator horn faces down.

! Glue the two aileron control horns to the ailerons, facing down.

! Install the servo control horns on the servos. The aileron servo needs a double sided horn and the

elevator servo needs a single horn. The aileron servo needs two micro control horn adjusters

mounted towards the servo. It is easiest to install them now. See the photo further down showing

the aileron servo.

! Insert two servos into the servo opening by wrapping the servos in tape, pressing them into the

openings the CAREFULLY gluing them in place with thick CA.

! Tape the pushrod tube to the top of the top carbon fiber tube such that the front of the pushrod

tube is even with the back of the fuselage. Tape the tube at the front and right in front of the

vertical stabilizer.

! Bend a Z bend into the 1/32” music wire. Slide the other end of the wire into the front opening of

the pushrod tube.

! Cut a piece of 1/32” music wire 2.5” long. Make a 90 degree bend 1/4" from one end.

! Slip a piece of 3/4” long heat shrink tubing over the tail end of the elevator pushrod. Slide the

long end of the L bend wire into the heat shrink and place the short end into the outermost hole of

the horn. Flip the end of the pushrod over the horn then carefully shrink the heat shrink tubing.

! Adjust the length of the push rods by sliding the L bend wire in or out of the pushrod until the

elevator is level with the carbon fiber tube. Carefully secure the wires in position with a drop of

thin CA into the heatshrink. Ensure that the locking arm is in place – opposite the L bend.

! Cut two pieces of 1/32 music wire 2 3/4” long. Make a Z bend in one end and put the Z bend in

the outermost hole of the aileron horn. Put the other end in the aileron servo micro adjuster.

! Assemble the two fan mounts. Glue with thin CA.

! Install the battery you intend to use centered in the battery holder.

! Place one fan mount on the top of the fan and one on the bottom. Slide the fan between the two

carbon rods and slide it forwards and back until the plane balances at the correct CG which is 3 ¼”

from the trailing edge of the wing, not including the ailerons.

! Once the fan is positioned properly, wrap some tape around the entire fan assembly to tape the fan

in place. I use ½” clear tape.

! Ducted fans work better if you add ducting. You can make extenders with Styrofoam coffee cups,

etc but I have not tried this myself.

! Install receiver and speed control. The receiver is velcroed to the side of the fuselage and the

speed controller is light enough to be suspended by its wires. Wire the speed control and servos to

the receiver.

! Adjust your throws so that the elevator has a total movement of ½” measured from the rear next to

the vertical stabilizer and the ailerons have a total throw of ½”.

Flying

Before you fly the ParkJet, check that the control surfaces move the correct directions. Always check the

directions while you are behind the airplane. I highly recommend that you check the control surfaces

before EVERY takeoff.

The center of gravity (CG) is 3 ¼” from the trailing edge of the wing, not including the ailerons. With the

battery installed, place a finger on each side of the fuselage just at the rear of the spar by the middle rib

(the middle of each wing) and lift the ParkJet. It should balance there. If not, adjust the battery forward

or backwards till the CG is correct.

For your first flight, be patient and wait for a calm day. Choose a large field where you have a smooth

area to land. You will need to throw the ParkJet fairly hard to get it to flying speeds.

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