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A new Failsafe ??? - Hear me out

R/C Submarine modelers

Postby ThierryC » Thu May 01, 2003 11:58 pm

When going over and over various designs for my sub, I suddenly had an idea for a new sort of failsafe.
One way of getting a sunken sub back to the surface is to blow the ballast tank, if no catastrophic flooding of the WTC happens the sub will come back up.
So I was thinking, if a gaz boat is out of propel or compressed air, how could we make new air from the available materials ?
Then I thought of it: all we would need is two stainless steel rods or bolts permanently sticking inside the ballast tank, when we need the failsafe to work, we take power from the main battery and divert it to these two stainless bolts, they become electrodes and start separating the water in two gases: oxygen and hydrogen.
The gases will displace the water (slowly) and after a while your ballast tank will be empty.
Of course it is not a fast process and if the main battery is depleted it will not work, but it is pretty cheap to implement and worth a try rather than loosing the sub.
Word of caution: hydrogen and oxygen are very flammable so no smoking when you take the sub out of the water.

Let me know what you think about this idea !
There are 10 kind of people, those who undertand binary and those who don't !
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Postby John » Fri May 02, 2003 5:31 am

Thierry,

It sounds a bit OTT to me. I doubt whether you could generate enough gas with the available battery power.

I have often thought that a chemical reaction might be the way forward. It ought to be possible to design a lozenge containing some indigestion tablets coated with a dissolving medium. After maybe a couple of hours the tablets come into contact with water and produce CO2. Obviously the lozenge would be throw away after every run. Maybe it could inflate a balloon to be ejected from a hatch on a length of line to float to the surface.

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Postby Skip Asay » Fri May 02, 2003 9:21 am

As with virtually everything we use or do, there are good points as well as bad points. Using a purely Propel or CO2 system has a negative point in that the Propel or CO2 are stored in liquid form until the valve is opened at which point these gases ?boil? and become gas which then forces the water out.
Proper procedure when first putting your boat in the water means making sure the supply tank is full. The next step is to make sure the boat is properly trimmed when the ballast tank is full. Personally, I run my boats with approximately 1/4 - 1/2 oz of positive buoyancy. With a supply tank made of 1/2? copper pipe measuring 4? in length, capacity is approximately 1 3/4 ozs. of liquid. The final result is that if I use up all of the Propel, I will have in excess of 1 oz of positive buoyancy which means that the boat will come to the surface (with the motor shut off) whether I want it to or not. No, it won?t fully surface, but most of the sail is out of the water at that point and it?s a whole lot easier to recover a boat you can see. Of course, if the only problem is that you?ve run out of Propel, forward speed and up angle on the planes will get you to the surface and allow you to get back to shore, too.

This, by the way, is an excellent example of why the ?Hybrid? system is at least a step or two better than a pure gas system. With a high volume/low drain pump, you can surface all day long without changing the weight of the boat. But you still have the ability to surface if (when!) you find that one piece of monofilament or run through some weeds while submerged. Your Propel supply lasts a heck of a lot longer!

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Postby dietzer » Fri May 02, 2003 2:47 pm

Thierry,

The electrolysis method you describe would be really slow. The sub might not surface for hours.

A much faster method would be simply to make your own gas by releasing water into a compartment with baking soda. The old toy subs (you know, the ones that came in the cereal boxes) surfaced and dived using baking soda, which reacted with the water.

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Postby Britt Boyette » Fri May 02, 2003 9:49 pm

Or Alka-Seltzer. It would give a whole new meaning to the word relief. Actually, I like Skip's idea better, no moving parts. KISS, baby!
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Postby Ramius-II » Sat May 03, 2003 10:20 pm

Thought I'd add a little to the topic, I had the same idea in high school for the purpose of adding air to a fish tank. The problem was the two gasses, hydrogen (as in Hindenberg) and oxygen, in pure form are both highly explosive! One spark and .... :(

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