Mountain Models DL50 DISCUS LAUNCH GLIDER User manual

DL50 Discus Launch Glider

DL50 Specifications

Length: 39 in. (99 cm.)

Wingspan: 50in. (127 cm.)

Wing Area: 275in2(1774 cm2)

Weight: 8oz. (227 g.)

Revision History

Date Revision Notes/Comments

6/12/2004 Document initial creation.

8/18/2004 Changes to instructions

9/9/2004 Update to version 2

Thank you for purchasing the DL50. This plane is an elevator/rudder discus launch glider,

designed for the intermediate pilot who wants a strong, easy to build and fly glider. The DL50

was a joint design effort between Doug and Matthew Binder.

Sincerely, Mountain Models

Doug Binder 465 D Street

[email protected] P.O. Box 762

www.mountainmodels.com Penrose, CO 81240

Phone: 719.372.6727

Created by Ross Design Group for exclusive use by Mountain Models.

Mountain Models DL50

Before You Begin

Before you begin building your DL50 make sure you read and understand all of the

instructions thoroughly.

Additionally, you will need to have the following items. Check to make sure that all of your

parts are there and in good shape, and review a couple quick building tips to make this

whole process go quicker and easier.

What You Will Need

• Smooth and flat work surface

• Wax paper

• Thin Cyanoacrylate (CA) glue

• Foam Safe Glue – 5 minute epoxy or foam safe medium CA

• Minwax water based Polycrylic

• Hobby knife with #11 blades

• Needle nose pliers

• Wire cutters

• Sanding block with 200 grit sandpaper

• 2 channel radio

• 2 channel receiver

• 2 micro servos

• 4 cell 350 mAH NiMH battery pack

Parts List

Number

in Kit Description of Part

Wire and Carbon Rods

1 26.5” tapered carbon boom

4 .060” carbon spars

2 .025” music wire pushrods

2 Pushrod tubes

Foam, etc

2 Foam wing sections

2 .7 oz Fiberglass

1 1.4 oz Fiberglass

Bagged Parts

1 6” heat shrink tubing

1 6” Velcro strip for mounting the battery and receiver

1 1/16” x 3/8” x 2” Launch Peg

1 12” Kevlar tow

1 1/2" x 64” carbon tape

4 8-32 wing hold down screw

1 8-32 self tapping screw

Mountain Models DL50 3

General Building Tips

• Balsa is a lightweight and fragile wood, so you do need to be careful with it;

however, you will also need to use a little bit of force to make everything fit

properly, so don’t be too timid.

• Join all of your wood pieces using thin CA (Cyanoacrylate) glue, unless we tell you

otherwise. In general, only a small amount of CA is necessary to glue parts together.

• Use only foam safe glue to attach the wing sections. Regular CA will dissolve the

foam.

• Don’t remove any pieces from the balsa sheets until they’re ready to be used. That

way, parts won’t get mixed up or disappear.

• After you remove pieces from the balsa sheets, carefully remove any of the extra

material from where the piece was attached.

• Don’t over force your pieces together. If they aren’t going together properly, make

sure you have the right pieces and that they are oriented correctly.

• If you want to remove the charred edges caused by the laser cutting process,

dampen a cloth with bleach and gently rub the affected areas. Removing the char

will not increase the strength but will make it look better.

Assembly Instructions

Okay, so now you are ready to actually build the DL50. If you follow these simple

instructions, we can have you flying in no time!

The Entire Process A to Z

Step 1: Prepare your workspace for assembly.

Step 2: Assemble the wings.

Step 3: Assemble the fuselage.

Step 4: Assemble and install the stabilizers, rudder, and elevator.

Step 5: Install the elevator and rudder servos.

Step 6: Finish the kit up with the battery, throws, and center of gravity.

Final Step: Go fly.

Step 1: Preparing Your Workspace for Assembly

Before you begin assembling the DL50, you must prepare your workspace.

Making space in what is probably the most crowded place in your home

1. Insure that your worktable is clean and flat.

2. Keep wax paper handy to prevent gluing the plane to the table.

Step 2: Assembling the Wing

The first thing you are going to assemble is the wing of your airplane. This involves shaping

the wingtips, gluing the spars, attaching the wing halves, covering, applying the

reinforcement, adding the launch peg support.

Mountain Models DL50

Shaping the wing

Carefully remove the two wing cores from the foam block. With a straight edge and a sharp

xacto, trim the trailing edge. The root chord is 6.25” and the tip chord is 4.75”.

We will now shape the wingtips. Using 220 grit sandpaper, shape the tips as shown. Take

care to get both tips the same.

Installing the Spars

The spar is created by gluing in four .060” carbon fiber rods into the grooves in the wing

cores .

