The Association of Model Submariners.

Would you like to react to this message? Create an account in a few clicks or log in to continue.

* THE FORUM FOR ALL THOSE INTERESTED IN BUILDING AND OPERATING MODEL SUBMARINES *



Join the AMS - Registered Forum users can become members of the AMS and it's free ...... To join send an email with your name , address and phone number to amstreasure@googlemail.com


For a guide to past events see the "Shows and Events" section.

Who is online?

In total there are 4 users online :: 0 Registered, 0 Hidden and 4 Guests :: 1 Bot

None


Most users ever online was 180 on Tue Nov 05, 2019 6:03 am

Latest topics

» Radio ideas -27Mhz
ballast and trimming EmptyMon Jan 17, 2022 1:35 pm by geofrancis

» Radio RSSI depth controller
ballast and trimming EmptySat Jan 15, 2022 11:30 am by geofrancis

» Mast mounted water level sensor.
ballast and trimming EmptySat Jan 15, 2022 1:52 am by geofrancis

» Newcomer to the forum?
ballast and trimming EmptyMon Jan 10, 2022 6:45 pm by Tom(ADMIN)

» Type II U-boat
ballast and trimming EmptyWed Jan 05, 2022 3:17 am by tsenecal

» Lipo cut off circuit - Practical Electronics magazine - November 2021
ballast and trimming EmptyTue Dec 21, 2021 3:40 pm by tsenecal

» bladder systems
ballast and trimming EmptyTue Dec 21, 2021 3:35 pm by tsenecal

» Looking for drawings and instructions for Hegi U-25 Kit
ballast and trimming EmptySat Dec 18, 2021 12:44 am by Telusboats

» Nautilus II by Robert Fulton
ballast and trimming EmptyThu Dec 16, 2021 2:20 pm by david f

Statistics

Our users have posted a total of 11579 messages in 1900 subjects

We have 941 registered users

The newest registered user is PaulBrown

4 posters

    ballast and trimming

    avatar
    dgp1957
    AMS member


    Posts : 42
    Join date : 2012-12-30

    ballast and trimming Empty ballast and trimming

    Post  dgp1957 Sun Dec 30, 2012 1:39 am

    hi folks i have just bought a darnell s type submarine
    all ready to go bar ballast and trimming, can anyone give me some hints?

    david
    david f
    david f
    AMS Treasurer


    Posts : 2214
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    ballast and trimming Empty Re: ballast and trimming

    Post  david f Wed Jan 02, 2013 5:09 pm

    Have you access to a test tank or will it fit in the bath.
    Basically you need to get the sub level on an even keel at neutral buoyancy, with the ballast tank full.

    Foam and lead can be used in combination if the boat is not very stable. I like using lead shot mixed with silicone rubber for the final fitting but don,t be afraid to place weights or foam pieces externally with ,say, rubber bands until you get close to a trial balance.

    David
    avatar
    dgp1957
    AMS member


    Posts : 42
    Join date : 2012-12-30

    ballast and trimming Empty Re: ballast and trimming

    Post  dgp1957 Sat Jan 05, 2013 10:10 am

    thanks David, I have access to a test tank at my local club in Greenock. The sub sit level when the deck isnt on, but heels over to starboard when the deck is put on also the stern slips under when I apply the compressor to dive so I think that the water is coming into the tank area then the weight of the water is building up in the back of the tank causing the stern to go down first, does that sound right? so today Im going to try adding some foam to the stern on the upper part of the sub and we' ll see what happens then :-)
    avatar
    Tom(ADMIN)
    AMS Forum Owner


    Posts : 3012
    Join date : 2010-11-05
    Age : 62
    Location : Nevada, USA

    ballast and trimming Empty Re: ballast and trimming

    Post  Tom(ADMIN) Sat Jan 05, 2013 11:31 am

    Might be worth mentioning to keep foam above the water line and lead ballast below the water line, otherwise one will be fighting the other. Oh yes...been there and done that, and wondered why I couldn't get the boat to sit level for more than ten seconds.
    avatar
    dgp1957
    AMS member


    Posts : 42
    Join date : 2012-12-30

    ballast and trimming Empty Re: ballast and trimming

    Post  dgp1957 Sat Jan 05, 2013 5:00 pm

    David finally got the level right (I think) however still listing to starboard would I be better adding weight to the bottom of the keel or add some foam to the starboard side above the waterline?
    salmon
    salmon
    AMS Forum Owner


    Posts : 312
    Join date : 2011-09-02
    Age : 62
    Location : Las Vegas, Nevada - USA

    ballast and trimming Empty Re: ballast and trimming

    Post  salmon Sat Jan 05, 2013 6:37 pm

    As long as the cause of the listing is static (fixed and not moving like a LiPo battery shifting) then move the weigh slightly to the port. You can add more weight and/or foam to counter act the listing issue as well. Testing, trial, and a bunch of patience.


    _________________
    If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.
    david f
    david f
    AMS Treasurer


    Posts : 2214
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    ballast and trimming Empty Re: ballast and trimming

    Post  david f Sat Jan 05, 2013 8:19 pm

    As everyone has said, move the weight to port or starboard to counteract the list. (Don't tell anyone but I put Velcro on the underside of the model to easily fix and move small weights last minute at the pond side!)

    Foam and weight are used together to counteract listing. (Keep the weight as low as possible and the foam as high as possible (Metacentric height is the technical term) However you don't want much foam above the waterline because that volume has to be displaced by the balance tank (Remember Archimedes!) Keep the superstructure displacement as low as possible for the same reason. And the superstructure weight down to prevent listing)

    Oh dear, a lot of factors interact hence Salmon's suggestion for trial and error and patience!

    It may console you to know that small trim problems tend to be masked once the model is underway at a reasonable speed. Twin screw subs like yours also have the advantage of not listing because of propellor torque (turning forces).

    Have fun!

    David
    avatar
    dgp1957
    AMS member


    Posts : 42
    Join date : 2012-12-30

    ballast and trimming Empty Re: ballast and trimming

    Post  dgp1957 Sun May 05, 2013 9:02 pm

    hi guys still no success as yet. The sub is an old Darnell kit, it has a large chunk of lead attached at the bottom of the hull, was that a standard thing or would I be better cutting it off and starting from scratch?

    david
    david f
    david f
    AMS Treasurer


    Posts : 2214
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    ballast and trimming Empty Re: ballast and trimming

    Post  david f Mon May 06, 2013 10:55 am

    I take it you still have a list to starboard?

    You have something heavy to one side.

    You may have to move that fixed weight, sorry. How is the overall waterline at the moment?

    David
    avatar
    dgp1957
    AMS member


    Posts : 42
    Join date : 2012-12-30

    ballast and trimming Empty Re: ballast and trimming

    Post  dgp1957 Mon May 06, 2013 4:54 pm

    Hi David its , as they say here in Greenock, "dain ma heed in" lol I'm just going to cut the lead from the hull strip it out and start from the begining :-)
    avatar
    dgp1957
    AMS member


    Posts : 42
    Join date : 2012-12-30

    ballast and trimming Empty Re: ballast and trimming

    Post  dgp1957 Mon May 06, 2013 8:27 pm

    Had some success tonight I took the cover off the middle section that is free flooding with two aerosol cans that hold air and are used to expel water (I think), had three bits of lead glued to the hull side I removed them and now the sub sits nice and level in the tank. Just need to get her diving and surfacing now. ;-)

      Current date/time is Wed Jan 19, 2022 3:55 am