Bladders & Bags

My friendly and tame chemist lady gave me this saline bag just now, and I'm hoping to be able to use it as a water ballast bag in Project 575.

The bag holds over 2000ml of liquid, and I'm thinking it's a bit too big, so the question is : can I cut it down and reglue it somehow? If so, with what do I glue it with?

Or would it be safe to use if I just fold up the end and tape it over? It will positioned on a styrene tray above the radio gear in the watertight box, so I definitely do not need it to leak!

Any ideas forthcoming, chaps?

.

I saw some clever use of layflat tubing up at the Edinburgh Model Boat Club. I think it was George. PM me Richard if you want to follow it up.

Any chance of the solution details as I'm looking to get my darnell u570 diving again. It's currently just setup for surface running and I have a couple of empty compartments?

Regards Will

My name is now on all the old Owners posts, so it is easy to think I made the post. I did not. Maybe Nigel can jump in here and remember what he recommended to get the dive system working.
There are many ways to get your sub to work. A bladder system is certainly one way.
Peace,
Tom

I have just spoken with Nigel on the phone and he said the conversation was some time ago but basically he recommended:

- Rolling the bags up and putting them inside a plastic tube with perforated end caps.

- He found that saline bags etc seem to be rather too large for use in models and so water "sloshes" around in them disturbing your trim.

- Enclosing them restricts the movement of the bag, reduces the volume and helps to prevent the bag bursting if it gets pressurised.

I have also been searching the old grey cells for my comments on lay flat tubing. I have looked at photos of Edinburgh but I didn't take any of these tubes.

The sort of tubing is shown below. Available on ebay and can stand 4 Bars pressure.



Easy to cut to length and lies neatly inside a hull. I can't remember how to seal the ends but I would suggest plastic end caps inserted and glued in the tube?? Perhaps with a Jubilee clip around it?? (Other clips are available!)

I need to qualify my statements by saying I have never used bladders (perhaps because of availability) I have only used PVC/ fibreglass pumped pressure tanks and (now) home made piston tanks.

David

actually, for the two bladder based systems that i have, one is just a large (24" diameter) thick walled party balloon. the other one (norbert bruggen delta) uses sheet vinyl glued with thick rubberized CA.