[PSUBS-MAILIST] Depth tests at Seneca

Tue Aug 31 14:56:06 EDT 2021

Very cool. Way to go, Trevor!Vance

-----Original Message-----
From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Tue, Aug 31, 2021 10:45 am
Subject: Re: [PSUBS-MAILIST] Depth tests at Seneca

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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