# Cement Ballast - Pros/Cons



## Adirondackman (Apr 6, 2013)

I'm looking at a boat that is claimed to have a cement ballast. Is this something that should concern me? The boat is a 1987 Com-Pac 23-2

Thank You for any input!


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## bobperry (Apr 29, 2011)

Cement weighs around 150 lbs. per cu. ft.
Cast iron weighs around 450 lbs. per cu. ft.
Lead weighs around 700 lbs. per c

I'd have to see a profile drawing of the boat showing where the ballast is to make a definitive statement. But consider that there is a very good reason the best boats use lead for ballast.


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## knuterikt (Aug 7, 2006)

Adirondackman said:


> I'm looking at a boat that is claimed to have a cement ballast. Is this something that should concern me? The boat is a 1987 Com-Pac 23-2
> 
> Thank You for any input!


As Bob wrote cement is not a good candidate for ballast
Cement weighs around 150 lbs. per cu. ft.
Water weighs around 60 lbs. per cu. ft.

In the some early GRP production boats they used cement mixed with scrap iron as internal ballast in an encapsulated keel.

Some of these boats suffer from "keel sickness", the iron inside the cement has rusted so badly that the encapsulated keel starts to expand.
The keel starts to loose its shape and in some cases open up.

Replacing the internal ballast with a construction like this is no fun.


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## capt vimes (Dec 2, 2013)

"keel sickness" hehe - never heard of that, but your explanation makes absolute sense...
not everybody knows that rusted iron increases in volume by the factor of ~3 but it also gets heavier...


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## Jeff_H (Feb 26, 2000)

While there have been a number of boats which have had cement ballast, there is nothing good about cement ballast and if that is really the case it would normally be a deal breaker for me. 

As Bob Perry pointed out there is a big difference in density between a proper lead ballast and the usually mix of steel and concrete that is typically referred to as 'concrete ballast'. The low density of that mixture (appoximately half of lead) means that it is harder to get the ballast as low in the boat as would be the case with lead ballast which usually results in some mix of a wider and/or longer encapsulation envelope inducing greater drag, more draft than might be required by a denser ballast, or less stability. The greater drag and the lesser stability result in measurably reduced performance over a normal encasulated keel, and even greater reduction over an external, bolted-on cast lead (or even iron) ballast.

Beyond the performance issues of low density ballast, there are serious issues from a quality control and from long term durability and maintainability issues that would concern me. To explain, normally when people talk about 'concrete ballast', that more typically refers to concrete with scrap steel mixed in. The scrap steel is normally in the form of 'boiler punchings' which has come to be used as a generic shorthand term for small pieces of scrap steel produced in various manufacturing processes. 

In the best case, the steel is carefully weighed and the concrete carefully mixed so that the ballast is of a uniform weight from boat to boat and the steel is uniformly distributed through the matrix. What more typically happens is that the steel is added 'by eye' and so the ballast can vary in weight pretty dramatically, and the steel can be located assymentrically in all directions.

Using best practices, the ballast is cast out side of the fiberglass keel encapsulation envelope allowing the concrete to cure (and shrink) before being inserted into the keel encapsulation envelope. Then the encapsulation envelope is generously filled with a slurry that is a mix of resin and a thickening agent and the ballast casting set into place. Once the slurry sets, the top of the concrete is carefully glassed over to a thickness that is close to the hull thickness. Lastly transverse framing is added over the top to stiffen the joint between the keel and the hull. 

That is rarely done. Often the concrete is cast in the hull mold. Most times a light membrane is added over the top of the concrete and that is it. The problem is with these items are that when concrete is poured and cures, it shrinks, pulling away from the mould, which in this case is the encapsulation envelope. Instead of a watertight bond between the concrete and glass, there is a small but perfect capillary to allow water/moisture to move around the casting. Once moisture gets into the encapsulation envelope the steel in the ballast can begin to rust and pry apart the concrete matrix, shattering it into small pieces. (I once helped a fellow dig out all of the ballast from a Buccaneer which had disintegrated. We removed pieces of damp rusty concrete that were as large as 3-4 inches and as small as sand.)

And in most cases, unless the boat is built extremely well, water does eventually get into the encapsulation envelope. It gets in by a number of routes. In the case of the Buccaneer that I mentioned above, we concluded that the boat apparently had a minor grounding. It was a grounding which did not pierce the encapsulation envelope, but it did cause enough of an impact that, in the absense of a heavy enough membrane and/or transverse framing, there was adequate deflection to cause the ballast to push up through the membrane above the ballast. It only made a small slice in the glass, but it was enough to allow bilge water to seep into the encapsulation and rust out the steel, and blow the concrete apart. 

