Te triune

[Alex Hughes 3Participant @alexhughes3]

Hi,

Im building a triune myself and am almost finished painting just adding water line mark how do you find where water goes up to without actualy having toget it wet is it just done on guess work?

Thanks alex

[Alex Hughes 3Participant @alexhughes3]

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[Malcolm FraryParticipant @malcolmfrary95515]

Its always guess work even if you have a drawing, You can never be sure until it meets water. You can know where it should be, and hopefully ballast down to that, but there are many factors that will change it. That's the difference between theory and practice.

[Paul TParticipant @pault84577]

Alex

To find how high the waterline would be, you'll need the weight of the boat and everything in it, and the area of the bottom of the boat.

Set the weight equal to the buoyant force W=B
The buoyant force is the weight of the water displaced by the boat, which is the density of water times the volume displaced. B=1000 kg/m^3 * V
The volume displaced is the area of the boat times the depth it is in the water V=A*h
So you get W=1000*A*h. Solving for h, you get
h=W/(1000 *A)

Make sure to keep you units consistent! i.e., your weight in grammes, your area in square mm, etc.

 

Paul

The density of fresh water at 4deg C at sea level is 999.9720 kg/m3

Edited By Paul T on 02/10/2012 09:56:20

[Dave MilbournParticipant @davemilbourn48782]

I couldn't agree more with Malcolm. Unless you have accurate plans of the real thing, with the waterline marked (in which case use that), I would suggest leaving any painting of the hull below the w/line until you have tried out the model in the water in various conditions (e.g. flat clam, Force 12 etc). Whe you've reached a reasonable compromise with the ballast for all conditions, mark and paint the waterline to suit. Cheating I know, but I promise not to tell on you……………….. Don't forget to spread the ballast out along the length of the hull to minimise "porpoising".

Dave M

Edited By Dave Milbourn on 02/10/2012 09:52:28

[ashley needhamParticipant @ashleyneedham69188]

Bath, pencil. Mark where you think it should be, then mark where it actually is, then either ballast or not according to taste! As per Malcolm and Dave. Ashley

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