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Old 05-05-2012, 22:33   #1
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Removing Concrete Ballast

does anyone have any advice on changing ballast from concrete to lead. i have a dreadnought 32 full keel boat. i hope it will be more stable.
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Old 05-05-2012, 22:36   #2
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Re: removing concrete ballast

Wow, sounds like a nightmare to me. I'm guessing the current ballast is fiberglass encapsulated in a full keel right?

Have you considered consulting a marine architect. You may be able to bolt/glass on a heavy bulb to the existing keel. Or something less destructive than removing the concrete.

Also what types of stability issues are you having?
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Old 05-05-2012, 22:40   #3
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Re: removing concrete ballast

looks like concrete and steel punchings, basically poured in. i just got the boat and it feels a bit like a rocking horse.
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Old 05-05-2012, 22:42   #4
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Re: removing concrete ballast

i am worried about leaving the concrete as sooner or later it will rust and expand.
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Old 05-05-2012, 23:07   #5
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Re: removing concrete ballast

The concrete and punching really shouldn't rust if they are correctly encapsulated in the keel.

If your boat is rocking badly have you tried adjusting where you are carrying weight? Move some trim ballast around and try to get the boat more comfortable.
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Old 06-05-2012, 11:38   #6
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Re: Removing Concrete Ballast

If your rocking is in a fore 'n aft motion, this is largely contributed to by the shape of stem and stern overhang and resulting ends bouyancy.
If you change to lead you have a few considerations to make.
Volume for volume, the lead is much heavier and will change your roll centre height, and the resulting sailing angle (your list).
This then involves the designed sailing lines for your hull shape.
As an example, but going the other way, my class of boat was designed with heavy wooden spars, and 12000lbs of lead.
The pendulum effect of the heavy spars dampened the stability motion speed of the lead.
Some owners changed to aluminum masts and found the lighter weight above no longer balanced the ballast weight equation, and the boats became jerky and not as "smooth thru the water".
There is a lot to consider before possibly ruining (improving ) the boat.
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Old 07-05-2012, 03:34   #7
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Re: Removing Concrete Ballast

You may wish to do a bit of research. I vaguely recall a post by someone, probably on a forum similar to this, where the person had removed the ballast (steel punchings?) and replaced it with lead.
I also recall another post, which may or may not have been on the same forum, that contained a comment indicating that a mild tendency to "hobby horse" in certain sea conditions was a trait of the otherwise stout and comfortble Dreadnought 32s.
BTW, for what it is worth, it is definitely now the "later" part of "sooner or later," and if no expansion has occurred the ballast material is well encapsulated!

Fair winds.
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Old 07-05-2012, 05:40   #8
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Re: Removing Concrete Ballast

Greetings and welcome aboard the CF, buzzstar.

Thanks for contributing.
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Old 07-05-2012, 12:42   #9
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Re: Removing Concrete Ballast

Thank you for the advice. the boat has wooden spars. you say volume for volume lead is much heavier. my thinking is the same weight of lead would be lower in thbe bildge, making things more stable.
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Old 07-05-2012, 12:53   #10
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Re: Removing Concrete Ballast

Your rocking horse may have more to do with hull shape. You are talking a jack hammer and a big mess. "fuggidaboudit".
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Old 07-05-2012, 13:49   #11
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Re: Removing Concrete Ballast

The Dreadnaught 32 was offered as a kit boat or a completed boat. You could buy an unfinished hull, a hull + deck, or a finished boat. Sounds like yours was a kit, originally, because I understand that the factory boats had lead keels. You may want to get in touch with the owners association to figure out your next step, especially in terms of whether anyone else has made such a conversion.

The big question I'd want to know before proceeding is whether your current ballast weighs less than the original design.
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Old 07-05-2012, 20:03   #12
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Re: Removing Concrete Ballast

Here's a question for you... will a boat with a heavier ballast roll more than one without? (with no sails up) (ie: will a weighted pendulum swing more times than an unweighted one?) The answer for the pendulum in my old clock is less swings with weight removed.....
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Old 07-05-2012, 20:13   #13
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Re: Removing Concrete Ballast

A simpler solution may just be to put a bomb on the keel. But a lot of motion also has to do with the natural righting moment of the hull shape itself.

If its just rolling at anchor, you could just "wing out some weights" to stiffen her up a bit.

Or a similar idea using buckets. Cheap and effective.
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Old 07-05-2012, 23:16   #14
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Re: Removing Concrete Ballast

Quote:
Originally Posted by dandreadnought View Post
does anyone have any advice on changing ballast from concrete to lead. i have a dreadnought 32 full keel boat. i hope it will be more stable.
A friend of mine here spent a couple of months jackhammering cement out of his bilge. It is not a job to be undertaken lightly. He basically wanted access to the steel hull and also wanted to reduce total weight of the boat. He has not put anything back in so far.

Are you planning to put the same amount of weight back in? Have you calculated the weight? Do you have a source and a price for this much lead?

As far as your question - "Does anyone have any advice?" - My advice is move weight around the boat first and see if it makes a difference.
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Old 08-05-2012, 13:19   #15
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Re: Removing Concrete Ballast

sorry for not being clear. i was talking about stability under sail.

a big reason i think it is worth removing the concrete, is we are concerned the steel punching will rust and expand and cause a huge problem.

we just bought the boat and intend to entirely re do everything, and don't want to have to then go back and tear it apart later.
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