Carvel or Strip Planking

[Stubing]

Greetings Forumites!! I'm getting close to starting a 34' Lobsterboat (or rather having it started to ensure completion in this decade). My question is what are the pros and cons of carvel and strip planking?
In my view nothing is more beautiful than a carvel planked boat but, there's alot of waste (Yellow Cedar) and I assume more labor hours especially when you consider caulking. Strip Planking may be stronger with the fastenings between planks, use less wood, eliminate butt blocking and save labor hours. What do you, with more experience than I, think?
Also, on a large boat, is the cove/roundover method viable? And should you goo or put nothing at all between planks? Thanks for your input.

[Bob Cleek]

Well, I think if you ask anybody who's familiar with both techniques, they are going to tell you it's six of one and a half dozen of the other. For my money, unless the boat was DESIGNED for strip, I'd go with carvel every time. Hulls need to be designed for monocoque construction. If you strip plank or cold mold a hull shape that was designed for plank on frame, you will inevitably have stress problems at the garboard seam, since the stresses will be focused there by the monocoque hull. If, on the other hand, the shape is such that a keel is merely attached to a "round" bottom with the monocoque construction continuous across the keel bottom, monocoque really delivers the structural advantages it is known for.

As for your concerns, I think strip offers no savings in material costs. Whatever you THINK you are saving in wood (you won't...) will be greatly exceeded by the cost of adhesives and coatings. In the end, if the boat is a traditional type, the strip or cold molded version isn't likely to hold its value like a traditionally planked carvel hull, either. Cold molding, especially, uses much, much more wood than carvel, since you have to factor all those saw kerfs when ripping the laminating stock, although you can use funkier wood and get by. With strip, you will be ripping all those strips and cutting a lot of molding edges and will have to work with clear stock or it will all be busting up on you. Both strip and cold molding will require finished stock, so there's another 1/8 to 1/4" off everything you buy. That's a big cost factor, so no savings in wood costs. Carvel, on the other hand, can be got out of rough cut flitches, curved so they are closer in shape to what you need, giving you a better hunk of wood, grain-wise, and less waste.

As far a labor goes, you can hang a traditional carvel planked hull a whole bunch faster than you can a strip planked hull, and light years faster than cold molding. And, down the road, when repairs are inevitable, carvel wins hands down. Cold molding you can patch, but strip is "forever," LOL. You don't want to go there! Especially if you've so carefully nailed every strip down on top of the other!

[Stubing]

Thanks Bob,
I was thinking of strip planking over steamed oak with no epoxy in or out and covering this with good old fashioned paint. I wasn't planning on a cold molded boat. The designer that has been working on this threw it out as an option worth considering. His suggestion was to edge nail each plank to the one before it and screw to the frames. I do see your point about carvel's advantage in repairability. Thanks for your input. Stu

[Mike Field]

I agree with much of what Bob said, Stu, but not all. In my view, strip-plank is the simplest possible method of construction -- especially important for a home builder without much boatbuilding experience. (It's really pretty difficult to go wrong with it.)

But --

The strips should definitely be glued together as well as nailed.
The hull should be sheathed.
You need a powerful lot of glue, not to mention Dynel (preferably) or other fabric.
It's messy work.
There's no time-saving to be gained during construction.

Having said that, a good stip-planked job --

Is indistinguishable from carvel once painted (you wouldn't think of finishing it bright.)
Never needs recaulking.
Is fully waterproof. (As I've said here before, my strip-planked 3-Tonner doesn't have her bilges pumped, they're vacuumed.)

I'd suggest you give it serious consideration, and try to find a few strip-planked hulls to look at before you decide.

