I am a retired civil engineer
and I have been active in ferrocement and marine
concrete since 1971. I have built two boats. I believe your problem is not a big one. If the surface rust after sandblasting is the only problem you have, it can be solved
. I built my first boat in NZ in the 70s, the golden decade of ferro
. We had user groups like the Waikato Ferrocement Association and the New Zealand
Ferrocement Marine Association. We had a shared grout pump
and I think every boat built was drilled and grouted.
If you do not have leaks
inside or outside that stream rusty water
, then I do not believe you have a serious problem. Cement paste is a high pH and dissolves rust and galvanizing. The fact that the cover was thin indicates the care the builders took in keeping the weight down. You may need only a cement wash after a light abrasion of the rust to control further mesh rust. An additive like Sika Latex makes the wash very sticky. For a sealer, I used a water miscible epoxy
and diligently pursued any breaches in the seal coat over the years. Sometimes I went 5 years between haul outs.
I thought I once found a ferro
boat beyond repair. I built a portable grout pump
and flew to Hawaii
to grout it. It was a big luxurious boat. When I pumped it, the slabs fell off revealing black paste. I wrote an article about it for the Journal of Ferrocement. A man bought the boat with a bag full of diamonds and put a 3/8 inch layer of fiberglass
over the hull
. He said he had done it before.
There is always a solution. My boat fell off a transporter and I repaired a hole in the hull. Later I sailed for 31 days with the rail down on that side from Pago Pago to Honolulu. I thought a lot about that repair particularly bashing into the NE trades and swells followed by Hurricane
A word of caution with epoxies. Coat tar epoxies are great but you need to control your application conditions and start other paints while the epoxy
is curing. There are "non-blooming" water miscible epoxies, easier to use and easy to clean up. If the epoxy blooms or forms a waxy cured coat, it must be abraded to get paint
In any case Sven, take heart. I can send you photos of ferroboats that were saved after terrible mishaps. It is easy to repair (or at least possible) in most instances I have seen.
As far as books
on ferrocement, there are two definitive works: Ferro-Cement by Bruce Bingham and Hartleys Ferrocement Boatbuilding. Gainor Jackson was a wonderful man and his book was interesting but hardly definitive. Morely Sutherland, the co-author, did not do any of the writing. He was commercially motivated and did not share many secrets. The US Navy
wrote a ferrocement boatbuilding manual. It is available on the internet
. There have been a number of advances in cements. I love the silica fume additive as a pozzolanic material.
I have tried to upload a file showing my 52 ft LOA
boat in a boat yard in Sitka, Alaska