This small glider—the Thorn Spy Plane—is part of a series that now has over ten designs. Instructables—YouTube—Instagram—Etsy.

I'm using a beige file folder or sheet of 80 lb. / 215 gsm card stock. Although 65 lb. / 176 gsm would probably improve flight performance, I prefer the durability of the 80 lb.

This glider doesn't glide much because the shape is meant for extreme speed. Nevertheless, it is entertaining in a hallway or backyard. Enjoy!

The SR-71 is a unique piece of engineering. Is it possible to admire the instruments of war and espionage without condoning them? I hope so.

Supplies

sheet of medium weight (80 lb. / 215 gsm) card stock
printer
white glue (PVA) and glue stick
metal ruler
scissors
hobby knife (optional)

Step 1: Print & Cut

Download the PDF. Print the plans at 100% scale. If you don't have a printer that can handle card stock, print the file onto paper and then photocopy onto card stock.

Using the scissors, carefully cut out the shapes. A hobby knife with a metal ruler can also be used. To minimize risk of injury when using a knife, secure the card stock and ruler firmly with one hand while cutting lightly with the other. A sharp blade helps reduce the force needed to cut, and is therefore probably safer than a dull blade.

Save a couple scraps of the card stock in case you need to make repairs to the glider later on.

micro_spy_plane_plans_ZDE.pdf
Download

Step 2: Fuselage—Dorsal

Attach the main brace (B) and nacelle braces (C) to the top of the main piece (A). Use a glue stick. Note that the tip of the brace is set back a couple millimeters from the tip of the main piece.

Step 3: Fuselage—Ventral

Glue the ventral nose brace (D) to the bottom of the nose, flush with the tip of A.

Apply liquid glue, then fold the engine pieces (E) in half. You may need to hold them in place for a while, or put them under a book, until the glue starts to cure. Using a toothpick, scrap of card stock, or other tool, scrape a thin bead of liquid glue along the long end of an engine, and attach it to the main piece. Make sure it is well aligned, then glue the other engine in place.

The ventral fuselage (F) requires several folds. The middle fold should be a mountain fold, and the four should be valleys. Glue the two central panels together, then carefully attach the piece to the center of A.

Step 4: Spine, Canopy, & Fins

If you want to accentuate the canopy (G), trace it onto material of a different tone or color. The front panels overlap the back panels slightly, allowing the piece to rest on a flat surface. Use small dabs of liquid flue to hold the sides in place. Attach the canopy to the main piece, using a tool to scrape a bead of liquid glue along the edges. A small mark indicates the foremost point of the canopy on A.

Next, use a ruler to establish the crease on the spine (H) and bend it to about 90 degrees. Attach it to the fuselage, with liquid glue, as you did the canopy. The spine should overlap the back of the canopy by about 3 to 5 millimeters. Pinch the aft end to a point.

Define the creases that create the rudders on the fins (I). Use liquid glue to attach them, be extremely careful to make them as close to parallel as possible. Lastly, glue a brace (J) to the base of each fin, on the outside edge, to help hold it in place.

Step 5: Contours

Use a ruler to define the inner and outer elevons, on the trailing edge of each wing. The middle pair should be raised about 7 degrees, the outer by just a few degrees. Continue using the ruler to carefull deflect the leading edges of the wings down by a few degrees. Lastly, hold the ruler on the outboard edge of an engine, then pinch and bend the wingtip to about 10 degrees above horizontal. Repeat the process with the other wingtip.

Step 6: Flight Tests

An aircraft with a short wingspan tends to suffer instability on the roll axis. This glider is no exception.

Try to test it when there is no breeze outside, or test it indoors if you have a big enough space. Throw it level and with moderate force. Make small adjustments to the rudders and elevons in order to achieve a straight, gently descending flight.

Good luck!