View Full Version : Ferro sheathing

Peter Heiberg
03-03-2006, 09:34 PM
A good friend is considering ferro sheathing his clinker replica of a Finnish freight carrying sailboat circa 1700 (44'). The hull was built a bit too light (by someone else) and tends to leak when working to windward. We would appreciate hearing any thoughts on ferro sheathing from people who have experience or by others with experience with other systems . Thanks for your help.

martin schulz
03-04-2006, 09:41 AM
This boat, the 1886 built victorian yacht WILLOW WREN was first sheated with a thin cement cover around 1910. During WWII she was laid up and was used a houseboat until 1970, when 3 enthusiastic brothers took her out and expertly put a feroo-cement sheathing on her. Since then she is dry and still sea-able.

Of course usually I am not in favour of sheathing wooden hulls, but to be honest this lovely boat wouldn#t exist today without the sheathing.


With a clinker-built boat I guess this will be much more risky and the boat will definetely loose the "clinker-look" on the outside during the process.
I once examined a folkboat with a professionally aplied epoxi-sheating, but there the guy put triangular batten under the clinker-gaps before he covered the boat. You will have to be very careful to completely cover the keel with cement. The WILLOW WREN is actually sitting in cement-bed which covers the bottom of a steel U-profile. The whole thing is then also covered with cement.

I hope I was some help.

03-04-2006, 10:17 AM
Sure seems there might be a number of options, particularly if the boat is relatively new, wood in good condition, etc.

Ferro has such an awful reputation, and even if well done could lower the value of the boat significantly.

One option (as long as you'll be losing the clinker shape) might be laying up diagonal planks over battens shaped to cover the lap edges.

Sounds like adding some frames to the interior might also be a good idea.

[ 03-04-2006, 10:20 AM: Message edited by: Thorne ]

Art Read
03-04-2006, 10:30 AM
[ 03-04-2006, 10:31 AM: Message edited by: Art Read ]

03-04-2006, 11:01 AM
laught it off doubters but do this
coat the hull with a waterproof coating such as permaflex by www.sanitred.com (http://www.sanitred.com)
or what the rot doctor sells

Do it properly, remove all the paint scrape out and seal the edges with polyurethane fillets and coat the hull with several coats of one of these poly products.

Art Read
03-04-2006, 11:28 AM
... And never hafta touch it again! ;)

Tom Robb
03-04-2006, 02:36 PM
Or perhaps glue on that rubber sheathing they use on flat roofs :rolleyes:
Seriously, is a proper rebuild out of the question?
I'd have thought that ferocement was to get a few more years out of a shot-to-hell hull that needs to make a living.

Frank E. Price
03-04-2006, 04:51 PM
Man, and it's only March 4th.


Bob Cleek
03-05-2006, 03:22 PM
Simply amazing! sheesh!

Your boat is clinker built. It won't be possible to put anything over the laps that is going to make them watertight if the boat "leaks when beating." The problem you are experiencing is caused by the STRUCTURE of the boat being insufficient to resist "panting" or whatever other stress is causing the planks to move in a headsea. Analyize what the problem is. Quite likely, adding some intermediate frames or beefing up the clamp forward, or both, will solve the problem without the need to turn the boat into a piece of rotting cement covered junk. (Ya, ya, I know people have done it... it's still a dumb thing to do.)

03-05-2006, 04:03 PM
We would appreciate hearing any thoughts on ferro sheathing Three words: Don't do it.

Bob Smalser
03-05-2006, 04:50 PM
Ignoring for a moment that the proposal is to apply it to wood, the problem with this construction isn't so much the cement as the ferro.

Shipyards in third-world countries of my aquaintance did a bit of ferrocement construction a few decades ago when mango and teak became scarce and polyester was still relatively expensive. These hulls can still be seen, all flaked, cracked and bleeding on the beach.

The salt eventually gets to the steel mesh, regardless of coatings. On the equator relatively quickly, and in Norway relatively slowly. It's just a matter of time.

It's like mixing concrete using salt water. The steel reinforcement rusts and expands until it cracks the concrete...this can take years, even in the tropics...then more salt water gets in the cracks and the process speeds up dramatically.

On desert islands where we couldn't produce enough fresh water for concrete, we built without reinforcing bar. The problem with that is, to achieve the same strength, it takes 10-fold the concrete and the resulting structures are massive.

Ian McColgin
03-05-2006, 05:03 PM
I heard of a fellow with a clinker boat of about this size and trouble. He was going to wood the boat and attack all rot and fastening. He then planned to epoxy an new but thinner plank onto each plank, bottoms flush and top of the new sealing the gap between the two olds. I think he also planned to put in light intermediate frames and rivit through them and both plank layers.