But water can also get in from the bottom if the encapsulation envelope is pierced in a grounding. Once water gets in there, its almost impossible to get out again since the concrete will absorb the water like a sponge. And that moisture not only attacks the steel in the ballast, it also can attack the fiberglass. One of the surprises on the Buccaneer was that the fiberglass was badly blistered in the interior of the encapsulation envelope. 

But beyond these issues is a bigger one in my mind. Concrete ballast is only used as a cost savings measure since there is no good reason to use Concrete ballast except to save money. And when I see a manufacturer electing to use concrete in the matrix, I always am suspicious of the overall quality of the boat thinking that, if a manufacturer chose to cut this large corner, I wonder what other, less obvious corners were cut in the process. 

I should note that I am a little surprised that Hutchins who built the Compacts used concrete ballast. I have always perceived them as being a better builder than that. Hutchins is still in business and you might want to contact them to discuss how these boats were built in more detail. 

Respectfully, 
Jeff


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## okawbow (Feb 15, 2007)

My Cheoy Lee 31' offshore ketch had concrete over cast iron ballast, with no issues after 45 years. 
I have to say that the motion of that boat was the most comfortable of any sailboat I've ever been on.


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## waterwks4me (Jan 16, 2010)

Compac sailboats by Hutchins Company is a well built boat and the numbers that are still around can attest to that. I am restoring a compact 16 as I write this and from everything I have read as well as confirmation from Hutchins the 16 has lead pellets for its ballast and a cement cap is poured over it with a layer of fiberglass over that. There is a strong forum for compac sailboats at:

Com-Pac Yacht Owners Association - Index


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## Jeff_H (Feb 26, 2000)

waterwks4me said:


> Compac sailboats by Hutchins Company is a well built boat and the numbers that are still around can attest to that. I am restoring a compact 16 as I write this and from everything I have read as well as confirmation from Hutchins the 16 has lead pellets for its ballast and a cement cap is poured over it with a layer of fiberglass over that. There is a strong forum for compac sailboats at:
> 
> Com-Pac Yacht Owners Association - Index


Perceptions like yours were precisely why I suggested that the OP contact Hutchins to hear it direct from horse's mouth. My sense is that the Com-pacs were simply but reasonably well constructed.

Assuming your description is acurate, certainly lead pellets in concrete is a better solution than iron in concrete. But even so, your description still does not answer the other questions about whether the concrete was cast inside the hull or in a separate mold, whether the lead pellets were mixed with the concrete (better) or poured in the hull cement cap is poured over it (which is a pretty poor way to do it), whether the fiberglass sealer membrane is structural of only a thin separator to keep water out and so on.

Jeff


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## Bene505 (Jul 31, 2008)

Last month near Tampa we rented kayaks to go see manatees and we needed an anchor. The rental lady got out a gallon water jug and effectively said "this is heavy, use this as your anchor".

I explained that no, a container of water would not make a good anchor. Seeing this thread about concrete reminded me of this. Concrete "partially floats" in water. 

One of our on-the-hard boat neighbors is re-doing his concrete keel. As Jeff mentioned, there was only a thin layer of fiberglass over it. If the boat ever capsized, the ballast would drop down into in the salon. That would be the end of it.

Regards,
Brad


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## miatapaul (Dec 15, 2006)

Island Packet uses a layer of concrete in it's ballast, not exactly confidence inspiring. It is separated from the metal ballast (I believe depending on year can be lead or iron) by a layer of epoxy. I think in a Compac 23 if used in sheltered waters should be fine. I would not want to take it out in the open ocean. If it is over lead that should be fine, but if over iorn I would be worried about corrosion as Concrete holds a lot of moisture, especially if not separated by some epoxy.


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## SloopJonB (Jun 6, 2011)

I've seen iron punchings poured into both cement and resin for ballasting a moulded keel. The usual practice was to pour in some cement then add metal and vibrate it until it would take no more, pour more cement and repeat. I imagine the net weight would approach that of solid iron if the bits of metal were small punchings (doughnut holes) from a big hydraulic punch press.

The resin option worked better but would be prohibitively expensive nowadays. I daresay with the cost of resin now, a lead casting would be cheaper.


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## duchess of montrose (Nov 26, 2011)

i dont think iron itself is that bad in terms of ballast, that being said lead is better but there are some good boats with cast iron ballast. cement and iron however is much less dense which is an issue in terms of righting ability and also as people have said they were generally poorly constructed. Not necessarily this boat but generally concrete doesnt mix well with a ferrous material like iron. 

in terms of qualities of ballast id say lead - iron then much less desirable is iron and cement and then theres water ballast that is next to useless. On that design and size of boat though your stability is probably not as much an issue as you are probably not planning on taking it out in really horrible weather. 

but check to see how the encapsulation was made. My boat has iron ballast thats encapsulated without any concrete and I know even with just iron theres issues of delamination, rust and cracking but I have no voids in my keel, you can do a preliminary inspection of the keel by tapping for voids but have a surveyor check it out because any ferrous keel is subject to voids if it was either improperly constructed or was damaged.


