[PSUBS-MAILIST] deep test

Fri Jan 26 14:05:55 EST 2018

Great feedback hank.  I really like the procedure where you hang a weight
below the boat and then get negative by dropping weight on the line
connected to bow lifting lug and having it slide down to the boat until it
gets slightly negative.  I like that fact you have one line only so no
change of fowling and you also have the option of pulling the boat back up
assuming the boat does not flood.   I also like the idea to eliminated the
incremental test stops.  I agree, KISS improves chance of success.  Would
sit off the bottom until PLC triggered MBT blow in say at 1-5 to 2 hours.
Can mitigate uncontrolled ascent to some degree by programming the PLC to
stop MBT blow when the depth starts to decrease.  Would still need to have
the surface boat move out of way during ascent.  I noted your earlier
comment on bottom not being flat around the Homewood launch site.  We will
find a location on the lake where the bottom is flat  near the 390-400 foot
mark.  This will mitigate the issue of the boat sliding to deeper depth.

On any of your unmanned depth qualification dives, did you have a salvage
plan in place the raise the boat if it flooded?  If so what was it?

Cliff

On Fri, Jan 26, 2018 at 12:25 PM, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Cliff,
> I have done a few tests unmanned, one with my escape pod to 638 ft and I
> simply had the pod positive buoyant by 50 lbs or so.  I had weights on
> small ropes made ahead of time.  I hooked the ropes to the pod and let the
> weights fall below the pod so the pod did not hit potential rocks.  I just
> kept adding weights till it was about 5 lbs negative and lowered it on a
> 5\16 line.  I went strait down no sops, for 1 hr and hauled it up with the
> rope.
> Gamma was tested to just under 500 feet by letting it sink to the bottom
> non-stop with a 1\4 in inch rope connected to a HP valve.  When I gently
> pull on the rope air is sent to the MBT's and it comes up.  That worked
> very well.
> Elementary was tested unmanned by lowering on a small rope same as the pod.
> In my opinion, one rope is all you can have.  I had problems in the past
> with two ropes.
> Your plan is a bit complicated, things tend to not go as planned on the
> water.  I would suggest to hang a weight under the sub so it does not touch
> down, say 5 to 10 feet.  Also I would just send it down, that 5 min rest is
> of no use because if it is leaking it will happen while travelling down.
>  you will feel the weight increase if it is leaking.
> If the weight gets stuck on the bottom I can cut it.
> I will do a 1,000 foot test in Slocan Lake as soon as the roads are good,
> just to be sure I can retrieve R-300 if it ends up sliding down a slope or
> something.
> Hank
>
> On Friday, January 26, 2018, 10:39:00 AM MST, Cliff Redus via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> Hank, I have not worked the details yet but I can give you my tentative
> thoughts.  The location of the test will be Lake Tahoe in Ca on June 25-29,
> 2018 as you know, with Homewood Ca. as the base.  We will use a tender
> vessel that will setup over the dive site.  We will find a dive site with a
> bottom at a little past my max test depth of 375 ft.  I plan on ballasting
> up the boat so that when the MBT are flooded, the boat is about 20 lbs
> positive.  I will then attach a 400 ft line that has been marked every 10ft
>  to the bow lifting lug. When we are ready to do the test and you are ready
> to submerge Gamma, I will add 25 lbs of lead ballast wrapped up in rubber
> so it will not damage the boat on a line just aft of the viewport.  This
> location is just above the CG/CB of the boat.  Boat crew will slowly lower
> the boat until reaches the first depth station at 75 ft. We will stay on
> station for 5 minutes.  At any point if the bow line starts to add weight,
> we will abort the test and pull the boat up immediately. Divers will be in
> water and follow boat to  75ft stop. Gamma will be monitoring the dive all
> the way and down and back up.  Also, if Craig Busell can make this date,
> his Phantom T4 ROV will also be monitoring/logging the dive and giving us
> real time video feed on the surface which would be great.  The boat will
> then be lowered in 20% of test depth increments (75ft).  At each depth stop
> we will stay on station for 5 minutes.  If all looks good we will proceed
> to the maximum test depth of 375ft where we will stay for 30 minutes. We
> will then pull the 20 lb weight off the boat which should change the boat
> into a positive buoyant state.  Gamma and the Phantom will monitor the
> decent and ascent.  As a back up, the PLC on the boat will be programmed to
> automatically blow MBT at 2 hours from the start of the dive.  The PLC on
> the R300 will have logging turned on so at the end of the dive I can
> retrieve the memory card to interrogate all boat systems during the test
> dive.  I will look into a number of backup steps including seeing if
> a local dive shop has a diver with a rebreather that would be willing to
> dive to 375 ft.  We will make sure we have some kind of harness on the bow
> lifting lug that gamma can attach to in case we need her to lift the boat.
> If the boat floods, the weight will be 4400 lbs in the water so will need
> to see if can  locate a lifting bag large enough to lift the boat in a
> salvage mode.  We would not bring the lifting bag to the site but just know
> where to get one if the test fails.  The maximum depth the boat has been to
> is 160 ft last year.  If the unmanned test is successful, and surface
> inspection reveals no surprises, then I will take the boat down to 300 ft
> to establish the maximum operating depth of the boat.
>
> For those of you that have gone through this type of unmanned test before,
> I would welcome feedback. What worked for you and what you would do
> differently.  I can't remember which boat but I remember one psub unmanned
> test dive using a similar methodology in which the two line got wrapped up
> and fowled. Alec, was this you with Snoopy?  I don't remember how they
> recovered.  I remember the test was successful.  I am not to worried about
> the test as the crush depth is 1100 ft (in theory!)
>
> Still lots of details to sort out.
>
> I know you tested Elementary 300 pressure hull in a pressure vessel but
> have you done the unmanned test on her?  Also after rebuilding Nekton
> Gamma, have you done an unmanned test of her?  If so how did you do it?
>
> Cliff
>
> On Thu, Jan 25, 2018 at 6:40 PM, hank pronk via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Cliff,
> How are you planning to lower R-300 and how are you retrieving it?
> Hank
>
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