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    Pressure tank ballast system - pressure tank

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    david f
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    Location : Cumbria

    Pressure tank ballast system - pressure tank

    Post  david f on Thu Oct 02, 2014 9:58 am


    dgp1957
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    Join date : 2012-12-30

    Re: Pressure tank ballast system - pressure tank

    Post  dgp1957 on Sat Oct 11, 2014 9:52 am

    Need a re-think I had a bit of a disaster trying to add fibre glass to re-inforce my cylinder, resin wouldnt stick to it, thinking about using threaded rod to secure the ends to the cylinder, is that a viable option? Regarding pump, if I use a water pump to fill cylinder with water then do I need to reverse the pump to empty the tank or will air pressure in tank do the job for me? if so how could I avoid water emptying from tank when pump stopped, is that what pinch valve/solenoid valve would do?

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    David
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    david f
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    Re: Pressure tank ballast system - pressure tank

    Post  david f on Sat Oct 11, 2014 12:08 pm

    Hi David,

    It sounds like you have hit a steep part of the learning curve!

    If it is any consolation you have identified the major problem in the pressure tank ballast system - making a suitable tank! Lot's of people giving advice out there but very few people have actually done it.

    My advice needs to be given with the background that I have made about 3 of these tanks and they have all worked well. Mind you I now have moved onto home made piston tanks using proportional control. (I am assembling my third one.) so you can perhaps see my preferred ballast system. (I know that Nigel for one does not like the pressure tank system.)

    Health warning over. Resin does not really need to stick to the plastic inner tank - you are sheathing it with a reinforcing layer of fibreglass. Cut the glass matt roughly to size and stipple it with resin. Apply to the inner tank and stipple it down with a roller or stiff brush (avoid air bubbles). You can repeat the process several times but don't leave too many days between coats to make sure that you get adherence.

    As I said earlier the plastic pipe can stand the sort of pressures we use - the problem is with the design of the end caps. Maybe this technology could move on by using stainless steel tanks like Sheerline. Could anyone out there oblige by making tanks, I wonder? Or perhaps buy them from Sheerline.

    The basic system does not need a reversible pump. The air bubble pushes the water out through the pinch valve. However I prefer to use a reversible pump and I use an electronic switcher. The reason for this is that you can "lose your bubble" after some minutes and hours. The reversible pump helps to get the water out.

    Sorry you are having these problems and let us know how you get on. It is good to see someone who is doing rather than just talking about it and mystification can be part of the process!

    David

    dgp1957
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    Re: Pressure tank ballast system - pressure tank

    Post  dgp1957 on Mon Oct 27, 2014 8:29 pm

    Guys having a serious re-think about this pressure tank system, mygut feeling is to install the compressed air system that was originally in the boat along the lines of the HMS Satyr dive system. Thanks to Fred I have a Darnell compressor so will be able to use that, I have also bought a water pump from ebay could that be used to pump air as well as the compressor?

    David
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    david f
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    Posts : 1920
    Join date : 2010-11-10
    Age : 67
    Location : Cumbria

    Re: Pressure tank ballast system - pressure tank

    Post  david f on Tue Oct 28, 2014 9:14 am

    Hi David,

    A water pump is unlikely to do well pumping air but try it.

    Regarding compressors, if you look at the thread on refurbishing an original Darnell Type XXI:

    http://www.theassociationofmodelsubmariners.com/t1092-darnell-type-xx1-graham-s-dad-s-boat-for-refurbishment

    You will see I gave up on the original air pump - it was slow and leaky. You may be best going for a more modern air pump combined with a Darnell type bag?

    Sorry to sound rather discouraging and I think I can see why you have gone off the pressure tank system - making a pressure tank?

    David

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