The Sparrow traces its origins back to the YD142-1 drone "technology demonstrator" prototype, which featured a box wing. Although it performed well in testing, I chose not to make an instructable for the YD142-1. Despite being several months old, the prototype remains airworthy. After the YD142-1 was designed, the Moth "double delta" drone was designed and published. The Moth featured two delta wings, one inverse delta and the other mounted conventionally below, like the RC airplane it was inspired by. Although the Moth was quite capable and successful, I did not feel designing biplanes was an idea worth investing in, due to their intricate nature, especially when installing the wings.
In early January 2012, I received a request for a miniature, realistic biplane paper airplane. To answer this, I looked back on the YD142-1 and the Moth. Quite quickly the delta wings of the Moth removed it from consideration. The YD142-1, although capable, had a chord of 2 boxes, making the mounting of the wing approximative. At this point, I decided to design a new aircraft, with some conceptual characteristics similar to the YD142-1 but with a somewhat different configuration.
After some design studies, I retained the similar Voyager's vertical and horizontal stabilizers. The wings and spars would be of entirely new design, however. Rather than have a box wing like the YD142-1, I decided the XD200-1 (which would later be named the Sparrow) would have a strut braced pair of wings. The required wing size was calculated from existing data from the Voyager paper airplane and the prototype was assembled. On its first flight, the Sparrow proved itself a worthy airplane, and it was given the slot for Instructable 155.
Some potential experiments and demonstrations possible with this airframe include:
- Glide ratio
- Weight and balance
- Hangtime versus other aircraft
- How surface inequality can affect aircraft (geometry/shape studies, flight dynamics)
- How each of Newton's three laws affect aircraft (a person acting as an external force on the airplane during launch and/or the air acting on the airplane as an external force characterized as drag (first law); the force of the airplane hitting something and transferring the force its built up with its mass and acceleration (second law); and lift versus gravity and thrust versus drag (third law))
- In a turn, circular motion is accomplished by lift directed toward the center of the turn.
TAA USAF Designation: D200-1
Step 1: Materials
1 Piece of 10.5 by 8 inch graph paper (4 boxes per inch)
Step 2: Begin Construction
First, begin by folding your your graph paper in half (excluding three boxes on the perforated side). Once the paper has been folded appropriately, make two marks--15 full boxes apart. Use a ruler to make a straight line with the length of 15 boxes directly up 1 row of boxes from the two marks you just made. Then make the rudder, spars, landing gear and counterweight as shown. Follow the photograph markings. Along the spars, make a dotted line one box in from the tip and another dotted line one more box inwards. Beneath the spars and one box in length forward and aft of it make a solid line with a dotted line bisecting it half a box in from the edges of the spars above. Then, below the rudder, mark a line that stretches 3 boxes. 1.5 boxes back from the beginning of this line, make a dotted line vertically. Once all is marked out, cut out the fuselage.
After the fuselage is made, take another sheet of paper that is folded in half along the lines of boxes. Mark out two wings as shown (each 3 by 10 boxes). On one, mark a dotted line half a box in from the wingtips. Then mark out the horizontal stabilizers as 2 by 3, plus a swept portion with a sweep of 1 box of chord decaying every 3 boxes outwards from the wing root. Then cut it out.
Solid lines indicate places to cut. Dotted lines indicate fold lines.
Note: 1 box = 0.25 inches
Step 3: Making the Fuselage
Cut our your fuselage along the outer solid lines. Once this is done, unfold the fuselage and cut off the right vertical stabilizer. Then refold it and fold along the vertical dotted line that bisects the fuselage in the middle of the fuselage. Cut along the sold line at that point. Proceed back to the vertical stabilizer and fold it along the vertical dotted line. Make a cut along the solid line that this line bisects. Then unfold.
Step 4: Making and Taping the Fuselage
Fold the spars down at the fuselage on each side. Then restore them to their upright position. Fold the left spar's outer box down along the dotted line you made earlier. Then fold the box below it down along the second, further inboard dotted line you made earlier. Repeat on the other side. Once this is done, open the folds of the spar tips and fold the spars down as shown. Then tape at the designated points.
Step 5: Applying the Wings
Begin the wing application process by cutting out your Sparrow's lower wing, and sliding it through the cut beneath the spars you made previously. Once through, fold the wings up and tape them to the fuselage. Fold along the dotted line you made previously half a box in from the wingtip to make the winglets/outrigger skids. Then repeat on the other side. Fold the wings down and then fold the spars down to sit on top of them. Apply tape to the designated points. Once you've taped the spars to the lower wing, apply tape to the bottoms of the spars with the adhesives sides facing upwards. Then install the top wing as shown. Cut off any excess, overhanging tape.
Step 6: Applying the Horizontal Stabilizers and Stapling
Cut out the horizontal stabilizers you made earlier and pull one half through the cut you made beneath the vertical stabilizer earlier. Then fold them up and apply tape to secure them to the fuselage. Then unfold them with a slight dihedral deflection. Proceed to the counterweight fold and apply two staples, one from each side. Your Sparrow is now ready for flight.
Step 7: Flight
The Sparrow is a fairly simple aircraft to fly. A moderately fast toss at a neutral or negative attitude is the best launch launch technique for long range flights. Additional applicable surfaces include slats, flaps, flaperons, ailerons, spoilers, spoilerons, (application would generally be best on the top wing. elevators, a trimmable rudder and air brakes. Enjoy!