Unfortunatly, I have no idea if it ever happened and have not heard from him in over twenty years. Still, sounds like a sufficiently expensive and tedious approach that maybe it would work.

Peter Heiberg
03-05-2006, 08:20 PM
First let me thank everyone for their thoughtful (and sometimes less than thoughtful) replies. I should emphasize that the boat in question belongs to a friend who is computer illiterate but an excellent shipwright (just the opposite of me). He was given the bare hull which was professionally built and has spent 15 years or so finishing it. He has only had it sailing for a couple of years so has made all his interior arrangements without finding out the basic structural problems. He has been reading a book by a NZ builder who has been ferro sheathing wooden boats for years with (like all builders) perfect success. He is not excited by epoxy sheathings for health reason as it will be a big job. He does plan to fair the clinker hull with triangular battens .
Some years ago, in Oregon I think, they were sheathing fishboats by coating them with 5200 and fibreglassing over that. Bet they didn't buy the 5200 in tubes. Has anyone heard of that?
Keep the information coming, we do appreciate it

maa. melee
03-05-2006, 10:10 PM
There's an article somewhere about a Diesel Duck being built with carvel on frame. After that, 5200 was slathered on with a trowel out of a bucket and door skin plywood was screwed on. Then on top of that came the epoxy and glass.

Don Kurylko
03-06-2006, 12:25 AM
“Covering Wooden Boats with Fiberglass", by Allan H. Vaitses is the book you want. This a no nonsense treatise about preserving old wood hulls with a significant thickness of fiberglass – in essence creating a substantial fiberglass hull over the existing wooden one. Much like the idea of the Ferro-cement covering proposed, but without the drawbacks of Ferro. I’m sure cost is one of the factors in using cement, but glass and resin can be gotten at wholesale prices to take a bit of the sting out of the costs. One just needs to dig around a bit for sources.

Another approach is to laminate several diagonal layers of 1/8” veneers over the old hull. This has been documented in Wooden Boat magazine and has been successful in a number of instances. I can’t recall the name of the article or the issue, but it was written by Pauline and Tim Carr. A search of the online index should turn something up.

03-06-2006, 08:27 AM
Personally I think Bob Cleek gave the correct answer. Go inside the hull and put reinforcement strips between the frames.They are not frames or do they have to attach to the keel, or even be full length or even in one piece.I believe that even Atkin used this reinforcement of the planking on some boats. It will take two people.
Simply position the slat from inside, mark around it, and drill refence holes for attachement. Then hold it in place, and have a person on the outside to attach it with, screws, clenched nails, or rivets starting from the middle and working towards the ends to draw it down as you go.This would be a whole lot cheaper, quicker and if done neatly, would not effect the value of the boat, in fact it would appear as if it was part of the original construction, of which it could have been.

A comment on ma melee's post, nothing against him, but about the method he states from a article.The method described is nothing but sloppy workmanship at it's best. Appearantly someone built a diesel duck and did such awfull fitting of the planks, that there is no need in learning how to caulk the seams. Because appearantly you can stick your finger in the cracks and it would take rope to fill the cracks. So they applied goop, and door skins and glass. They just piled krapt on top of krapt to try and seal the hull.I pitty the next person that might buy that boat, and if they are smart enough to have it surveyed, the surveyor is going to tell them it is not worth squat, avoid it like the plague.All because someone would not take the time to do it reasonably right. This is not wooden boatbuilding but backyard butchery.

When garbage like this fails, particularly on the 2nd. owners and lives are lost, that will result in big law suits and will give the coast guard their foot hold to inspect all home builts and to sit standards and periodical inspection during the construction stages.Thus will end the back yard boat builders, or the title will state NON TRANSFERRABLE. Methods like this should be condemmed by one and all. This ain't horsehoes and getting close doesn't count, if you are not up to it, then you shouldn't be doing it. Boats are not model airplanes.And yes someone's life could depend on your workmanship, or lack of.

Tom Robb
03-06-2006, 04:09 PM
Hmm, I'd have supposed that anyone who calls himself, or is thought to be an excelent shipwright would know exactly what the boat needs and how to do it in a workmanlike manner.
No matter...
Listen to Cleek. You may take exception to his manner if you like, but he's worth listening to.
And if Bob Smalser, Dave Fleming, or RGM jump in here w/advice I'd listen and mark them well too.

[ 03-07-2006, 05:17 PM: Message edited by: Tom Robb ]

03-07-2006, 08:25 PM
I to have some "expert shipwright" stories, and never tire of hearing others. Most people that have been around boats and boatyards any length of time and have even a rudimentary knowledge of whats proper have seen firsthand what some of these misguided soles are doing, or have done. It's scares me !!!