Rudder Too Buoyant

[winjamerk]

I am about to look at a used sailboat which had its rudder replaced. The original was stock and the replacement was made with Fir. The new one is considerably more buoyant than the original and the previous owner added weights in the aft end of the boat inside the hull to achieve original balance in the stern as the rudder buoyancy lifts the stern. I had a prior project boat years ago which had plastic coated weights attached to the upper part of the rudder in which the tiller became attached. Would this method be the recommended approach or are there lead weights which can be attached to the buoyant rudder below the water line?

[Pete7]

Certainly wouldn't attached weights below the water line, that would destroy the smooth flow of water over the rudder.

How sure are you that the buoyancy of the rudder lifts the boat? How about marking the water line, then remove the existing weights to see what happens before doing anything else.

Pete

[a64pilot]

Assume if you will that 25 gls of water weigh roughly 300 lbs and that you rudder weighs nothing and displaces 25 gls of water.
That will lift the stern the same amount that two people sitting in the cockpit will lower it.
Unless you have a very small, lightweight boat, I’m saying that it’s likely that it isn’t making much difference.
My guess is that if your having to ballast the stern to get the boat level, it’s more likely that the bow has too much weight in it, as the bow can’t handle weight as well due to the smaller surface area.
In other words 300 lbs in the bow will sink it more than 300 lbs in the stern will.

[Spot]

How large (height x width x thickness) of a rudder are we discussing?
Douglass Fir is 33 lb/ft^3 and seawater is 62.4 lb/ft^3

Displacement of seawater (volume of rudder ft^3 * 62.4) -weight of rudder (volume of rudder ft^3 * 33) =spare buoyancy in pounds, divide by 2.2 for kg.

[winjamerk]

Previous owner, not current owner rebuilt rudder and reportedly added ballast to compensate for increased buoyancy impact on stern of boat. Have not seen boat yet and when I do (currently on the hard), will look at what is carried at the bow, 1-2 anchors, chain possibly stored near deck level, etc. If only 1 anchor, then look at where chain is stored. Since it is on the hard, cannot asses impact of waterline change when excess ballast is removed.

[a64pilot]

I used to worry about carrying too much weight forward etc.
Then noticed with the entire family on the bow watching the Dolphins play that the waterline seemed to be not affected at all, I didn’t worry so much.

I think once the boat is in the water, observing the waterline closely and having several people move from bow to stern will tell the tale.
People are a whole lot easier to move than installed ballast

[psk125]

Foils (like rudders and centerboards) often have weighted inserts built into them to help them go down. This might make a rudder easier to ship. A pocket is made in the foil for a lead block or disc. How big a boat are we involved with, here? Other than the ease of shipping and unshipping the rudder on a small boat, (you'd want the rudder to be easy to submerge, but not to sink!) having a more buoyant rudder would be offset by anyone simply sitting in the cockpit.

[Cheechako]

I seriously doubt the rudder bouyancy (if any) is an issue. How big is this rudder? Sounds like maybe the owner is off on something, or trying to hide a boat that is bow heavy... As others said, see what's in the bow, how the boat is balanced or unbalanced by other loading.
Is it an outboard rudder or does it have a SS shaft? If shaft, then it's not bouyant. Every new modern rudder is filled with foam which is bouyant, but the rudder weight counteracts it(until it fills with water!) but not an issue.

[winjamerk]

Thank you for all the replies. Have been unable to travel as yet as the owner has been away for awhile. Will explore all areas suggested when I see it. Thanks again for your assistance.