Designing for ferrocement vs wood or steel

This just isn't correct. Wooden boats, even cored wooden boats will tolerate neglect the least amount of all hull material choices.

Bruce you are absolutely correct, a well made ferro design follows a well design plan. There aren't many that design good ferro boats, but I've seen a few and one of the biggest pit falls is the armature. This is the key to a good ferro build and the first place a home builder will skimp. Chicken wire just doesn't work, but many have tried, which just helps fuel the distaste for ferro.

 

One MUST, it´s the only possible way Thudpucker! At least when we are talking cold moulded or strip planking.

Sheathing a conventional built boat is a different animal, but a newbuild should (S&G and cold moulded), or must (strip planked) be glass epoxy coated!

What I do not get, is the change from the heaviest possible material to the lightest in hippo´s plans???

Regards
Richard

 

It's a matter of finding a hull material that will not only work and be minimal on maintenance, but is also something I can comfortably do myself.

The reason I was considering FC is that my parents did at least one back before I was born and so I know more about it than some. The downside I'm seeing is that it HAS TO BE DONE RIGHT THE FIRST TIME and has very little tolerance for error.

Fiberglass or some sort of fiberglass composite is attractive from the maintenance standpoint, and the inherent buoyancy of foam sandwich is also attractive. Depending on which technique I used I could do it at home. I also have some experience with it

Wood has the advantage of being something I'm familiar with, but I'm concerned about how hard it will be to maintain.

The sailboat I'm working on restoring at the moment is something close to 40 years old (Early 70's vintage Macgregor 22') and has not been maintained, well, much at all. So far I've replaced all the wood, all the wiring, most of the stays, all the blocks, the upholstery, etc, etc. The hull on the other hand just needed an hour or so with a pressure washer and was good to go.

Contrast that with every trip to the marina and seeing people out there stripping down wood boats, caulking seams, replacing rotted timbers and generally putting a massive amount of effort trying to keep them above the water.

Steel has the advantages of durability and ease of maintenance, but I know absolutely nothing about working with it, and it also appears to be the most costly material to work in.

I know that the hull is supposed to be one of the cheaper items in construction, but once I get a deck on I am much more comfortable with the interior finishing. I do a lot of work with recycled materials and while some things need to be bought new (Heads come to mind, ew) a lot of used pieces are perfectly suitable.

 

I have to vote for wood. Very fast build with proper design, extremely easy to change and modify (difficult with f/c and steel after painting and insulation), good insulator, excellent strength to weight ratio. Cheapest possible way to build a one-off of traditional type is plank on frame. Cold molding, and I mean NZ style with weldwood and not epoxy, is a close second. Saw 2 NZ boatbuilders loft, set up and plank a forty foot on deck cold molded ocean racer in 8 working days.

 

Also remember all those people are probably working on OLD wooden boats. A good wood boat, even a traditional work boat, has a working life of 25 years or so, then the maintenance becomes repairs and rebuilds, not just painting and caulking. Any wood boat, like a person, after 75 years old or so, is a whole different thing than when young.

 

cthippo,

you might be impressed to see that GRP is not maintenance free, as many people assume! It is just not as obvious when the boat becomes a gonner!
I bet London for a brick that your boat has some water in the laminate after decades of service. Then the fatigue of GRP is a severe problem after such time, etc. etc....

When I walk through the marinas, I see more touching up done on the GRP boats than on many steel, Alu or even cold moulded vessels.
Of course the classical plank on frame lasts forever when you are willing to maintain the boat excessively and to replace parts after two decades.

The cold moulded (the proper way, using epoxy!), or strip planked boat (again using epoxy), is as maintenance "free" as a GRP boat, but has much less fatigue issues and no water ingress.

So, my recommendation would be a modern wooden build boat. Make the best out of your skills and tools!

Foam core is not for a hombuilder, it is already difficult to manage for the pro´s. When you screw that stuff up, which is really easy to do, you end up with expensive scrap.

Do not use woodweld! Epoxy is the superior material.

Regards
Richard

Do you refer to strip planking here? Because you say "planking".

