Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Balast tanks for an oil tanker  (Read 1866 times)

markrider

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 60
  • Model Boat Mayhem is Great!
  • Location: United Kingdom
Balast tanks for an oil tanker
« on: October 15, 2016, 01:09:17 AM »

Hello so my next project as going to be a oil tanker
What I want to do is fir balast tanks so I can raise and lower it for full and empty  running.
Has any onedone this its about 1.2 m long .
So I'm going to make waterproof tanks but not sure about the pump and getting water in and out . So any tips would be nice  many thanks


Mark
Logged

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: Balast tanks for an oil tanker
« Reply #1 on: October 15, 2016, 10:36:17 AM »

Have a look at my SS Ohio build thread over in the  Working Vessels section. Pages seven and eight show the introduction of the pumps. These are full size marine bilge pumps, 12v rated and somewhere in the region of thirty quid each at the moment. I picked these as they will outlast the model! They are built for far harsher environments than we would ever use. Don't forget to baffle your tank to avoid water sloshing about, causing stability issues.
Logged
Listen politely, nod approvingly, then do what you want, works for me!

markrider

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 60
  • Model Boat Mayhem is Great!
  • Location: United Kingdom
Re: Balast tanks for an oil tanker
« Reply #2 on: October 15, 2016, 11:34:37 AM »

Great thanks very much will check it out
Mark
Logged

g6swj

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 313
  • Short Wave Jammer! -.-
  • Location: Northamptonshire, UK
Re: Balast tanks for an oil tanker
« Reply #3 on: October 15, 2016, 11:39:42 AM »

Mark,

Depending what level(sorry for the pun) you want to take this to you might get some good ideas from Mayham user John Redearth

http://www.modelboatmayhem.co.uk/forum/index.php/topic,54401.msg562917.html#msg562917

Not sure if this is the ballast tank control stuff but serach for John's posts and you will find it...

Cheers
Jonathan
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,888
  • Location: North London
    • Dive-in to Model submarines
Re: Balast tanks for an oil tanker
« Reply #4 on: October 15, 2016, 12:28:03 PM »

Will it need to have a variable waterline, or is just switching between two waterlines?

If it's the latter then you can build a system very cheaply, and I would use an air pump rather than water, as it's quicker and more efficient. I would also use a main and trim tank system. The main tank would be worked off a diaphragm compressor, and would be completely empty or completely full. The tank would be vented at the bottom, and you need something like a tyre valve or ball valve actuated by a servo, or a solenoid air valve to vent the top of the tank, and allow it to fill. To empty, you would close the valve and use a small compressor to blow out the air. Good high volume diaphragm compressors are available very inexpensively on ebay. They can blow a large tank extremely quickly

The trim tank only needs to be small about 1% of the boats displacement when at the low waterline. A trim tank isn't essential, but it makes it easy to adjust for different water conditions. This tank would be best controlled with a small bi directional water pump.

NFMike

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,062
  • Location: Hythe, Hants, UK
    • Plague Marine Services
Re: Balast tanks for an oil tanker
« Reply #5 on: October 15, 2016, 01:57:15 PM »

Given you presumably need the tanks empty when getting it out of the water I would be thinking along Subculture's lines - open at the bottom and pump/vent air at the top. Then if there is a system failure you should still be able (with care) to retrieve it from the water without breaking yourself and/or the boat.

markrider

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 60
  • Model Boat Mayhem is Great!
  • Location: United Kingdom
Re: Balast tanks for an oil tanker
« Reply #6 on: October 17, 2016, 01:36:03 PM »

So yer just want 2 levels empty and full.
 Still cant get my head round it.
 So I have tanks I just need to pump water in is it better from underneath then and then pump air in to force it out. If so what do people use for the valves I read up the links but still can't understand
 Or am i beeing thick lol
Logged

Crossie

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 234
  • Model Boat Mayhem is Great!
  • Location: Norfolk UK
Re: Balast tanks for an oil tanker
« Reply #7 on: October 17, 2016, 02:17:58 PM »




 Mark, perhaps this will help to clear away your confusion.


