ferro-cement

[JonathanCole]

Originally Posted by D'ARTOIS

Jonathan, a diamond disc makes very smooth cuts, and that is just what not is needed - the rougher the surface, the better the repair will hold.

Actually a diamond coated disc can be used to cut grooves in the surface for greater surface area and greater adhesion. I agree though that the best thing would be to then sand blast the surface for increasing surface area at the sand grain level. The two issues for adhesion are surface area and porosity. If sand blasting, then a high pressure air nozzle at an oblique angle (so dust is not driven into the pores) is a good idea for removing fine particulates from the pores.

[jonsailor]

Ferro cement is quite heavy and our 40ft hulls were 11-12lbs per square foot.
with frame spacing in a plastered truss web design at every 4ft with the same design backbone. Most earlier models had pipe frames and this was a down fall as they in years to come, had water penertrate them and they rusted and split the hull. This was most evident around the stem where perhaps a bob stay attachment was bolted through and where an anchor and chain may have lived to add a salt water enviroment.
As I have said, there were some shocking examples out there and some boats left a lot to be desired. We ended up doing cement hulls with plywood decks supportrd on a through bolted beam shelf on the hull sheer and we could get a 36ft fast cruiser around the 11000lb mark.
In todays technology, you probably would not intentionally build yourself a new cement yacht. I am building race yachts in the 40 ft range with a panel weight of around 1lb ft2.
see www.sayerdesign.com
The best book I know but only because I have not researched the material for 25 years is a NZ publication from Richard Hartley on ferro cement construction. The material is quite strong but is poor in repeated impact.
We used to build survey work boats for the marine industry and these were tested with panels and core samples.
cheers
jon

[glenville]

I've certainly been extremely pleased with all your replies! I'll post pictures within a week or so of the damaged 37" endurance and look forward to further discussion. unfortunately the snow has arrived in Nova Scotia Canada and the boat is under tarps but I'll do the best I can with the camera.

[D'ARTOIS]

Repeated impact capacity/ resistance.....that is something new to me... at least something to consider seriously.....Very good jonsailor, I never heard this frasology before.

[glenville]

here are some pictures of my repair project. I could not get a good
picture of the indented areas or where the bow was damaged. Any further
comments or suggestions would be appreciated. Is it doable or should
I cut my losses early and scrap the project? Thanks

Originally Posted by D'ARTOIS

Ai, that is a very considerable damage. Let's see if other guys chime in - contact this Sauereisen Company for further advise. Can you post some pictures? The galvanised mesh is correct - that is always used as a reinforcemnt layer, mostly two or three and rods as kind of frames and stringers. You can weld to it but make sure that it cannot rust any further. Main concern are the small haircracks. If there are so many, the basic structure might have left - personally I would grind them open and repair those haircracks with epoxy mixed with silica - the larger damages I would ask for advise - there are specific epoxy's used for fastening steel bolts / anchors into concrete. I have repaired once an engine-mounting in a ferrocement hull with that specific material. I believe the repair is still holding and the engine vibrates a lot - so the connection might have some strength

[D'ARTOIS]

This is beyond my knowledge - here you need real expertise - I hope that Jonsailor will be of advise. This is an expert's job!!

[itaero]

I Own a 32' Trawler. She is 14 tons strong. She was built in 1975. I have pulled her out every 4 years and she has held up fine. Only One problem about a ferro boat...You can't get insurance for them. No One is writing any insurance for this boat out of Florida. I have contacted about every insurance company out there and I can't find anyone.
I love the boat. What nice cruising boat! 5/6knots and handles like a big tub in the water but very stable...
If anyone else has a ferro I would enjoy talking about it. If anyone knows where to get insurance for One, please let me know..
best to all. VINCE

[AdamoMare]

Hello itaero, Have you tried ORM? Here is a link to their website. Let me know how it pans out. http://www.offshorerisk.com/home.htm

[FOsorio]

22Jan. 2006

Can any of you experienced ferro cement guys give me some advise of this impending project.

I live in the Philippines where there is a lot of free sand and low cost labor and so for this reason, I plan to build a trimaran with a ferro cement hull. Only the hull would be in ferro cement. The cross beams connecting the main hull with the two hulls on each side would also be in very good hardwood. We've got some teak, camphor wood and oak which I would use for the deck, the pilot house and the rest of the superstructure.
The trimaran would be about 40 feet long and would be powered with a marine diesel engine. Would any of you guys know of a good trimaran design specifically for ferro cement construction.

Francis N. Osorio

I'm amazed this ferro thread is still running! Heck - the thread lasts longer than the building material!

