[PSUBS-MAILIST] Shackleton test report

[Alec Smyth via Personal_Submersibles]

Hi friends,

I've updated the project page with new photos.

http://www.psubs.org/projects/1234567810/shackleton/

Best,
Alec

On Mon, Dec 3, 2018 at 11:02 PM Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Thanks for that great report Alec.
> Glad it went well.
> Alan
>
> > On 4/12/2018, at 1:29 PM, Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
> >
> > Hi friends,
> >
> > Today with Mark Ragan and Brian Hughes' help I'm delighted to say we
> were able to sneak a test in just before winter makes its appearance. It
> was tee shirt weather, with high tide at the warmest time of day.
> >
> > You may not be familiar with Shackleton, so here's a summary. She uses
> the main cylinder of an earlier project called Solo, which was to be a
> hydrobatic sub and therefore had a very slender (i.e. only 31" diameter)
> main hull. Solo lost her wings and tail but gained battery pods, a CT, a
> deck, etc. Shackleton herself has already been through several iterations,
> specifically of the MBTs. In the first iteration I made a big mistake - I
> concentrated my calculations on submerged stability, just assuming the MBTs
> would provide stability when surfaced. Nope! The second iteration used a
> raft MBT, which is far more stable than the streamlined hull-hugging
> initial version. That solved the surfaced stability issue. However, it had
> a new problem. The raft was composed of a bunch of small aluminum tanks,
> plumbed to valves on the CT just like a Kittredge sub. The problem was that
> the plumbing had do cover quite a distance and suffered from water
> blocking. This is the third iteration, an!
>  d uses a raft of four MBTs but with mushroom valves rather than the K
> boat arrangement. Water blocking can't happen because mushroom valves go
> straight on the tanks and have no plumbing at all. I can already say that
> although it took me a while to arrive at, I'm a fan of the raft
> configuration implemented with mushroom valves. BTW the valves are
> controlled in pairs, so the pilot can open or shut the two forward valves
> or the two aft ones independently.
> >
> > What worked well:
> > - As mentioned, the raft MBT provided good stability.
> > - The boat floated at the calculated waterline and in trim.
> > - The vertical thrusters blow water through the deck grating. I was
> curious how much efficiency this would cost, but it appears a very
> acceptable compromise.
> > - The four thrusters are jettisonable. They are held against the hull by
> a bolt, and they seat against electrical connectors that are insulated from
> the water by an O ring. I have a short-detection circuit to make sure those
> O rings aren't leaking. I used it, and found no leaks. Thruster controls
> worked great.
> > - The boat uses a combination of trawl floats and steel ballast to
> adjust buoyancy, with no VBT. Today's test was with just one person aboard,
> and in salt water. In other words, the scenario that calls for max ballast.
> We turned out to be balanced with a tad less than the full complement of
> weights - the theoretical numbers turned out near perfect.
> > - I love the fast submergence!
> >
> > Needs work:
> > - The thrusters are fine going forward but quite miserable in reverse. I
> think this is due to a combination of two factors. First, in reverse the
> prop wash hits the MBTs - I can't really do anything about that. Second,
> I'm using after market props that are supposedly faster than the stock
> Minnkotas. But I think they accomplish that by being biased for forward
> motion. I'll be switching back to the stock props.
> > - Two of the mushroom valves don't seal 100%. I'll be putting in
> slightly thicker O rings to see if that stops it.
> > - The hatch leaked, even though it didn't on past tests and didn't when
> I tested water-tightness with a vacuum two days ago. The hatch is bolted to
> its hinge, and washers on those bolts adjust the fit. This is just
> something to tinker with, but I know it can seal successfully.
> Unfortunately I have to remove the hatch each time the sub goes in and out,
> to fit under the garage door opening.
> >
> > And now... let winter move in! The next step will be a nice spring day
> dialing in ballast configurations for one or two occupants.
> >
> > Thanks,
> > Alec
> > <47258859_10217781304468113_8654460041761390592_o.jpg>
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