[PSUBS-MAILIST] Mushroom Valve?

[Alec Smyth via Personal_Submersibles]

Hi James,

My Snoopy saddle tanks worked fine, but recently I have become a specialist
in building saddle tanks that don't work, so take my suggestions with a
grain of salt. The first thing I'd worry about looking at those tubes is
the proportions. They are really long, which means when you are in the
process of diving and they are half full, there is a danger the water will
rush forward or aft and destabilize your trim. They might also trap an air
bubble if you are at anything but perfect trim. I'd suggest much stubbier
tanks, but since you have them in hand already you might want to put them
on and see what happens. It's possible that testing will indicate the need
to cut them in half lengths, or put a bulkhead in the middle of them.

As to the means of valving them, it would be nice to put mushroom valves
inside the tanks but I don't know of a way to actuate those mechanically.
I've just built a set of mushroom valves but they are pneumatically
activated. Note, however, that I had to build them from scratch because I'm
not aware of any that are available off the shelf - and it was a three
month job. It doesn't mean OTS ones don't exist, but I couldn't find any.
The closest I got was a suggestion from Greg Cottrell that turbo blow-off
valves might serve, but I'd have to research those as I know nothing about
them. The alternative is to use the Kittredge method. If you have
sufficient rise in the tubing it works really well, but to get that rise
you might need to put the valves on the CT. Or, mount ball valves right on
the saddle tanks if you can get a rod to them from a mechanical
through-hull. I think Nekton Gamma uses that method. On Snoopy I just had
flexible hoses from both tanks go to a T, and from there to a ball valve
mounted on the CT. If you figure there's space to do that, it's certainly
the simplest method.

Best,
Alec



On Thu, Feb 1, 2018 at 10:59 AM, James Frankland via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi All,
>
> I am adding saddle tanks to Jodie B.
>
> Im not 100% sure what to do with regards to the vent plumbing.  I would
> like to ask if anyone has any advice?
>
> I am thinking of putting 2x through hulls on the top of the main pressure
> hull.  For and aft of the tower and then piping the vents to a valve that
> would operate through them.  Similar to the existing vents.
>
> OR, fit the through hulls at the side so they penetrate the tanks and have
> a linkage of some sort that operates valves attached to the top of each
> tank, for and aft.  Some sort of mushroom valve??
>
> Any ideas?  What have other people done?
>
>
> ​
> ​
>
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>
>
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