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[class37]

Hi all,

another question from a newbi, hoping I can get some experienced answers from you all...

I am about to start building a 1/72 scale platform supply vessel, and have concerns about ballasting. I know, lots of threads before, and have read lots.

after working out displacement as per that archie medes fellow, was staggered at the weight of water involved.

due to advancing years and a bad back don't want to be heaving a heavy hull around so came up with a three part strategy.

my idea is to use some free flooding compartments, filling via the side thruster tunnels, with tops at the loaded wl level to prevent them overfilling and with straight vent pipes to the outside of the hull.

secondly a couple of pumped tanks for leveling fore and aft, with baffle plates inside to prevent surges, possibly even working the pumps by rc.

the third part of the system will be to have a number of compartments filled with offcuts of foam insulation panel to prevent water getting into them, and so give some residual bouyancy.

some ballast will be set in resin at the bottom of the hull [ got a pile of big old bolts in the shed] but will try to make most up with additional batteries for longer sailing time = fun while retaining liftability.

does this seem reasonable, or am I about to commit some terrible error ?

awaiting all you constructive, and destructive, comments

cheers

alan

[tigertiger]

The only thing I would say is that this sounds very complicated, what iwth pumps and all.
Flooding compartment can be very simple, not that I am any expert.

Simple usually does the trick, and is less likely to go wrong.

Just some thoughts.

[derekwarner]

Alan......model [water] ballasting can be a very interesting & functional capability to your vessel

1) free flooding tanks are fine....need baffle & above deck vents as the water level will only fill to the given space & you also need the initial mass of the vessel [who was that man in the bath?] a vessel will only displace its own weight story...  
2) free flooding tanks are fine....but you need to remove the water ballast on comletion of your run ........or your back will suffer 
3) as you have noted.......ballast discharge pump/s can be used [over board looks more attracrtive]..... however prior to dumping the ballast water... you must close off your under water sea chest entry points
4) it certainly would not be too difficult to manufacture a number of fabricated plastic knife type isolation valves & servo opened/closed with similar water proof glands to our model submarine use
5) if you did not fancy manufacturing your own plastic knife type isolation valves ....you could use those 1/4" BSPP low pressure brass plated 90 degree isolation ball valves [WOG nomination = water, oil & gas] and similarly open close with a servo
6) the more we think the less complicated it becomes...the ball valves need not be located within the tank....but external via plastic ballast piping & so hence eliminates the need for waterproof glands etc

Whilst I have never constructed any model ballast system ....suggest you keep on similar lines to real vessels........a suction sea chest equally spaced P & S of the vessel axis...& the ballast main running the required length of the vessel on vessel centerline ....

Keep the system symmetrical & make sure you build in removable ballast hold tank tops ...sufficient to get your hand in to clean out any obstruction  - ...keep us posted...should be interesting.....Derek

[class37]

Hi Derekwarner decoy,

many thanks for that. I am considering using the thruster tunnels fore and aft to fill the free flooding tanks, with a tee off the tunnel to run to the tanks.

it should not be too hard to fit a normal plumbing service valve into this pipe, with the operating arm extended up through the hull, and mounted inside a container on the deck.
valve normally open, but at end of the run, lift roof of container and close valve, then use pump to empty the tanks.
that way there is no need to have valves etc in the vent pipes.

the other option would be to have a valve in the vent pipe, and then use a pump to push air into the tanks to empty them.
have got a 12v tyre pump with a knackered hose & connector, so may try that idea out.

it can't hurt to experiment a bit.

the pumped tanks fore and aft would just be for final trimming.

started cutting the wood today, so will hopefully soon see if the idea will work in principle !

cheers

alan