My curiosity has been aroused, and was in need of any input regarding my 32 scale u-boat which had been set up to be positively bouyant. With a full bottle of propel the boat was positively bouyant with water level at about 1" from top of tower, as propel was used the boat became lighter. On one particular dive to several feet motors were stopped and after a few minutes the boat did rise to the surface. However, once on the surface it began to sink. My question, why, once on the surface did it not stay afloat. Especially that the weight of the boat had been reduced by a nearly empty bottle of propel. Any input will be appreciated. Thanks Al email@example.com
...can you determine whether or not the ballast tank vent as properly closed? That would seem the most likely culprit. I'm assuming that the motor/electronics (dry) space of your dive module did remain dry.