coldmolding vs traditional construction (carvel)

[Georg Moe]

Greetings,
A couple of months ago I bought the book "Details of classic boat construction" by Larry Pardey, quite a nice book! However, one starts wondering about modern construction techniques, and thinking that the only possible way to build a boat is the traditional way.
For those of you who have read the book:
It seems that Pardey is extremly concerned about delamination and repairability of cold molded hulls, and to some extent the costs (labour and materials) of cold molding vs. traditional construction. For the last 10 years I have thought that cold molding was the 'ultimate' answer for the amateur :D , but reading his book I start to wonder if I have missed something. One gets the impression that cold molded boats have a potentially short life, after they start delaminating, well, throw them away (or burn them).
Pardey also points out the need for good working temperatures. Living near Oslo/Norway, and having to work out doors, cold molding represents a challenge during the winter (I would assume) ;) Would that basically mean that cold molding is not suitable for the amateur unless it is an extremly small project here in the north ('nice' temperatures between May and September)? Traditional construction seems to be more independent of the climate?

Kind regards,

Georg

[Andrew Craig-Bennett]

Georg, I have that book too; it is indeed a very nice one.

There is another excellent book written from the opposite point of view, but also written by a hugely experienced cruising yachtsman and professional boatbuilder, who also wrote the book around the construction of his "dream ship" - the book is John Guzzwell's "Modern wooden yacht construction", which contains equivalent details of cold moulded construction.

I have seen several cold moulded boats pass through boatsheds for repair near where I live (we have some very good wooden boat yards, here) and they tend to show a common defect. If fresh water enters the topsides at the rail or deck edge, it always seems to find voids. It travels down these, sits between the veneers and eventually causes damage that requires a major repair. But on the other hand, these repairs are always possible.

I think the climate is a very big issue. If I was building a boat in the tropics, I would be very tempted to use cold moulding, but in Northern Europe I would think more of carvel plank on frame construction.

[Keith Wilson]

Larry Pardey is a fine traditional boatbuilder. I'd give tremendous credence to his opinions on traditional plank-on-frame techniques. He also has strong anti-epoxy opinions (prejudices, perhaps) which are at variance with a lot of other people's, people who have a lot more experience with that type of construction than he does. Maybe he's right, maybe he's not. Wood-epoxy boats have been around for quite a while now; their record is pretty good. I have never seen nor heard of a well-built cold molded boat that delaminated, although that doesn't necessarily mean there aren't any. One CAN repair damage, although the techniques are very different than with traditional construction. Personally, I'd trust Larry Pardey or Bud Macintosh on how to fit floor timbers, but John Guzzwell or Meade Gougeon on cold molding.

As far as the weather goes, we have a similar problem here in Minnesota. (There's a good reason so many immigrants came here from Norway.) Some epoxies are usable down to maybe 40F (3C), but cure time is awfully long at low temperatures. Any kind of epoxy requires a specific temperature range for the chemical reaction to work correctly. Working on an epoxy-glued boat year round requires heat and some sort of a shelter to keep the heat in; there's no way around it.

[ 07-09-2004, 04:43 PM: Message edited by: Keith Wilson ]

[Frank Wentzel]

In a recent edition of their free magazine "Epoxy Works" the Gougeon's speak of a recent race, the Mackinac I believe, that was hit by a sudden storm. A number of boats were damaged but their "Adagio" was unharmed. Adagio was their first all epoxy, no fasteners allowed, cold-molded boat, which was built over 30 years ago. I think this says a lot about what can be done. I think many disasters are built when people adopt a building technique then change it based on "common sense" and "this should be just as good". If you don't understand the technology or haven't thoroughly tested your proposed modifications you are asking for trouble.

/// Frank ///

[Dave Gray]

I read one of his books, it might have been this one. Is this where he details building a hull from teak? After reading it I had the same questions. He was mostly worried about epoxy delaminating or coming apart at high heats found in the tropics, and couldn't get an answer that was satisfactory to him from any of the epoxy vendors.

It is true that epoxy will soften at high heats. Dynamite Payson mentions in one of his books that painting an epoxy/glassed boat is not a good idea but he was mostly worried about print through of the weave of the fiberglass.

Which way I would use to build a new boat (assuming I ever complete the first) is still one of those questions I have been in a conundrum over

[Meerkat]

I've read that CM has a bad reputation in the UK due to some shady builders who did not do a good job on early CM offerings there.

"Normal" epoxy will start to have heat problems at around 140F, but there are some (heat cured) epoxies that are good to over 300F.

