Ferrocement questions

[baboonslayer]

I know the traditional ferrocement boat building method is to build a re-bar frame and put a chicken wire mesh over it, then coat it with concrete (I know it's not really that easy and simple, but that pretty much sums it up). The question I have is about the re-bar frame. Why do you have to use re-bar when you could just build a wooden frame? A wooden frame would be so much easier to construct, and not to mention lighter. Some other questions I had were about the hull. Do you (or should you) coat it with anything like marine paint, and also, what is the best mix ratio for the concrete?

[gonzo]

A wooden frame will swell with moisture and crack the cement

[baboonslayer]

I see. So no wood on a cement boat then. Thanks for the input. Another question I had was about the mix ratio of cement/sand/water. Isn't it 15% cement, 65% sand, 20% water for the best strength?

[viking north]

The other factors are strength and adhesion. The mixture for boatbuilding has other additives and depending on which stage of the build you are into(hull layers) some builders vary those additives and add other ingredients. The final hull should be coated with a good barrier coat--many use epoxy paints. If you are serious about building such a hull you need to dig into the literature on such and track down an experienced ferro builder to work on the actual building of the hull with yourself and all the friends that owe you favours on the big lay up day. If you need 10 people ask 50 -- 40 will have excuses they can't make it--I call them TAKERS not GIVERS in life. Good idea to cull these out every 5 years-----Geo.