Ferro-Cement hull building?

[Sparky00]

First, I know I am opening a can of worms here and going down this rabbit hole, but I want to ask this question on Ferro-Cement boat building. Has anyone used it lately, and if so have you gotten away from using steel rebar and thought about using Rock Rebar / Basalt rebar instead, or even fiberglass rebar? Before you explode with a bunch of hate and words of Oh what a piece of $#$#% it is or anything else there, hear me out and think with some logic first and foremost. I am not writing this out of fun to stir up an angry mob of haters and nay sayers, I am just throwing an idea out there and asking the question of “Has anyone done this and if so how did you get away from the main issue of steel rebar?” If you look at cement in general, it does a wonderful job of protection from the elements, used in many areas of construction, to include bridges and damns, dikes and more. Used in corrosive environments like saltwater... So why is it ok for a bridge which holds up tons of weight, or a damn which holds back a lot of water, but not a hull?
I have had a Samson ferro-cement sailboat once. The biggest issue was the rust bleeding. There was even a 6 inch crack under the waterline that was inspected by a marine inspector and no issue of integrity. Yes it was a heavy beast and yes it did not roll as much as the fiberglass boats in the mooring, especially when a gator freighter slipped by. But again the question is “Does anyone use Ferro-Cement?” And If so have you considered alternatives when using without steel rebar? Thank you and I hope the rabbit hole was not too deep...

[Chotu]

Cool thread!

Composite rebar is 20% stronger than steel so it would make an excellent choice and have none of the corrosion problems.

[Jim Cate]

Well, ferro cement without steel reinforcing ain't FERRO cement, is it?

And FWIW, even with some sort of non-ferrous reinforcement I see no compelling reason to build a hull thusly. There are so many better ways...

Jim

[skipperpete]

The bigger problem is insurance after you build the boat., no insurance , no marinas. I have no problem with ferro cement or ferro epoxy construction but its damned hard to sell em after you get over the cruising bug. I don’t know about using composite rebar, I didn’t know it existed til now but I have heard gal rebar can’t be used. The epoxy ferro is a quick alternative, a guy in Ballina built a 60’ hull with this method a bit at a time, apparently you don’t have to do the full plastering in one session.

[Bowdrie]

Originally Posted by Sparky00

I have had a Samson ferro-cement sailboat once. The biggest issue was the rust bleeding.

Back about '70>'71 I had the Samson book, and there was a yard near me that only had Samson designs being built in it, (perhaps a dozen or so).
The yard owner, (a franchise?) had a pro crew that would do the plastering after you built the armature.
In those days, rust bleeding invariably came from 2>3 reasons.
1, Not having a sufficient covering of the armature, (gotta watch the weight).
2, Not using Pozzolan in the mix.
3, Not using galvanized "chicken wire" for the armature and tie-wires.
I've seen some real disasters and some boats that never had any problems over 40>50 years.
But I agree with an above post about using Ferro for a boat, why?

[Sparky00]

The tensile strength of fibre rebar is 20% higher in comparison with a steel bar. The material bonding force of fibre reinforcement is considerably stronger compared to steel; this explains better operational endurance of FRP rebar.

Basalt Fiber contributes to reduction in concrete coverage by 25 – 30%, and its weights 4.5 times less than steel fiber This means you'll need less manpower to lift and place the material during construction.

Basalt rebar is 3 times stronger than steel rebar (the strength of basalt reinforcement is about 800–1100 MPA, while steel reinforcement has a strength of 225-365 MPA).

[Chotu]

there are definitely much better ways to build a boat but it’s an interesting topic. Also, you would not have to call it a ferrocement boat. You could just call it composite. Since that’s what it would be with the FRP framing.

how does this technique compare to solid glass for weight if you drop a few pounds by using the frp rebar?

Generally, this is just an interesting topic.

[MicHughV]

As a retired structural marine engineer, I look forward to reading the responses on this thread.
I've come across a few homebuilt ferrocement boats in my day...emphasis on "home built" as I don't think I've ever come across a factory built ferrocement boat.

I can't say that I see much merit on trying to build a ferrocement boat in this day and age when so many more viable options exist.

Nonetheless, am looking forward to the dialogue.

[Sparky00]

There is the DIY "Home Built", than the shipyard built using skilled labor and quality control, but you are right there is no production line Ferro-Cement boats out there. I have had the in the shipyard built sailboat. A pretty good sailboat, but as it was worth only what the eye of the beholder deemed it worth. My thoughts are on using a building material and method, replacing the main issue of weakness and also providing an idea for areas of the world where fiberglass, wood and steel come at a premium vs ferro-cement or call it composite since the stigma of ferro-cement is so negitive....

[boatman61]

Windboats Marine of Wroxham, UK built the popular Endurance range in Seacrete..

[Wotname]

As an aside, some might like to read about a former CF member (yachtrodney) and his home built 75', 75 ton ferro boat which had to be cut in half (longitudinally) in order to transport from the building site to the launch site and then re-joined.

https://www.cruisersforum.com/forums...ars-11518.html

[skipperpete]

Thanks for reminding me Wottie, I was in port Botany recently and Rodney was anchored about 300 metres away, his boat still looks good.
I’ve only seen one professionally built ferro cement yacht, she was called Helsal and affectionately referred to as “ the flying footpath”. Made using using pre tensioned concrete technology , she was a Sydney-Hobart contender and for a long time after, was used as a charter vessel. I think she foundered on a reef at Lady Elliot island after many years of hard use.

[GordMay]

Originally Posted by boatman61

Windboats Marine of Wroxham, UK built the popular Endurance range in Seacrete..

100 YEARS OF WINDBOATS ➥ https://www.hardymarine.co.uk/wp-con...EARS-of-WB.pdf

An interesting article [1968] on Concrete Boats & Ships, focusing on Windboats, by the USN Office of Naval Research:
➥ https://apps.dtic.mil/sti/tr/pdf/AD0840223.pdf

Evidently, Windboats Marine Limited, based in North Walsham, Norfolk, entered administration, in 2020, in part due to the impact of Brexit, and ultimately the Covid-19 pandemic.
➥ https://issuu.com/mercatormedia/docs..._2020_flipbook