I built a Hartley RORC 32' some years ago so if I can be of assistance please ask.
I could probably give better answers if I knew the design and where you are building and the condition of the building site.
I am not aware of any long term difference between using weld mash and hex wire mesh. I used galvanised hex wire mesh. The weld mesh probably gives a greater density of steel, but the wire mesh would be easier to work with and give more zinc on the wire.
I used hard drawn steel rod for the stringers. I don't know if the book still recomends it. I felt that it gave a much fairer hull
Other key questions that you need to answer at this stage are about the ballast, the waterproofing of the cement, the sand and the cement itself.
I queeried Richard Hartley about using modern waterproofing when I was about to plaster and his reply was that you don't polute your lungs with smoke and you don't use modern waterproofing. He recomended the use of pozzolan, which I think is the same material the Romans used in their cement. I found an internet
reference here :- http://www.westernpozzolan.com/
As you watch your hull
cure you will see the an interesting interplay between the components, particularly with regard to the microcracking that occurs with cement. I believe that pozzolan is a key part of that interplay, and that the interplay will continue for the life of the boat.
I used a mixture of boiler punchings and cement as ballast. This was the worst mistake I made with the boat although it was common practice at the time. The boat was stable enough, but when hit by a gust it would develop major weather helm
. I cannot recomend strongly enough the use of solid lead ignots, properly isolated with a suitable coating, deep down in the keel
, and properly secured.
You will need to use clean fresh cement of the type recomended by the designer
. It is essential that the cement be fresh.
The sand must be clean, sharp silica (river?) sand with a particle size recomended by the designer
. Some of the reports that I have seen of total disasters have related to use of unclean sand, particularly that contaminated with salt
. The use of coral
sand may render the hull useless.
I would urge you to reconsider the use of ferro
for the hull only. I built a ferro
hull and deck
and felt that it gave a substantial increase in structural rigidity. Some care is necesary (waterproofed wooden struts to hold up the deck
between frames to prevent sagging) to ensure a thin deck but in the end I feel that it is worth the effort.
I would also urge you to reconsider plastering the hull in one shot. It is difficult for even a skilled plasterer to ensure that there are no voids in the hull with single
shot plastering. Two shot plastering almost guarantees a solid hull, and the use of clean fresh cement, sand and pozzolan will help to make sure there is a good bond between plasters.
When I did my boat the plasterers used slightly wet cement which pushed through the mesh and protruded slightly on the other side causing knobs all over the inside. I consulted Richard Hartley on this and he advised me to take a "scrutch cone" (stone masons chisel) and to cut them all off. Not a pleasant job but worth it in the end, as I ended up with a three quarter inch hull.
As a side comment here a friend finished off a 34' hull, no deck, that he brought that had been plastered single
shot. He sailed the boat to Europe
, and along the French canals untill one day he touched a solid wooden post and the side of his boat caved in!
If my memory serves me well it took me about 500 hours of very part time work to get the hull ready for plastering. That does not include head
The first shot of my plastering took four skilled plasterers one very long day (from memory). I would strongly urge you to use skilled plasterers. They will give you a much nicer hull.
The second shot took (my memory is hazy) three men
less than a day, and the third (to finish off the deck) only a few hours.
This all happened quite a few years ago, alcohol was involved. My memory may not be reliable.
The other thing that you can do that will shorten your building time is to make special plugs for where ever a hole is needed in the hull, for example through hulls, prop shaft, rudder
shaft and holes for bulkhead, chainplate and stanchion bolts. The plugs will need to be protected to prevent them from leaching water
from the cement during cure. You begin to appreciate just how tough ferro cement is when you have to get inside the hull and drill lots of holes in it.
My final recomendation is that as you build the armature you frequently take the time to step back and check the hull for fairness. If you have a friend with a good eye ask for their opinion.