Cement boat? What? You're crazy! No, really, it's true! I wish we had known some of this information when we started out, but we had to live and learn, and we took our share of strange looks, and a lot of advice, both good and bad, right and wrong, useful and not so useful. But, yes, concrete can float, just like steel aluminum, fiberglass or wood, all you have to do is keep the water out! I'll share some resources and debunk a few of the myths, and hopefully it will help someone else along the way.
Right off the bat - a couple good books:
- Ferro-Cement Boats, the definitive manual for Builders and Owners by Colin Brookes. Covers history, design, buying, surveying, building, repair, maintenance and ferro sheathing
- How to Build a Ferro-Cement Boat by John Samson and Geoff Wellens (Samson Marine Enterprises LTD. (Our boat [C-Lord Schooner] was designed and built by Samson Marine we found out much later! The Seawolf is on page 121).
This book explains about ferro cement's content, strength, maintenance, repair and so much more.
I'll share some information out of these just to answer a few of the first questions everyone asks, but these quick answers will be lacking in greater detail:
1. What is ferro-cement? highly reinforced mortar of common portland cement, fine sand and pozzolan trowelled onto a framework of ribs, reinforcement rod and chicken wire.
2. What makes it watertight? the density of the mix reinforced by the rod and mesh framework.
3. How does it stand up to impact? not indestructible but at least equal if not better than a heavy displacement wooden hull. Generally, impact will not produce large cracks, but rather an eggshell type of local damage preventing water from entering the hull in large volume.
4. How do you repair it? clean area of cement particles, replaster and epoxy or latex bonding agent applied to edges of damaged area.
5. Damage from electrolysis and galvanic action? apparently not.
These boats have been around for 100+ years, fighting for some years to break down barriers of prejudice and ignorance. Cement actually gains strength throughout it's life, is fireproof, impervious to rot and bug infestation, virtually maintenance free and thoroughly seaworthy. Some of the first were 230' to 420', warships, freighters, and barges with tonnage capacities from 2000 to 10,000, with dead weights of the ships from 800 to 5,000 tons.
A pioneer of early sailboats the Awahnee, sailed 150,000 ocean miles and circumnavigated the globe twice. I would say that proves that sidewalks float!
If you have more questions, you can always leave comments on the blog or email us (firstname.lastname@example.org - Scott never checks his email so you better try mine).