[PSUBS-MAILIST] Ballast Tanks

[Alan via Personal_Submersibles]

Just did some experiments & answered my own question.
If you put an upturned glass in a container full of water & push it down till
it is just fully under the surface, the water enters the bottom of the glass to
a level that is 6% of the volume of the glass.
This is less than what I thought. You would only gain 6% more floatation by
going from a free flooding ballast to having a flood valve.
The pros of having a flood valve are the added floatation & added security that 
your sub won't sink if the vent valve fails.
The cons are that you would need a much larger valve than the vent valve 
& there would be more pressure in the ballast tank when blowing the ballast.
Alan

> On 18/05/2020, at 7:45 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Has anybody got an idea or guess as to how much water comes in to
> a free flooding ballast tank? Ie. would it fill up to 1/4 of the volume
> of the tank with water? And does this vary much after towing.
> Also if you know the volume of your ballast tank that would be helpful.
> Am considering inlet valves at the bottom of the tanks as I will be towing 
> the sub a lot.
> Thanks Alan
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles