Suggestion: Instability at Periscope Depth

[VonHoffman]

Originally Posted by derstosstrupp

That’s how I do it as well yeah. Typically at the start of an engagement I will do a trim dive and adjust the tank to achieve neutral at dead slow speed. And the ballast tanks should be completely flooded always on diving.

Yes - I leave them open for a few minutes after diving to be sure they're full.

That raises another question: when blowing the tanks, do you wait until near the surface? Do you blow them quickly or slowly?

I did some testing and the external water pressure seems to be factored into how much compressed air is required to empty the tanks. If you blow the tanks when deep it requires far more compressed air than if you blow them near the surface (great!!!).

The only thing I couldn't quite determine is if blowing them slowly is more efficient than blowing them quickly? My guess is there is a maximum rate the water will leave the tanks, and it might be possible to compress the tanks with air, thereby losing air when the tanks finally empty and the pressure equalizes with the atmosphere??

A low-pressure blow, cutting the compressed air before the tanks are completely empty, would therefore reduce the compression in the tanks, and save compressed air as well by not using more air than necessary?

I need to do some more testing!