[PSUBS-MAILIST] Bouyancy

Fri Jun 13 04:58:31 EDT 2014

One thing i did think about being a possible idea is a moveable weight that
can be cranked back and forth to adjust trim, a bit like you have on a
plane.  Would be quite easy to do and would be handy for fine tuning trim.
Would need another through hull though.  Another winter modification maybe.
Regards
James

On 13 June 2014 03:15, swaters via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

>  That is one way of fixing it. A bigger line would help prevent it some
> times, but not 100%. Dan's solution works well. It isn't a major problem
> with the K-350 design, just more a pain in the butt.
>  Thanks,
> Scott Waters
>
>
>
>
>  Sent from my U.S. Cellular© Smartphone
>
>  Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
> wrote:
>  OK thanks I see now.
> So if the ballast tank air fill was on a T in  the ballast vent line, just
> below the
> ballast valve, that would blow the water out when surfacing & solve the
> problem?
> Alan
>
>   ------------------------------
> *From:* swaters via Personal_Submersibles <personal_submersibles at psubs.org
> >
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Sent:* Friday, June 13, 2014 1:41 PM
> *Subject:* Re: [PSUBS-MAILIST] Bouyancy
>
>  Alan,
> It normally happens after the first dive and water gets trapped in the
> line. The gravity pulling the water is counteracted on by the pressure in
> the MBT pussing the water up therefore the water is trapped not letting the
> air out of the MBT.
> Thanks,
> Scott Waters
>
>
>
>
>  Sent from my U.S. Cellular© Smartphone
>
> Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
> wrote:
>
>
>  Dan / Scott,
> I'm a bit puzzled by this.
> There wouldn't be water in the line initially unless the valve exit was
> facing upward & rain
> or wave splash entered it. Does water enter in as the sub bobbles about &
> the ballast
> air exit dips below the water? I guess then the water in the line would be
> held in place
> by the small air pressure in the ballast tank, which wouldn't be enough to force
> the water up & out,
> but is enough to hold it in position.
> Alan
>
>   ------------------------------
> *From:* Dan H. via Personal_Submersibles <personal_submersibles at psubs.org>
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Sent:* Friday, June 13, 2014 3:03 AM
> *Subject:* Re: [PSUBS-MAILIST] Bouyancy
>
>  Scott,
> To clear the lines, I screwed a T onto each of the through hulls that feed
> air to the MBTs.  (on the open end under the MBTs)  Then I fashioned a
> piece of copper tubing that directs a stream of air right into the MBT vent
> line but not actually connected to it.   I put a restriction in the other
> end of the T to create enough back pressure so the tubing emits a pretty
> good blast of air directed at the vent port.
>
> To vent the MBTs, I open the conning tower vent valves then give the tank
> blow valve a turn till I see the water blow up and out the vents.  That
> seems to clear the lines and then it vents properly.
>  It's not a great fix but it works.
>
> ----- Original Message -----
> *From:* swaters via Personal_Submersibles
> <personal_submersibles at psubs.org>
> *To:* Personal Submersibles General Discussion
> <personal_submersibles at psubs.org>
> *Sent:* Wednesday, June 11, 2014 10:37 PM
> *Subject:* Re: [PSUBS-MAILIST] Bouyancy
>
> 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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