[Ross Faneuf]

Hey, Bob! Let's start an argument! Well, maybe it won't be an argument smile.gif

While it may be true that garboard stresses rise too high in some boats naively converted from planked to some form of monocoque, doesn't that just mean that someone has more-or-less copped out on the engineering? Garboard strake problems in traditional planking can be seen as evidence of the inadequacy of traditional techniques to provide adequate longitudinal stiffness; consider that much of that stiffness is provided by the caulking itself, which attempts to provide enough friction between the planks to slow down the boat's tendency to behave like a basket. If you mate up a rigid (monocoque) hull shell with a keel/backbone through a flexible joint, you're begging for trouble.

I've noted in several conversion designs, and even the design of my own boat, that people don't always engineer the connection between the monocoque part of the hull and the backbone very well. If the monocoque is continuous with the backbone acting as an internal stiffener, and as adequate foundation for things like keel bolts and engine beds, well and good. Many boats are essentially 2 monocoque halves joined by the backbone, however, and then the engineering of the joint is critical. But I've seen too many designs with a backbone dimensioned for traditional planking, often complete with rabbet, where the hull itself is strip plank or something like it. This is likely to be inadequate.

The design for my own boat, Ceol Mor (stip planked w. backbone), was done this way, at the insistence of the guy who commissioned the design, and over the objections of the (experienced) designer. The customer was convinced that only a traditional rabbet would do, even where that meant there was this stubby little landing for the strip planks. I redesigned it on the loft floor with no rabbet (the strip plank runs to the faying surface of the backbone all around) so each plank was landing on 3-5 inches of backbone, where it's both glued and screwed. And at that, I had to increase the molded depth of the backbone.

I think this is because too many people don't understand what the rabbet is doing. One of its main functions is to provide a seam which can be caulked, so that the join between planking and keel isn't a (brief-lived) exotic fountain. In terms of connecting planks to the backbone, it's weaker than a plain bevel of adequate size. But you've got to have it if you have a seam which must be sealed by caulking.

Bob is correct about most of the disadvantages of strip planking; it does indeed use up more stock, and it is slower (that is, if you're really good at carvel planking). Note, though, that there's also a fair amount of waste with carvel, as you have to get the planks out to the correct shape; you can help yourself a lot here by buying live-edge stock and working with the natural curves, though you won't believe how many times you pick through the pile looking for the right pieces.

Strip requires less skill than carvel, and the stock doesn't have to be quite as good. It will go faster as you get experienced (as will carvel).

If you epoxy between the strips (which I recommend), you can use plain-edged stock. I am convinced that molding the edges is a waste of time which actually makes for a worse job at the cost of more labor (this may not be true of, say, a kayak but I'm sure it's true of larger boats). The biggest drawback to epoxy is that you have to be quite fanatical about cleaning up as you go, or you'll have an unbelievable mess. Also, you'll almost certainly want to work upside-down, presenting you with the challenge of turning the boat over. Still, it's certainly doable; Ceol Mor is just about the same size as the boat you're talking about, and I managed.

[ 06-26-2002, 02:49 PM: Message edited by: Ross Faneuf ]

[ishmael]

To sort of quote Joel White, "The problem with strip planked boats is that they always look strip planked."

A bunch of good information here.

A glued, strip planked hull, properly engineered, is going to be stronger in the clash of stresses the water is. But most failures, in new construction, don't happen in the hull anyway, rather in the house or deck structure.

Strip originated as a cheap means to build. Some Maine fisherman, cum farmer, cum house carpenter, saw the potential in the wane off white pine logs, which he could haul from the local mill for free. With the advent of modern adhesives it became a superior way, from a strictly engineering perspective, to build a hull. Life is not all engineering.

Building carvel will make your hands and heart sing in the wood; it won't have you living in tyvek overalls; and it will make sex with your wife better too.

The choice is yours.

Jack

[Stubing]

Okay Jack you sold me!! Cavel she'll be.
Thanks for everyone's help.
Stu

[Beowolf]

Ironically enough, I chose to build a strip planked design because I could get an unlimited amount of rippings from a local saw mill for free. How about that.

Take Care.

Jeff.

[Memphis Mike]

Watch it leak like a sieve all the time.