Model glider

A 60 cm hand-launched glider of thin wood, balanced and trimmed by test: the Wrights' order of work in an afternoon, and the stability every aircraft depends on.

Build Tier 4 · Industrial revolution Transport Easy An afternoon; trimming takes longer Crew 1

Home: In the air, Level 4 · Engine, level 3 of 6 in its track. Serves 1 step.

Every build on this site has hazards that injure or kill — quicklime, carbon monoxide, molten metal, collapsing ground. Read the safety notice before starting, and read this build's own failure modes below.

**A hand-launched model glider a moment after the throw, climbing out over water.** Handlaunched Glider · Summer 2005date QS:P,+2005-00- · Tord55 · Public domain · Commons ↗

What it is and why this shape

Every aircraft is stable in pitch only if its centre of gravity lies ahead of its neutral point (NASA), and a model glider shows it in a minute: balance too far back and it swoops up and stalls; too far forward and it dives. Trimming one teaches the method that made the Wrights fly: build, test, change one thing, test again. Its wing's span is six times its chord, as on their 1902 glider.

Model glider, 60 cm span Fig 1

TimberMetalLoose fill / grain

Wing 60 × 10 cm, tips 4 cm up; fuselage 50 cm; tailplane 20 × 6 cm with its leading edge 32 cm behind the wing's; fin 8 × 6 cm; balance 3.3 cm behind the leading edge to start.

Keyed parts

1	Wing	60 × 10 cm, curved about 1 in 20, each tip 4 cm up.
2	Fuselage	50 cm stick; carries everything in line.
3	Tailplane	20 × 6 cm, flat, square to the fuselage.
4	Fin	8 × 6 cm, upright, in line with the fuselage.
5	Nose weight	Added until the model balances a third of the chord behind the leading edge.

Specifications

Wing	60 × 10 cm	Span six times the chord; curved about 1 in 20.
Dihedral	each tip 4 cm up	About 7.6°: it rights a roll by itself.
Fuselage	50 cm stick, 10 × 5 mm	The wing's leading edge 10 cm from the nose.
Tailplane	20 × 6 cm	Its leading edge 32 cm behind the wing's.
Fin	8 × 6 cm	On top at the tail.
Balance point	3.3 cm behind the leading edge	A third of the chord, to start; the glide decides.
Weight and speed	about 25 g, 3–4 m/s	From the lift equation at a lift coefficient of about 0.6.

Bill of materials

Material	Quantity	Notes and substitutes
Thin wood sheet	about 70 × 20 cm, 1.5–2 mm	Basswood, spruce or balsa, straight-grained; for wing, tail and fin.
Fuselage stick	1 × 50 cm, 10 × 5 mm	Straight-grained spruce or pine.
Nose weight	10–15 g	Modelling clay, or a wrap of lead or steel wire.
Glue	a little	Wood glue or cement.
Sandpaper	fine	To round the leading edge and thin the trailing edge.

Tools: Sharp knife · Straight edge and ruler · Pencil · Pins or clothes pegs to hold joints · A tape measure for the glides

Construction

Cut the parts

Cut the wing 60 × 10 cm, the tailplane 20 × 6 cm and the fin 8 × 6 cm from the sheet, with the grain running along the span. Cut the fuselage stick 50 cm.

Shape the wing

Sand the leading edge round and the trailing edge thin. Give the wing a gentle curve front to back — about 5 mm of rise over the 10 cm chord, 1 in 20 as on the Wrights' 1903 wing — by bending it over a warm, curved surface and letting it cool. Both halves must match.

Set the dihedral

Cut the wing in half across the middle, bevel the two root edges, and glue them so that each tip stands 4 cm above the centre with the middle flat on the table. When dry, the wing is one V-shaped piece.

Assemble in line

Glue the wing on top of the fuselage with its leading edge 10 cm from the nose; the tailplane flat at the tail, its leading edge 32 cm behind the wing's; the fin upright on top at the tail. Look from the front and from above: wing and tail square to the fuselage, fin in line, no twist anywhere.

Balance it

Mark a point 3.3 cm behind the wing's leading edge on each side. Add nose weight until the model balances level on two fingertips at the marks.

First glides, and trim

In still air over grass, hold the model level at shoulder height and push it forward at walking pace; do not throw it hard. - Swoops up, stalls and drops: add a little nose weight, or bend the tailplane's trailing edge down by about 1 mm. - Dives: take off a little weight, or bend the trailing edge up by about 1 mm. - Turns: bend the fin's trailing edge a little the other way. Change one thing at a time, and write it down.

Measure the glide

From a measured launch height, measure how far the model travels before it touches the ground: distance ÷ height is its glide ratio. Try the balance point a few millimetres further forward and back, and record the best.

Tolerances that matter

Dimension	Target	Why it matters
Wing halves	matched within 1 mm	A warp in one half turns the model.
Balance point	±3 mm, set by gliding	Small moves of the balance change the glide more than anything else.
Alignment	wing and tail square, fin in line	Any twist makes it turn or roll.

How this fails

Balance too far back: it swoops and stalls. Add nose weight.

Balance too far forward: it dives. Remove some.

A warped wing or tail: it turns or rolls. Check against a straight edge.

Thrown hard: it loops and dives before it can glide. Push it at walking pace.

Wind: trimming in wind teaches nothing. Still air only.

How you know it worked

VerificationThe model glides straight in still air from shoulder height, returns to its glide after a push, and its glide ratio has been measured and recorded with the balance point that gave it.

Scaling and variants

Bigger models glide faster and further; wing area and weight both grow. The same balance, alignment and one-change-at-a-time trimming apply to every model and to every full-size glider, whose balance limits are fixed in its flight manual and never exceeded.

The same thing, built

**A modern sailplane on the grass at Borkenberge airfield, Germany, 2014: long, thin wings for a flat glide.** Lüdinghausen, Flugplatz Borkenberge -- 2014 -- 2466 · Taken on 12 April 2014, 10:14 · Dietmar Rabich · CC BY-SA 4.0 · Commons ↗

**A replica of the Wright 1902 glider in a museum: biplane wings, the elevator in front, the rudder behind, the pilot lying on the lower wing.** Wright Brothers 1902 glider · 2009-01-02 · Jarek Tuszyński · CC BY 3.0 · Commons ↗