[PSUBS-MAILIST] Ballast Tanks

[hank pronk via Personal_Submersibles]

 Alan, Oh man I really need to proof read.  I must have been low on O2 Hank
    On Monday, May 18, 2020, 6:42:47 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Hank,I managed to interpret that email & In my calculations I forgot about putting a burstof compressed air in to get the water completely out, although I was automaticallydoing that when I was diving.A bit of a no brainer now for me to have a free flooding ballast tank. Alan
On 19/05/2020, at 12:08 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


 Alan, I know after laughing Gamma I always gave a boat of air to make sure all was open and good.  I could not quantify the amount but know there is not much difference.Hank
    On Monday, May 18, 2020, 6:00:12 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 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
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