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Old 16-04-2011, 20:31   #496
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Re: Ferro Cement Hulls ?

Originally Posted by Pete7 View Post
Yes, please do.

As a general question to the forum, how thick is a ferro cement hull say on a 40 foot yacht? Just curious.

My 42 footer by the late Sydney designer/builder John Perry (constructed 1978) is 3/4" (19mm) at the raw water thru hull. The total steel framework thickness (rods, mesh etc) would be 1/2", while the cement plaster fills the voids and adds an additonal 1/8" on each side.

BTW, a nice but rarely mentioned virtue of ferro hulls is that they are all round and often with sweet tumblehome - it's impossible to do chines in ferro.

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Old 17-04-2011, 04:05   #497
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Re: Ferro Cement Hulls ?

Just spent some time looking at design specs we have at the shop. It looks like most of the 40' are calling for between 5/8 to 7/8".

Sam McGee a 38' Samson in Ferro Cement has a 7/8" at the turn of the bilge, Tin Cup a 42' Samson in Fer-A-Lite has a 3/4" at the turn of the bilge.

Platt Monfort's original specs called for a 5/8" thickness for a 45' boat in FAL. (3/8" armature thickness, plus 1/8" per side.)

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Old 17-04-2011, 05:31   #498
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Re: Ferro Cement Hulls ?

Thanks, quite interesting. That is quite a bit of insulation from sound and heat.

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Old 17-04-2011, 09:38   #499
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Re: Ferro Cement Hulls ?

Originally Posted by Pete7 View Post
Thanks, quite interesting. That is quite a bit of insulation from sound and heat.

This brings to mind a post I was reading in another forum where a non-owner was giving his reasons for not owning a ferro cement boat. On his list was they were very cold inside and constantly sweat. I've heard you have this with steel hulls. Is this just another naysayers imagination or do you find this to happen in certain climatic conditions with ferro cement hulls? Pete mentions sound and heat, but I would think they are better insulated from this as well. Which scenario Is true?
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Old 17-04-2011, 11:16   #500
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Hull thickness & insulation

I was under the (misguided?) assertion that 'sweat' is a result of atmospheric conditions/ventilation/dew point etc, and would therefore have nothing to do with hull material, but I could of course be wrong about that.

IMO ferrocement provides good sound insulation & moderate heat insulation, but not as good as a wooden hull, especially when it comes to colder temperatures*.

*NB just my observation thus no hard evidence to offer

Regarding the hull thickness; the UN FAO ferrocement fishing boat technical paper brought together several leading ferro experts from around the world - their collaborative (and arguably 'evolved') effort called for a 30mm thickness on a 12-14m fishing vessel:

2mm mortar only + 7mm mesh layers + 12mm stringer layers + 7mm mesh layers + 2mm mortar only = 30mm

[I think it has been linked to before but anyone interested can find the comprehensive publication here: Table of Contents]

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Old 17-04-2011, 15:15   #501
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Re: Ferro Cement Hulls ?

49ft Walu 1/2" of stainless steel mesh layers with 1/8" on outside only and trowled to the mesh on the inside gives 5/8",the only thing in her bilge is some dust
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Old 17-04-2011, 15:20   #502
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Re: Ferro Cement Hulls ?

My suggestion is DON'T DO IT!

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Old 17-04-2011, 20:16   #503
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Re: Ferro Cement Hulls ?

Originally Posted by Mark Johnson View Post
My suggestion is DON'T DO IT!


Is this directed at me?
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Old 05-07-2011, 04:18   #504
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Re: Ferro Cement Hulls ?

i thought that was a load of rubbish from jeff. glass fibre, wood, steel, and very small rocks sink if they are put in water. so its ok to build in concrete. i have owned mine 42' for a year. she is warm, well insulated, strong, solid, and weighs the same as the sporty steel yacht next to me (39'). she is MUCH easier to care for than grp or steel, and much betetr insulated - temp/sound/condensation/odours.

i make any repairs by soaking the area in epoxy, which sinks straight into the concrete and cocoons the steel, and is stronger even than the original. her ballast ratio is 43%. her topsides are marine ply, just the roll in from the hull makes the side decks concrete. i dont have rust streaks. repairs ar echeap because i mix cement with epoxy

a few key points in no order +'s and -'s mixed up

1 a ferro yacht on this w coast of australia was charged by a bull whale, who bumped her. because the structure is brittle, she caved in like a breakfast boiled egg, and sank in less than a minute! for this reason i would only have a ferro with grp sheathing in and out. you can do this. dont forget steel and alloy boats split when they collide with whales/objects, and grp often loses the contest too (particularly because the modern trend is to 'skin' a frame)

2 ferro boats are always cheaper - you get a lot more boat for your money

3 some places will not insure ferro. in australia (which i hope is unique) it is impossible - becuase our insurance industry is crap. so register somewhere having checked they will insure!

