Help with ballast system

If you read one of my earlier posts you will know that I bought one of Steve Webbs Submarines off Ebay. The model is a German class 202 coastal U-Boat S-173. Steve had already started to fit this out but had not completed it. His son Nigel has been very helpful and provided me with as much information as he could find but I am struggling to get my head around what type of ballast system Steve was fitting. I have added some pictures of what is already in the hull and any help anyone could give would be most appreciated. I would like to complete the build as near to what Steve intended but I am open to suggestions. Am I right in thinking a vented system was intended, I hope the pictures help.

Hi,Kevin
Steve would never have use a vented system he hated them,this boat was modified by Steve it originally was a radial bayonet seal,it was either a norbert brugen or engel I cant remember which,the last I can remember he was going to fit a bag inside the tank operated by a peristaltic pump,this was a method he regularly used on small boats,some of the parts where stolen whilst on show at ally pally one year after that he seemed to lose interest in the boat and moved on.

Hi Nigel

Thank you for the information, this confirm's what Nigel Webb told me after he had spoken to someone, maybe you?

I'm going to show how green I am now!!!

In the base of the tank there is a hole which I guess is the water intake, this hole is a threaded brass fitting, why has the lid got two pipe connections?

How would the bag be connected as I'm assuming it would be a bag with two pipes, but with the intake hole and the double ended pipe on the lid I have three pipe connection points?

Below are two more pictures one shows the inside of the tank lid the other is the valve Steve was intending to use, these may help with the above questions.

Where could I get a bag to fit the tank as it's very small?

Apologies for all the questions.

If anyone has any pictures or diagrams of a similar set up I would love to see them.

Looks to me like that may have been set-up to use either gas or compressed air.

If it was designed for peristaltic, why the pair of servo actuated valves?

Also why would the bottom of the tank be vented?

Mainly because they have nothing to do with that boat,the boat was going to be used for indoor shallow pool displays where lager models would struggle to turn or submerge,the Idea was to pump air not water into the bag inside the ballast tank,the hole at the bottom allows the water in when the air is removed from the bag,the pipes in the top one goes into the bag from the pump,the other one comes out of the bag to a pressure censor which stops the pump at a set pressure,this system is only suitable for shallow diving as the bottom hole is open and at depth the peristaltic pump would be unable to pump air into the bag because of the pressure of the water.

Yes you are correct Nigel did phone me asking if I could remember what his dad was going to do with this little boat.

Steve would never use a gas system he hated them with a passion,and as far as a compressor is concerned the boat is just to small,I remember a discussion about fitting it with a piston tank which is certainly the best option,but sadly Steven was ill by this time so it went no further.

Thank you again Nigel, it's a whole lot clearer now, I'll save the valves for another day.

As I live in Norwich and will be using the submarine at the Eaton park club pond then it sounds as though the original idea is still feasible for this venue.

So basically I need a Bag, Pump and Pressure switch, RC Subworks on Ebay or can anyone recommend another source?

The peristaltic pumps supplied by the RC workshop are small, slow and expensive.

If you have a search on ebay, you will find peristaltic's of equivalent spec for almost a tenth of the price.

If this system is pumping air, would it not be better to use a pair of small diaphragm pumps, one to pump in the other to pump out. The pumping rate would be quicker and the pumps are generally cheaper.

Hello, my first true post...

This sounds like the setup I have in my 1:32 Holland class. The pressure switch, material and instructions to make the bag, peristaltic pump and controller were all bought from Norbert Bruggen. The bag is flooded from think plastic and glued with special glue. Works well. Freek

Hello Freek,

Nice to hear from you on here and good to meet you both at Bournville. (I trust you have seen the photos on here and I hope you made it to the Ferry OK.)

Interesting that Norbert uses a special bag arrangement. I have never used a ballast bag, mostly because of the difficulty in finding a suitable bag of the right size.

Norbert may have cracked the problem as usual!

David

David,

I own one of Norbert's Delta submarines that uses a peristaltic pump and bag. exactly as described. he ships it with a sheet of what appears to be a thick vinyl sheet, thicker than 1mm, large enough to glue together a custom sized bag.

i have searched for a US distributer of the vinyl, and may have found some at McMaster/Carr, but haven't ordered any yet. as to the glue, it is a specific type of CA glue that is waterproof, and it comes as part of the kit.

I have also seen people use hospital IV bags. the trick is in the pressure switch. I think it switches at 60 mbar over pressure, so provided your ballast tank controller can stop the pump the risk of breaking the bag is absent. Freek