Thanks Waffle, I've been doing a bit of digging and I found an on-line version of the Motor Torpedo Manual here;
http://www.ibiblio.org/hyperwar/USN/ref/PT-Manual/index.htmlAnd it states for the Mk-2 Generator-
"21. As the atomized FS smoke mixture leaves the nozzle of the generator, it combines with the moisture of the air to form finely divided fog particles. The heat developed by this chemical reaction causes the smoke screen to rise. Normally the screen will rise from 200 to 300 feet, forming a solid screen from the water to this height. One tank of smoke mixture may be expected to give a screen about 3,000 yards long. A number of shorter screens may be obtained, the number depending on the length of the shorter screens."
But I think the new PT Boat has the later Elco generator-
"The FM or "Elco" smoke generator consists of a steel bottle of the type in which commercial gases are contained. It has a single threaded opening at one end, which is controlled by a valve. This valve is part of the bottle assembly, and the wrench that opens it is furnished with the original bottle (or generator) of smoke. This wrench has a hinged handle so that a steel protective cap may be screwed onto the bottle over the valve assembly with the wrench attached when the generator is not in use.
To spray the smoke liquid from the generator, a smoke pipe is furnished. This pipe is about two feet long and is bent slightly. On the lower end it carries a fitting to connect the pipe to the nipple on the generator valve assembly. A hinged wrench for this fitting is clipped to the smoke pipe. At the upper end the pipe is threaded to receive a single nozzle.
Four nozzles are provided, and are quickly interchangeable. They are marked for 3 min., 5 min., 8 min., or 12 min.; the time the smoke will last in a continuous screen, using the respective nozzle. The 8 min. nozzle is for use under average condition and the 12 min., nozzle is for night use. If the weather is very windy either a 3 or 5 min. nozzle would produce a better screen."
And this doesn't sound like much fun,
"The liquid that produces the smoke is titanium tetrachloride, which, when sprayed into the air, combines with the moisture in the air to form hydro-chloride acid and titanium hydroxide, thus forming smoke. The liquid is very corrosive on steel or flesh. Burns from FM are to be treated in the same way as FS burns."
OUCH! That's one mean smoke screen!
