Sub Ballast systems - snorkels

kimwhite
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Sub Ballast systems - snorkels

Postby kimwhite » 03 Feb 2011 23:05

Can our submariners explain to me briefly just what a snorkel system is in the context of model submarines?

Years ago when I was a boy and fascinated with model submarines that dived I knew all about pushing subs under with just propellers. I knew it was not very good as it meant high dive speeds and unrealistic appearance. I remember reading a Popular Mechanics magazine when I was at Primary school - late 1950's - which described a ballast system using complicated valves and baking powder but the technicalities were lost on me at the time.

Much later I saw that modelers had started using flooding tanks which were emptied with gas. Then came those tanks that had pistons, much better as subs could finally dive without motors at all but I understood they were complicated and hard to balance/trim the sub longitudinally.

Now, as it happens, about 30 years ago I myself designed a system where the sub would have a ballast tank which would fill or empty using a small electric pump and sucking air through a "periscope", all so arranged that the boat could be trimmed down with maybe 10 grams of "buoyancy " when flooded down - thus requiring almost no power to drive it fully under or run at periscope depth, or the sub could be pumped out to ride much higher.

I never actually built the system or even discussed it with anyone, but I think that is what these snorkel systems are now. Is that right? Wish I'd patented it!! Can someone explain what the current state of the art is?
kim
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SlatsSSN
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HMS Conqueror S48 -Churchill Class SSN.

Merchants:
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Re: Sub Ballast systems - snorkels

Postby SlatsSSN » 04 Feb 2011 10:03

kimwhite wrote:Can our submariners explain to me briefly just what a snorkel system is in the context of model submarines?

Years ago when I was a boy and fascinated with model submarines that dived I knew all about pushing subs under with just propellers. I knew it was not very good as it meant high dive speeds and unrealistic appearance. I remember reading a Popular Mechanics magazine when I was at Primary school - late 1950's - which described a ballast system using complicated valves and baking powder but the technicalities were lost on me at the time.

Much later I saw that modelers had started using flooding tanks which were emptied with gas. Then came those tanks that had pistons, much better as subs could finally dive without motors at all but I understood they were complicated and hard to balance/trim the sub longitudinally.

Now, as it happens, about 30 years ago I myself designed a system where the sub would have a ballast tank which would fill or empty using a small electric pump and sucking air through a "periscope", all so arranged that the boat could be trimmed down with maybe 10 grams of "buoyancy " when flooded down - thus requiring almost no power to drive it fully under or run at periscope depth, or the sub could be pumped out to ride much higher.

I never actually built the system or even discussed it with anyone, but I think that is what these snorkel systems are now. Is that right? Wish I'd patented it!! Can someone explain what the current state of the art is?
kim



Hi Kim,
yes lots have changed over time and nice to have you share that story.

The snorkel these days works to assist in ballast tank changes in a number of systems.

First in the 1/1 scale world the Snorkel's primary use was to allow fresh air to be supplied to diesel engines that were used to either:
1-Run the diesels for propulsion near the surface but still submerged
2-Run the diesels for battery charging near the surface but still submerged
3- A combination of the two

Secondary purposes in some 1/1 scale submarines allowed the snorkel to also "change" the air inside the sub, and recharge via compressor High pressure (HP) air tanks that might have been used for surfacing.
But another key purpose is that some subs. especially modern types, will drive there way close to the surface, usually by pumping water out too, with no or very little high pressure air is used and will get via some sort of air induction mast (and it might not be the snorkel), an airflow to a LPB (low pressure blower). The LPB then forces air into the main Ballast tanks that are free flooding. This empties the tanks, surfaces the boat, and saves the subs HP air reserves used primarily for emergency surfacing (emergency blows). The Merriman Subdrivers work pretty much along these lines

Turning back to your question.
In RC subs the primary purpose is to assist with ballast changes.

The simple pump setup and snorkel
In a simple submarine using a reversible water pump water is pumped into the ballast tank. The air inside is vented via the snorkel and escapes as the water comes in. This dives the boat. To surface the tank you pump in reverse. Air is drawn in through the snorkel as the pump empties the tank. In this setup you need some sort of a check valve in the pump or line to the pump to prevent water flowing through the pump when switched off. The biggest disadvantage is you cannot surface if the snorkel is under the water. Best for submarines that use a high degree of dynamic force to dive. I.e. the full tank only takes the boat down as far as decks awash.

