By Bill Kuhl
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Check out his website for a lot of great science activities!
Image by Jim Buxton
9″ Diameter Foam Plates 5 1/2″ or 6″ Diameter Propellers 1/8″ thick Balsa
Paperclips for Rear Hooks Rubber Strip 1/8″ for Outdoors
For fast assembly I use low temp hot melt glue guns. Foam plates can be cut with a scissor. To bend the rear hook a needle nose pliers is needed. Parts are traced with an ink pen. To cut the balsa for the fuselage a razor blade or modeling knife can be used. A stiff ruler such as this wood ruler is used to bend the wing crease and for measuring.
Balsa strips can be cut with knife or razor blade but it is also possible to purchase 1/8″ x 3/8″ x 36″ balsa strips. Using a balsa stripper makes cutting the strips an easy task.
For a recent class, I pre-made the fuselages, traced patterns on the foam plates, and installed the rear hooks on the balsa fuselages. Now the students did not need to bend the wire or cut balsa with a sharp blade. The only tools needed were a scissors, ruler, and hot glue gun. I cut and tied the rubber strip because students have trouble tying knots.
I will start here in case you wish to build the fuselage for a group ahead of time like I did. The 3/8″ x 1/8″ x 36″ sticks are cut to 16″ long. This will give enough for two fuselages, leftover material can be used for cutting the wing pylon mount.
Bending the Rear Hook
I usually bend the rear hook out of paperclips but the rear hook could be bent from a straight pin or music wire.
With the paperclip flat on a surface bend the smaller inside part of the paperclip up 90 degrees and then cut it off.
With the larger section leftover hold that section perpendicular to flat surface and bend the top part up about half way back up 90 degrees.
Cut off the bottom portion of the wire even with the portion that is now pointed up. Bend up a small portion at the end of the bottom portion.
Cut a 16″ length of the 3/8″ x 1/8″ x 36″ balsa straight across. Markings for the pylon wing mount and the taper at the rear of fuselage can be done before or after the 16″ length is cut.
Mark from the left side of the balsa 3 1/2″ for the position of the front of the wing pylon mount.
Draw the angle on the rear of the fuselage, starting at the right end mark on the top 2 1/2″ to the left. From the bottom at the right side of the balsa mark up 1/8″. Then draw a slanted line between those two points.
Now if you have not cut the 16″ length yet, make that cut and then the angle cut.
Wing Pylon Mount
Cut the wing pylon mount from leftover 3/8″ x 1/8″ balsa if available.
Glue wing pylon mount to top of fuselage at spot marked previously.
Create a hole for the rear hook to go into the fuselage bottom by using a push pin first.
Try placing rear hook into balsa and remove. Now put glue in hole and in area where hook will rest on balsa. Insert the rear hook again. The rear hook needs to be pushed down farther than shown in this picture. Extra wire sticking out the top can be cut off.
This is what the fuselage should look like.
Download: Foam Templates in PDF format.
Tracing the Foam Parts
Four 9″ foam plates are required to build the airplane, I cut out thin cardboard patterns and trace on to foam plates with ballpoint pen. Cut foam with a scissors.
This is what the foam pieces should look like.
Building the Wing
Bend all three wing panels at the same place with a straight edge. Ease the bend in slowly as the foam can crack if done too quickly.
Glue the edges of the foam wing panels together and block in dihedral before glue hardens.
Panel blocked up to proper dihedral angle of 2 inches.
Glue the vertical fin on the slanted area at the rear of the fuselage, leave a small part of the rear of the vertical fin hand past the rear of the fuselage so this can be bent as a rudder trim tab.
When this has setup, turn the fuselage over and glue the stabilizer on.
Glue the wing on the wing mount pylon, the bend in the bottom of the wing should match up with the high point of the wing pylon mount.
Push the propeller assembly on the front of the fuselage, the propeller shaft must be on the bottom.
Rubber motors can easily be 1 1/2 times the length from the propeller shaft to rear hook but for hand winding I find it works best to make it that length with little extra.
Center of Gravity Balance
I find that this plane flies well when balanced at the spot that the bend in the wing occurs. If the airplane will not climb, try cutting the front end of the fuselage by a small amount and trying again. If the propeller you are using is heavier this might be needed for proper balance.
Cut the rubber strip and tie a knot with the ends.
Attach the rubber with the knot in the rear hook.
Spin the propeller clockwise to wind with your finger.
I purchased a bunch of the Sig 5 1/2″ propellers so have been using those, I am going to try other propellers such as the Midwest 6″ black propellers and the Guillow’s 5 1/2″ propeller that is common to their smaller slip-together all balsa airplanes.
A rubber winder makes winding much easier and a greater number of turns can be wound into the rubber.
For more Information on the basics of trim adjustments and rubber motors check out my other webpages:
Videos of the Fantastic Foam Flyer
30 Second Video of Construction and Flight