[PSUBS-MAILIST] Pilot Fish unmanned -255m dive report

Mon Jul 4 06:02:15 EDT 2016

Hi Antoine,

Congratulations!  Thanks for the report.  Very interesting.

Many thanks
James

On 4 July 2016 at 03:49, Brian Cox via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Great account of your test dive!    Must be a very rewarding experience
> !   Thanks !
>
> Brian Cox
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Antoine Delafargue via Personal_Submersibles <
> personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Pilot Fish unmanned -255m dive report
> Date: Sat, 2 Jul 2016 22:07:27 +0200
>
> oops early send...
>
> Hello Psubbers,
>
> Yesterday the Pilot Fish hull went down to -255m off the coast in the SE
> of France.
>
> For a long time I have wondered how to pressure test the Pilot Fish hull.
> There was the Aberdeen Hypobaric center option, but way up in Scotland, and
> also a test chamber in Cherbourg, France operated by DCNS, closer but much
> more expensive and requiring loading the hull vertically, so fully stripped
> out, with a special support.
> Other option: deep lake. Unfortunately there are not that many options in
> France with easy access. At last, a deep spot in the sea. Ever wasted time
> on the internet looking for things like where is the deepest point on the
> planet or where is the farthest point from land in the ocean? I did some of
> that, discovered the existence of a mysterious deep cutting canyon (Gouf de
> Cap Breton) near my town in SW France. But it is narrow and swell is big
> there.
> Then the mediterranean sea with Toulon came as natural choice. the depth
> drops off to 1000m less a few miles from the harbour. And a friend of mine
> I did my military service with in the area, found the perfect boat
> (Coquimar) for the job, not too expensive, but only with perfect weather
> though, and careful preparation.
> For the last few weeks we were watching weather, and availability of the
> boat and all people involved. this week the planets aligned so I prepped
> the sub and drove to Toulon on Wednesday to do the job on Thursday.
> I had loaded a wooden berth on the back of the rental truck to use on the
> boat to put the hull, keeping the trailer on shore. So we leave shore at
> 5h30 on Thursday. Nice weather but a bit foggy. When exiting the harbour,
> we are contacted by radio by the harbour control tower asking us what we
> are up to (probably spotted the hull on the deck...). After a short
> discussion which we cannot escape, we are told to come back as we do not
> have an authorisation to do the job. We did not know about this and soon
> discover it normally takes one week to get approval, even when it is the
> French navy who asks for their exercises... Really bad news. Weather window
> would close. I have to say that on top of the French administrative
> complexity, Toulon is where the navy hosts their nuke attack subs, hence
> the local authorities are looking closely at all underwater activities.
> (and which is why I did not want to use acoustic pingers on the hull for
> the test in case of retrieval, just out from the subs hide nest...). And it
> does not help to tell the authorities we are testing the hull of a british
> flag registered submersible!!
> Back to the harbour. To avoid a pricey cancelling of the operation, the
> only and near impossible hope is to get approval during the day, and test
> the next day, for which the weather forecast improves. Long story cut
> short, tens of phone calls later to various offices and people, including
> cold calling a retired admiral back from the golf course to grease the
> process, I get a grant at 5pm.
> So same process the next day. Weather just perfect. See the pics on the
> facebook page. We even see dolphins.
> at 6h30 we arrive on location.
> The boat has a crane just rated over the hull weight. But accounting for
> dynamic loads due to movement of the crane boom, and suction effects when
> pulling the hull out, we come close to the rated capacity of the crane,
> hence the need for a nice weather window with almost no swell. Swell is
> also not good as a hull low on water can easily bang the boat and fenders
> are too high to help. And the crane boom cannot reach the winch tie point,
> so we decided to first crane the sub in the water, having it slightly
> floating (-50kg) then move the boat to bring the sub on the other side
> where the winch is, and then, clip some lead weights on the sub's hull to
> get it to sink for the test.
> I filled the sub with sand bags and sodalime buckets to make it just
> buoyant. I check all the through hulls, and add a touch of silicone on the
> hatch oring. A Scubapro 330m bottom timer is attached on the nose frame.
> To minimize the use of a diver, we attached  7m long twin ropes at both
> nose and tail of the hull with a pressure resistant trawler float at the
> end I got from Emile. This helps orienting the sub, especially when the sub
> will be coming back up. On each rope, at around 2m from the tie point on
> the hull and 5m from the float, we clipped a lead weight from the boat's
> deck and then lowered it in the water. This gave the hull a negative
> buoyancy of around -50kg.
> We then lowered the hull with the boat winch. We did a station at 20m for
> a few minutes to check tension. I had bought 300m of semi static nylon rope
> in 3 pieces, which could hold the weight of the sub in case it flooded, but
> not by much margin, so I spent time making special knots which would not
> lower the overall resistance of the rope by more than 20%. The ropes were
> marked every 10 and 50m.
> The usual best practive is to test at 125% of the max operation depth, so
> in our case we would go at 120m max in the English Channel so needed only
> 150m.
> Since our hull is designed for 250m operational depth, (rather than
> carrying lead we d rather have a thicker hull) and all the conditions were
> ok, we pushed down to the 250m mark on the rope. We arrived at 250m at 7h10
> and waited an hour. Tension was ok, no air bubble. An hour later we started
> ascending slowly. At around 9am, we saw the sub by transparency. We could
> grab one float and unclip some lead, but the other float was entangled so
> we sent the diver to clear the leads and ropes. The sub became buoyant
> again. Good news, as a sign it did not fill with water. Then the delicate
> crane operation went ok, the weather still perfect, but we just first
> checked for boat wake around us.
> The depth gauge was recovered. Max depth 262m, but that s configured in
> fresh water so it is actually 255m in the mediterranean. The rope stretch
> minus knots consumption explains the 5m off the 250m rope mark target.
> Opening the hatch we check the hatch closely as the mismatch between
> conning tower diameter and acrylic dome diameter induces massive stress on
> the dome ring, and hatch flange. We had FEA done for that, but still...
> We got scared as I saw water in the sub. But soon tasted, it was fresh...
> relief. Actually I had embarked fresh water bladders to add weight to the
> hull, and noticed they were leaking due to weight placed on top of them. I
> once read on psubs emails about bladders that the question is not about
> whether they could leak but when...  the other through hull seem tight.
> At 11am we are back to the harbour. and at 9pm the sub is back in Pau
> after a long drive. Mission complete.
>
> regards,
> Antoine
>
>
>
>
>
> On Sat, Jul 2, 2016 at 9:01 PM, Antoine Delafargue <
> antoine.delafargue at gmail.com> wrote:
>
> Hello Psubbers,
>
> Yesterday the Pilot Fish hull went down to -255m off the coast
>
> For a long time I have wondered how to pressure test the Pilot Fish hull.
> There was the Aberdeen Hypobaric center option, but way up in Scotland, and
> also a test chamber in Cherbourg, France operated by DCNS, closer but much
> more expensive and requiring loading the hull vertically with a special
> support.
> Other option: deep lake. Unfortunately there are not that many options in
> France with easy access. At last, a deep spot in the sea. Ever wasted time
> on the internet looking for things like where is the deepest point on the
> planet or where is the farthest point from land in the ocean? I did some of
> that
>
>
> _______________________________________________ Personal_Submersibles
> mailing list Personal_Submersibles at psubs.org
> <http:///eonapps/ft/wm/page/compose?send_to=Personal_Submersibles%40psubs.org>
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20160704/1c4ec59e/attachment.html>