weight/ ballast question

[NHDORY]

I have an 17 foot Swampscott dory and have read that adding weight, such as 2 bags of sand on either side of the centerboard box improves the handling and makes the boat feel much more stable. If this is the case, could I achieve the same result by just adding weight to the centerboard itself? The weight would certainly be in the right area of the boat, there would be no chance of sand touching my varnish and I wouldn’t have to sacrifice what little space there is in the boat itself.
Thoughts?...

[james burt]

not sure about the mechanics of it. but i would
say yes. i replaced my centerboard in my first
sailboat with an aluminum one, cut same size.
added and extra 25 lbs. or so. i could tell a
difference. from what i have read, the lower the
weight is the better, and tht would be as low
as possible.

[mmd]

Standard designer's reply - it depends.

Additional weight (within reason) will certainly make the vessel more stable - the Swampscott has flaring sides and a rather narrow bottom at rest so adding weight will increase draft which in turn will create a broader wateline waterplane which is a good thing for initial stability. If adding sandbags, the mass is low and contributes to mass stability. Adding the mass to the centreboard will certainly add stability when the c/b is down, but (depending on its shape) might actually decrease stability when drawn up into the trunk due to it's CofG being somewhat high in the boat. Check to see if the centre of area of the centreboard when fully retracted is higher than the centre of a bag of sand in the bilge to determine if the results will be the same.

[Bruce Hooke]

One thing to be aware of is that adding weight to the centerboard adds stress to the centerboard case, which may cause it to develop leaks, or at least that seems to be the "conventional wisdom." There is a big difference between adding a little lead to the centerboard to make it sink and adding the weight equivalent of two to four bags of sand to the board. Among other things, you may need to consider how you are going to hoist the board...

[kenjamin]

In moderation it's a good idea. It will increase the effort it takes to raise your centerboard and you have to be careful not to weaken the centerboard with too much lead and not enough wood structure. Is your current centerboard solid wood or layers of plywood? Is it glassed? Another easier solution might be bags of lead shot which would be more compact than sand but of course cost more. I called my local gun shop and they sell lead shot for $25 for a 25lb. bag. For the 21' Alpha dory that I'm about to build it's reccommended to have 50 lbs. on either side of the centerboard case but my boat will be set up for fishing so I'll be figuring in the weight of heavy tackle boxes and a marine deep cell battery or two as ballast. A nice gel deep cell battery weighs 26lbs. and cost $100 but it can power an array of electronic devices, electric trolling motor or lights.

[NHDORY]

I do have two batteries that I was going to build a nice case for. I was planning on the batteries being stowed on either side of the centerboard box. The batteries are for the electric trolling motor (the A/C and ice-maker projects for next winter). I could easily incorporate the weight I want to add into the floor of the case.