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Ballast tank size?

R/C Submarine modelers

Ballast tank size?

Postby Andreas_dk » Tue Aug 18, 2009 8:47 am

Hi everyone

I have just started building a USS Ohio in 1:80. (about 2,1 meter long)

I have decided for a RCABS-R, but I don't really know, how large a bladder I should use. Any help would be appriciated.

Would 2 liter bladder be too much? I will use piston tanks for trimming about half a liter in total trim volume.

Thanks alot

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Postby raalst » Tue Aug 18, 2009 4:11 pm

generally, with a two liter tank you
can push the weight of two liters
out of the water. this amounts to 2 kilo's.

so, you have to determine the weight of the part
of the boat you want to be able to lift out of the water.

how that is done other than guessing I don't know.
maybe someone else can chime in on this ?

any way, good luck with the build !

Ronald van Aalst

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Postby Robert F. » Tue Aug 18, 2009 4:29 pm

The German submarine modellers' club Sonar used to have on their website a nice little program which enabled you to calculate several data like total displacement, size and volume of ballast tanks etc.

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Postby U552 » Wed Aug 19, 2009 8:16 am

The likn to SONAR, Please? :wink:
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Postby JWLaRue » Wed Aug 19, 2009 8:57 am's not weight....its displacement that determines how large the ballast tank needs to be. The ballast tank needs to displace the same (or more) water than does the part of the hull above the water.

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Postby Sub culture » Wed Aug 19, 2009 9:25 am

It's really tough to calculate the correct size of tank for a submarine if it's a wet hull boat or an unusual shape. if the boat is a dry hull design, and straightforward in shape e.g. a spindle or a cylinder, then it's fairly easy to calculate the volume that needs to be displaced, although even here there can be a margin of error as things are rarely 100% spot on.

I would have a search on this site for ballast tank sizing. This is a question that often crops up and I guess folk get a little brassed off repeating themselves.
'Why are you staring at an empty pond?'

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