So before we get into the nitty gritty, a bit of backgroud: I have about 3 years and change of an engineering degree (graduated with a different degree though), during which I took several materials classes, including a few where concrete figured in significantly. I did a project on Ultra-High Performance Concrete, and another on concrete mix design. I also took a fluids class (incompressible) and a materials class (mostly focused around metals, but some time on ceramics).
With that said, I think it's time for a ferrocrete renaissance. Or, more accurately, a glass-fiber reinforced reactive powder concrete renaissance.
My daughters are 8 and 5 (and 1), which is about the right age to start sailing. I wanted to join a class that's got a lot of personality, and PDracers seem to have lots of fun.
So, for my first trick, I'm making a tunnel hull puddle duck out of concrete. Obviously, it won't be class legal, but if all goes according to plan, it will be relatively easy to churn out another hull that would be class legal, and I'm not terribly worried about not being eligible for regattas anyhow.
Currently making forms out of polystyrene insulation foam. I built several test panels, and my favorite so far is a 2:1 vermiculite:mortar mix. I think I'll try adding some water reducer and pozzolan as well to give it more strength, but even as it is, I'm under 2lbs per square ft for a 1/4' panel.
Types of concrete - Wikipedia https://en.wikipedia.org/wiki/Types_of_concrete#Ultra-high-performance_concrete
FISHSTONE Bottle-Pozz, 40lb bag - Fishstone - Concrete Countertop Supplies
Supercizer 7 Super Plasticizer - Fishstone - Concrete Countertop Supplies
Basalt Mesh Reinforcement for Concrete | Concrete Exchange
AR Glass Net (Scrim) - Fishstone - Concrete Countertop Supplies
Link to self healing concrete paper:
http://www.drfixitinstitute.com/download/rebuild_2010/Rebuild vol 4 no 4 Oct-Nov 2010/Rebuild Vol. 4 No. 4 Oct-Dec 3rd.pdf