Semi-Aspirated Ballast System

[Reckless]

aha! .. I get it ! ..

thats very cool... and with some clever wiring would allow the removal of a channel too (unless you stay with the gas backup ofcourse) ... the vent and pump could run on 1 channel

would possibly be on my list for the type 7 .. (although once it's working I'll more then likely leave the thing alone and just run it.. LOL ) definately wanted for my next sub ... a smaller 1/144 nuke sub

keep it up Dave...

[He Who Shall Not Be Named]

David,

I've read the article in the Gazette, done this trick with the floatvalves some decades ago with my type VIIC, i think you have to turn your system 180 degrees, so the floating body will be after the inlet.
In your configuration the flow of the water will press the floatingbody against the inlet, so releasing under speed will be more difficult, even worse, if you have some underpressure inside your WTC it will stick more, don't know exactly at which pressure it will stay sticked against the inlet.
Like you mentioned before, best way is to build a WTC testbed to see if the valve will be released with underpressure inside the WTC, just my two cents.


Greetings Manfred.

I learned of this system four decades ago, as I qualified aboard the USS TRUTTA, though that head-valve was shut by a pneumatic actuator as commanded by a water-detector. Mine's not as sophisticated as that.

As to the float that operates the head-valve: It's within the sail structure, the fairing, so is not subject to any flow forces, just the presence/absence of water. So, orientation of the float relative to bow/stern is not an issue in the GATO installation.



In consideration of your second point about head-valve closure; the differential pressure between the valve seat and element as a consequence of the partial vacuum within the SD. A valid observation and something I hope I have addressed through head-valve design: The fulcrum point is placed so that as the float arm drops, the reduction in the seating force appears across the face of the seat disproportionately; the seal will break across the seal face, a bit at a time, and will permit air to enter the induction line enough to reduce the differential pressure, eventually busting the vacuum enough to permit the weight of the float to complete the opening of the head-valve.



Good stuff. I very much appreciate your input, Manfred. You lead, we follow.

David

[He Who Shall Not Be Named]

aha! .. I get it ! ..

thats very cool... and with some clever wiring would allow the removal of a channel too (unless you stay with the gas backup ofcourse) ... the vent and pump could run on 1 channel

would possibly be on my list for the type 7 .. (although once it's working I'll more then likely leave the thing alone and just run it.. LOL ) definately wanted for my next sub ... a smaller 1/144 nuke sub

keep it up Dave...

Indeed, put it on channel-4: left stick, left/right motion (left-vent, right-blow). Put the gas emergency back-up on the same channel through a Y harness to the receiver, just set the end-point of the gas blow valve so that it blows with the servo traveling to the 120% point (fail-safe trip point). There! How's that! .... two ballast sub-systems on one channel, you cheap *******s!

[Reckless]

Indeed, put it on channel-4: left stick, left/right motion (left-vent, right-blow). Put the gas emergency back-up on the same channel through a Y harness to the receiver, just set the end-point of the gas blow valve so that it blows with the servo traveling to the 120% point (fail-safe trip point). There! How's that! .... two ballast sub-systems on one channel, you cheap *******s!

hahaha... hey my lack of a wallet actually had nothing to do with that.. it was more of a simplification of running... instead of jumping between 2 channels to vent and blow it's all on 1

if over all price bothered me that much (over reliable running, customer service, experience.. and "freindly banter" ) .. I'd probably have a basic subtech boat, or be swearing at an Rcabs-R system... or simple just dream about subs from afar.

as it is for now it's just careful planning/saving ... and some spousal deception here and there (read: hide the ******* for now)

[oztruck]

Hi Dave, looks like it will be a winner.

Just a thought, if the air inlet inside the SD was positioned on or near the bottom of the cylinder and as close as it can be to the end cap it could also be used to remove any H2O that might have found its way in.

Cheers Chris

[Albion]

I think this is awesome and provided sufficient insurance against water in the WTC, (but looking at the double valve system there shouldnt be a risk), it looks fool proof. I have avoided gas systems because it just didnt seem right to me. I went for it when the snort became available, and am building up my Type VII but looking to avoid filling the gas tank, and trim it with the sail broaching. But this new addition to the set up makes a whole world of difference and blows out every other system on small / medium subs.

Lots of room inside the M1 sail for a float :)

[redboat219]

Nice suggestion there Oz.