 

The NZ guys used the Weldwood glue for a bunch of reasons, first the low toxicity and also the much lower cost. They'd mix a big jug of it and use it half a day, then mix another for the afternoon. No having glue go off in the pot and smoking like epoxy can do if you get slowed down. It's a stronger glue than epoxy if you have tight fits and strong clamping, and the 1/8" lams and stapling approach gives that. After all the laminating was done and the shell off the form, the inside was sealed with 3 coats of epoxy for water resistance before painting, and the outside coated with Dynel and epoxy.
When I was an apprentice in the early '70s we used Weldwood on every sort of glue job from masts to joinery and most of them are still around. It's not a filler glue though, and you can't make lots of different mixes out of it like epoxy.
Epoxy is wonderful and I use it a lot in repair work of everything from restoring a smashed lapstrake rowing gig, to building an otherwise impossible stem apron in place in a big workboat, but for cold molding a new vessel I would use the NZ method and Weldwood glue for the laminations, coated and finished with epoxies, painted with Awlgrip polyurethane paints. I have a nice little cutter in mind....
Epoxy makes wonderful and expensive cold-molded boats, but the Weldwood-type plastic resin glues which are mixed from a powder with water, have been around a very long time and are actually much easier to work with than epoxy. Again, I have worked with both for 40 years.

 

No strip plank. Built over mold with ribbands. The 'planking' was six each 1/8" laminations to give 3/4" hull thickness, all at 45 degrees to the keel, one straight edge and one curved edge on each lam, lams were gang-cut about 6 at a time and were very well fitted in every layer. One guy each side of the upside-down hull going like crazy and the darn thing just sprouted to life in a week. Neatest thing I ever saw. About 6 weeks after launching it went racing to Hawaii and did well.

 

Weldwood plastic resin is troublesome across several areas. You have to use it above 70 degrees, the joints have to be well matched, clamping pressure must be 50 PSI or better on well fitted parts and 150 PSI or better on roughly fitted stuff. Then there's the DAP debate. Since the glue was purchase they have given up on certain government certifications and changed the glue formula. The net result is a product that should be tested and used with caution on a per basis need.

Considering what epoxy brings to the table, you'd be still to not invest in it.

 

We used that weldwood stuff on very small boats to lay the first strips along the frames, but thats it.
In larger scale and on a more professional engineered and crafted method Epoxy is the better product, no doubt.
Being not in that business as long (just 36 years now), but after many, many thousands of tonnes of boats built, I do NOT recommend weldwood.

Regards
Richard

hmm, PAR typed faster again.........

 

Since my experience with Weldwood was many years ago (I've used epoxy since the 80s in the repair business), and second hand when I viewed this NZ building method, I must agree that epoxy is all around superior for the job these days. I'm a plank-and-frame guy myself and used WW for spars and doors etc, not hull building, except for a strip plank job we did under contract and used what was specified which was WW at the time instead of Resorcinol (we called them brown glue and purple glue at the time, because this was before wide spread epoxy use and no one knew much what it was).
One yard I worked in for 5 years as the head wood guy only did laminated repairs (no steam bent frames) and only used West systems, so that's what I still use today. It's very nice to be able to make good, reliable, versatile joints, fillets, coatings and more with epoxies. Just watch out for the sensitivities that can cause problems with proper protective gear at all times.

 

Epoxy suits the NZ method of 45 degree lams nicely, but would be easier if a third person could mix and deliver glue to the two fitters so all they did was fit and staple. W/ epoxy the fits don't have to be as precise and the temperature tolerance is greater and of course the epoxy doesn't do well with too much clamping pressure so again is more suited. I was just saying what I saw done. I am not much of a new build guy, specializing in repairing the things the builders got wrong.

 

Well, we make the entire boat with epoxy (cold moulded).

And one should avoid direct skin contact with uncured Ep, that is right. But that was it! No additional effort is required, just some latex gloves in case one cannot work clean.

 

Circumnavigator, Designer, Builder John Guzzwell got so sensitized after many years of laminated building with epoxies (up to 130 foot vessels) he switched to urethane glues. I have had no problems, but some people are quick to get allergic.

 

Some people get senstized to water, who cares.

None of my several hundred labourers got sensitized by so far, in 36 years. But as mentioned, direct skin contact has to be avoided. And that is the only way to get sensitized by Ep.