Waterwulf
Contributor
it was a long time ago but if I remember correctly, it was about 4 inches in diameter. Our club dive boat had a davit that would hang it over the side but close enough to whack it with the attached hammer. I think there was a couple of feet hanging in the water. Both ends were uncapped so water could just flow up inside. As far as wall thickness: Beats me but I would think a piece that size would have to be at least a quarter inch.
There was nothing special about it, just a piece of scrap put to use. I know it worked very well. A smaller piece would probably work as well. The code for emergency, surface now and return to boat was something like six bongs followed by six more followed, etc., etc. The one time that it was a real life or death emergency, whoever was beating on it gave up on any codes and was just beating the crap out of it like they were trying to beat it to death! No code but we all got the message.
