Dave,

I'm not sure if you're serious about this project, but if so, I suggest
you follow plans based on a boat that has been built and tested. I have
a water-ballasted boat, and there are several design factors unique to
these boats. - For example, how are you going to ensure that the
ballast tank doesn't deteriorate over time, leak, or break away from the
hull in rough seas? What's the shape and position of the tank in the
boat, and how are you going to fill and empty the tank? If it's a
sailboat, you will of course still need some sort of keel or dagger
board, etc.. - Are you going to extend it through the tank, or affix it
to the hull? If the latter, how are you going to attach it to the hull,
below the ballast tank? For added stability, our boat has about 400
pounds of fixed ballast in addition to the water ballast, which helps
keep the boat stable if the water ballast tank isn't filled. Another
option is to have tanks on both sides of the boat that can be filled
individually, which offers some advantages but would be pretty much of a
hassle to maintain and fill and empty the tanks when underway.

Jim


Dave Doe wrote:

In article .com,
says...


I have been getting interested in building this boat:
http://www.duckworksbbs.com/plans/jim/cormorant/
Of course, I have to finish the Tolman Skiff first, but a trailerable
water ballast sailboat that I can build to my needs is attractive to me
but I have some concerns
1. Do water ballasted boats tend to be exceptionally "tippy" before
they are filled?
2. Could this be alleviated by including a few hundred lbs of lead
sheeting along the bottom?
Any other useful thoughts? Yes, I know you do not save money by
building boats but its become an obsession.



I have a couple a questions...
1. How much water ballast (approx litres) does it take to equal say
200lbs of lead hanging 6' down (on say a swing keel)?

2. How much righting moment does a water ballasted boat provide given
the ballast is below the waterline?

And a cheeky Q3? - How much does water weigh - in water?