Ballast- concrete beam

[Ari]

Hello,
My boat need a big ballast, the original plan is to have one lead beam of about 20 tonne assemble in the form of long keel.I'm looking into alternative, my option is to have a concrete beam constructed in the form of long keel instead of lead. Do any of you know about this technique(concrete), the pro and cons of it ?
Photos at my photo gallery have some description.

[PAR]

Lead is much more dense then concrete. Even if the concrete has lots of iron and steel in it, you'll be lucky to have 200 to 220 pounds per cubic foot, where lead will be in the 650 to 700 pounds per cubic foot range.

This doesn't mean you can't use concrete, you can and many boats have a concrete ballast, but you'll need a much bigger ballast casting. Also the center of gravity will be considerably higher on a boat with a concrete ballast, that was designed for lead. This can cause some concerns in certain designs. Contact the designer and talk over the change with them. If the designer isn't available then you'll need to have a different designer look over your plans and ballast suggestions, to insure she'll have a reasonable level of safety and stability. As a rule this isn't an element of the design an amateur should be fooling with, seek a pro's help on this one.

[Ari]

Thank you Par, actually I'm at the stage where a lot of changes still can take place without endangering anything. I'll be seeing the builder/designer in April. Now is still monsoon season and raging floods every where. The cost of lead had shoot up, can't even park a lorry un attended, the battery will be gone..!

[Milan]

If you can't afford lead, you should at least mix a lot of steel in concrete, as concrete by it self is to light.

[PAR]

If you replace the aggregate with steel or iron and use steel or iron as the reinforcement, you'll still only have 200 - 220 pounds per cubic foot of ballast. This means the concrete ballast casting will need to be huge in comparison to a lead version. For example if your lead ballast casting was 14 tall, the same weight of heavily steel/iron reinforced concrete will be over 5 feet tall. This assumes the length and width are the same (which would be typical of a ballast casting)

I'm reasonably sure your designer is going to have problems with this change, though you may have the latitude in the design.

[Ari]

Par, the different in size is hugh..!The ballast in the photo attached in earlier post is about 14 inches H x 12 inches W x 45 feet L. about 14 tonne.The owner told me it is about 12 tonne ++.Thank you for the comparison. Maybe I should seriously looks into recycle lead acid battery industry.Maybe there will be ways to recycle some for my purpose.

[riggertroy]

Hi Ari, I know of one sailing ship (wooden) that has had an RSJ(ridgid steel girder) fitted as an addition onto the original keel, the girder was filled with cement to add more weight.
There were 2 main reasons for doing this, the first was to reduce the hog (ship had been a cargo ship in her early years and is now only carrying passengers) and to lower the centre of gravity by shifting some of the internal ballast lower, it worked on both counts and also reportedly improved the sailing abilities, less leeway. The one big disadvantage was that it increased the draft by the height of the RSJ.

[Ari]

Hello Riggertroy,
This RSG equip wooden sail cargo boat is one very interesting avenue that can be explored further. Those cargo boats in Indonesia did not have permanent ballast. When empty they will sit real high above the water, they can only sail real good when fully loaded, I meant to the brim. Some photo at my members gallery will testify that. I'm very keen to buy some used cargo boat and convert it to a yacht for this purpose, still looking for the pro and cons because I don't want the ballast to be the most expensive parts of that boat.

[riggertroy]

Hi Ari,
The ship I mentioned did not originally carry much if any permanent ballast but as she no longer carries cargo the owners decided to fit permanant ballast. She was originally built as a motor sailing cargo ship, schooner rig I think, now she is rigged as a brigantine and sails are her main motive power now, same main engine as when she was built.
The RSJ helped to strengthen her, she apparently was hogging badly and now even with the RSJ she still has a small amount of hog, a couple of inches. Waterline length is about 95 feet approx.
Good luck.

[BOATMIK]

Originally Posted by Ari

I'm at the stage where a lot of changes still can take place without endangering anything.

Howdy Ari,

From the pics you already have the keel cutout for the lead done - I don't think you are very free to change.

As a correction to some of the figures above.

Lead's specific gravity is 11.4 - not the lower figure quoted above
Concrete is 2.5.

So you need 4 times the volume of concrete.

If you like sailing I wouldn't change the ballast material - it is a tiny fraction of the overall cost.

Best wishes
Michael Storer

[Ari]

Hello Michael/boatmix,
Those pictures are not from my boat, they are from another boat constructed in Malaysia. I put it there to ensure the others understand what do I meant/my question. I had stayed with lead ballast after understanding the differences between the two material. Thank you for your comments Michael.

[CapKos]

Hi Ari,

You can also check the printing industry. Several years ago they used lead letters, but now everything is electronic. Could still have some lead. Casting 20t of lead is not a simple work, especially when considering that the lead is dangerous poison. What I can’t understand on the pictures is that the lead apparently is put in iron form, which should be bad for the electrolysis. Note that with lead you should use bronze bolts for the same reason.

Good luck,
CapKos

[Ari]

Hi Ari,

What I can’t understand on the pictures is that the lead apparently is put in iron form, which should be bad for the electrolysis. Note that with lead you should use bronze bolts for the same reason.

Good luck,
CapKos[/quote]

Thank you for your suggestion on the printing company.The steel container is actually the die/casing for lead casting. It will be remove after lead had harden up.Silicon Bronze screws,stud and bolts were used on this boat.