The semi vented tank.
This situation uses a float valve with the snorkel. You dive the boat via pumping in water. Like the scenario above the air in the ballast tank escapes through the snorkel, BUT at some given point (say the tank being half full), the rising water in the tank causes a float valve to close off. The boat is trimmed to be at a little lower than decks awash at this stage. The remaining water being pumped in starts compressing the air left in the tank. By the time the tank is 60% full of water (40% compressed air), the pump will still run if its centrifugal type but fails to push any more water. At this point you have just dived the boat, You need a check valve to stop water being pushed back through the pump. You release this valve to surface back to the position just below decks awash. Here the snorkel float valve opens and you pump the rest of the water out. – Have used this myself. Jim Russell uses it and makes the float valves.

The snort system used in the new Merriman Subdrivers.
The ballast tank is free flooding. A valve at the top of the tank opens and lets the air out – just like a real sub. With the tank 100% full you are at Periscope depth (PD).
To surface the valve at the top of the tank is closed, a Low Pressure Blower AIR pump (SNORT Pump) with a check valve inside forces air through the snorkel (above the water at PD) into the ballast tank. The air being forced in via the pump, forces the water back through the free flood holes. – You surface.
The system won’t surface the boat where you are deeper than PD. At greater depths you use a small copper bottle reservoir of liquid airbrush propellant which delivers a small burst of gas inside the Ballast tank. With the valve atop the tank closed. This brings the boat up fast. A float arm is connected to the gas release valve inside the ballast tank so the gas won’t work if the tank is empty. The bottle is contained within the ballast tank.

The original gas systems used for more than 20 odd years did not have the SNORT pump, so you used gas every time you surfaced. For that reason I did not convert my fleet over to any form of gas until the SNORT system became the mainstay. Why – because the quantity used of airbrush propellant was an expensive consumable. Nowadays with the SNORT system in combination with gas, the reality is you use very little if any gas at all. Eg. at the Subregatta in Canberra I ran Rankin the whole weekend on just a single tank (about 30ml). The reason being is you should ballast you system so it is always slighty positive. PD is a positive state, any positively ballasted boat will require some dynamic force to dive, so getting back to PD is in most cases quite easy, and from there you run the SNORT system and need no gas. The gas is simply a backup, for emergencies such as signal loss at depth, or doing say in deep pool where you can control the boat with great visibility an emergency blow. Some people don't even bother with this but in my view I'd rather be safe than sorry. Sorry with subs equals $$$$$ gone and in some cases means forever.

There are other variations you can use Kim, the snorkel by the way can really be built into any mast or periscope that allows airflow.

Hope this helps.

If you are thinking of doing a sub Kim, I'd be very happy to help with input, as I know Justin would too.

J
He who dies with the most toys, just dies...you can't take it with you.
kimwhite
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Re: Sub Ballast systems - snorkels

Postby kimwhite » 04 Feb 2011 10:41

Hi John,
thanks for the explanation! If I ever do build a submarine the snort system sounds perfect. The sub I would choose is the WW1 steam-powered K-Class - see attached - as it has a very prominent superstructure. In the 1:1 version, when diving, the boats had to be trimmed down for diving very carefully as experience showed they could become uncontrollable. Once the Captain ordered a dive the boiler room had to be shut off and evacuated due to residual heat, the hull had four large mushroom vents to be closed, and the funnels had to be folded back into the superstructure. Oh yes, the two tall telescopic radio masts had to be retracted too.
The best dive speed recorded was about 3 and a half minutes but usually over 5. Apparently some Captains took a walk back along the superstructure to ensure the mushroom vents HAD closed.
So, in a model K-Boat, when diving, one would have to devise a funnel closer. Then the boat could be flooded down so just the conning tower and upper deck are awash, and then flooded until the conning tower roof is awash, then the boat dives. It would all be "in scale". And the large superstructure should allow the placement of bits and pieces to make it work.
Looks like a possibility.
thanks
Kim
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SlatsSSN
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Posts: 954
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My Ship Yard: Fleet - in service and under construction

Submarines:
USS Seawolf SSN21.
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN.

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
Harbour Tugs x 3.
MS Christina O.
MV Titan Uranus - Coastal Cargo.

Warships:
HDMS Peter Willemoes F362 - Iver Huitfeldt-Class Frigate.
Location: Sydney

Re: Sub Ballast systems - snorkels

Postby SlatsSSN » 04 Feb 2011 10:57

Looks interesting mate, and of particular interest is her diving time. Did you know modern nukes are not designed like the WW2 counterparts to crash dive. In fact its not uncommon for a dive sequence to take half an hour.
I think there is a kit of this sub.

J
He who dies with the most toys, just dies...you can't take it with you.

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