A Full Bladder

[Kazzer]

I just noticed on another forum, that there is a problem with RCABS stopping the bladder from over inflating. WOW! How do you do that?

The more I learn, the more RCABS sucks.

[Rick Teskey]

Mike
Your forum your opinion.
Don't be so hard on rcabs, it is still a viable ballast system.
Over inflation can be controlled by a restrictor of some sort, a tube too contain the bladder or use a bigger bladder you can not fill with the available air.
You still have pumps and such in stock and want too move them? Don't scare off the potential customers!
My humble opinion( please no pink shorts!)
Rick

[Kazzer]

Hah! After Slats lambasting of the system recently, I thought my little jibe inferring it 'sucks' was rather timid! Good points though Rick. I'd like to see more comment on the subject here.
Your avatar has cut you off at the waist, so I guess I can't bring out the pinkies (not that I saw any cussin' going on). It's comforting to know that most people are scared of them. The Wizard seems to be immune to the humiliation however.

[Subculture]

Really only becomes a problem with RCABS rather than RCABS-R, and then only if the bag is not constrained in some way or fitted with a pressure switch. The former is simpler and failsafe.

[Slats]

Its not the system so much sucks its the mass morons out there who keep shovellin' this **** as "THE" system.
My well balanced research and testing showed 2 things.
1- It does work
But more importantly 2- It does NOT work as a 'One size fits all' ballast system, ESPECIALLY in gaining scale water line in boats that have high reserve buoyancy.

As someone coming up on 2 decades in this hobby, I would never be arrogant enough to come up out and state that there is THE one and only universally applicable system- having said that I do have the brains and intellect to discern that there are some systems that can be applied to a wide range of boats. Gas and Snort is indeed one system -so are sealed tanks and pumps and baffles in the tank.

The fact is other forums continue to flog RCABS as THE system through petty jealously and burning bridges. In fact I was kicked clean out of SP for simply objecting to having my posts altered where I could no longer make mention in build threads the words "Caswell, Merriman, or Subdrivers", just a taste of how pathetic the hobby is at the ****** end of the pool.

But lets look at the results on paper. My money is valuable to me as it should be to everybody. Any body can market up component parts and call them Experimental kits - where in that is the product backup or refund when it all goes to ****. Few however have off the shelf WTCs these days that actually get you running. Money talks. RCABS has big limitations period. The money will be where the success is - I pay for performance, and that is why I shop almost exclusively with Caswell. If the RCABS / other forum types are so jealous of the success that Mike and David has - then I guess they're just the commie lovin type.

J

[Subculture]

I think that depends on the kit you are using, and your level of ingenuity.

The systems on the market are squarely aimed at smaller boats (e.g. three feet and under), with their miniature diaphragm low pressure compressors. However, over here RCABS-R has been in use for the best part of thirty years (perhaps longer) and was used in Darnell boats. I've seen a Darnell Type VII - 1/48th(ish) scale, which isn't a small model by any means and has a high freeboard, perform flawlessly with such a system.

It has a large main bag in the centre of the boat, a converted tyre inflator compressor and a GRP bottle to hold the recirculated air.

Having said that, most modellers now use either water pump based systems or piston tanks here in the Uk. Why? Easy availability is one side of the equation. The other is that modellers copy one another- they see what works and mimic it. Back in the early nineties a company called Eden Model submarines sprung up. It was run by Dennis Cater and produced a range of model submarines featuring water pump ballast modular systems. I believe the modules (WTC's in U.S speak) were developed with assistance from Nick Burge, who was interested in making a cheaper system than the more complex compressor based system that was developed earlier.

Well these kits proved very poular, and are still available from Chris Cloke at Sheerline Models after Dennis sold the business on.

People saw what was in them, and aped them.

At the end of the day, all we're doing is shoving water about. Many ways to skin that cat.

[pjdog]

Slats:

You mention 'SP' in your post. For us new comers what's 'SP'.

I agree with both of your points. I also use what has been proven. Everything I've seen from Caswell and the cave works. Also I could get a ready-to-run so to speak Sub Driver. It was the only RTR I could find. That's why I started with Caswell and all his people that provide his components. Plus you get super support when you have problems. Support from the whole team.