4 i love my ferro boat and i would pay extrta, not a disount, for its qulaities

5 if you new build, you could consider the method that made mine special:

-the hull was laid up with concrete mixed with epoxy resin, not water. this saved 1-2 tonnes because her skin is thinner than it would have been. also stronger, and more tensile strenthg

- she was epoxied in and out

- she was then glass fibre sheathed in and out

- she was then cured in a shed for 4 years (curing (ie water evaporation) takes a long time and should be slow)

6 I bought her as a shipwreck, she had been dumped on a sandy beach with a 6m tidal range in a tropical cyclone in northern australia, when her owner had a stroke and was medi vac'd. she was pounded for six weeks. when recovered, she was found to have a 12in diameter 'dent' in one impact spot. total water ingress was about 60 litres. she was repaired for the recovery by stuffing in a few kilos of quick cure epoxy bog. evrything in and out remained in place. these boats can be very tough indeed.

I wish you luck

cap'n John
sy Shanaly
Two Rocks, W Australia

Originally Posted by marleman View Post
Thank you Jeff for giving us considerable food for thought! I appreciate the time and detail of your reply.

Some of what you say though is what I have already read in various books and web resources... which leads me to ask whether or not your comments are based on general opinions, or whether they come from actual experiences or contact with ferro-cement owners? My partner and I are finding it very difficult to make any decisions because in our own (limited) experience we have found that those who actually own these yachts usually speak highly of them....and those who don't, run them down! Perhaps its just a 'pride of ownership' thing?

Is there anybody out there who actually has one, has had one in the past...or who at least knows somebody who does? I'd really appreciate your views...but of course anybody's view will help us with our decision-making.

Thanks so much,
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Old 05-07-2011, 05:26   #505
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Re: Ferro Cement Hulls ?

Our vessel does have tendency to sweat in winter, however, I think most boats would under the same conditions. As ours is unlined, this may contribute. what I can tell you is that it is a very dry hull. As someone above has said the bilges have dust in them.

As to the argument about should you or shouldn't you, the 2 greatest arguments against are:

1) resale value (only important if you need to sell in a hurry)

2) insurance. In Australia you cannot enter a marina without it. We have taken insurance with Northern reef.

Ours sails sweetly and is very comfortable.
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Old 05-07-2011, 06:03   #506
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Re: Ferro Cement Hulls ?

So the take away from this thread is that some people love their ferrocement boats, but by and in large part fiberglass composite is a more forgiving material with a proven track record.
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Old 05-07-2011, 09:08   #507
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Re: Ferro Cement Hulls ?


I donít believe anybody reading this thread would come away thinking ďfiberglass composite is a more forgiving material with a proven track recordĒ over ferro cement as a hull material. I came in here as a total ferro cement skeptic. After seeing the objective responses from FC boat owners, reading stories like, many good books on the subject, along with other research Iíve done, Iíve come to the conclusion from this thread that FC would be my hull material of choice.

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Old 05-07-2011, 18:19   #508
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Re: Ferro Cement Hulls ?

I don't know much, but I thought I knew that cement hardened via a chemical process with water as the activating agent. No water, no chemical process, no hardening. So I'm curious, if you substitute epoxy for water, where does the water come from to start the curing/hardening process in the cement? Just wondering.


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Old 07-07-2011, 16:06   #509
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Re: Ferro Cement Hulls ?

very interesting topic/debate.

just a few comments to contribute:

i helped build a FC sailboat about 30 years ago. its owner died a few years ago. the boat is still alive and going strong.

i have a friend who lives aboard a 55' FC sailboat with his family. they love it.

the romans were good with concrete. some of their stuff is still good over 2,000 years later.

i made a kayak out of fibreglass 30 years ago. it is still in perfectly usable condition. but it is stored out of the sun. i wonder what it would look like after 30 years in the sun. probably worse than me.

i own a 52 year old wooden sailboat. it needs regular maintenance (some paint and varnish). no big deal. it sails beautifully. in a race last year (about 80 miles) it came 49th out of 900 boats. it was probably the least valuable boat in the race. it was designed by nicholson and took two people three months to build, by hand. it cost about $10,000 back in 1958. i paid $3000 for it in 2008. how much would $10k invested in a house back in 1958 be worth today? probably a lot of money. it is only 27' long. the previous owner got caught in a bad storm in her. the tiller broke because it was replaced with oak and not willow so it wouldn't flex. the waves were 20' was self-draining cockpit...the coastguard arrived after 4 hours...said they were lucky they were in a good quality old wooden boat because a modern fibreglass equivalent would have struggled.

i own a 32 year old steel trawler. it is very strong. i bumped into a wreck a few years ago and got away with a dented keel. i'm pretty sure it would have sunk if it was made of fibreglass. i have to keep it painted everywhere or else it will corrode and be worthless. i work on it all the time.

i was in a force 10 gale in the bay of biscay three years ago. the waves were 75' high. we didn't see another boat for two days. i was scared. the professional skipper said that he was glad we were in an old moody 65. very heavy and well-built. he said boats of a more recent vintage would have had big problems in the same conditions. he sails lots of boats all over the world all the time. it's all he does.

