New project - Neptune - a fantasy boat project

[redboat219]

Would it be simpler to use a close tank than venting into the WTC?

[DrSchmidt]

Would it be simpler to use a close tank than venting into the WTC?

How do you fill a closed tank? The Air has to go somewhere.....

[redboat219]

How do you fill a closed tank? The Air has to go somewhere.....

Gases (Air) have
nice characteristics, one of the is compressability. As you fill the tank with water the air gets compressed and it's volume decreases. So it's still inside the tank.Look up Boyle's law.

[DrSchmidt]

Well I have a Phd in physics and know about compressability. The question is, why would I pursue an approach that puts immense pressure on tank, pump and hoses while leaving 20-30% of the tank empty.

[RCSubGuy]

The sealed pressure ballast system is a tried and true method of ballast control in RC subs. OTW and Sheerline have been using it for decades. Engel boats also pressure up the dry compartments of their boats during piston tank actuation.

The lost volume of the ballast tank is less of an issue with the large boats that typically use these systems. They're not suitable for small boats where space is at a premium, but for big boys, they're a completely valid alternative.

Bob

[DrSchmidt]

The sealed pressure ballast system is a tried and true method of ballast control in RC subs. OTW and Sheerline have been using it for decades. Engel boats also pressure up the dry compartments of their boats during piston tank actuation.

The lost volume of the ballast tank is less of an issue with the large boats that typically use these systems. They're not suitable for small boats where space is at a premium, but for big boys, they're a completely valid alternative.

Bob

Exactly......the air from the tank goes into the dry space of the wtc and the pressure rise is accebtable. Sealing off the tank and pumping water into it till the pressure of the pump is maxed out is just hard on the hoses, conections, the pump, and last but not least the battery, as the pump will draw allot of current when working againts the pressure in the tank.

[DrSchmidt]

Finished the WTC for my little fantasy boat Neptun. Ballast system uses a peristaltic pump with a float and a water switch to turn the pump off when the tank is full. Pump controlled by a Brüggen BTS and auto-leveler by Engel. 3s lipo as power source, corona receiver, and a outrunner brushless to drive the prop. I like how compact is turned out...

[SubDude]

Finished the WTC for my little fantasy boat Neptun. Ballast system uses a peristaltic pump with a float and a water switch to turn the pump off when the tank is full. Pump controlled by a Brüggen BTS and auto-leveler by Engel. 3s lipo as power source, corona receiver, and a outrunner brushless to drive the prop. I like how compact is turned out...

Looks very clean and well thought out.

[DrSchmidt]

Thanks. Proper CAD designing prior to a built helps allot ;-)

[DrSchmidt]

Good news, WTC is water tight and the ballast system works fine! Just the snorkel missing and then trimming.

[He Who Shall Not Be Named]

Good news, WTC is water tight and the ballast system works fine! Just the snorkel missing and then trimming.

Gotta get those off to you -- long ago promised, but life got in the way. This week, I promise.

David

[DrSchmidt]

Started printing parts for my version as well. But I doubt that it'll work right away. Might need some iterations....

[DrSchmidt]

The WTC and the diving system are working fine. I added a snorkel valve and I just need to add a guidance for the float of the valve. Then everything is ready for trimming.

[redboat219]

Any photos?

Wait, a snorkel valve? I thought this uses a peristaltic pump that fills and empties a tank that vents into the WTC?

[DrSchmidt]

Yes, the pump vents into the WTC, but: Peristaltic pumps also pump air. If you empty the ballast tank long enough, i.e. too long, the pump will create a vacuum in the WTC. To avoid the vacuum, I've attached a snorkel valve on the WTC that equillizes the pressure between inside and outside when surfaced.