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Use a pump to force water into a tank to dive - pump out to surface. Should the tank be vented - aspirated - allowed to breath air, you'll be fine at PD snorting, however going deeper and your just changing the water in the tank and you will not surface.
Next seal the tank - you then have the mainstay for what myself and a lot of Aussie sub drivers have used for years. You compress the air in the tank with each drop of water forced in, and you need a reasonably rigid tank to deal with the pressure. Eventually the pump will quit pushing water, typically IME its around 60% full. You need a valve to hold the water in the tank, which you release to surface.
With the sealed tank i have many years of fun, and parts fatigue, mainly pumps, but the concept has worked well.
I have played quite a bit with Gas with snort, and IMO this remains as rock steady approach to sailing. AND if it wasn't for my persistent curiosity I would have happily stayed with it.
You'd have to be on the dark side of the moon to not know that I have some strong opinions about RCABS. I won't regurgitate them too much in this new thread except to say here is a photo of my RCABS conversion:
RCABS does in some circumstances (low reserve bouyancy boats) work well. But it ain't the system for all situations.
RCABS does have a place in the hobby and some use it as a system within its limitations- but sadly there are those who think its a real religion - lets call them the Sub Scientologists. Sure as **** feels like that -some $400A out of pocket and no chance of refund. The cultist following, by some, of this ballast system -forsaking all others -is not in the name of hard science or from a view point of adding substance to the literature, but the drive and push has more to do with a sad little soap opera involving burnt egos and petty jealously. Scrap away the surface and you will find a deep hate of gas ballast systems for one reason only - David Merriman's success. Sad but the target of RCABS fundamentalists is never pumps, pistons, it always tends to be gas.
Moving right on long. Some in the hobby myself included are in it to learn and to experiment with new techniques and systems.
For others the end point is stick time and lots of it. I seem to swing between wanted stick time and learning. If you want an off the shelf fully backed product - you can't go past the Subdriver range that Caswell / Merriman put out, and I have in the past gone this way for almost ready to dive fun.
But.... Getting back to that pesky learning and curiosity of mine - Jim Russell - the grandfather of the hobby in Australia, recently fixed me up with a new pump system and solenoid valve. The system can be used as I have many times previously - with a sealed tank, and given that this unit is a geared pump that stays in the dry section of the boat it shows cf my old equipment a greater degree of reliability. Its a good pump- it will pump against 3 bar (around 45PSI) on 12 volts before quitting. Its called a "Dark Horse" geared pump- flow rate max is 2.8L per minute.
Here is a photo of the setup in a 3.5" end cap. Solenoid is closest the cap. You can see a simple on / off micro switch setup for servo operation against the momentary micro switch arms.
Jim in talking with me about different setups had been testing the pump solenoid on a range of boats. I explained that one thing I really did not want to go back to for my Collins sub was using a sealed tank as the airspace tends to oversize the tank so much it would compromise in this small boat around a (1m) the avaliable space for torpedoes and other goodies. Jim suggested I give the pump / solenoid a try but in union with a float valve. So doing so, the tank is temporarily aspirated right up until its around 70% full of water. At this point, a float valve (which Jim modifies from a fish tank accessory) pushes a float against the vent sealing the tank. At this point you boat is at decks awash or slightly lower, and the remaining pump in cycle occurs as a sealed tank. Fully dived you surface by reserving the pump and opening the solenoid, the pressure in the tank rockets the water back out, the float valve recedes and at snorting depth you empty the rest.
That little float valve made by Jim - the nipple on the top connects to a snorkel:
I am sure this has been done before (semi aspirated tank). The advantages over a sealed tank is you get away with a small airspace in the tank and you can have a smaller tank more full of water, which means less sloshing. BUT you won't come back like a rocket to the surface they way Gas will pop you back.
Unlike the Jihad sorry RCABS fundamentalists, I won't dare be arrogant enough to say this is a system for all situations but in preliminary tests in my Collins - where I need 700mls difference between true water line and dived, this system is showing great promise.
Here are some photos of construction.
