[PSUBS-MAILIST] Trim weight

Fri Jun 13 09:26:35 EDT 2014

James and Scott,

I had planned to have the weight tray inside the hull with a  screw drive 
such as on a garage door opener driven by an electric motor in order  to 
adjust the trim.  I think Cliff has something similar on the  R300.

However I've almost abandoned the movable tray  idea in favor of something 
more like Scott's egg  carton.  Once the initial test dives establish the 
proper trim, there  shouldn't be a lot of need to reposition the weight unless 
I add  equipment.  I have tandem seating so [Human+Lead] in each seat  
should remain constant no matter the weight of the pilot or  passenger.  In the 
K-350 where they could swap positions while underway,  there might be more 
need to move the trim weights.   When you  change passengers and/or pilots 
you might have to add or subtract weights, so  it's more convenient to have 
the tray inside the hull.

Cheers,
Jim

In a message dated 6/13/2014 3:59:02 A.M. Central Daylight Time,  
personal_submersibles at psubs.org writes:

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_ (mailto: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_ 
(mailto: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_ (mailto:personal_submersibles at psubs.org) >
To: Personal Submersibles General  Discussion 
<_personal_submersibles at psubs.org_ (mailto: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_ 
(mailto: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_ 
(mailto:personal_submersibles at psubs.org) >
To: Personal Submersibles General  Discussion 
<_personal_submersibles at psubs.org_ (mailto: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_ 
(mailto:personal_submersibles at psubs.org)  
To: _Personal Submersibles General Discussion_ 
(mailto: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_ 
(mailto: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_ (mailto:personal_submersibles at psubs.org) 

To: _personal_submersibles at psubs.org_ 
(mailto: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_ (mailto: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

James Frankland via  Personal_Submersibles 
<_personal_submersibles at psubs.org_ (mailto: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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