How do I work out the rake on the stage?

[torch1972]

I have been updating the tech specs for the theatre collecting all the information I think any incoming theatre company would need. I have got stuck as the theatre has a raked stage and gone though all the paperwork that was already and cannot find what the ratio for rake of the stage.

 

I can get a measurement in degrees by putting a spirt level on the stage. But then I need to convert that in to a ratio. There must be a simple trigonometry way to work this out but it been a long time since I have done trigonometry. Does anyone know the right formula?

 

Cheers

[bruce]

take the slope in degrees, punch it into your calculator, press the "tan" button, press the "1/x" button, and round it off.

 

eg if the slope is 3 degrees from horizontal, the above gives 19.08

 

So it's a 1 in 19 rake.

 

But I suspect the angle measurement on your spirit level may not be accurate enough - eg a 2 degree slope would give 1:30 and a 4 degree 1:14. Can your measuring device measure to sub-degree accuracy?

 

Possibly a better way would be to take your (1m, 1000mm) spirit level, and place it on the stage. Lift the end until it is level. Measure the distance you've had to raise it (say 40mm).

 

so the rake is then 40 in 1000, or 1 in 25

[Ynot]

And for a more accurate measurement, find yourself a decent quality length of preferably planed timber, check that the face is straight by laying it flat out on the deck and checking for warps. If it passes that test, then place the length (longer the better) up stage to down and level with your spirit bubble, then measure as above, using the extreme ends of the timber.

[ramdram]

Laser level from back of stage to ruler at front of stage, take measurements, do maths, adopt smug mode, job done.

[adam2]

Another simple method is to use a length of transparent hose filled with water.

Place one end at the front of the stage, and the other at the back.

Adjust the lower end such that the water line is say 100mm above floor level, then measure the height between stage floor and water level at the high end.

 

This is the same in principle as the use of a spirit level suggested above, but is not limited by the length of the level. It is very accurate.