my mechanic buddy tells me about modern fibreglass power boats that come into the boatyard with cracks in the hull, sometimes almost breaking in two parts. he doesn't tell stories. he used to look after all the diesel submarines for the canadian navy and teaches mechanical engineering at a local college. he knows a lot about boats and fixes the ones that get used a little. he says the ones that don't ever go anywhere don't fall apart as fast.

another buddy of mine with a recently built 45' yacht bumped into a wall. it ripped a small hole near a porthole. i looked at the damage. i could not believe how thin the fibreglass was...probably no thicker than my 14' fibreglass kayak. scary. it was an expensive boat. i wonder why. we were in some big seas in the english channel and the water was coming in everywhere. scary.

my dad was a metallurgical engineer. he loved steel reinforced concrete. he said it got stronger with age, and as long as the steel stayed covered it would last virtually forever.

i was cutting some 10mm marine grade aluminum the other day. this was after cutting some steel for several days beforehand. i was really surprised at how strong the aluminum was. very impressive.

i also got a chance to compare the strength of 32 year old steel with brand new steel. i could not believe the difference. the old steel was much tougher to cut. my boat's hull is 10mm, the sides (above the waterline) are 8mm, of old steel. new builds of a similar size vessel are proud of the fact that they are 3-5mm thick, of new steel. scary.

my conclusion, based on anecdotal evidence (mine)?

i am pretty sure that i would not want to be caught in bad storm in a new boat unless it came from a manufacturer with a deserved reputation for quality. however i am sure that i could not afford to buy the quality i would need to feel comfortable in a force 10 gale. so i would buy an older boat, subject to a proper survey, because i think they are better made, and because they cost a fraction of the price of a new one.

my preferred choice of material, all things considered, would be FC. they are not overly heavy as you might think. built by a professional, they will outlast me. they are strong. they don't corrode. if you don't paint them they don't rust. they don't get osmosis. they are not hard or expensive to fix. they can look good. and they are dirt cheap considering their performance. i hear that 35' FC yachts are the old timer live-aboards' favorite.

genuinely good steel or aluminum boats are much more expensive. steel needs lots of maintenance and good design. a pin prick in the paint will look bad if you use it in salt water.

fibreglass can be good as long as it is old and thick. i have a sneaky feeling that new boats are built thin, not because of new and improved technology, but because it is cheaper that way so the manufacturer makes more money, and because they know that very few people actually use their boats very much, and almost never in a big storm, so they (the manufacturer) are safe.

wood is good in a cold climate but doesn't do too well in humid hot conditions. if i was sticking to northern europe then wood would be fine. otherwise probably not. i would not like to refasten the planks every 10 years. big job.

why do people avoid FC? it has to be a combination of ignorance and fashion. if i could find a good 45' FC trawler i would buy it after selling my steelie. i would then spend about 90% of the difference in price on women and beer, and i would probably waste the remaining 10% on non-essentials.

does anyone know of a good 45' FC trawler for sale, preferably one with a decent gaff ketch rig and single screw?
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Old 24-07-2011, 15:58   #510
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Re: Ferro Cement Hulls ?

First, let me say this thread is the most interesting I have ever read, nearly got through the whole lot in one night

As a person who has lived on an amateur built ferro for 22 years which was launched in the 70s, and is still sitting on it typing right now, let me give my opinion as to why ferro has such a bad rap. Basically, it is a nightmare for the boat market! Ferro hulls are expensive to mass produce and last a long time, as opposed the `disposables' that everyone finds these days from cars to washing machines to houses to boats. Why isn't everyone driving a Willis jeep these days, even though Dad still has one from 1945? Why doesn't everyone have a diesel in their car, even though you can put just about any flammable liquid in it and it will last `forever'? Because a Willis jeep is built like a tank and short of a bomb under the chassis will never fall apart. The Perkins diesel on my boat is a reconditioned truck engine from when it was launched, and recently sat in salt water from a seacock accident for 9 months. Looked horrible from the outside, but afterward cranked a purred like brand new. Try doing that to a modern car engine. A petrol engine is high wear and tear and these days so complicated that if you need to change the oil you have to take it to a mechanic. For that matter, why is it just about impossible to find a NiCad battery except in the very tight aircraft industry? My boat has some Saft batteries that are going on 25 years and I have no intention of replacing them. Lead acid is crap and you have to have a controller nannying it or it will die, and even then it only lasts a few years. BUT it is close to 100% recyclable! Can anyone smell good business?
Point is, ferrocement is a no no for the industry, because it is low maintenance and lasts a long time. So people who want a boat and ask a `reputable boatbuilder' what material to get, well, chances are the builder has only worked on fibreglass and GRP and will join the secondhand opinion club about ferros only being good for a reef. THAT is why only ferro owners are the ones who praise their boats, because, like those with a WWII jeep or Land Rover, they wake up in the morning knowing that they have something under them that, while it has little resale value, will probably outlast them.
I know ferro is not magic and has its problems, but from the stories I've heard about other materials its by far the best.
My 2c worth.

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