[PSUBS-MAILIST] Bouyancy

Fri Jun 13 09:00:07 EDT 2014

Good idea scott.  I made mine more or less as per the plans and i can tell
that they are going to need to be re-moulded soon enough.  The steel
channel inside is starting to rust already.  Could maybe make something
similar to your tray.

On 13 June 2014 11:22, swaters via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

>  James,
> I had thought about that when I started to build my K-350. What I did is
> designed a removeable weight tray. It is alot like a egg carton. It allows
> you to move weights where ever you want on the tray to trim up. It has
> worked great so far!
>  Thanks,
> Scott Waters
>
>
>
>
>  Sent from my U.S. Cellular© Smartphone
>
> James Frankland via Personal_Submersibles <personal_submersibles at psubs.org>
> wrote:
> 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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