Putting sand in a gas locker and fitting the vent pipe higher up

webcraft

webcraft

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In many small boats getting a gas vent line from the bottom of the gas locker to run downhill with no low point and exit above the waterline is problematical.

I saw a suggestion somewhere that it would be possible to fit the vent line higher up if the annular space round the bottle where gas could accumulate was filled with sand. Is this a good idea? I can see problems when changing the bottle.

Why not just make the bottom half of the locker very tight fitting? E.g. by making a wooden ring? The amount of gas that could then accumulate would be minute, and pose no significant risk. The drain can exit higher up and so exit the hull genuinely above the waterline with a continuous drop from the locker to the hull opening.

Or am I missing something?

- W
 
webcraft said:
.
In many small boats getting a gas vent line from the bottom of the gas locker to run downhill with no low point and exit above the waterline is problematical.

I saw a suggestion somewhere that it would be possible to fit the vent line higher up if the annular space round the bottle where gas could accumulate was filled with sand. Is this a good idea? I can see problems when changing the bottle.

Why not just make the bottom half of the locker very tight fitting? E.g. by making a wooden ring? The amount of gas that could then accumulate would be minute, and pose no significant risk. The drain can exit higher up and so exit the hull genuinely above the waterline with a continuous drop from the locker to the hull opening.

Or am I missing something?



- W
Click to expand...
I will have a similar issue when I get around to making my locker 'compliant' I plan to just glass in a false floor to give me the required height.
meanwhile we have a strict gas on- cook- gas off policy and a labelled on/off indicator on the locker as a visual reminder!
 
Place the bottle in the container with some sponge cut to shape round it. You could coat it in some flexible rubber solution to aid bottle removal, but this would need some research. Alternatively place some packing round the bottle & fill the remaining void with a sand & resin mix then remove the bottle packing so that afterwards it would be easier to get the bottle out & the container can only retain gas in the part where the packing was
 
What are you trying to do?
A) have a bottle locker that's safe?
or
B) pass a BSS inspection or similar?

Don't forget that part of the purpose of the drain, in fact what it mostly does in reality, is to drain water.
Gas bottles cool as you use the gas.
They get a lot of condensation on them in some conditions.
You don't want your steel gas bottle sat in several inches of water.
 
Actually, condensation's the least of my worries, on STBD tack the "gas drain" is under water, and salt water gets in around the bottles. Mind you, the idea of 20kgs or so of wet sand added to the stern isn't appealing at all. She's already trimmed down at the stern when two blokes sit in the cockpit. Polystyrene packing is light and pretty impervious to sitting in water, if that's what you want to do or carve something from any closed cell insulation foam, but it must be closed foam, not sponge.
 
webcraft said:
.
In many small boats getting a gas vent line from the bottom of the gas locker to run downhill with no low point and exit above the waterline is problematical.

I saw a suggestion somewhere that it would be possible to fit the vent line higher up if the annular space round the bottle where gas could accumulate was filled with sand. Is this a good idea? I can see problems when changing the bottle.

Why not just make the bottom half of the locker very tight fitting? E.g. by making a wooden ring? The amount of gas that could then accumulate would be minute, and pose no significant risk. The drain can exit higher up and so exit the hull genuinely above the waterline with a continuous drop from the locker to the hull opening.

Or am I missing something?
Click to expand...

There's no problem filling the space around the bottle with something solid, below the level of the vent. However, I wouldn't use sand. Foam covered with fibreglass would work. The idea is simply to remove a void in which gas might accumulate.
 
You "can get round the problem" by switching to an alcohol (Origo 3000?) stove, and keeping the bottles of fuel in the anchor locker. Instead of gas you have some "petrol" inside the boat, and lots of water vapour to condense on stuff.
I share Webbie's dilemma...
 
