Wednesday, 15 September 2010

Its Been All About Ballast Today

According to the designer of the boat it needs to displace 24,500kg to set the boat right in the water.  I have a spreadsheet running and I have been adding to it as I have added materials.  Up to now this has been retrospective, but as I am preparing to put the floor down I need to work out future materials weight.

Armed with the weight of ply I am going to use I have calculated that this will weigh in at 1100kg, the rest I have had to estimate.......
Kitchen and bathroom with stone work tops and appliances 1000kg, engine, gearbox, stern gear, steering gear and rudder including batteries, generator, waste tank full 1500kg, water tank full 2000kg, bedroom furniture 500kg, misc. fixtures, fittings equipment and services 1000kg, fuel 250kg.

At the last count the boat was weighing in at 14,800kg, the known weight of the ply + the estimated weight of everything else adds up to 7300kg comes to 22,100kg so I need to add at least 2400kg of ballast.

Now you may recall if you have read for a while I was going to use granite off cuts from my brothers company.  I have decided instead to use compressed stone paving slabs.  They come in various lengths x 600mm wide.  So it works out that 1 x 750mm and 1 x 600mm is just right.  The 750mm weighing in at 52kg and the 600mm at 41kg  so each bay adds 93kg.

744kg worth going under the bathroom floor

I am going to add this to the middle of the boat and leave the rest of the floor removable so I can add ballast to trim the boat as required.


  1. When I built Harnser, a narrowboat I worked out the weight and how much ballast I needed. I got it almost spot on and covered the floor with 2" paveres 2 deep. After I launched I had to throw it all away and ues iron ingots to get the same weight in the right place to get the boat trimmed right.
    Good Luck

  2. It is a worry I have to admit. My boat has 20 ribs each side of the base. I have filled the middle 10 each side with slabs. The 5 each side at the front and back will be left accessible for final adjustment.

  3. Did you get it right?
    I've been told I need 7.5t in my widebeam so yours seems quite light to me?

    1. Yes. Spot on. My Hull is chined so is less displacement