[PSUBS-MAILIST] Shackleton testing

Tue Oct 1 13:57:54 EDT 2019

Love to hear you happy with all the mods!
Regarding trailers:
On top of having good tongue weight i am always careful with driving speed,
below 100kph.
i feel more safe in my sub deep down than on the road...

Regards,
Antoine

Le mar. 1 oct. 2019 à 19:34, irox via Personal_Submersibles <
personal_submersibles at psubs.org> a écrit :

> Congrats on the successful test!  Very exciting to see it's all coming
> together.  Would love to see any pics/videos you took.
>
> Cheers!
>  Ian.
>
>
> -----Original Message-----
> From: Alec Smyth via Personal_Submersibles
> Sent: Oct 1, 2019 9:28 AM
> To: Personal Submersibles General Discussion
> Subject: [PSUBS-MAILIST] Shackleton testing
>
> Hi everyone,
>
> Just a quick update on Shackleton test dives we made last week. Many
> thanks to Brian Hughes, Dan Lance, Steve McQueen, and Mark Ragan, who all
> drove big distances and set aside three days in the middle of the week.
>
> An earlier trailering issue has thankfully been resolved. Make sure you
> have sufficient tongue weight!!! The longitudinal location of the sub in my
> case produces about 300 lbs of tongue weight per inch that you move the sub
> forward, so it's absolutely key to locate the sub accurately. The earlier
> problem was that the trailer went into harmonic oscillation and decided it
> liked to travel next to the tow vehicle rather than behind it. Solution:
> Increased tongue weight to 580 lbs, reinforced the tongue to deal with
> that, and added a damper between trailer and tow vehicle. Here is the
> damper:
> https://www.campingworld.com/curt-manufacturing-curt-17200-sway-control-kit-91408.html?gclid=EAIaIQobChMIzZySh9vx5AIVD2yGCh1lOQXZEAQYAiABEgIZ3fD_BwE
>
> I added buoyancy foam bolt-on flotation for operating in fresh water with
> a crew of two, which is the maximum payload/minimum buoyancy scenario. It
> worked perfectly, and is cheaper than syntactic foam. The sub happens to be
> the right shape for a material that comes in sheets. In the pics, these are
> the flat white slabs on the side of the MBTs. The material is R-3315,
> described in this article:
> https://sea-technology.com/feature-article-low-density-polyurethane-foam-for-subsea-buoyancy-systems
>
> Diving with the mushroom valves is sure different, and decidedly easier.
> In a K boat, you flood MBTs somewhat tentatively, intermittently opening
> and closing one or the other valve to keep the boat level. I've abandoned
> that practice in Shackleton, and just leave both MBT valves open until
> under. That only takes seconds, so there's no concern about getting out of
> trim because there isn't time to - she stays flat.
>
> The sub dives so fast that flooding MBT puts her in vertical oscillation.
> Lets say you dive in perfect trim, just a few pounds positive. The sub will
> descend until the CT is 7 feet underwater, come up and break the surface,
> then go down again but not as far, bob up again and break the surface, and
> finally stay there. Initially we were looking to dial in the ballast and
> this was a little confusing, because the first impression upon venting is
> that the boat is heavy. However, once ballasted there is no need to bounce
> up and down when you dive. If you add down thrust while flooding MBT, she
> goes straight down.
>
> The system of using trawl floats to adjust for different crew weights
> worked beautifully. When changing crews, you just lift a trapdoor in the
> deck and add or remove floats. They are located under the front half of the
> deck, since that is above the passenger and thus aligned with the weight
> variability you are adjusting for. I'll never use VBT again, this is
> simpler and works really well.
>
> Stability was also really good. Several people can walk around the deck,
> and you can go to any edge of the deck without inducing much heel at all.
> After diving for a while, if the crew wanted to switch positions we
> surfaced, both got out on deck, and got back in again in reverse order.
>
> The only thing that was fidgety, although it still did its job, was the
> pressure compensation regulator. I have a differential pressure gauge in
> the sub, which allows me to see how the compensation pressure compares to
> ambient. I set it at +4psi but this sometimes (other times not) went to
> zero at depth. On surfacing it seemed to have trouble venting and climbed
> to +9. Cliff uses the same exact regulator with no problem, so I might just
> have a dud. It is an industrial regulator, but I think I might trade it out
> for a SCUBA 2nd stage because that would have a far larger vent valve.
>
> A surfacing blow consumes about 300psi. That does not completely fill the
> MBTs, I could blow far more, but it is sufficient to get out and walk
> around. So a set of tanks is good for about 10 dives and I will plan on 8.
>
> Shackleton has two battery pods with 6 batteries each. We dived all day on
> one bank and it's charge indicator only went from 10 to 8 bars. So I'm not
> sure how accurate or proportional that instrument is, but it said we had
> only used about 10 percent of battery capacity in a full day.
>
> At last, I've a compass that works and we were able to follow headings
> submerged with no problem. It's on the deck, about a foot above the main
> cylinder and two feet in front of the CT. You just look out the window to
> read it. I tried running the thrusters hard but did not observe any effect
> of their current on the compass. In Snoopy my compass would spin.
>
> We tested the emergency release float. It worked fine, and the nice thing
> is that the release can be stopped when the float reaches the surface, to
> avoid trailing a super long line. But someone said there is a mechanism
> that allows you to wind it back in from the sub, and that would be even
> better!
>
> Freeboard came out to design, 24 inches. Even trim.
>
> We only went to 25 feet, and next up will be a depth test - most likely in
> the spring.
>
> Best,
> Alec
>
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