Re: [PSUBS-MAILIST] Self Adjusting Soft Ballast Tanks

[DJACKSON99@aol.com]

In a message dated 12/11/2003 7:09:56 PM Eastern Standard Time, Ray.Keefer@Sun.COM writes:

> 
>   Subj:  Re: [PSUBS-MAILIST] Self Adjusting Soft Ballast Tanks
>   Date:  12/11/2003 7:09:56 PM Eastern Standard Time
>   From:  Ray Keefer <Ray.Keefer@Sun.COM>
>   To:  personal_submersibles@psubs.org
>   Reply-To:  personal_submersibles@psubs.org
>   Sent from the Internet (Details)
> 
> 
> 
> 
> Hi Doug,
> 
> Will the 3CFM air flow be enough to compensate your cabin, engine compartment,
> that all three ballast tanks at the same time? As you said, if the decent is slow enough it will. My question is how slow is slow. 
> 
> If for example your spaces had a total volume of 36CF and they were half full with air at 33 foot depth. Going down to 66 foot the air would be compressed from 18CF down to:
> 
>    36CF/2 * 2ATM/3ATM = 12CF
> 
> To compensate for that you will have to add:
> 
>    18CF - 12CF = 6CF
> 
> At 3CFM you will have to take:
> 
>    6CF / 3CFM = 2M
> 
> 2 minutes to decend 33 feet. If you would ever exceed this decent rate your balast tanks would suffer uncontrollable compression as their air spaces were compressed by the every increasing pressure.
> 
> You might want some way to add pressure on demand. Or better in some kind of automated fashion.

Yes the CFM meter and valve will be in the cabin.  I was planning on water level sensors for the ballast tanks.  Perhapse contact switches near the lower ends of the adjustable pipes conneted to LEDS in the cabin. When lite they'll warn me that the tanks are not getting the needed flow.  Actually my ears are so lousy for scuba that they will be warning me first :)   But it wouldn't be to too hard to pipe a second air line that connects to the High Presure Air via a silanoid with is relay driven from the sensons in the ballast tanks. It could provide a boost to the flow.  Of course I'd need another valve to manually shut that off in case it stuck open.  But it sounds like a good idea.

> 
> The air diverter is an intriguing concept.
> 
> The pipe outlets in all the ballast tanks need to be as high as possible. If the water level ever got over the end of any of the pipes water will descend down the pipe into the engine compartment.
> 

Yea, but thats ok.  I'm planning on the oil pan sitting in a little watter and that's how I plan to dry out the cabin from the water left over once the bottom hatches are closed.  I'll likely have to put a valve there too in order to minimize the amount of water leaking into the engine compartment when the hatches are open.  Maybe your right though. I could use a second line to drain the cabin floor and put that on a valve, then move the engine compartment line up high.  Yes, I think I like that better. Good point. A dry engine is a happy engine.

> Since the bottom of the rear ballast tank is lower the the forward ballast tank's  bottom, the rear tank will be under a slightly higer pressure. Will that pressure force the air out of that tank and up to the forward tanks? What if enough air was forced out of the rear ballast tank to let water level get above the pipe, letting water down the pipe? Of course the read air diverter will now let more air into the back heavy submersible.  Will a 3CFM air flow be enough to keep up with the air
> transfer from the rear to forward ballast tank? Perhaps all three ballast tanks need to be at the same height in the sub.
> 

I originally had the rear tank vent to the forward tanks but if the nose is down, that would not happen, so I am going to just dump it over board.  The air entering the rear tank actually bubbles up from the flow diverter that is under it.  when the tail is level or high, the air should flow up hill to the front. If the pipe is 3/4" and the air is flowing at a slow enough rate, it should let and water trapped in the pipe flow back to the rear, otherwise I'll have something like a an air powered vacuum pipe and it will be trying to pump water to the front along with the air.


> You might want to mock out a scale model of your design and take to a pool.

Now there is a good idea.  I am sure it will pay off to play with the flow diverter. 

Thank you Ray, I appreciate your ideas.
Doug J

> 
> Regards,
> Ray
> 
> 
> DJACKSON99@aol.com wrote:
> > 
> > I would sure appreciate it if you kind sirs would look over what I think will work for ballast tanks on my dry ambient. It's explained with diagrams on my web page.  Just select "Self Adjusting Soft Ballast Tanks" from the table of 
> contents. Here is the link: http://jackson.parcabul.com/sub/
> > 
> > I am much obliged,
> > Doug Jackson