Center board weight?

[Maria CS20 104]

I just weighed my unplaned centerboard made of old growth walnut and hickory, it comes in at 23 pound but I am sure it will still float.  I will plane and sand about 40%  off the board I am sure based on sanding down of the the rudder.  I like the idea of a "negative" buoyant board. A negatively buoyant item (to me) is that it is an item that sinks and to some extent I want that.  but I also want it to sink only until it reaches neutral buoyancy around the full extent of it's reach, or close to it.  Negative buoyancy is a term used by us submarine riders, it keeps us able to get to the deep quick or as needed, but there is a balance we never want to exceed.  I would think having the board "floating" just at the fullest extent of it's reach would be ideal, it's just a matter of displacement which will be based on weight and density of materials used.  I would think I'll have to add 8 to 12 pounds of material to achieve what I want and each person will want something unique to there sailing conditions.  It also depends or wether or not you are a fresh water sailor or a salty.  I suspect lighter would be better in light winds and heavier would be more appropriate in heavy wether and winds especially better than seas of four feet and winds of 15 plus knots.  I would also think that it really depends on sailing conditions for each local condition, your experiance as a sailor and do you like and enjoy heavy winds and seas.  I am planning on sailing both but look forward to some open gulf and Atlantic opportunities were I think I want the full board in play to play.

Jim Atkinson

[Hirilonde]

Water weighs 8.8 lbs/gal..  1 gal. water = 231 cu/in..  With this data and the measured volume in cu/in. of your centerboard you can determine whether it floats or not without getting it wet.  And if you weight your centerboard you can determine the weight of it in water which will be the force to lower itself.

[Gordy Hill]

I weighted my centerboard because, when just left on it's own it would float with about six inches showing below the boat. I sail in very shallow water. When the board hit bottom I would release the downhaul and let it float. The problem I had was that there was no way to really tell when the water was deeper again. There's a big difference in sailing quality between 6" and 12" of board showing. With the board weighted to float 12" to 18" showing it would tend itself. It would be light enough to adjust itself at 6" and pretty much follow the bottom down to 18". If the board is too heavy you'll have to lift it in shallow water and then you have the same problem of having your board higher than necessary. As mentioned in an earlier post, I also cut back the leading edge of my board. I let the board out about 8" and then drew a line parallel to, and about 4" from the keel. By cutting off that triangle I had much more board exposed when there was only room to expose 10" or 12". I felt that light-air sailing in shallow water was definitely improved and the workload was lessened.

[JeffM]

I like Gordy's idea of cutting off the tip so that you can get more area with the same draft.  Keep in mind also that the centerboard is a sort of lever, so that WHERE you place the weight matters in any board that (like Gordy's) is not meant to be fully weighted.  The pivot is the fulcrum.  The bouyancy centers on the part of the board that is submerged.  The same amount of weight will have the most effect near the tip of the board and least near the pivot.  For the same reason, be careful in any test that involves pulling or pushing the board down and measuring the force needed: WHERE you apply the force will influence the amount of force needed.