Little Sir Echo (oz5351)

About this Plan

Little Sir Echo. Rubber sport biplane by Gordon Allen from Model Aircraft Sept 1954.

Quote: "EVEN in this jet-age there is still something very fascinating about biplanes. For modellers who would like to recapture just a little of the charm of these old-timers without making anything elaborate, here is a 15 in span all-balsa job that should fill the bill.

The fuselage is in one piece, cut from 1 in hard balsa. All edges are rounded off with the exception of those at the wing positions and at the extreme nose. The nose is reinforced at each side with pieces of 1/8 hard sheet and is then carved to a streamlined shape. A small reinforcing plate is added as shown. Aluminium tube, 20 swg, is fixed in the nosepiece and a 5 inch diameter medium pitch balsa propeller complete with 20-gauge shaft is fitted.

The undercarriage legs are bent from one piece of 20 swg piano wire. After the laminated, bushed wheels have been secured by soldering cup washers in place, the whole unit is clipped over the bottom of the fuselage and securely bound. Leg fairings are added as shown.

Tail surfaces are made from 1/32 hard balsa and the trim-tabs are fixed by hinges cut from aluminium milk bottle tops. Fin and tailplane are cemented in place as shown.

A rear hook bent from 20 swg piano wire is fitted and glued in place and a celluloid cabin window is added.

The wings are cut from 1/32 sheet. Top wing is 15 in span and has a chord of 2-9/16 in. Bottom wing is 11 in span with a chord of 2-1/4 in. These are cut, soaked in hot water for an hour, and each is then clipped with rubber bands over four 1/8 in thick ribs, made to the contour of the respective airfoil sections, which have been spaced out and cemented on strips of ply.

When thoroughly dry the top wing is given a liberal coat of thick banana oil or thinned down cement and is finished smooth. It is then removed from the 'form' and cemented in place on top of the fuselage. Squareness with the fuselage is essential. Next the wing struts are cut, their edges rounded, and fixed in their appropriate places They must be at 90° to the top wing which has no dihedral.

The bottom wing is treated with banana oil as before and when dry is cracked in the middle and cemented again, after 3/8 in dihedral, measured at the tips, has been given to it. It is then cemented to the fuselage in conjunction with the bottom of the wing struts. Finally, four reinforcing ribs, cut from 1/8 sheet, are glued to the fuselage at the junction of the wings.

Power for Little Sir Echo depends upon what performance is required. For aerobatics a pretensioned loop of 1/4 in flat rubber 10 in long is required. For cruising flight, a loop of 3/16 in flat rubber 15 in long is excellent.

Usual refinements such as a freewheeling prop, and valve tubing round the hooks can be introduced as desired."

Direct submission to Outerzone.

Supplementary file notes

Planfile includes article.

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