In my opinion you cant say an exact rolling boil time - only rough!
There are a lot biological factors to consider:
- different wood (dry, wet, type, etc.)
- temp. of the water (when start)
- wind factor (wind direction, windpower, etc.)
- different billy cans (diff. metalls, sizes, Airflow between can and cooker, etc.)
- and so on......
roughly I would say, that my cooker will need between 6 and 10min. from start to rolling boil. (Ikea Hobo stove).
With my gascooker (Primus) I have a rolling boil in approx. 5 to 8min.
The trangia also have approx 5 to 8min. for 500ml of water.
With my Esbit cooker and the fuel tablets I have times between 8 and 15min.
But one thing I´d like to say:
In the bush (anywhere outdoors) I dont have any hurry - as you can see above: there are only a few minutes different from one cooking system to the other - and yes I have tose few minutes spare in every situation.
As Ray Mears said in one of his videos:
Things are cooked when they are done!
The whole life is controlled by hurry and time - and when I´m out in the bush I dont have this "panic" that everything should be finished as fast as possible!
Enjoy your stay, your calmness, the quiet and the fact, that 500ml of water didnt have to boil up in seconds......
cheers
Mike