Theis,
If yer talking about a delicate watch or a coffee pot, expansion is an issue.
If the lead ballast in 338 was dropped in at shop temperature (80 degrees) 40 years ago and is now suspended in liquid (40 to 70 degrees) - if anything it has shrunk a 1/16 of in inch in length, 1/128 of an inch in width.
Being a massive chunk of metal I can't imagine (I can't imagine a lot of things) a ton of lead changing its dimensions very much. The change in temperature to get the lead to change dimension would have to be significant - let's say 100 degrees from datum.
When would that happen?
I think that encapsulating the lead (non-scientifically) is perfectly safe. (Of course I do, since I did it!)
If the boat is going to stand on its keel anytime in the future it would be a great deal better for the weight of the boat to sit on a SOLID foundation. That's just my opinion.
There is certainly more arguement for immovable ballast if the boat will ever spend time on one tack or in bad wave action as a cruiser. From the standpoint of running aground and damaging the encapsulated ballast keel area it may eliminate leak potential if the hull gets gouged. Doesn't guarantee it, just increases margin. This is an area that cannot be repaired from the inside.
I also have the feeling that if there is any environmental expanding and contracting the whole boat is going to be doing it. Lead is a non-corrosive, pretty inert, element unless you've turned it into a battery by carrying acid around in your bilge. Then you'd have a bloating problem
Something to seriously think about:
I've gotten some Sanitred product to test on the boat. One of the products is a LIQUID polyurethane that will cure at ANY THICKNESS. (Will set up in the container like epoxy.) Maybe this rubber which cures tuff but pliable would be just the filler for the spaces between the lead and the hull in your boat. To preserve an A/C, I think it is important to keep water out of the laminate* - along with the reasons mentioned above if the boat goes offshore. There can't be any arguement for doing nothing about it....when you are renovating and have the boat out.
*I also argue in favor of SEALING (barrier coating) below the waterline with epoxy or vinylester outside and inside.
There are NO ONGOING TESTS ON 40 YEAR OLD LAMINATES that I am aware of. It is prudent to keep water (especially salt water) out of polyester laminates until such tests are published. We are dealing with first-ever materials in first-ever applications that never have been adequately explored in terms of longevity, soaked or dry, stressed or not stressed.
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