! Putting together the spar

1. Verify the spar rods fit properly in the grooves and that there are no foam beads in the

grooves left over from the foam cutting process.

2. Cut the rods to length and lightly sand the rods with fine sandpaper to remove any surface

coating. Note that the top spars are a different length than the bottom spars.

3. Glue the spars in place, one at a time. Don’t try to do more than one as you will be too

rushed. Mix up a small amount of 5 minute epoxy and lay it into a groove. Press a spar

into the groove and scrape off the excess epoxy. If you want to play it safe, use 30

minute epoxy. The wing core is on a flat surface, right? Lay wax paper over the epoxied

spar and gently press for a smooth finish.

Mountain Models DL50 5

! Gluing the wing halves

4. Lay the two wing cores next to each other, bottom side up and centers touching. Run

three strips of tape across the center joint to hold the two halves together.

5. Flip the wing cores over, mix up a small amount of epoxy and flow the epoxy into the

center joint. Lift one wing to close the joint and force the epoxy out. The tip should be

approximately nine inches off the table. Wipe off the excess epoxy. Place something

under the raised wing to hold the wing up and let the glue dry. You may want to place a

weight on the wing against the table to keep it from lifting.

6. Cut two strips of ½” carbon fiber tape 12” long but cut at a sharp angle so that the ends

come to a point. This is to distribute the load over a larger area and not create a stress

riser. See the photo. Cut both ends this way.

7. Epoxy the strips to the top and bottom of the center joint. The easiest way to do this is to

lay the tape on a piece of wax paper and apply the epoxy to the tape. Lift off the tape and

place it on the wing joint. I like to line up the points with the spar rods.

Mountain Models DL50

8. Cut two 1.4 oz fiberglass darts 16” long and 6” wide as shown.

9. Apply the darts to the center wing joint, top and bottom. There are three ways to glue the

fiberglass. You can lay the glass in place and paint Minwax Polycrylic over the glass, you

can glue the glass down with foam safe CA, constantly spreading the CA around with a

sheet of wax paper or a baggie, or you can mix up some epoxy and spread the epoxy over

the glass with an old credit card or something similar. Another hint is to spray the

fiberglass with 3M77 to hold the glass in place while gluing.

10. Next you will cover the wing. (If you are experience at working with epoxy feel free to use

that, otherwise, proceed as follows). Lay plastic or wax paper over your work area, this

process can get a little messy. Carefully lay one piece of ¾ oz fiberglass over the top of

the wing insuring that there is at least 1/2” of overlap all the way around. Starting from

the center of the wing, brush Minwax water based Polycrylic into the glass with a foam

brush, working from the spar out and towards the LE and TE in a herringbone design. Use

as little Polycrylic as possible, just enough to saturate the cloth but not enough for it to

appear shiny. Go beyond the TE but only to 1/4'” shy of the LE. Always brush with the

grain of the cloth, if you brush at an angle it will stretch the cloth and cause wrinkles.

11. Once the Polycrylic dries, cut the glass ½” outside the LE and tips. Do not cut the TE. Cut

slices in towards the tip to make wrapping it over easier. Starting from the center, wrap

the glass over the LE and adhere with Polycrylic.

Mountain Models DL50 7

12. Cover the bottom of the wing in the same manner, overlapping the top. Once everything

is dry, trim the TE 1/16th beyond the foam. You may wish to reapply Polycrylic to any thin

areas. They will appear whitish.

13. Install the 1/64” ply center reinforcements. Very carefully line up the1/64th top ply sheet

so that it is centered on the center wing joint and ½” back from the leading edge of the

wing. The top 1/64th ply sheet is wide sheet. The end with the split faces forward. Epoxy

in place. You can also use foam safe CA. Sand the 1/32” ply reinforcement plate so that

the edges are beveled to improve airflow. Using the holes in the 1/64” plate as a guide,

glue the 1/32” plate over the 1/64” plate.

14. Drill out the wing bolt holes using the hole in the plate as a guide. Be sure to drill straight

down, taking into consideration the wings dihedral. You will use these holes to line up the

bottom reinforcement plate.

15. Glue the 1/64” bottom reinforcement plate. Use the holes you drilled through the wing as

a guide. The plate should be centered to the wing and ½” behind the leading edge.

Mountain Models DL50

16. You will now make the throwing peg. Find the 1/16” x 3/8” x 2” plywood in the parts

bag. Cut a strip of carbon 8” long. Mix up some epoxy and spread the epoxy on the

carbon tape. An easy way to do this is to lay the tape on a sheet of wax paper. Wrap the

carbon tape lengthwise around the plywood peg. Lengthwise means the tape will go

around the peg 4 times. Lay the peg on a sheet plastic and lay another sheet of plastic on

top. Weigh down the plastic till the epoxy hardens.

