Ferro Cement for Dreamers

[Jim Cate]

I've found the detailed comments about what constitutes good practice in ferro builds quite interesting. Damn complicated to get it right, and not quite as "nearly free" as the enthusiasts used to tell us.

It fully explains why there are so few really well conceived and built ferro yachts around and so many that are simply poor boats... at any price!

Jim

[TeddyDiver]

Originally Posted by Maclir

In civil engineering construction projects the recommended minimum cover to steel reinforcement is 50 mm. In ferrocement hulls a cover to steel is maybe 1 mm. Otherwise the hull it too heavy, therefore ferrocement reinforcement rusts and spalls the cement. Unless it is protected by some magic coating.

There's a big difference with concrete and ferro cement. The cement/stone/water ratio's are way of each other..

[MicHughV]

Heavy construction concrete usually always has some percentage of "stone" in the mix, the size and quantity of which varies, but does impact the " thickness" of cover.
While 50 mm is the general standard of concrete cover, along the coast or other salt water environments this is usually increased to 75 mm.

Ferro-cement boats don't have such luxuries. In recent years there has been some attempt at adding fiber mesh to cement placed in thin quantities, basically thin strands of fiberglass mixed in with the cement, but there is no telling which way the strands will oriented themselves once mixed in and the practice has dubious results.

Placing the cement/concrete is also an art, so as to provide an even mix and not have any voids, air bubbles and the like.

Ferro cement boats seem to have been a fad when home built boats was a
" thing", but are rarely seen today.

I have only ever come across one ferro-cement boat, which was a schooner design. It had quite a thick hull I can recall. I had an opportunity to sail aboard it once and it was certainly no speedster.