Who said that rocks don't float?
For sure the said person doesn't know the history of the concrete ships of WW1 and WW2:
http://www.concreteships.org/ (*))
I wasn't aware of these experiments... but I'm always learning.
Best regards from Lisbon,
Paulo Mestre
Well.... most folks are not into independent thinking. It always amazes me
why folks claim that concrete doesn't float but steel does !
being that steel is 3 times as heavy as concrete (specific weight)
Historically Man will explore any new material for anything, Concrete being no exception. Early concrete ships/boats include a steam launch in the german ship museum in Bremerhaven about 1900, a norwegian built several motor coasters around 1917 and then went to the US to push the idea for bigger ships. There are 2 concrete coasters, MS Capella in Rostock, MS Treue in Bremen.
both restored, they date from the 40's and Dyckerhoff built about 60 of them.
You may notice right there one of the problems with the new material.
Dyckerhoff is a leading concrete manufaturer in germany, not a ship builder!
Shipyards have no clue how to build a concrete ship since they try to built them along the lines of a steel vessel, but for concrete a different construction is required, namely shell not rib construction.
Concrete ships are much easier to maintain than steel and quite sturdy.
So why are there not more of them?
Weight and knowledge, i.e. economics.
First came wood, not because it floats but because its easy to work with stone age tools and (used to be) in ample supply.
When the switch was made to Iron and then Steel it took years to create the new knowledge base needed to build them successfully.
Since concrete is ever only used in war time, this experienced pool of men simply doesn't exist. Not counting "Ferro Cement" boats for a moment, and even there are maybe 100 fiberglass boat experts for every ferro cement expert.
Add Government "guidance" to such a project and you can easily see how concrete ships went "in the tank"
Steel ships have been build for a hundred years by the thousands, concrete ships haven't and considering the economics of modern mass production
concrete ships will be at a disadvantage before you even address the weight issues, i.e. less pay load.
I saw my first concrete ship in the 60's, a hulk of a good sized freighter in Brest/France and around 64 actually moored alongside a concrete coaster in the baltic, took me a few minutes to figure out what felt "odd" about that ship.
FYI there is an annual Betonkanu / Concrete Canu competition by technical University students in Germany with a regatta in Heidelberg.
and that gets us to a language problem, since in many non-english speaking countries "concrete" isn't concrete you can't google it !
But you can google: "Beton" -schiff, boot, shep, skib
I had some great pictures but no clue what I did with them, so here a few urls,
for some odd reasons i didn't get any UK sites, but some of them are already posted
some in german and norwegian, but all the pictures are in pixels.
The best are on the bottom.
http://www.coltoncompany.com/shipbldg/ussbldrs/wwii/merchantshipbuilders/concreteships.htm
http://www.concreteships.org/
http://www.unmuseum.org/concrete.htm
http://en.wikipedia.org/wiki/Concrete_ship
http://www.crystalbeach.com/selma.htm
http://www.findarticles.com/p/articles/mi_qa4442/is_200406/ai_n16066101
http://de.wikipedia.org/wiki/Betonboot
http://www.betonkanu-regatta.de/Warum_ein_Kanu_aus_B.402.0.html
http://72.14.209.104/search?q=cache...05-10.pdf+beton+kanu&hl=en&gl=us&ct=clnk&cd=3
http://www.ship-photo.de/modules/myalbum/photos/454.jpg
http://www.ostsee.de/rostock/betonschiff-capella.html
That should be enough Concrete / Beton you keep you busy for a minute.
Happy Travels, Bearsie