Parnall Elf (oz12206)

About this Plan

Parnall Elf. Radio control scale model. Wingspan 61 in. For 45 to 60 four-strokes and 4 functions. Scale is 1/6.

Quote: "The Parnall Elf was one of Harold Bola's designs, a follow-up from his Parnall Scout, the Peto and Pixie and, of course, the Parnall Imp. I have always liked the design, and what I've seen of it flying it looks a very capable aeroplane with its Cirrus Hermes 111 power unit.

The staff at Old Warden were very helpful when I asked about taking photos and, of course, I acquired the scale drawings from the Argus Plans Dept (Plan No.3026) which includes three-view and a full description of the Elf, now housed in the Old Warden museum from which I copied the decor. So build, enjoy and don't bend it!

Let's start: Study the plan carefully and cover with some clear plastic sheet, making sure there are no wrinkles and that it lies flat; tucks and wrinkles distort measurements.

Start the fuselage by pinning sown the 1/4 square top logerons, then the bottom 1/4 in square, gently bending this up to the front shape. Start from the rear with this and pin it down firmly as you go. Now fit the other verticals and diagonals until completed, then fill in the front end round the nose with 1/4 sheet. Now build another on top, making two identical sides. When these are set, unpin them and turn them over on your building board, placing them opposite each other top to top and cut out the 1/32 ply sheet side doublers, that fit from the engine bay to rear of cockpit on the dotted lines. This way you will not end up with two righthand sides; the 1/32 ply is on the outsides of the fuselage. To make a good joint rub a coat of white glue onto both sides with your fingers, allow to almost dry then apply another thin coat and fasten down until really set.

Next fit the 1/8 ply inserts flush with the inside face. These take the wing hinges and centre section strut fixings, then leave all to set really thoroughly. You can now fit the fuselage formers starting from the front end and carefully draw in the end at the rear and fit the rudder sternpost. (If you picked your 1/4 square balsa strip carefully you should not have any banana shapes). It is safer at this stage to fit a 1/4 strip along the top centre from the nose to the tail - any that is not needed can be taken out after.

The tank bay and engine housing can now be fitted. Measure a piece of 1/4 ply to fit in the engine bay (it is best to first make a cardboard pattern) then fretsaw the ply for the engine. Drill out the engine bolt holes then glue the plate and your engine in between the side cheeks, reinforcing underneath with hard balsa (but first solder the heads of the engine bolts across with tin plate or thin wire; you may want to take out the engine sometime and this should stop your bolts turning.) Now mark and cut out of 1/4 ply the engine plate and its air intake holes. Glue this in place and, taking out the 1/4 square strip you fitted earlier, replace it with 1/8 ply shaped to fit from firewall to nose. Remove just enough to enable you to get a plug spanner through. Then sand to an oval shape at the top for the contour of the alloy engine cover.

While these are all setting nicely, make up the aileron crank from lOg wire. Cut or file some brass strip for the bellcrank, drill a centre hole to fit the rod and two holes to fit a pushrod clevis. The clevis fits 1/2 in from the centre of the crank. Push the bellcrank along rod and solder in place, then fit into the fuselage along with the spacers so that there is no end to travel. Temporarily fit the 13 amp earthing plugs, one each end and secure with its own stud.

There comes a time when the radio has to be fitted and at this stage I built the tailplane and rudder. Sand them all up, fit hinges and cover; I used Solartex. Temporarily glue the tail surfaces in place, fit the servos to servo tray and fix permanently in position behind the tank floor and close up the partition.

The rudder is coupled by closed-loop using nylon fishing trace, elevator and engine by commercial snakes and devises. Test to see that everything works nicely. I always fit my radio at this stage - it's much easier to get at.

Now make the undercarriage and fit. This is from 10g wire for the two main legs and 12g for the two centre spring wires. Bend the parts to shape, and make a groove in a piece of 3/4 x 1/2 in hardwood for the rear legs and the top spring piece. Solder the two together and sew and epoxy into the groove. Now do the front leg and the bottom spring, fix the front, then draw altogether and silver solder. Don't forget the axles for the wheels; these are part of the rear main legs. Now fit the tail skid, and test to see if the whole thing stands level.

Next, build the top wing centre section, cutting the 1/8 ply base and six ribs two CS1s and four W1s) from the same wood, saving two ribs for the bottom wings. Drill the ply base to take bolts from the centre section struts as close to the CS1 ribs as possible. You may find it more convenient to bolt this on before adding the CS1s themselves and the wing fixing. Then cut out the slot at the front of a pair of CS1 ribs for the wing tongue to pass through and glue one each side on the top edge of the base. Now glue a piece of 3/4 x 1/8 ply across vertically up to the back of the slot at the front of the base. This forms the rear section of the dihedral guide.

Also glue a piece of 1/8 across the back horizontally. leaving 1/2in short on each side, plus a similar piece across the whole width which makes the slot for the back hinge. Then fill up to the top at rear with balsa, to be sanded later..."

Direct submission to Outerzone.

Jack Elson's Parnall Elf 'Superplan' from October '91 Radio Modeller. Jack won the Shuttleworth Trophy for this model at Old Warden in that year.

Note this plan was originally printed in colour (blue and red lines). Here the main planfile is monochrome. See supplement file for colour version - a compressed jpg file at at 240 dpi.

Supplementary file notes

Article.
Alternative colour plan.

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