A uniquely angled and stealthy little flying wing, the Intruder is a cool little paper airplane. The Intruder has a faux intake and ventral fins which double as skids.
TAA USAF Designation: A97-1
Step 1: Materials
1 Piece of 8.5 by 11 inch Paper
Step 2: Cover Fold Preparation
Fold one corner of your paper to the edge of the opposite side. Then open and repeat on the other side. Then pull the top half of the X onto the bottom half.
Step 3: Cover Folding
Tuck the paper in under itself. The pictures represents what the paper should appear like.
Step 4: Counterweight Folding
Pull the edges of the cover folds up to the front as pictured. Then fold the diagonal edge to the center line and repeat on the opposite side. Then fold it in half along its center.
Step 5: Mark and Make the Faux Intake
Measure half an inch from the back of the airfoil and put a mark there. Then measure an inch from this mark to the airfoil, which should appear close to a 40 degree angle if made properly. Put a mark at the point where it intercepts with the airfoil. Then draw a line from one point to the other.
Cut the paper along this line, then flip the paper over. Pull this up to the other side, then with the airfoil side on the outside, make creases. This should complete the faux intake. Apply a piece of tape to the airfoil at its center.
Step 6: Fold the Wingtips and Make the Fins
Fold the wingtips down to creases of the intake. Fold the airplane up along its center again, but unfold the wingtips. Using your ruler, measure 3/4 of an inch forward of the trailing edge. Put a mark here. Then measure into the wing about 7/8 of an inch, at about a 25 degree angle from the previous mark. Put a mark there too, and then cut from the mark on the wingtip to the inner one. This will have created your fins.
Step 7: Wing Fold Adjustments
Fold your wing roughly as shown. The inner sections should have a dihedral deflection and the outer, anhedral. The two fins should be able to both touch the ground while the counterweight does too.
After a check flight, you may need to trim the Intruder specifically to your needs.
Step 8: Flight
Flying the Intruder is a relatively easy task, especially if you hold it properly at launch. When launching it, advance it through the air for about 3 feet at slow to moderate speed. You should be holding onto it by its counterweight, not through its "intake". Enjoy!