Model Boat Mayhem
Mess Deck: General Section => Model Boating => Topic started by: mickyrubble on April 29, 2012, 03:28:23 pm
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Has anyone ever tried using containers filled with water as ballast (IE plastic milk jars).I'm building a large scale steam drifter and it would have a high hernia value if filled with lead.
:o :o :o :o :o :o :o
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Our Gas Tanker used for tug towing is ballasted with waterfilled 5Litre plastic bottles.
Fill them with lake water before sailing and empty them back into the lake afterwards
Simples!
Ned
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Another way is to build in a flooding compartment. Or fit your plastic container and plumb it so that it fills with water as the boat is put in the water, or use a pump to fill, empty. John.
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The trouble with free flooding isthat you have to
Lift the boat and ballast to allow it to drain
Ned
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Yes you do. But draining time depends on pipe size and size of tank or tanks used. John.
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"Free Flooding" isn't ballasting....it's a loss of buoyancy. Using this system severely reduces the ship (model)'s ability to remain stable,
A boat of any size is meant to keep water out, not let it in.
Floppy plastic bags may well add "weight", but will do absolutely zilch for the stability unless the bags are constrained within a compartment.
My personal preference is to use sheet lead cut into squares and bundled up together with "Duck-Tape" as a handle.
Plonk the bundles into the hull and later just lift them out again. Easy. BY.
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leads ok if you can afford it... however sainsburys basics flour (asda smartprice etc) in sandwich bags seems to do the trick too.
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Funnily enough, I was contemplating a model today which, if the scale calculation is correct, requires a model weight of 131lbs :o
Can you build ballast tanks into a model that you can fill with an onboard pump and then empty again with the same?
My online calculations say that a volume of 50cm by 50cm by 20 cm of water would equal 50 litres and be 110 lbs.
If this volume could be compartimentalised would it work?
I would be interested in any responses, plus any links or pointers to fellow modellers who have done something like this successfully.
Thanks in advance.
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Yes, you can pump the holds full of water, then pump them back out.
http://www.rcgroups.com/forums/showthread.php?t=1152361
:-)
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"Free Flooding" isn't ballasting....it's a loss of buoyancy. Using this system severely reduces the ship (model)'s ability to remain stable,
A boat of any size is meant to keep water out, not let it in.
Floppy plastic bags may well add "weight", but will do absolutely zilch for the stability unless the bags are constrained within a compartment.
My personal preference is to use sheet lead cut into squares and bundled up together with "Duck-Tape" as a handle.
Plonk the bundles into the hull and later just lift them out again. Easy. BY.
Brian brings up a very good point here. Dividing the free-flooding section into smaller compartments with perforated baffles will greatly reduce the instability problem.
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Brian brings up a very good point here. Dividing the free-flooding section into smaller compartments with perforated baffles will greatly reduce the instability problem.
Agreed, you still have to ensure that the heavy (solid) stuff is placed low enough that the centre of gravity is low enough for the stability needed, quite apart from the dangers of unrestrained water sloshing about and altering the centre of gravity as in the Herald of Free Enterprise disaster.
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The "perforated baffle/bulkheads in an eclosed compartment was the base idea behind what became known as the "Flume Tank", which actually became a rather cheap (if space consuming) stabiliser. The LSLs had this system....it worked, but made the ship very "jerky" and it's movement a little unpredictable. BY.