Semi-Aspirated Ballast System

[Kazzer]

might be over designing in my head.. but I would add a brass or plastic tube where the float rides the pipe .. just to prevent the foam from being worn down and misaligning with the seal to the pipe head opening, and add a little weight to help drop the float when as the water drains.

silly people like me might even want to attach periscope, etc to the top of the float ...

You mean like this?

And, yes, a nylon tube inside the foam, and a weight on the bottom of it, would finish off this design. Oh! I forgot - add a periscope and we've completed this project.

OK! Mr. Merriman, lets see it working!

[Reckless]

yeah with kit scope, snorkel, mast... etc on the foam.. as you submerge they would auto extend up.. as you surface they would retract. but dunno if there would be enough travel.

[Kazzer]

....................... but dunno if there would be enough travel.

Aha! That would be a factor in the design. Sounds like the foam would need to be wider and shorter. Would it all work? That is the question.