Mini-Tutor (oz12335)

 

Mini-Tutor (oz12335) by CS West from Aeromodeller 1968 - plan thumbnail

About this Plan

Mini-Tutor. Free flight rubber sport model. Low-wing layout.

Quote: "IF YOU REALLY must satisfy the urge to get something flying quickly but have no wish to build anything which is too crude, Mini-Tutor is the model for you, and it can be built alongside your larger project during the periods of waiting time which are bound to occur.

The whole model can be built with the aid of cardboard templates which will ensure accuracy and ease of assembly. They can also be passed on to friends who may wish to build a similar model.

Guide points for glued on features can be transferred to the sheet wood through the templates with a pin.

Fuselage: Lay up two pieces of light 1/16 sheet balsa with the side template on top and pin right through with two drawing pins. Cut round carefully with a thin, sharp and rigid blade. Sand the edges. lightly. Pin prick the positions of uprights and reposition the sides with the straight edges together but flat on the board to stick the 1/16 x 1/8 uprights right across both. Trim off the ends and cut down the centre to separate. Fit other details.

Glue the tail ends together and put on a spring clothes peg while fitting two card rectangles at positions 3 and 4 with rubber bands so that the cross braces can be glued in. Cut out the top stringer in one piece and glue it straight down the centre of the upper cross braces. Fit the tri-angular supports oversize for sanding down. Shape the undercarriage from 18 swg wire and sew it in position at three points with a needle and thread; finish with glue on the sewing.

After sanding the top and bottom level, fit the upper 1/32 sheeting with an overlap joint on the top ridge. Follow with the bottom 1/32 sheeting with two small nicks to clear the undercarriage wire. Trim and sand each piece as fitted. Put in the tailskid wire with glue and a bamboo peg through the top loop, sanded off on each side. Glue on the ply nose former and lightly sand the whole fuselage.

Wings: Cut the outline with the template from 1/16 medium sheet and prick through the positions of the flaps and dihedral joints. Score these lines halfway through the wood against a steel rule. The flaps are scored from the top and the dihedral joints from underneath. Cut right through at the dihedral joint of the flaps only.

Pin the wing down with a piece of 1/8 x 1/8 strip under the flap line and after depressing the flap to the building board run glue along the score line. Give the flap 'washout' at each tip by inserting a 1/8 x 1/8 wedge under the corner.

When set, raise the wing tips to 2-1/2 in on each side and glue the dihedral joints. Cut two identical wedge-shaped pieces to fill the gaps which now appear in the flap. Make the two holes in the flap on either side of the fuselage seating and glue in four bamboo pegs for the wing bands. Glue the flap line and dihedral from underneath. Finish by light sanding round the edges.

Use the same method as for the wings to produce the tailplane and sand the edges all round before glueing the fin on the centre line. Cit a small nick in the tailplane trailing edge to locate the rubber band.

Cut two identical prop blades from 1.5 mm ply using the template and sand them smooth as shown. Make the hub from a piece of hard balsa 1/2 x 1/2 x 1 in, cutting the diagonal slots with a piece of hacksaw blade so that they almost meet in the centre. Drill the centre hole and fit a piece of 18 swg brass tube with a ply washer at each end. Glue in the blades as straight as possible and when set, strap the whole assembly to a flat piece of wood with rubber bands. The back of the prop should be against the wood. Hold in the steam of a kettle for a few seconds until tips are almost flat on the wood and the blades are hollow at the back.

Release after a few minutes and shave off the hub corners. When completely dry, apply colour or silver dope. Shape the nose block and fit a bush (18 swg); thread the shaft, with a square loop on the front, through the prop and bush, with cup washers in between. Carefully shape the rubber hook and slip on a piece of plastic tube.

Clip down a pin for the pivot of the 20 swg pawl which engages the square loop to drive the prop.

Finish: Four strands (two loops) of 3/16 flat rubber, making a complete motor length of 20 inches, form the power unit. This should be carefully washed and dried before lightly lubricating with pure castor oil.

Assemble the model with thin rubber bands so that the point of balance is under the centre of the wing. Test glide and correct by warping the tail assembly trailing edges. When correct, try power and pack the nose block if required to maintain proper climb.

There is no need to worry about the stall as long as the wing tip washout is correct. The prototype has been seen to come down like a slow lift from a height of about 30 ft.

This model is great fun to fly and can even be made to perform aerobatics by cutting the control surfaces and spot glueing them in the required positions; more power can be added also for this purpose. In any event it will create a diversion from the building chore on the more complicated model."

Note: Aligned, stitched, missing sections now repaired.

Supplementary file notes

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Mini-Tutor (oz12335) by CS West from Aeromodeller 1968 - model pic

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Scaling

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