[PSUBS-MAILIST] Bouyancy

Thu Jun 12 05:08:33 EDT 2014

Personally, the reason for going to 3/4 inch is that the valves are 3/4
inch.  So thats the maximum i can go without changing the valve as well.

But, i think Alec makes a really good point on the safety aspect as well.
It would be very easy to catch the valve handle by accident.  So maybe 3/4
is a good compromise.  Still, im not going to change that until the winter,
want to get some diving in now.

Regards
James
On 12 June 2014 03:37, swaters via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

>  Dan,
> I have the exact same problem with hydrolocking in the vents. I have to
> open the hatch and blow the water out with my mouth. Pain in the butt.
>  Thanks,
> Scott Waters
>
>
>
>
>  Sent from my U.S. Cellular© Smartphone
>
> "Dan H. via Personal_Submersibles" <personal_submersibles at psubs.org>
> wrote:
> If I were to do mine over again, I wouldn't vent it as it is in the
> plans. Instead of running piping from the MBTs to the conning tower, I
> would run linkage, and have the actual valves mounted on the MBT.
>
> Besides slow venting, my biggest problem is getting water in the piping
> that won't escape to let the air come through when venting.  A homemade
> mushroom valves made from bathroom sink drains controlled by linkage going
> to the conning tower, or anywhere easy to reach in the hull, would solve
> all the problems.
>
> My thought, Dan H.
>
>  ----- Original Message -----
> *From:* via Personal_Submersibles <personal_submersibles at psubs.org>
> *To:* personal_submersibles at psubs.org
> *Sent:* Wednesday, June 11, 2014 9:53 PM
> *Subject:* Re: [PSUBS-MAILIST] Bouyancy
>
>  Scott, Alec, Vance, and all,
>
> A 3/4" vent is going to be about 2.25 times as big in cross section as the
> 1/2" vent.  A 1" vent would be about 4 times as big as the 1/2". What are
> your thoughts/comments on 3/4", 1" or any other size vent vs another?
>
> Thanks,
> Jim
>
>  In a message dated 6/11/2014 5:45:10 P.M. Central Daylight Time,
> personal_submersibles at psubs.org writes:
>
> James,
> I totally agree with you on the 1/2 inch vents being way to small.
> Eventually I am going to switch mine out to 3/4"
> Thanks,
> Scott Waters
>
>
>
>
>  Sent from my U.S. Cellular© Smartphone
>
> James Frankland via Personal_Submersibles <personal_submersibles at psubs.org>
> wrote:
> Hi All,
>
> A member has asked me to post a description of what was going on with
> bouyancy on my dive.  Which was as follows:
>
> I'd asked the crane driver to be prepared for the first dive to hold me
> just below the surface as i was expecting to be a little out of control.
>
> At first, i got a bubble stuck in the forward tank.  Ive put quite a large
> lip on the inside of the tanks in an attempt to cope with Guernsey seas.  I
> could see the bubble stuck through the forward dome and i squished myself
> right up into the front to try and force it a bit more level so it could
> escape out of the vent.  It didnt make any difference and then all the lead
> i had inside, slid along the deck right to the back, making the entire
> situation worse.  Closed vents, blew mains and re-surfaced.
>
> Next attempt, i got the bubble stuck in the aft tank.  This wasnt as bad
> because the motor cut away allows air to escape so i got under a little
> further, but not enough.  I flooded the variable in an attempt to get
> under.  Still no good, so i asked the divers to shove on the back.  This
> got the boat under, but then because of the total lack of air in any tanks,
> i sank to the bottom like a stone.  Depth was 6m (20ft).  I expected to
> stop on the crane ropes, but the driver must have misunderstood me and
> before i knew it, the bottom was in sight and then i was down with a gentle
> bump.
>
> I sat for a bit talking to my brother on the radio and then shut the
> variable vent and pumped a little air into the tank.  I slowely started to
> rise.  Flooded it again and started to sink.  Really quite straight
> forward.
>
> Blowing the VBT completely brought me up fairly quickly until i seemed to
> be just awash with the surface.  Filling the mains then brought me right
> out.
>
> I did several more test dives after that and as long as i evened out the
> venting of the main tanks to avoid the bubbles, i could dive without the
> divers assistance.
>
> I next got the boat neutral just off the bottom and then used the motors
> to drive up and down. I was not aware at the time that one motor was not
> working but it still seemed quite responsive and i could drive all the way
> up to the top or down to the bottom, stopping anywhere in between.
>
> I need to add some extra vents to the main tanks to prevent the air pocket
> from occuring again, and also those half inch vents are far too small.  It
> takes forever to vent the main tanks.  Thats one for a winter modification.
>
> I think that was it.
> Regards
> James
>
>
>
>
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