The World Tour Flyer

The World Tour Flyer is a miniaturized version of the "Cloud Tramp," originally designed by Charles Grant and published by Model Airplane News in 1954. Many people from around the world participate in a simultaneous "mass launch" of their Cloud Tramps each year, and the first official flight of the SFA World Tour took place during the 2006 Cloud Tramp mass launch. More info on the Cloud Tramp mass launch is available on the Cloud Tramp Home Page.

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Building & Flying the World Tour Flyer

Major assemblies:
  • First, download the plan. The model has a 12 inch (30.5cm) wingspan, so when you print the plan be sure the wing half is exactly 6 inches (15.25cm) long.
  • Cut the motor stick (fuselage) from stiff 1/8" x 3/16" (3mm x 4.5mm) stiff balsa stock. These dimensions can vary slightly, but be sure the stick is stiff (and preferably light).
  • 2 wing halves, the stabilizer, and the rudder are cut from very light sheet balsa, 1/32" to 1/20" thick (0.8 to 1.25mm).
  • Wing ribs are cut from 1/16" (1.5mm) sheet balsa.
  • Lightly mark rib locations on both wing halves, and glue the center portion of each rib (peak of airfoil) to it's proper location on each wing (approx. midway between leading and trailing edges). After glue is dry, apply glue to remaining lengths of ribs and flip wing assemblies over. Place wings on a flat surface and use weights along leading and trailing edges to make the balsa sheet conform to the rib profiles while the glue dries.
  • (Optional step) The wing can be made damage-resistant by gluing thread along the leading edge, from wing roots to wing tips.
  • Both wing halves must fit together with 1.5" (3.8cm) dihedral under each wing tip. Sand the top section of each wing half where they meet (root ribs) until a good fit is achieved, and glue halves together with proper dihedral.
  • Cut a square notch out of the rear of the motor stick to accomodate the stabilizer, as shown on plan. Make the cut straight & square, and approx. half the height of motor stick. Length of cut should be longer than width of stab by about 1/4" (6.5mm). Next, cut a piece from 1/16" (1.5mm) sheet the length of the motor stick notch, and the width of the motor stick. Assemble this piece and some small pieces of 1/16" scrap onto the motor stick to create a slot for the stab to slide through. Position the stab in the notch during assembly to ensure it sits squarely in the slot while glue dries.
  • The wing mount pieces are cut from 1/16" (1.5mm) balsa sheet and assembled as shown on plan. The mount should fit snugly over the motor stick, and must be able to slide freely along the length of the motor stick.
  • At this point, 2 to 3 coats of Nitrate dope should be applied to all balsa parts. Hold stab and rudder flat while dope dries. Dope only one half of the wing at a time, and weight it down on a flat surface as it dries, with a shim under the trailing dge to create washout. The shim should be approx. 1/16" (1.5mm) thick, placed under the trailing edge approx 1/4" (6.5mm) outboard of the outer rib.
  • Sand very lightly between coats of dope, and be sure to brace parts as described above while drying each time.
  • Slide stab into stab slot, and glue rudder to motor stick as shown on plan. Ensure that rudder is square with stab while drying.
  • Assemble wing mount to motor stick (do not glue). Glue wing to wing mount with a 1/16" (1.5mm) shim underneath the leading edge. Ensure wing is square with rudder and stab, and also square in the top-view, before glue dries. When dry, remove wing/mount assembly from motor stick.
  • The thrust bearing mount is made from aluminum-angle, approximately 1/16" x 1/2" x 3/4" (1.5mm x 1.3cm x 2cm). Cut off a section of aluminum-angle about the width of the motor stick. Next, cut a section of thin aluminum from a beer or soda can, and wrap it tightly around the long section of the aluminum angle piece. It should wrap only one time around, and overlap itself about 1/8" (3mm), creating a "socket" that the angle can slide in and out of. Bind the thin aluminum wrap with several truns of thread, and lock the thread with a thin coat of superglue (CyA). Be careful that you do not glue the aluminum angle to the thin aluminum.
  • The socket (with aluminum angle still inserted) should be glued to the motor stick as shown on the plan. When glue is dry, lash the socket to the motor stick with thread and glue (Cya) to create a solid attachment. Once glue is dry, slide the angle out of its socket and back in a few times to check the fit.
  • The short leg of the aluminum angle should be filed so the that the end mates to the round profile of a Peck plastic thrust bearing (as shown in sketch on plan). Lash the plastic bearing to the angle with 10 or 15 turns of thread, and harden the joint with superglue (Cya).
  • Bend the rear motor hook out of .025" (0.6mm) music wire as shown on plan, and lash to motor stick with thread and Cya glue.

Final assembly:

  • Small areas of bright paint or tissue are recommended to make your model easier to find.
  • A 4.5" grey plastic Peck prop works well for the World Tour Flyer. Scrape plastic from the front and/or back of the prop to make it balance. For best performance, a great deal more plastic can be scraped away to lighten the weight.
  • Use pre-formed motor hooks, or bend your own to attach the prop to the thrust bearing. Ensure that the free-wheel mechanism functions properly.
  • Attach the wing to the motor stick using a single small rubber band.
  • Slide the thrust bearing assembly into its socket.
  • Slide the stabilizer into its slot.
  • Tie a loop of 3/32" (2.5mm) or 1/8" (3.2mm) rubber, about 8" (20cm) long. Stretch & lube the motor, and attach to front and rear motor hooks.

Flight Trimming:

  • Slide the wing to a position on the motor stick where the CG (center of gravity) is about where the airfoil peaks (1/3 to 1/2 of the way back from the leading edge). Mark the motor stick and the wing mount so you can easily find this position again.
  • Hand-wind 25 to 50 turns into the rubber to begin flight tests.
  • Adjust wing position to cure problems in the glide.
  • Thrust adjustments are made by bending the aluminum angle portion of the thrust bearing assembly. Use two pairs of pliers for this operation.
  • If flight surfaces need to be warped (or if warps must be removed), hold the warp in position while brushing dope thinner over the balsa. Continue holding until dry. Steam also works well for this.