     A tank totally sealed except for a hole in the bottom which is piped in a straight line through the bottom of the hull to the water, and a hole in the top connected to an air pump with it's inlet high above your loaded waterline level, any type of pump but with no non return valves.


  What will happen when the boat is launched is that the water will slowly fill the tanks by displacing the air through the pump i.e. the boat settles to the loaded waterline level which is determined by the size of your tanks. When you want to run empty, turn on the pump which will raise the air pressure in the tank and push the water back into the pond. You do not need a big powerful pump the unloading needs to happen slowly - - not like a bow thruster! The type used in car seat inflation systems is quite adequate for the couple of psi that is required, you only have head of water a few inches high


 The pump runs for as long as you want to sail empty, if you don't want a constantly running pump the you will have to place a valve on the inlet side of the pump and either control it with a servo or solenoid.


       Alternatively, a  tank with a water pump to the bottom and an air vent in the top of the tank to overboard, switch the waterpump one way and it fills the tank, switch it the other way and it empties. Control the pump by a standard servo with two switches driven by the servo arm/disc.


 Both systems are simple and pretty foolproof and as long as any opening in the tank is not directly into your hull, it will stay afloat and you'll not be sailing a submarine- -now there's a challenge!
Logged

markrider

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 60
  • Model Boat Mayhem is Great!
  • Location: United Kingdom
Re: Balast tanks for an oil tanker
« Reply #8 on: October 17, 2016, 02:38:38 PM »

Crossie that's perfect
Totally understand it now and very simple to do.
 Thanks very much.i will see what I can do now.
It's quite long so could make 2 tanks front and back so it settles in the water evenly
Thanks again


Mark
Logged

Crossie

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 234
  • Model Boat Mayhem is Great!
  • Location: Norfolk UK
Re: Balast tanks for an oil tanker
« Reply #9 on: October 17, 2016, 03:14:25 PM »




  Great! Don't forget to follow unbuilt's earlier advice about baffles in the tank, I would second that and suggest that you use the type of foam used in petrol tanks which is a really easy way to do it


Trevor
Logged

plastic

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 979
  • Bobbing Along!
  • Location: Watford
Re: Balast tanks for an oil tanker
« Reply #10 on: October 17, 2016, 03:40:03 PM »

Why not have a neutrally bouyant free-flooding hull? SS Colander?

Large vents top & bottom mean it will sit at one level and to adjust the waterline you only need a tank that displaces the weight of the mass of the hull material?

Could be less than 1 litre (1kg) in total needed so water or air could be used for the mass-adjustment - possibly a couple of saline bags & a car-tyre compressor or little water pump?
Logged

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
Re: Balast tanks for an oil tanker
« Reply #11 on: October 17, 2016, 07:30:03 PM »

Have a look here at something I knocked together a few years ago:


http://www.modelboatmayhem.co.uk/forum/index.php/board,157.0.html
Logged
if at first you dont succeed.....have a beer.....

markrider

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 60
  • Model Boat Mayhem is Great!
  • Location: United Kingdom
Re: Balast tanks for an oil tanker
« Reply #12 on: October 17, 2016, 08:02:43 PM »

Thanks for all your help people
Boatmadman I did look at your thread looks amazing
Did it work as expected ? Have you still got it ?
Logged

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
Re: Balast tanks for an oil tanker
« Reply #13 on: October 17, 2016, 08:17:49 PM »

Hi,
I sold the boat on a few years ago, don't know where it ended up.


It did work, but, if I was to do it again (which is unlikely), I would do it a little differently.


The boat submerged and lifted up well, but, there was no spare capacity to enable it to lift any more then it's own weight. In hindsight, I would not have free flood ballast tanks,but instead have all the tanks filled and emptied using the pumps. However, this would have introduced stability problems when it first goes in the water and before any ballast is introduced, so, a compromise of enough fixed ballast (lead) to ensure initial stability and pumped ballast is probably the way to go.
Ian
Logged
if at first you dont succeed.....have a beer.....
Pages: [1]   Go Up