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[funtimefrankie]

Somewhere, sometime, I read an article about ballast.
I think it was saying that putting the ballast at the bow and stern would have a different effect to having it all amidships.
Am I remembering right and if so can someone tell me the difference?

Similarly is there a difference having it spread across the bottom of the hull against having it down the centre line.

The model I'm ballasting is the SS Manxman 4 foot long 7 inches beam.
I'm thinking of putting some lead on the outside of bottom of the boat..( to get it as low as reasonablely possible). any problems with that (apart from the look of it)
Thanks
Frank

[tobyker]

You're right - one makes it turn faster than the other, but I can't remember which. Look up "polar moment of inertia". But I suspect it affects cars more than ships/boats.

[dreadnought72]

Moving the ballast to the bow and stern will increase the moment of inertia of the hull - it'll take more effort for the model to pitch than if the ballast was nearer the centre. (Think of seesaws, and moving weights along the arms.) I'd suggest the model may be somewhat wetter, but would pitch more realistically (i.e. slower) than if the mass was in the middle of the hull.

The same effect will occur in a roll, with regards to the ballast on the centreline or away from it. A slower roll will happen if the ballast is further from the middle.

Things get more interesting as the ballast is placed higher up the hull, especially at the sides. As long as stability isn't compromised, you'll get a slower roll as the ballast moves up, and less "toy bobbing".

Definitely experiments for the indoor test-tank!  

Andy