Realistically, what matters is that the locker is totally sealed from the interior of the boat.
If you have a major gas leak, a lot will come out of the top of the locker anyway, instead of squeezing through a long thin pipe.
Gas is heavier than air, but it's still a gas, not a liquid.
Common sense says fill the space with anything that won't absorb gas.
I would not worry too much about a bit of water on one tack though. When you are sailing, any gas that comes out the top of the locker will be lost astern.
Why did so many boat designers make such a hash of providing a gas locker?
Maybe make an insert out of foam and GRP. It could stop the bottles rattling.
 
I am currently upgrading my own gas locker to improve the overall safety and dryness. My drain isn't a problem, being out of the bottom of the locker. And by the time I'm finished the locker will be air-tight (apart from the drain :rolleyes:).

However, I'm interested in remarks above implying there should be a vent at the top of the locker, out onto deck or wherever.
Is this essential?
I thought anything that reduces/eradicates air and gas mixing would be a good thing?
 
Robert Wilson said:
I am currently upgrading my own gas locker to improve the overall safety and dryness. My drain isn't a problem, being out of the bottom of the locker. And by the time I'm finished the locker will be air-tight (apart from the drain :rolleyes:).

However, I'm interested in remarks above implying there should be a vent at the top of the locker, out onto deck or wherever.
Is this essential?
I thought anything that reduces/eradicates air and gas mixing would be a good thing?
Click to expand...

I think officially it's OK for the top of the locker to be sealed.
And it would be a good thing if gas escaping that way was liable to seep into the interior of the yacht.
E.g if the locker opens into a cockpit with a low companionway and/or opening portlights and maybe a high transom.
Something to think about if you have a cockpit tent perhaps?
OTOH, drains do get blocked.
 
lw395 said:
I think officially it's OK for the top of the locker to be sealed.
And it would be a good thing if gas escaping that way was liable to seep into the interior of the yacht.
E.g if the locker opens into a cockpit with a low companionway and/or opening portlights and maybe a high transom.
Something to think about if you have a cockpit tent perhaps?
OTOH, drains do get blocked.
Click to expand...

I think my post was a little ambiguous in that I intended to ask if it was a good idea, or essential, to have a "breather" vent at the top of the locker while still having a drain through the hull at the bottom of the locker.

If all works as planned, my locker will be airtight, except for the drain hole.

I fully accept and agree with your point that gas draining/flowing into the cockpit and/or the cabin, is not a sensible situation.
 
Buck Turgidson said:
https://www.boatsafetyscheme.org/media/164540/bss%20guide%20chap7.pdf

7.3.2/R
Click to expand...

Thanks Buck.

Relevant section:

Is the drain opening at or close to the bottom of the cylinder locker or is any volume beneath the drain-opening minimised by the use of suitable material?
Check the location of the cylinder locker drain-openings. If the drain opening is above the bottom of the locker check that any area below the drain opening that could retain leaked LPG is filled with LPG-resistant material.

Cylinder locker drain-openings must be located at the bottom of the locker or at the lowest point of the side. Any area in the cylinder locker below the drain that could retain leaked LPG must be filled with LPG-resistant material.

- W
 
Wrap the bottle in cling film, stand it in the locker and squirt some expanding foam in. When set, remove bottle, trim and sand the foam and seal/protect it with 2 or 3 coats of polyester resin.
 
webcraft said:
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In many small boats getting a gas vent line from the bottom of the gas locker to run downhill with no low point and exit above the waterline is problematical.
Click to expand...
Not been my experience as most gas lockers are directly above a cockpit drain that exits the hull above water level.
 
on my boat the gas bottle locker opens into the cockpit. from there the gas drains out through the self draining cockpit drains. ( except for the fact that Hanse has dips in the pipes which retain water thus blocking them off from gas escaping but !!!!)
 
Mine open into the cockpit, but has it's own drain above water level, in the transom. Cockpit drains are also above the water line, with no kinks, so if the gas bottle locker drain blocked gas still wouldn't get into the boat.
 
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