Join Date: Feb 2000
Location: Annapolis, Md
Thanked 432 Times in 362 Posts
Rep Power: 10
Re: Another $1 Boat Thread, Water Ballast Conversion
I must admit that this has been running through my mind ever since I saw the original post yesterday. Its not simple, but its very doable.
I will start by saying I had never really paid attention to the design of a Cal 21 before. That is a wildly efficient hull, rig, keel and rudder for that day and purpose. I would have to think that it would be a good platform to do what you are proposing but it will take some serious skill to sail that boat if you remove the swing keel since stability from the deep draft with a bulb layout of the swing keel will be hard to replace.
I suggest that reading the comments, that there seems to some misunderstanding about how you would move water ballast on a boat this size. You don't pump it. You use a water tank that is mounted on a trolley that allows the water tank to be pulled across the boat. The tank itself would be moved by a block and tackle system that could be controlled from the cockpit. If the long axis of the tank were oriented fore and aft, I would think that you would roughly need a 25 gallon tank (roughly 200 lbs) to equal the righting moment of the original keel. The tank and trolley could be mounted high enough that it can clear the top of the centerboard trunk. Center-line water ballast tanks do almost nothing useful unless the boat has a huge amount of form stability which this boat does not. I would forget about adding a center-line water tank. I might consider building a deep draft centerboard that had maybe a 100 lb lead shoe, but I am not sure that is even necessary.
To tack, the traveler would be dropped to stand the boat up, and then the tank would be lowered to the center-line of the boat. The boat would then be tacked and settled in. Once settled in the tank would get pulled to windward in much the same way you pull up the traveler after a tack. Lastly the sail plan gets fully loaded up. Its probably a 30 second tack vs a 15 second tack.
A boat this light could be rowed in much the same way that a Dovekie is rowed. The only downside of this particular boat for a raid boat is that the rig is not easy to step and un-step, and also is longer than the boat so does not stow neatly. On the flip side, this is an easy rig to sail short-handed and there is plenty of sail area. I might be tempted to turbo the boat by perhaps rigging running backstays, and go to a square head mainsail and a masthead chute.
Whatever you do, you will probably want to add additional internal framing to offset the strains of increasing the stability of the boat and the spot loads of the water tank trolley and its supports.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay
Last edited by Jeff_H; 06-04-2019 at 01:09 PM.