Stimulus: Theatr y Bryn Lighting Rig and Props List

Angle fact file for stage lighting

Acute angle: greater than 0° and less than 90°.
Right angle: exactly 90° (quarter turn, marked with a small square).
Obtuse angle: greater than 90° and less than 180°.
Reflex angle: greater than 180° and less than 360°.
Angles on a straight line (lighting bar): always add up to 180°.
Angles around a point (360° swivel clamp): always add up to 360°.
Angles inside a triangle: always add up to 180°.

Part A: Six angles recorded on the Theatr y Bryn lighting rig (for Step 1)

Part B: Rig diagrams with missing beam angles (for Step 2)

#	Lantern or rig measurement	Measured angle	Stage use
1	Fresnel floodlight beam spread	`55°`	Washes the harbour backdrop in warm amber light.
2	Safety barn-door flap wide open	`135°`	Keeps light off the proscenium arch curtains.
3	Vertical downlighter bracket to horizontal bar	`90°`	Points straight down onto the smugglers’ table.
4	Moving-head lantern pan sweep across stage	`240°`	Sweeps from stage left wing round to the auditorium arch.
5	Narrow profile spotlight beam cone	`28°`	Picks out the captain’s solo monologue in a tight circle.
6	Power cable safety loop around the rig hook	`195°`	Stops tension pulling the plug out when the lantern tilts.

1. Straight overhead lighting bar (angles on a straight line add up to 180°):

Junction 1 (find angle a): Three beams meet on the underside of the straight horizontal bar (180°). The left beam angle is 65°, the middle angle is a, and the right beam angle is 50°.
Junction 2 (find angle b): Three angles sit along the straight bar (180°): a vertical support bracket at 90°, a side spot at 42°, and missing angle b.

2. Full-circle swivel clamps (angles around a point add up to 360°):

Swivel Clamp 1 (find angle c): Four lantern arms radiate around a central ceiling mount (360°). Three of the angles between the arms are 110°, 95° and 85°. The fourth angle is c.
Swivel Clamp 2 (find angle d): Three lantern arms meet around a central point (360°). Two of the angles are 140° and 90°. The third angle is d.

Part C: The trapdoor spotlight geometry check (for Step 3)

The director’s rule: For the dramatic entrance through the stage trapdoor, the centre ray of Spotlight L4 must strike the flat stage floor at an angle of 45° (the standard theatre lighting angle so the actor’s face is lit naturally without long nose shadows).

The right-angled triangle formed by the rig, wall and floor:

The vertical stage tower wall meets the horizontal stage floor at a right angle (90°).
At the top of the tower, the horizontal lighting bar forms a straight line (180°) with the outer arm. Currently, the outer obtuse angle on the straight bar is set to 128°.
Therefore, the interior angle inside the top corner of the triangle is 180° − 128°.
Because the three angles inside the triangle add up to 180°, you can work out the angle where the beam hits the trapdoor floor and check whether it is 45°!

Part D: Props supplier price list and budget rules (for Step 4)

The PTA has given the Year 7 production a £75.00 props grant. Stagecraft Cymru Ltd gives schools a 10% discount off the entire order subtotal.

Prop item required for Smugglers of Porth Ddu	Quantity needed	Unit price (before discount)
Battery brass storm lantern	4	£6.50 each
Coiled hemp mooring rope (5 m length)	2	£4.50 each
Painted wooden tavern sign (The Anchor)	1	£14.00 each
Prop wooden tankard	3	£3.00 each
Printed canvas treasure sack	1	£12.00 each

Optional extra prop: The director would also love to buy a rubber prop spyglass costing £11.00 (after discount). Check whether your remaining grant after the 5 main items is enough to afford it!