[PSUBS-MAILIST] Depth tests at Seneca

Tue Aug 31 10:23:19 EDT 2021

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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