David,
Wouldn't a partially filled float valve assembly pose any threat to the electronics inside the SD?
The low pressure inside would suck moisture from the open float valve into the dry space.

[He Who Shall Not Be Named]

Nice suggestion there Oz.

David,
Wouldn't a partially filled float valve assembly pose any threat to the electronics inside the SD?
The low pressure inside would suck moisture from the open float valve into the dry space.

It get's a tad humid in there, so what? If you perform the Mission checks I've outlined so, so many times, then that cylinder gets aired out at the end of the day. Big whoop!

Have you got a single r/c submarine into the water yet?

Stop thinking so much and get something finished and working.

Ones mind builds demons out of imagined circumstances that in reality are revealed to be benign events. Hardware is usually found to be more robust than imagined during the planning phase.

You are suffering from builders/assemblers angst! Get off the dime, stop worrying, FINISH something and get it into/under the water!

Don't make me come over there! (though I'm sure Ellie would enjoy the trip).

David

[MFR1964]

I've dugged up some pics from the archives to show how i've build my floating valves for the type VII,



The container that will catch up the leaking water, complete with sensor for my water detection system.



Once fitted together, you get this, the sensor is placed about 1/3 of the total height of the container.



Placed under the intake of my front floating valve, which is the same intake i use for my compressor to suck in the needed air.

You really need this container to catch the droplets of water which will stay at the rubber of your floatvalve, every time i dive up the compressor will suck up the air with such a force that it will draw droplets inside.
David made the right choice to build such a container, you never can avoid this problem of droplets, adding the floating device inside the container is very good low tech solution, i opted the more complicated one, because i build dry hulls and not closed WTC's.



The two floatvalve's i use, the construction is different than David's but they do the trick, the left one is to seal off my ballast tank valve, and the front one will seal off the inlet for the compressor.



A closer view of the front one, the foam has a magnet glued in, on the inlet itself i've placed a reedswitch, doing it this way gives you a sensor that will registrate when the sub is under water.
I need this to shut down the compresser when submerging, it also shuts down all the extra gizmo's on board, like the torp system, the antenna lift, and the anchorwinch.
For sealing off the inlet i've used open cell rubber, works fine for me.

Greetings Manfred.

[He Who Shall Not Be Named]

Manfred,Exce

Excellent stuff.

That water catcher of yours (and my safety float-valve) is akin to the sump at the bottom of our 'pump-room' on the TRUTTA or the 'fan room' of the DANIEL WEBSTER: A container to catch (and hopefully contain all or a portion of the water) the head-valve or main-induction fails to keep out of the induction line.

And thank you so much for sharing your Type-7 plumbing. What a smorgasbord of great ideas to feast on, Manfred. A joy to study.

David

[redboat219]

Manfred,

Can you explain the reason for the ballast tank float valve, the compressor intake I understood but not the first.
Also why the reason for shutting down the antenna lift and torpedo firing mechanism during submerged operation.

Thank you.

[MFR1964]

Thanks David,

Your watercatcher will work, in your case you have to deal with the vacuum created when you use your airpump underwater, therefore you always will suck up some droplets that stay on your rubber.
Only thing what i would add on your container is a kind of tappingpoint for removing the access water during maintenance, i can visually check if there's water inside my container, if i do nothing, the water detection system will kick in, and will show me where the problem is, wether in the container or inside one of the two scanned compartments of my sub.
Since i use a constant ventilated WTC the water will evaporate easely, so small amounts will evaporate by itself, in your case it stays inside the locked container and will evaporate much slower.


I shut down all not needed systems for preventing signal loss on my not needed servo's and switches, unlike the small boats, mine is always cruising, due to it's size, at least at 0,5 mtr depth, loss of signal is greater at that depth.
Almost forgotten to mention, the gyrosystem, for keeping the boat level, is also controlled by this floatvalve.
So, if you don't need those functions underwater, just shut them off, the torp system is a different story, normally i can use it on the surface, when i drive inside a swimmingpool i can overwrite the system by using a seperate switch on the watertight deck, allowing me to fire torps when i'm underwater, this way i can control the situation, prefenting to loose my torps in open water.
The second floatvalve for my ballast tank valve i use to prevent getting water in the electric valve itself, in the past i had to clean this valve on a regular base, because it got stuck by corrosion, adding the floatvalve solved this ever returning problem, these days the valve is cleaned once a year during the winterstop.


Greetings Manfred.