You'll note the back end is the newly engineered Caswell/Merriman 3.5" engine room with twin motors and a single shaft through a reduction gear box. In the fore ground are PVC end caps and a PVC conduit that connects forward and aft WT sections. Note in the background the corresponding hole for the conduit in the 3.5" end cap. After the tank is glued together and pressure tested for leaks the end caps of the WT sections are glued on to the ballast tank end caps
Next seal the tank - you then have the mainstay for what myself and a lot of Aussie sub drivers have used for years. You compress the air in the tank with each drop of water forced in, and you need a reasonably rigid tank to deal with the pressure. Eventually the pump will quit pushing water, typically IME its around 60% full. You need a valve to hold the water in the tank, which you release to surface.
With the sealed tank i have many years of fun, and parts fatigue, mainly pumps, but the concept has worked well.
I have played quite a bit with Gas with snort, and IMO this remains as rock steady approach to sailing. AND if it wasn't for my persistent curiosity I would have happily stayed with it.
You'd have to be on the dark side of the moon to not know that I have some strong opinions about RCABS. I won't regurgitate them too much in this new thread except to say here is a photo of my RCABS conversion:
RCABS does in some circumstances (low reserve bouyancy boats) work well. But it ain't the system for all situations.
RCABS does have a place in the hobby and some use it as a system within its limitations- but sadly there are those who think its a real religion - lets call them the Sub Scientologists. Sure as **** feels like that -some $400A out of pocket and no chance of refund. The cultist following, by some, of this ballast system -forsaking all others -is not in the name of hard science or from a view point of adding substance to the literature, but the drive and push has more to do with a sad little soap opera involving burnt egos and petty jealously. Scrap away the surface and you will find a deep hate of gas ballast systems for one reason only - David Merriman's success. Sad but the target of RCABS fundamentalists is never pumps, pistons, it always tends to be gas.
Moving right on long. Some in the hobby myself included are in it to learn and to experiment with new techniques and systems.
For others the end point is stick time and lots of it. I seem to swing between wanted stick time and learning. If you want an off the shelf fully backed product - you can't go past the Subdriver range that Caswell / Merriman put out, and I have in the past gone this way for almost ready to dive fun.
But.... Getting back to that pesky learning and curiosity of mine - Jim Russell - the grandfather of the hobby in Australia, recently fixed me up with a new pump system and solenoid valve. The system can be used as I have many times previously - with a sealed tank, and given that this unit is a geared pump that stays in the dry section of the boat it shows cf my old equipment a greater degree of reliability. Its a good pump- it will pump against 3 bar (around 45PSI) on 12 volts before quitting. Its called a "Dark Horse" geared pump- flow rate max is 2.8L per minute.
Here is a photo of the setup in a 3.5" end cap. Solenoid is closest the cap. You can see a simple on / off micro switch setup for servo operation against the momentary micro switch arms.
Jim in talking with me about different setups had been testing the pump solenoid on a range of boats. I explained that one thing I really did not want to go back to for my Collins sub was using a sealed tank as the airspace tends to oversize the tank so much it would compromise in this small boat around a (1m) the avaliable space for torpedoes and other goodies. Jim suggested I give the pump / solenoid a try but in union with a float valve. So doing so, the tank is temporarily aspirated right up until its around 70% full of water. At this point, a float valve (which Jim modifies from a fish tank accessory) pushes a float against the vent sealing the tank. At this point you boat is at decks awash or slightly lower, and the remaining pump in cycle occurs as a sealed tank. Fully dived you surface by reserving the pump and opening the solenoid, the pressure in the tank rockets the water back out, the float valve recedes and at snorting depth you empty the rest.
That little float valve made by Jim - the nipple on the top connects to a snorkel:
I am sure this has been done before (semi aspirated tank). The advantages over a sealed tank is you get away with a small airspace in the tank and you can have a smaller tank more full of water, which means less sloshing. BUT you won't come back like a rocket to the surface they way Gas will pop you back.
Unlike the Jihad sorry RCABS fundamentalists, I won't dare be arrogant enough to say this is a system for all situations but in preliminary tests in my Collins - where I need 700mls difference between true water line and dived, this system is showing great promise.
Here are some photos of construction.
You'll note the back end is the newly engineered Caswell/Merriman 3.5" engine room with twin motors and a single shaft through a reduction gear box. In the fore ground are PVC end caps and a PVC conduit that connects forward and aft WT sections. Note in the background the corresponding hole for the conduit in the 3.5" end cap. After the tank is glued together and pressure tested for leaks the end caps of the WT sections are glued on to the ballast tank end caps
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