Self Sealing Hull Material

[DrCraze]

Thought I would share a little about this little unsung hero. As some forum members know I have built a cement proa, well I have learned a lot about ferro-cement in the process.
I hear people often worry about it cracking and eventually leaking. Well that isn't really a problem. You see ferro-cement self seals. When water is allowed to seep into the hull through a crack minerals are carried with it and deposited as they pass.
I took a few photos to show the before and after. The photo on the right was taken 2 days after filling the hull with water for a leak test. After 3 days there was no trace of moisture left and the hull was still full of water.

P.S. The hull is red because I added pigment to my cement plaster.

...and if there is much more water the salts that clogged the crack are washed out. Reminds me of pouring pepper in a cooling system to plug leaks as opposed to fixing the leaks but I am truly glad you like your choice of building material. Be careful out there.

[DrCraze]

That's not salt forming it is calcium carbonate. This is all normal procedure for building in ferro-cement so please don't patronize me with your words of caution.

[CDK]

Calcium carbonate is almost insoluble in water, except in the presence of CO2 when it forms Ca(HCO3)2 which slowly dissolves. In an acid environment where salt is present CaCl2 and its hydrates are formed: they are all soluble.

As a temporary safeguard against sinking it will be OK, especially when you stay away from pollution and seawater.

[DrCraze]

Originally Posted by CDK

Calcium carbonate is almost insoluble in water, except in the presence of CO2 when it forms Ca(HCO3)2 which slowly dissolves. In an acid environment where salt is present CaCl2 and its hydrates are formed: they are all soluble.

As a temporary safeguard against sinking it will be OK, especially when you stay away from pollution and seawater.

You are forgetting the fact that unconverted cement is always present creating insoluble calcium carbonate when combined with carbon dioxide.

Salts - including calcium carbonate.

[Landlubber]

"I hear people often worry about it cracking and eventually leaking."
....looks like it didn't take all that long eh to see if this was correct then.....

[DrCraze]

Well it looks like all our foundations are going to miraculously become soluble and wash away because they are made of salt.

No, this material looks good to me... run with it.

[DrCraze]

That is not ferro-cement you half-wit When you are dealing with ferro micro cracking seals itself. Anything with a gap visible to the naked eye gets dug out and filled with a finely ground cement paste. The repairs hold and due to the unique nature of ferro they hold extremely well

[capt littlelegs]

The same thing happens frequently with plumbing, a minor leak will seal itself quite well with lime scale as we call it. I have a 25 year old sea going ferro boat, no sign of any leaks anywhere. Some people have a fear of the unknown!

[Fanie]

DrCraze ( I was going to say jokingly 'DrCrazey' but won't out of fear of being called a half-wit too )

Why ferro-cement ? I have never seen such a boat and it seems a weird choice to build with, I think we all associate 'cement' with the stuff we build houses with, although building cement doesn't lose it's integrity under water.

[DrCraze]

Originally Posted by Fanie

DrCraze ( I was going to say jokingly 'DrCrazey' but won't out of fear of being called a half-wit too )

Why ferro-cement ? I have never seen such a boat and it seems a weird choice to build with, I think we all associate 'cement' with the stuff we build houses with, although building cement doesn't lose it's integrity under water.

I am building with ferro-cement because it is very durable low upkeep and I have more muscle than money
I intend to build a proa 75 feet in length way down the road so in the mean time I will be doing a series of little builds trying new techniques and materials. I was skeptical myself until I tried it.

[Fanie]

Thanks, it would be nice and learnfull for us if you could maybe tutor us on the advantages and or the processes, even the ones you are about to try.

One often gets stuck in believing left is the best way, but simply because to the right is never explored.

I suppose this is more sensible for larger boats because of the weight, similar as steel boats ?

[capt littlelegs]

Originally Posted by Fanie

Thanks, it would be nice and learnfull for us if you could maybe tutor us on the advantages and or the processes, even the ones you are about to try.

One often gets stuck in believing left is the best way, but simply because to the right is never explored.

I suppose this is more sensible for larger boats because of the weight, similar as steel boats ?

http://www.ferrocement.org/

http://www.ferrocement.org/fandf.html

http://www.boatdesign.net/ferro-ceme...ing-1/001.html

http://www.concreteships.org/history/