[He Who Shall Not Be Named]

Manfred's caution about water getting into the dry-spaces -- even through the snorkel head-valve is functioning properly -- were born out through a simple experiment:

I attached the snorkel head-valve to the induction line, through the normal manifold block located over the ballast tank. I disconnected the flexible hose within the dry space, between induction nipple (that passes through the motor bulkhead) and LPB pump inlet nipple. Induction air (or water if things go sour) now went into the dry space, not directly into the LPB; the LPB takes a suction on the SD dry space, not the induction line (which now dumps air/water directly into the dry space). I then flooded the ballast tank, submerging the entire SD to the bottom of the test tank. I then dunked the head-valve to close it, then raised the head-valve above the water (the float drops, opening the valve), then turned on the LPB.

And ... just like Manfred said ... the little water that clung around the recently wet snorkel induction head-valve was immediately sucked into the induction line and spewed into the SD dry space! Not much water at first, but after three vent-blow cycles, there was an alarmingly large amount of water-droplets in the SD's dry space. Yuck!



I then re-configured the plumbing to once again run a flexible hose inside the SD forming an internal induction line between the motor bulkhead and LPB nipples. In the center of that line I branched off a line, through the use of a tee, to the safety float-valve -- the equivalent of Manfred's sump (at least, as to the job it did of becoming the means of trapping those pesky little water droplets and fog). Now, there were two sources of air from which the LPB could draw: outside air through the snorkel head-valve, and the available air from within the SD through the safety float-valve.




I then subjected the sub-system to several vent-blow cycles in the test tank -- the SD now fully in the semi-aspirated mode.

First few cycles was by broaching the snorkel head-valve, the air source being atmosphere and the ballast tank was completely blown within fifty seconds. And what water got into the induction line went straight through the plumbing and into the pump. The SD remained dry.




I then vented the tank, the SD once again on the bottom of the test tank, I submerged the head-valve to shut it, then commanded a blow. This time the pump took a suction through the safety float-valve leg of the induction line taking air from within the SD itself. After fifty seconds the pump reached the DP where it would no longer move gas -- the ballast tank blown half empty (that's half-full for you optimists out there). Enough to get the boat to the surface.

I raised the snorkel head-valve up into the air -- and yes, Andy! it stuck shut owing to the par tical vacuum within the SD. I manually pulled the float down, opening the valve, I could hear the 'whoooosh' of air as the induction line equalized the interior of the SD with outside air.

I increased the weight at the end of the snorkel-induction float and repeated the exercise, and everything cycled as it should. No water at all within the SD.



I then tested the utility of the safety float valve: I dived the SD. Turned on the LPB with the snorkel head-valve under water to create a partial vacuum in the cylinder and then manually opened the head-valve to sea, flooding the induction line. I then turned the LPB off. The induction plumbing up to the safety float-valve was now open to sea, and a vacuum in the SD was working to suck that water out of the induction line and out the open nipple atop the safety float-valve. This is the worst case scenario for the sub-system!

But, the safety float-valve did its job: as it quickly filled with water the float within rose and pressed the rubber element atop it into the the seat of the nipple that communicates the air within the SD with that of the induction line. Now, nearly full of water, the safety float-valve is shut and will remain so till the water is pumped out of its chamber. The result: the safety float-valve isolates the induction line from the SD if a significant amount of water gets into it. No water gets into the dry space.



Also, each time air is drawn into the induction line through the snorkel head-valve by the LPB, what little water that did get into the safety float-valve from previouse cycles, is scavenged out and dumped into the ballast tank.



Happy-dance time.

I didn't get the correct combination of safety float-valve length/float-by-pass-channel/rubber type/rubber geometry right on the first try. I suffered long hours coming up with the right configuration before I had an item that worked the first time, every time. I'm now ready to transition into a production mode on the safety float-valves.



Basic look at the componets and plumbing arrangement of the semi-aspirated ballast sub-system.

[trout]

This is really great! I so enjoy the learning I am getting while I see a wonderful addition to our hobby being created. I know that at the end of the day there is going to be moisture. That is the environment that our subs will run in. And as David pointed out, do the pre, running, and post checks, however.... would adding a silica filter or pack above the tank help absorb the nominal moisture that might be blown out?

Something like this?

Or am I over thinking this? Is it necessary?
Peace,
Tom

[trout]

I just had another thought (scary, I know). You could make your sub slightly negative buoyant (is there really such a thing - when a sub does not come up?), then use this system to partially blow the tank to hover????