My advice Glenville?

In the enduring words of Forest Gump...

Run Forest - Run!

and, like Lot of Soddom & Gomorra fame...

Don't look back

lest you too, should turn to a pillar of ferro cement!

Course- you could always sell her to a dive company to scuttle as a future dive wreck / artificial reef - in fact a lot of artificial reef projects are springing up around the world, constructed of ferro cement...

Finally - the community have realised the perfect use for ferro cememnt - artifical reefs, sadly - some still insist on making it into a boat before it completes it's pre-destined jouney to the bottom of the ocean as a artificial reef.

Really i'm just sugesting - cutting out the middle man and saving all that time & effort and go straight to end use - artificial reef.

Some materials - are just suited to some uses and some are not.

When planning to build a boat, take a piece of each of your potential boat building materials - and throw them in the bathtub. Whichever one floats - build your boat out of that!

Cheers!

Cheers!

[PAR]

FOsorio, try not to pay attention to the man behind the curtain.

Ferro is a valid building material, but has reputation difficulties in some parts of the world. I'm not sure about the Philippines, but they are well regarded in Europe.

That said, the construction of a hull (2 hulls in your case) is actually a small percentage of the over all cost and effort that go into building a 40' yacht. It averages under 10% in 40' vessels. This combined with the inherit weight of the material makes selecting ferro as the hull material in a catamaran an unwise choice.

In short, you'll not save much by using ferro in the hulls. The light weight requirements of catamarans also plays a big factor in the material selection process. Then there are the repair issues, discussed earlier in this thread, insurance and survey difficulties, all of which are conspiring against the use of ferro. The choice is yours, but the path seems clear, at least in this case.

For what it's worth, no 40' yacht is going to be cheap, even if the hull is prebuilt and free. Finishing off a 40' hull is a major undertaking and will require fists full of cash, buckets of time, tears, sweat, maybe a little blood and truck loads of materials.

[FOsorio]

22 Jan2006
Thanks for the very prompt reply. I was involved in building two tugboats in ferro cement in 1979. We are still using those two tug boats now. These are workboats used to tow logs up and down the river. These tugboats take a lot of banging, bumping into logs and oftentimes beaching in sandy river banks. Very few places in the Philippines do not have piers especially in the places where I will use these boats. I am not concerned about insurance. In the places where I will operate, no insurance company would cover me anyway. In fact the ferro cement is in itself my insurance. A bullet from an armalite rifle cannot pierce a ferro cement hull. I have seen this myself with the two tug boats we now have when it is occasionally borrowed by the Army to fight the rebels.

I am also not concerned about aesthetics since it will be a workboat. Nor am I concerned about resale since I will use this boat till I go 6 feet under or the boat goes under, whichever comes first. So you see, my situation and my considerations are quite different.

What I need for now is some recommendation for a good hull design or hull designer for ferro cement. I realize that since ferro cement is a heavy material, the design considerations would be different. And I want to build a trimaran not a catamaran. This boat would be used chiefly as an island trader carrying cargo to remote islands south of the Philippines where I expect to run into a few pirates occasionally. There will be a wooden deck and closed hatches for the cargo. No bunks, no saloon, no pantry since interisland crossings would take no more that 6 hours of cruising. The only luxury is one toilet for the crew of 6 people.

Very truly yours,
Francis N. Osorio

[SamSam]

I don't know of any designs and it sounds like yuo've done ferrocement before but this site might be of some help in construction anyway. Sam
http://www.fao.org/DOCREP/003/V9468E/V9468E00.HTM

[FOsorio]

23 Jan. 2006

Thanks Sam for the recommendation. I have been through the FAO handbook already. Right now, I am looking for a hull design in ferro that would suit my needs. When we built the tugboats 27 years ago, we had a boat designer from New Zealand who was with us during the whole length of the construction . I cannot quite recall his name and he would probably be dead by now. On the hull design, would you know of a good designer. I have been asking around and everybody is telling me ferro cement would be too heavy for trimaran. I which case then, I am thinking to build a mono hull with a cathedral bottom in ferro cement. Would you know of a good cathedral hull design that can be done in ferro cement.

Very truly yours,
Francis Osorio

[D'ARTOIS]

There are three names I can give you: Ian Baugh, G.L. Bowen and Graeme Kenyon, all from New Zealand. They are experts in Ferrocement, wrote books about this subject.
I must fully agree with Par - nontheless if you can make a 20'sailing boat, why not a tri.
There is (was) a magazine called "The journal of Ferrocement", POBox 15-447
Auckland 7, New Zealand.

As long as you know what you are doing you will find a way.....