In the UK they have seen what works with the RCABS so they use that other system. You have to admit David's is prettier

Jack

[Rick Teskey]

O.K. so we have firmly established that there are many was too change the displacement of a boat.
How do the big boys do it? Compressed air.
If this system sucks or that system is flawed , then what would be the best system too use or is it dependeant on too many factors i.e size of boat , available space, power requirements, ease of build , service and safety.
Question and answers? or do we put it too bed and say too each his own?
Tor Johnson

[He Who Shall Not Be Named]

Here's my take as to the utility of the most discussed types of systems used to manage ballast water, along with their liabilities:

GAS
A gas (don't matter the chemical make-up of it) is used to force out the water from a tank(s). As the tank can be conformal, and subjected to a near zero differential-pressure (DP), this is the best means of employing the available volume within the submarine as a ballast tank. Very friendly to boats requiring a high reserve buoyancy. Problem is the system has to be periodically charged with the gas as its consumed through use (some guys put an on-board compressor to handle that chore while the boats on the surface, closely emulating actual submarine practice). And if a liquefied gas is used, there is a slight trim change as the on-board bottle goes from full to empty. Some guys don't like handling the gas, and the green-weenie, girlie-men types think the liquefied gas (propellant) is killing children, saints, and small cuddly animals.

PISTON
A means of physically changing the geometry of the dry-space volume, effecting displacement change to surface/submerge the boat. the motor(s) involved suck up a lot of current and the jack-screw and associated pick-off and drive-train take up a lot of valuable real-estate within the dry space of the submarine. And there are CG issues as the tank piston(s) travel from 'dry' to fully 'wet' positions. Expensive!

PUMP- CLOSED LOOP
This is the so-called RCABS and RCABS-R system. The in-submarine air is shuttled between the internal dry space and the ballast tank/bag/balloon/goat bladder/whoopee cushion/IV bag/floating piston (Hi, Rick!). With a few exceptions OK for boats of low reserve buoyancy as this systems performance diminishes as the internal/external DP increases. Tough on seals, watertight structure, and a pain-in the ass if you use an air bladder as the water displacing element -- getting the bladder to assume the same shape and position with each cycle can be an issue, failure to do so presents trim variances between cycles. The system uses a lot of current as the compressor labors against the increasing DP. And these systems take up a lot of room within the submarine -- especially the RCABS-R, with its need of a dedicated volume tank.

PUMP- OPEN LOOP
Simplest system out there, a reversible pump pushes water in and out of the tank. But you have to broach a vent line for it to work. Will not expel water if the vent line is below the surface ... you're screwed!

SNORKEL
Same advantages and liability as the open-loop pump system. Only difference is your pumping air into the tank to displace the water. And if you're using a compressor that can pump water without damage or seizing, then all you need is a compressor motor switch and you're of to the races -- no muss, no fuss.


Me? I do it like the "big boy's": Low Pressure Blower most of the time, a gas blow in an emergency or when I want to show off.

When I was on the TRUTTA (SS421) just about the only thing we used the air-banks for was bow-buoyancy, the negative tank, rolling the diesels, and blowing the ****-tanks - the majority of the time the LPB was used to empty the MBT's. Hobby emulates prototype -- works for me.

Today I combine the advantages of gas and snorkel-LPB, just like on the real boats. The snorkel used most often, except in those awful situations where the boat is lost underwater, then I count on the fail-safe to activate the gas sub-system (or I do it from the transmitter) to bring the boat back up into the sunshine.

RCABS is over-rated, and over-sold. the system often touted by guys who have as yet to assemble a model submarine! Too often the misinformed spout off about something that (without critical examination) appears to originate from an 'authority'. The INTERNET is full of excellent information, and a lot of bull-****. The RCABS topic has received its fair share of fertilizer.

[Kazzer]

Lest we forget!

The first RCABS system was developed by Darnell in the UK in the 1950's. He made a box with all the parts inside, using a pump to inflate an old rugby (US football) ball bladder.
I have the original drawings somewhere (I'll find them eventually) and I previously posted them to a couple of submarine forums. No doubtless, those files have been deleted by they who wish to alter the truth to claim this revelation as their own.

It's OLD HAT guys! Get over it! Move on! There are better pumps, better ideas and more foolproof ways of blowing a ballast from a model submarine.