[PSUBS-MAILIST] Shackleton testing

Fri Oct 4 18:25:44 EDT 2019

No, sorry, I've never towed her yet. I don't expect it to go well in terms
of being streamlined, and she'll probably tow like a parachute. But at
least there's freeboard, so the towing can be done without being on board.

On Fri, Oct 4, 2019 at 6:22 PM David Colombo via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi Alec, she looks great! With the new deck shape, did you have a chance
> to tow it and see how she tracks? On your float release i am building a
> retrieving motor to coil in the line. I'll let you know how it works.
> David
>
> On Wed, Oct 2, 2019, 4:53 AM hank pronk via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Alec,
>> Congratulations!  I know you had some hurtles to overcome with that small
>> diameter hull.  I love the deck and stability.  The fast valves must be
>> nice.  It sure looks sharp sitting at the surface and the three big floats
>> add to it.  The sub is inspirational and shows  what can be done by a home
>> builder in a garage.
>> Hank
>>
>> On Wednesday, October 2, 2019, 4:19:28 AM MDT, James Frankland via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>> Alec,
>>
>> Great report.  Sounds like really succesful dives.
>> Do you have any pics?   Interested to see the pressure regulator.
>>
>> Regards
>> James
>>
>>
>> On Wed, 2 Oct 2019 at 03:11, Alan via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> Alex, Cliff,
>> thanks for the report Alex, I hadn't thought about the oscillation from
>> flooding the ballasts too quickly.
>> As for the compensating regulator, Cliff I am about to try it out on my
>> thruster on an inflatable boat. I am having an air over oil system. Just
>> bought
>> a 18 cuft pony bottle for it.
>> There is silicone oil in the thruster housing & in the line leading to
>> the compensating
>> regulator. So very little air is required to compensate, & if oil leaks
>> out it is
>> replaced by air & indicated by the oil height in the line.
>> Alex, as for the pressure differential in the regulator; I am not sure
>> what operating
>> range you chose for that regulator. Did you go for the lowest range?
>> I think they have a piston which could stick a bit in that low 4 psi
>> range, hence your
>> zero pressure. The relieving part of the regulator is set by the size of
>> its spring.
>> You could put a weaker spring in if you want the pressure relief on
>> ascending
>> to be closer to your set pressure, however you run the risk of it free
>> flowing.
>> In commercial spring pressurised compensators they get a variance in
>> pressure
>> larger than what you are experiencing, but this is over time due to the
>> spring
>> extending as the oil level goes down.
>> Alan
>>
>>
>>
>> On 2/10/2019, at 6:31 AM, Cliff Redus via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> Alex, great report on mods to Shackleton.  It sounds like the mods you
>> made to both the trailer and MBT system worked. The discussion on the fast
>> acting MBT mushroom vent valves was interesting, particularly the part
>> about the vertical oscillation.  My guess is another way to null out the
>> oscillation would be to open the MBT vents for a specific amount of time so
>> that you were shooting for flooding 80% of the MBT volume, close the MBT
>> for a short time then open them again to finish the flood.  I bet if you
>> experimented with this you would find a set of time constants that would
>> generate a fairly fast but smooth flood without oscillation.  As you say,
>> it is not a big deal as you can null out with vertical thrusters.
>>
>> On the air pressure compensation issue.  On the R300, I have gone over to
>> the dark side and switch to oil compensation on all my thrusters.  Yes air
>> compensation with the pressure reducing regulator has worked fine for years
>> but at the Flathead Lake Expedition, I had issues with the the aft
>> thrusters partially flooding.  It could have been that the pressure
>> reducing regulator needed servicing.  The primary reason I switched is that
>> I just don't like using up my HP air with this task.  For shallow dives it
>> is not big deal but for deep dives to 200-300 ft air consumption is
>> significant.  I am using WD-40 for the pressure compensation and the small
>> plastic accorfdian bottles you sent me for expansion.  I put a strobe light
>> on the thrusters to measure rpm of the Minn-Kota 101s with both air and oil
>> compensation.  There is about a 5% reduction in shaft speed under no load
>> conditions out of the water.  I did not detect a significant change in
>> current again under no load conditions.  Next step is to take the R300 to a
>> local lake to test the "dark side" pressure compensation for the thrusters.
>>
>> Back to your test.  How was the underwater maneuverability and the view
>> through that magnificent bow viewport?
>>
>> Cliff
>>
>> On Tuesday, October 1, 2019, 11:29:37 AM CDT, Alec Smyth via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>> 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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