[PSUBS-MAILIST] Depth tests at Seneca

Tue Aug 31 10:45:02 EDT 2021

A really nice thing was the diving the next day. In particular, that my
teenage son got to dive in a sub for the first time. The focus was not on
video, but here's a short 3 minute one that was an accidental byproduct.

https://vimeo.com/594808783

On Tue, Aug 31, 2021 at 10:24 AM James Frankland via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi Alec
>
> Saw some pics on facebook.  Looks like a great test day, even with the
> flooded pod.  Glad it all worked out.
>
> On Tue, 31 Aug 2021 at 00:17, Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Another fun thing was that Cliff got to take a dive in Shackleton. Maybe
>> he can give us a review, a la Road and Track or such!
>>
>> :)
>>
>> On Mon, Aug 30, 2021 at 5:38 PM Alan James via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>> Great report thanks Alec.
>>> Glad you survived the battery pod flooding, that could have been
>>> expensive.
>>> I know GL had a similar rule to what you are saying ABS has, but it was
>>> that any compartment (apart from the pressure Hull) that can flood has to
>>> be able to be mitigated by drop weights etc. Can't remember the exact
>>> wording.
>>> Good to hear & learn from the fails.
>>> Thats a pretty good check list for testing;
>>> it should be up on the Psubs site somewhere.
>>> Alan
>>>
>>> On Tuesday, August 31, 2021, 09:18:56 AM GMT+12, Alec Smyth via
>>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>
>>>
>>> Hi Friends,
>>>
>>> Steve McQueen and I just depth tested our subs in Seneca Lake, and I
>>> thought I'd send a little writeup. But first, many thanks to Cliff Redus
>>> and Dan Lance for crewing!
>>>
>>> We prepared our subs by installing temporary MBT plumbing outside, with
>>> valves that could be operated by swimmers. The subs were to be sent down on
>>> an anchor line, and would blow tanks an hour later automatically. The
>>> "auto-pilot" that blows ballast uses a timer, but will also blow ballast
>>> ahead of time if a water detector senses a leak.
>>>
>>> Both tests were successful, but both were also a little too exciting.
>>>
>>> In my case, Shackleton developed a 45 degree list during the tow out to
>>> the test site. I was pretty certain it was a flooded battery pod, and could
>>> see the cabin was dry by looking into the bow dome, so decided to go ahead
>>> and send her down because, even though a flooded pod is a lot of extra
>>> weight, the pods are sized not to result in negative buoyancy when flooded.
>>> That is an ABS rule. The sub did indeed come back up after an hour, with
>>> the cabin still dry.
>>>
>>> Once back on land, we found the source of the battery pod leak had been
>>> owner stupidity (surprise!!!) I normally open the pods for charging, but in
>>> this instance had thought it unnecessary because the charging was just a
>>> really small top-up. Wrong... battery off-gassing had dislodged a pod cap
>>> O-ring. On top of that, my pods have over-pressure valves that would have
>>> avoided the issue, except that I'd bolted them as an extra security measure
>>> to prevent a leak path on the test. After all, I don't think anyone else
>>> has put OP valves on their pods so reached the conclusion they weren't
>>> necessary. Well, lessons learned. Moving forward, caps will be coming off
>>> during any charging, and the OP valves will go back into operation too
>>> (e.g. to prevent against heat expansion.) The good news is that the flood
>>> does not appear to have affected the batteries, which are AGMs. We dove the
>>> sub the next day. All worked perfectly and the battery voltage had not
>>> decreased in the slightest.
>>>
>>> Steve's sub, The Great Escape, had a minor issue involving the temporary
>>> MBT plumbing. Steve had plumbed both MBTs together, to a T, and put a ball
>>> valve on that. What happened was a siphon effect between the two tanks.
>>> Whichever MBT was slightly lower in the water would transfer air to the
>>> higher one, from which it would escape. Steve redid the temporary plumbing,
>>> putting a separate ball valve on each tank, and the issue was fixed. His
>>> test went well, except he was conservative turning the knob on the timer,
>>> so the autopilot went off about 20 minutes later than planned - and he
>>> probably aged 20 years in those 20 minutes.
>>>
>>> Seneca Lake is 600 feet deep, and the bottom is very fine silt that's
>>> another 600 feet deep and has been deposited since the last ice age. We
>>> were concerned about the subs diving into that silt and getting stuck by
>>> suction, so we held them off the bottom. One interesting thing is we could
>>> see the subs on the boat's fish-finder. Really big fish, at 500 in the
>>> first test and 300 feet in the second.
>>>
>>> Here was our M.O.:
>>>
>>> 1) Trim out buoyancy at the ramp so the sub will be neutrally buoyant
>>> with MBTs flooded. Set the auto-pilot timer, seal the hatch.
>>> 2) Tow to test site.
>>> 3) Swimmers flood MBTs and make sure to close the valves before the sub
>>> disappears.
>>> 4) Add some ballast for modest negative buoyancy. Enough to prevent the
>>> sub from floating on a thermocline, but not so much you could not pull her
>>> up.
>>> 5) Let sub down a little, check for leaks by looking through the view
>>> ports. We marked the rope with labeled heat shrink, at 50 foot increments.
>>> We used a rope that was longer than the depth of the lake. It had a trawl
>>> float 20 feet from the sub, to keep it clear from the valve handles, and
>>> another float on the end in case we had to let it go. The rope was not tied
>>> off on the boat, we just put a turn on a cleat and kept a hand on it. An
>>> imploding sub could sink the surface boat.
>>> 6) Wait, tracking time on a timer that was set at the same time as the
>>> one in the sub.
>>> 7) The angle of the line indicates where the sub is. Ensure the surface
>>> boat is not directly above when the sub surfaces.
>>>
>>> If anyone wants to borrow the auto-pilot for a depth test, just let me
>>> know. I think we've used it for testing about 4 subs by now.
>>>
>>> I'll post some photos and video on FB...
>>>
>>>
>>> Best,
>>> Alec
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