[PSUBS-MAILIST] Pilot fish first dives

Wed Apr 13 01:22:14 EDT 2016

Congratulations, Antoine.  Very impressive!

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Antoine Delafargue via Personal_Submersibles
Sent: Tuesday, April 12, 2016 2:28 PM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: [PSUBS-MAILIST] Pilot fish first dives

Hello Psubbers, 

Pilot Fish sub has now made its first dives, 

What a feeling to live this for real after having imagined it for years! seeing the water fully covering the dome is quite a dramatic view. 

at last i feel like a real psubber, after having been on this group feeling like a junior kid for ten years... thanks to you all, this project would not be anywhere near it is without your precious advice!

some pics and movies can be found at

https://www.facebook.com/Projet-Poisson-Pilote-Pilot-Fish-Project-294329844027226/

The tests went well overall. we were quite anxious as there were many systems to be tested, some with quite original features. Launching the sub with the trailer and an extension rope was the first unknown. Hopefully Emile came from Amsterdam to help us out. Techno diving lent us some diver phones, and the local dive club helped out which is good for a first dive.

First day we stayed in the harbour checking buoyancy. We were a bit heavier and nose heavy than anticipated, so we adjusted for this by removing some solid ballast. We had also a bit of air exiting our emergency regulators so we figured we should add an isolation valve upstream that regulator to prevent such events increasing the pressure of the cabin.

once MBT emptied we tried bringing in water into our bladder to be neutral, but I soon realized I had forgotten to remove a little plastic cap protecting the threaded seawater intake outside when prepping the sub. It would be a hard reach to remove even by a diver from outside as it was located inside the tail fairing between oxy bottles.  

All the tv crews were also there waiting to film our first dive..., we had like 4 go pros and 2 microphones inside the sub recording, and diver cam man, a towing boat in a small harbour trying to keep us away from other boats, some people watching, and for whatever reason I wanted to control most of the tasks inside the sub, leaving michael my copilot only pedaling. So quite a lot of multitasking for a first dive! I would advise to do first dives in a quiet place first!

After thinking hard about whether the cap was threaded or not, we decided we should try pumping against it with our manual bilge pump. It did not work initially as our low pressure circuit was full with air so the pumping was not very efficient. So we poured water from our drinking bottle into it and pumped again and this time when reversing the circuit, water came in so we had managed to kick the cap out and we finally started diving. By the way, this was the very first time we tested our bilge pump, and it visibly worked... 

Having done already several cycles of ballast inflation to adjust solid ballast we did not have enough air to exit the harbour in confidence (although we had plumbed our ballasts to allow divers to inflate our ballasts with direct system connection, which turned out quite useful). so we stayed in, only diving to 1m as the bottom 2m of the lake harbour were covered by very long sea weed on which we were sort of floating.

The next day we went out for a tow then dives in 3 to 5 m water depth. We could then check most systems, which worked as anticipated. the task sharing with the pedaller became obvious: pedaller pedals, and takes care of life support and MBT upon instruction from the pilot, the pilot does the rest. We would deflate the ballasts, which turned out quite stable despite the saddle shape. Then we would bring in seawater to fully cover the dome to get neutral buoyancy, then pedal downwards, using the trim tray on rollers beneath the pilot seat. The first surfacing with Emile as a pilot was quite impressive by inflating the ballasts. Nobody filmed it but it felt like we raced upwards with steep inclination.

We did another dive with Michael on the same day. We could check oxy consumption, really sober, 0.75L/mn at rest for us two, and 2L/mn at cruising pedaling level. The temperature and humidity did not shoot up as we feared when pedalling to the sweating remained quite efficient and confortable, despite all the body heat. Quite happy too with the scrubber as we had 0.15-0.2 % CO2 only. 

 Pedaling resistance lower than feared, we ll see next time if we try a more agressive pitch. Our blade design may be a bit basic but the speed looked around the 3km/hr expected. The friction in the drive train and prop shaft seal is impressively low. we can testify that the water lubricated bearing for the shaft outside the hull works well when in the water...

During that second dive  a funny thing happened: we beached on the seabed without noticing, as the seabed was moving up, and did not have the altitude sounder installed yet and the ground felt further below due to optical distortion in the dome. Then we used the bow thruster  which sucked sand inside the bow fairing (I had not cut the definitive thruster intake ports in the fairing) which kept us landed. We kept pedalling without understanding why we stopped moving, thinking we may have got caught in something or the prop blades may have loosened?. That was when the surface boat told us they had an engine pb so we came up gently with ballasts and the diver told us we had landed and was wondering why we kept pedalling!!

We will do another series to check the speed accurately in deeper water depth area. we will also do longer dives to check the scrubber capacity, and if all goes well spend the night underwater for a 30hours long dive. 

regards,

Antoine

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