17. Sand a flat on the tip of the wing where you want the peg to go. The peg will be

positioned so that the front of the peg is even with the carbon fiber spar.

18. Mix some 5 minute epoxy and glue the peg to the tip of the wing. Ensure the tip is

perpendicular with the wing and centered vertically. The epoxy should form a small fillet

between the wing and the peg.

19. You will now cut 8 strips of ½” carbon fiber tape. Two strips are cut 5” long, two are cut

to 4”, two are cut 3”, and two are cut 2”. One end of the tape is cut square and the other

end is cut to a point. See the photo below.

20. Take one set of 5”, 4”, 3”, and 2” tape and epoxy one side. Lay the longest strip from the

top of the peg, down along the peg, and then along the wing. The square end of the tape

is at the top of the peg and the point lines up with the spar. Repeat with the other three

strips. Remember, longest first, shortest last. Press the tape down with a sheet of plastic.

NOTE: The point needs to be towards the front of the wing. This means you need to be

careful what side of the carbon tape you apply the epoxy.

21. Repeat the previous step on the bottom of the peg.

22. Sand the peg to round the carbon tape at the edges.

23. Work some epoxy into the Kevlar tow then tightly wrap the peg with the Kevlar tow

equally top and bottom. The Kevlar is wrapped at the junction of the wing and peg. In

other words, where the carbon tape makes the turn from going down the peg to going

along the wing.

Mountain Models DL50 9

Step 3: Assembling the Fuselage

You will assemble the fuselage by first assembling the wing hold down plates to their

respective formers then attaching them and the rest of the formers to the fuselage sides.

After that, you’ll attach the fuselage bottom then top. The fuselage wood is glued with thin

CA.

Putting together the fuselage

24. Glue the 1/64 ply fuselage doublers to the fuselage sides. Make sure they are carefully

aligned with the top of the fuselage sides. Glue with thin CA. You did make a right and a

left side and not two of one side, right?

25. Glue the wing hold down plates to their respective formers. These parts only go together

one way so it isn’t too difficult to figure out how to assemble them.

Note: The rear former is delicate, handle with care.

26. Place the just competed parts in one fuselage side and add the rest of the fuselage

formers except the front most one.

27. Attach the other fuselage side.

28. Attach the fuselage bottom. It is easiest to start at the middle and work back. Don’t glue

the front yet.

29. Attach the fuselage top.

30. This is a fun step. Position and glue the front most former into place while holding

everything into position. Extra points if you don’t glue your fingers to the fuselage.

31. Glue the three 1/4” blocks to the nose of the fuselage then sand the fuselage to shape.

Mountain Models DL50

! Fiberglassing the fuselage

You will fiberglass the outside of the fuselage to give it strength. As discussed in the wing

section, you have various options for gluing the fiberglass into place.

1. Cut a piece of 1.4oz fiberglass about an inch longer than the fuselage and wide enough to

wrap completely around the fuselage.

2. Spray the fuselage with 3M77 and position the fiberglass on the bottom of the fuselage.

The glass should be off center because one side will cover the side of the fuselage and the

other side will cover the other side and the top of the fuselage. Wrap the glass around the

fuselage and press it into place. You will need to cut small slits around the nose to make

the glass conform to the shape of the nose.

3. There are three ways to glue the fiberglass. You can paint Minwax Polycrylic over the

glass, you can glue the glass down with CA, constantly spreading the CA around with a

sheet of wax paper or a baggie, or you can mix up some epoxy and spread the epoxy over

the glass with an old credit card or something similar. Whatever method you chose, try to

keep the glue to a minimum while still being sure to completely wet out the glass.

4. Once the glue is dry, trim the fiberglass flush with the openings in the fuselage.

5. Position the fuselage cover on the fuselage and sand to match the fuselage. It would be a

good idea to also glass the cover.

6. As I use a switch jack to charge my receiver battery, I don’t need to get into the fuselage

much. As a result I just tape the cover to the fuselage. Another option would be to tape

the front of the cover to the fuselage to form a hinge and hold the back in place with a

rubber band. You can also hinge the back and hold the front in place with a piece of large

heat shrink tube that has been shrunk to shape.

7. You need to tap the holes for the wing bolts. The kit comes with a self tapping screw for

this purpose. Make sure the screw is perpendicular to the hold down plate when you

thread the screw in. You may wish to flow just a bit of thin CA into the threads after they

have been cut to harden the wood.

Step 4: Assembling and Installing the Stabilizers, Rudder, and Elevator

You will assemble and glue the horizontal and vertical stabilizers, sand a bevel into the

leading edge of the elevator and the rudder, and then sand the parts smooth. Once the

parts are ready, they will be attached to the boom. The control horn will be positioned on

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