I'm building a steam box to bend some timber. Does anyone know the rate at which water is used in such a setup? (That will help me determine the size of the boiling water container and how often it needs to be topped up.)

i know nothing about bending wood apart from what i learnt in the past few minutes. that said, to my untrained eye the plastic bag method looks pretty nifty:

www.core77.com/posts/35838/A-Better-Way-to-Steam-Wood-for-Bending-Use-a-Plastic-Bag



www.tipsfromashipwright.com

Yes, I've seen that guy's videos. Unfortunately he doesn't say how much water he uses. Other internet searches haven't answered the question either.
I steam bent 50 or so ribs for a 28 ft wooden boat many years ago but I cannot remember how much water I had to use to keep topping up the boiler.
I'm hoping someone with current experience (or a better memory than mine) will know.

the seabreezer 'boty' on here does work on wooden boats, he probably knows...

Okay, here's part of the answer. While waiting for a response on this forum I decide to do a test. I boiled 1 litre of water in a saucepan, with the lid on but the lid vent open, for 30 minutes and measured the difference in volume before and after the 30 minutes. 700 mls of water was used as steam.
So roughly I reckon 1.5 litres per hour would be a good enough guess. It does of course depend on heat applied, how much pressure is built up, etc.
So I think I'll build a boiler size of about 4 or 5 litres for my steamer box size of 150mmx150mmx1.8m. Then I should be able to get a steam time of 2hrs before I have to top it up with some more hot water.
If you have any other suggestions I'm all ears........

do a fair bit of bending at the slipway just knocked up a new box out of 12mm ply make sure the timber doesn't sit on the bottom we put pins through so you can stack several layers at once we get our steam from our 3 phase diesel powered steam cleaner these days but previously ran a copper coil, hose in one end steam out the other , with a gas fire though a wood fire works as well you just have to keep more of an eye on it
if your just bending a small amount of timber grab a bit of steel pipe bung up one end half fill with water put at 45 degree angel boil for 1 inch an hour thickness
remember timber selection is just as important as temperature only use dead straight grain timber
dont let the steam go dry
be real quick once its out of the box its surprising how it stiffens up as it cools even a small amount
have fun i love steaming its so cool getting big lumps of spottie gum to bend through 90 degrees or more