Displacement hull centre of gravity

by Gilly
(Leeton NSW)

I have a 28ft custom bay cruiser approx 60 years old that I am re building it has a 3 cyl cabota engine that weighs approx 350 + kgs.

I would like to replace it with a couple of outboards.

Do I need to replace that 350 + kgs in the hull to maintain the stability of the boat?

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Mar 13, 2011
by: Mike

I'm sure Naval Architects have some complicated formula for working out ballast ratios and the like, taking weight, hull shape etc, etc into consideration.

Way beyond me I'm afraid.

My gut feelings though, (not very scientific) is that some of the weight loss will be covered by the weight of the outboards.

However, as the weight will be in a different position, the stern, I think that she may need extra some ballast to correct her trim if nothing else.

My suggestion would be to experiment with bags of gravel and or sand until you figure out how much ballast is needed and where it works best.

Using sand bags of an easy size to lift and move is cheap and can be replaced with something more permanent later when you are happy with the results.

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