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## boatpoker (Jul 21, 2008)

miatapaul said:


> Island Packet uses a layer of concrete in it's ballast, not exactly confidence inspiring. It is separated from the metal ballast (I believe depending on year can be lead or iron) by a layer of epoxy. I think in a Compac 23 if used in sheltered waters should be fine. I would not want to take it out in the open ocean. If it is over lead that should be fine, but if over iorn I would be worried about corrosion as Concrete holds a lot of moisture, especially if not separated by some epoxy.


I have seen one Island Packet (40' 1994) keel opened up by a grounding. It was not built that way. it was filled with rusted scrap metal of various shapes and sizes embedded in poured concrete that had been largely turned to powder by the expanding rusty rebar, angle iron and various other junk. this boat is still on yachtworld and advertised as "rebuilt" .


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## Adirondackman (Apr 6, 2013)

A lot of good info here - Thanks. I'm partial to lead also but finding good boats 24' - 30' in my price range with lead ballast has been a challenge.


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## Bene505 (Jul 31, 2008)

Adirondackman said:


> A lot of good info here - Thanks. I'm partial to lead also but finding good boats 24' - 30' in my price range with lead ballast has been a challenge.


Don't be afraid of an iron keel. Our Beneteau 50, as well as many sailboats made in Europe use iron keels as lead is expensive over there.

Maintaining an iron keel involves wirebrushing to shiny metal then coating with a couple things followed by bottom paint. All-in-all, quite straightforward.

Regards,
Brad


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## Dog8It (Jan 2, 2007)

I have been sailing a 1995 Com-Pac 35 with cement balast for the last six years. No problems so far. Had a few soft groundings, again no problem. I am aware of the fact that cement is not the best material but I think Hutchins company has done a fairly good job on these boats. They are definitely coastal cruisers though I found the boat to be well built, comfortable and reliable. Also, the company provides pretty good support.

PM if you need any additional info.


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## Stuart_sailor (Apr 18, 2020)

Concrete is a relative term. To me the point here is this is not an after market diy or unkown builder. The ballast density and construction on the CompaC were worked out whith Clark Mills the designer. Compac has built tens of thousands of hulls and has a fantastic reputation for durability. It is in this case an engineered and proven application.


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## Jeff_H (Feb 26, 2000)

Stuart_sailor said:


> Concrete is a relative term. To me the point here is this is not an after market diy or unkown builder. The ballast density and construction on the CompaC were worked out whith Clark Mills the designer. Compac has built tens of thousands of hulls and has a fantastic reputation for durability. It is in this case an engineered and proven application.


I respectfully suggest that is an oversimplification. While it is true that Compac has built a lot of boats, and they were designed by Clark Mills who was and ingenious designer who was a master of designing affordable boats, it doesn't change the reality of using concrete for ballast.

In all ways, except being a cheap way to build a boat, concrete is inferior to pretty much all other ballast materials in terms of stability vs drag, life cycle durability, and structural capacity. The use of concrete ballast made early Compacs affordable but it didn't make them as good a boat as they could have been.

I suggest that you read the discussion above so that you have a better understanding of how much of a hard to justify compromise using concrete ballast actually is.

Respectfully,
Jeff


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## Ajax bailey (11 mo ago)

Jeff_H said:


> While there have been a number of boats which have had cement ballast, there is nothing good about cement ballast and if that is really the case it would normally be a deal breaker for me.
> 
> As Bob Perry pointed out there is a big difference in density between a proper lead ballast and the usually mix of steel and concrete that is typically referred to as 'concrete ballast'. The low density of that mixture (appoximately half of lead) means that it is harder to get the ballast as low in the boat as would be the case with lead ballast which usually results in some mix of a wider and/or longer encapsulation envelope inducing greater drag, more draft than might be required by a denser ballast, or less stability. The greater drag and the lesser stability result in measurably reduced performance over a normal encasulated keel, and even greater reduction over an external, bolted-on cast lead (or even iron) ballast.
> 
> ...


How long did it take for the cement ballast to turn into rocks and dust?


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## boatpoker (Jul 21, 2008)

Ajax bailey said:


> How long did it take for the cement ballast to turn into rocks and dust?


It depends ... on everything Jeff said.
I saw cement decayed to almost sand, re-bar, angle iron and what I swear was an old damper plate pulled out of one high end boat less than 10yrs old. I've mentioned the name before but I don't need those insults from owners again. PS it's an American built boat.


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