[PSUBS-MAILIST] PSUBers in Training

Brent,

You misspeak for the group. Those people that have been operating submersibles for some time and those with submarine experience strive for KISS (and they keep telling you this) while those just building and/or no experience love redundancy and extra safety features.

Please review the emails and note that anyone with any submersible experience has repeatedly told you that dive brakes are a poor idea. While on the surface they sound like a great idea (go-cart, bicycle, or car…what about boats?), they don’t work. You are better to rely on procedure than a mechanical gimmick underwater to avoid a hazard, especially in your typical PSUB. Speed is hazardous underwater:

1. Close to the bottom you are going to run into something despite any mechanical or electronic contraption;

2. Speed will force you out of your operating envelop in a jammed planes causality resulting in a violation of your test/crush depth.

It has been demonstrated that dive brakes and braking chutes have not worked to mitigate these two safety issues. A five-point safety belt doesn’t do you much good when you are stranded on the bottom, just makes it more difficult to get the body out.

Speed was designed into Deep Flight for one reason only and that was to get to a very deep bottom, not for cruising on the bottom. Graham Hawks recognized that much of the ocean was very deep and most submersibles only penetrated the top veneer. Alvin took hours to get to an even moderate depth and Graham wanted to return to the bottom of the Marianas Trench, over seven miles down. He knew he would need a unique vehicle to get there fast and Deep Flight is the proof of concept. If you can go to the bottom of the Trench it is tough to operate outside of your depth envelop and small propulsion motors were to be used for cruising at a safe speed on the bottom. Hawks promoted this concept back in the 80s and hasn’t reached it fully yet.

Jay

Respectfully,

Jay K. Jeffries

Andros Is., Bahamas

Talk sense to a fool and he calls you foolish.

- Euripides (484 BC - 406 BC)

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Thursday, August 28, 2008 6:18 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Stopping Flaps

Greetings Sean,

Your items one thru four, I find to be very sound. As a general rule, this group tends to love redundant and extra safety features. So having brakes of some sort seem very important/useful/desirable. Braking flaps can be used when on the surface as well. If you have paddled a canoed or kayak much, you will know that you usually can only go as fast as an average K-boat and if you turn your paddle flat you stop very quickly. Of course a canoe is lighter so that just means we need larger flaps, if we want/need to stop that fast.

Having only two seconds to react, as Jon was writing about, many times isn't enough time to do much of any thing. One reason Alec might not of even seen the cable, could be he wasn't looking out the forward port at the time. Look at how little time and stopping distance we have in a car many times over and over and yet still stop in time. I was thinking about installing a braking flaps system, that operates much like a cars brakes, with a foot peddle in the same position as a cars, and hydraulic assist, or perhaps a brake lever like used on many cars for there emergency brake, could work very quickly as well. Even if you still hit the boulder, you might of slowed down enough to make the collision far less of a problem. But that's just me, I like convoluted mechanical means if I can learn from those prototypes how to make them really function properly, or abandon them to explore other ideas.

Have you ever driven a go cart, bicycle, or car that didn't have brakes. It's quite hard unless you stay with in a safe operating envelope, which would be on pretty flat ground, and at very low speeds. So your safe operating envelope will change in a sub if it has good braking flaps and you know how to use them. Of course with a car with no brakes, you usually have some built in collision protection like bumpers, air bags, and seat belts. But you still don't want to hit people and there flower gardens. In are case we don't want to hit nasty rocks, coral reefs, boats, SCUBA divers, etc., etc., etc.....

I plan to have a five point seat belt system installed in my gliding hydrobatic subs, much like those installed in the Bionic Dolphin and Bioniorca. Perhaps I need a air bag system as well. It might be a really bad idea for a air bag to go off in a small sub. My be it would be better to use them on large subs. I would expect a lot of the injures that have a cured to sailer's on subs that have hit some thing, were a result of them not being seated with a seat belt on.

Another possible use for braking flaps is to help you drift with the current, if it's going the same way you are, to save power.

Your resident possibility thinker ;)'

Regards,
Szybowski

Date: Wed, 27 Aug 2008 17:46:48 -0600
From: cast55@telus.net
To: personal_submersibles@psubs.org
Subject: Re: RE: [PSUBS-MAILIST] Stopping Flaps

Not to make light of the many creative contributions to this discussion, but I can't help but feel like this is an unnecessary solution to a self-imposed problem, much like the guy who lined his car windshield with pillows in case he had a collision from not being able to see correctly due to the gas mask he wore in case of a leak from the gasoline canister strapped in the passenger seat which he carried in case he ran out of fuel. Sometimes, the solution requires taking a step back and eliminating a problem further up the chain.

In the case of submarine collisions, you have two identifiable primary risks: 1) entanglement, and 2) damage. In the context of the anticipated operating conditions, I can't help but wonder if design effort to reduce entanglement potential by

1) streamlining the hull and superstructure, and minimizing appendages to prevent entanglement or entrapment
2) accomodating impacts to the hull and superstructure by incorporating such features as collision bulkheads, space frames and guards where appropriate
3) implementing better systems to warn of impending collision, including attempts to increase range of visibility, lighting, sonar, etc.
4) defining operating parameters consistent with the vehicle design and anticipated operating conditions to firstly avoid collisions altogether, and where a collision may not be avoided, to enable the vehicle to withstand collision without sustaining critical damage

- are better uses of resources than convoluted mechanical or other means of reducing vehicle momentum on an impending collision, which may represent increased risks from other perspectives.

A common error made in "what if" contingency planning is failing to determine if the "what if" event in question can be avoided (preventative), thus eliminating the requirement for a contingency plan (reactive).

Just my $0.02.

-Sean

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