Thanks guys for help with the munitions
It makes sense now. I guess the diode prevents the current from going back through the reed switch. What diode do I ask for at the Radio Shack store?
I'll post a few pictures and video when this thing is finished. Next project is operational depth charges, but very little electronics needed here, just paper tube, balsa end caps, black powder, waterproof cannon fuse and a model airplane engine glow plug. A servo will energize the glow plug, set off a few grains of powder to ignite the fuse and blow the depth charge clear of the rack on the PT boat. Several people have done this already. Do a search on YouTube for model ship depth charges to see short video.
Regards,
Mike in Honolulu