[PSUBS-MAILIST] Safety Concerns

Hugo wrote:

"It distresses me greatly when I feel that safety is given a second place ahead of cost and ingenuity, and I would hate to see any Psubber involved in a fatal accident."

I can't help but see another parallel to aviation here in terms of safety. In the course of my research for this project, I've come across relatively few fatal accidents among the amateur built submersible community. I attribute this to two things, local reporting which is lost to a wider audience, and a relatively small amateur submersible community.

The PSUBS website lists two tragedies. One involving JSL (hardly an amateur project) and an amateur prototype which was apparently planned for production, and resulted in a fatality during testing.

My point is that there are literally tens of thousands of homebuilt aircraft both flying and being built. There are thousands of accident reports and one can learn from the online NTSB reports from another's mistake or misfortune. There is no such body for this group, the amateur or homebuilt psub. ABS and Lloyds standards are designed for commercial applications. There is no FAA watching over us. As a pilot, I am lost in a sea of pilots.

What you have here is a unique opportunity for a relatively small group of people to help keep one another out of trouble so long as ego does not interfere. There are people here with truly impressive credentials and others with equally impressive success stories.

From time to time, I have sensed a degree of frustration among those most experienced, with those of us less so. To you I say, keep at it because anyone who pilots, builds or just "thinks" about personal submersible, is a member of a small unique fraternity. Really small!

Joe P

From: Hugo Marrero <HMarrero@hboi.edu>
Reply-To: personal_submersibles@psubs.org
To: "'personal_submersibles@psubs.org'" <personal_submersibles@psubs.org>
Subject: RE: [PSUBS-MAILIST] Compressable ballast tanks
Date: Wed, 4 Jan 2006 14:32:38 -0500

Rick,

I don't think that a bilge pump has enough power to pump against the head pressure at depth, and if they do your flow capacity would be greatly diminished. If your regulator fails, you will not be able to pump water out.. Also most bilge pump housings are made of plastic and the motor housings would implode and flood under ambient pressure as you descend. Bilge pumps are basically centrifugal pumps which are not really suitable to operate against a lot of pressure. I personally wouldn't use it. But again, this is each individual's choice.

One of the important aspects in the design of a VBT system is that it should work to 1.25 times of its mawp (maximum allawable working pressure). This is not an arbitrary number. This is designed as a safety margin and to ensure that the variable ballast system will function in the event that you end up by accident deeper than you intended to.

Hugo

On another note this is for the entire group in general.....

There is a lot of material out in the reference books in the reference material section of the PSUBS web site with lots of information on proven manned submersible systems designs that are guaranteed to work and which are reliable. I don't want to discourage anyone here, however, sticking to proven designs and keeping it as simple as possible for your application will save the prospective psub builder a lot of grief and headaches. If the psub builder is adamant to build a submersible with innovative designs into the submersible's systems which have never been proven to work reliably in real world applications he should do a thorough testing of his design under the same conditions he expect to dive.

I strongly suggest that anyone building their own submersible thouroghly study (not just read) and at least try to understand the reasoning behind the ABS or Lloyds guidelines for designing and building manned submersibles. These guidelines are there for the safety of the human lives in the submersible as the primary concern. They were created as a result of accidents that cost the lives of people who were smart, but who did not put safety in the first place. NEVER ASSUME THAT EVERYTHING WILL BE OK. If a sub builder goes about designing and diving submersibles with the mentality that "this will never happen to me" he is putting himself (and others) in a very precarious situation. I hate to be the one that keeps bringing this up, and I am sorry if I am raining on someone's parade. It distresses me greatly when I feel that safety is given a second place ahead of cost and ingenuity, and I would hate to see any Psubber involved in a fatal accident.

Like Forest Gump would say... "That's all I have to say about that"

regards,

Hugo

-----Original Message-----
From: Rick and Marcia [mailto:empiricus@telus.net]
Sent: Wednesday, January 04, 2006 1:41 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Compressable ballast tanks

Hi, Bill, Hugo -

I'm considering using a hybrid ambient VBT using a bilge pump to empty out the VBT with a second stage reg venting into the tank to compensate. If I'm heavy, just push the VBT bilge pump (momentary action) switch and the tank ejects water while the reg compensates. Very simple at scuba depths. If I'm light, just flip the switch (reverse the polarity) the other way and the bilge pump runs water back into the VBT. The tank's air is vented out the exhaust ports of the reg.

Hugo, I've considered your boat's system. It probably works better at depth to have a hard tank that you manually compensate but I have to wonder if my idea would actually work at the depths you go to. Hmmmm. Pump out the water, let the reg compensate. Start surfacing, let the reg do the venti

Your hissing overpressure valve serves the same function as the regulator's exhaust ports.

Your thoughts?

Rick L

Vancouver