Unless you paint a boat's hull/deck in a dark color, I would doubt that it gets hot enough, even in the tropics, to be of much danger to a boat built with "normal" epoxy. Otherwise, where are the reports of boats in Florida and similar places falling apart due to heat?

[Bob Smalser]

Anecdotal...but I routinely use epoxy in temps of 30-40 degrees (otherwise I wouldn't get much done in winter) with zero problems.

I also store mixed epoxy leftovers in the freezer for reuse the next day (and sometimes the day afer that)...also with zero problems.

But any epoxied hull baking in the Gulf of Oman sun when it's 130 degrees F in the shade gives me pause. That's why the dhows in dozens of traditional yards I've visited throughout that region are still planked today with thick, solid teak heartwood and caulked with coir and a shark oil/lime slurry. Not a goop friendly climate. Fiberglass works...but even that doesn't last as long as teak. Aluminum has its own problems there too.

[ 07-10-2004, 12:39 AM: Message edited by: Bob Smalser ]

[bainbridgeisland]

Mr. Pardy is an excellent plank on frame boat builder. I have seen his work; he obviously understands the subtle requirements that will produce an outstanding timber on frame vessel. I would like to respectfully point out that until he has gained the same level of knowledge about other methods of construction, he does not have the full picture.

A well designed and built boat of ANY material that is correctly maintained can give outstanding service.

I have repaired or supervised the repair of a handful of cold molded boats. It is more time consuming than repairing plank on frame boats. I would estimate it took 20% more time without paint. Paint repair would vary with the paint system.

My experience is that cold molded hulls do take longer to build than caravel hulls. However, strip planking usually takes longer than cold molding. With knowledge and skill the time differences are not large though. Besides, the hull is only 20% of the job of producing a boat if it has accommodations, electrical and power systems.

I think good quality materials can be found for any standard boat building method. Sometimes we have to work pretty hard to find them though. Cold molding requires smaller timbers. This allows the boat builder to trim out local flaws. Thus, workable materials are somewhat easier to find.

Epoxies with elevated temperature resistance have been available since at least the early 1960s. Before 1960s, hot molding was very successful and is very similar structurally. Some builders have chosen epoxy by price and not by performance. This would produce the same results as substituting white pine for white oak, an inferior product.

I thing Georg is right about cold temperature being less of a problem with plank on frame construction than for cold molding. The fellows I apprenticed under used to complain when the temperature got above 55 degrees because it wasn't "working mans weather". Working on plank on frame boats with the temperature in the 20s is not really a problem if you keep out of the wind and active.

Most epoxies have a problem with cold temperatures. While it is true that some will cure at very low temperatures, such properties severely limit your choices. There are more than 1,500 curing agents for epoxy. Also, some vendors specialize in delivering custom formulations. Chances are good that the right epoxy exists for boat building in temperatures below freezing, but you probably won't find it in a boating supply catalog.

A well maintained cold molded boat will last as long as any other timber boat. Hot molded boats are still with us from the late 40s. They are structurally the same as cold molded boats. Epoxies have been around as long too. The real question is: Did the builder do a good job with good materials. This question is answered in the same way as with carvel planked boats, knowledgeable inspection.

There are aesthetic differences between construction methods and also real weight, stiffness and damage tolerance differences. The job of the designer and builder is to produce the correct mix of properties. To say that any standard material or method is not suitable to build boats is just plain ignorant. Bad builders and bad designers produce bad boats; it is not the method by itself.

Don't get me wrong here, my personal preference is to build plank on frame boats over any other method, I enjoy the work more. As a professional though, it is my job to know how to produce high quality boats from any standard material or method. I apprenticed as a plank on frame shipwright followed by 3 years building cold molded boats and then a few years with fiberglass. This was followed by more education, two years as a yacht designer and now a Naval Architect.

[RodB]

I finally got a a copy of the book you mentioned and also had some of the same concerns.

In my future boatbuilding I seriously will consider using the newer (gap filling) resourcinol for "stressed or torqued" bonds, ie., such as laminating the mast . I am quite comfortable with using epoxy for coldmolding or strip-planking if done properly and sheathed properly. In most normal hull constructions the forces are spread out well and the sheathing barrier is the most important factor for longevity assuming your scantlings are correct.

I also think that when one is in doubt, apply fiberglass cloth in lieu of just double or triple coating with epoxy. You get a much better barrier to resist moisture and heat cycling that way. I have personally seen epoxy only coatings fail here in the hot, humid climate of the Texas Coast and I am confident that glassing the "rotted'" areas would have made all the difference. THere were other factors involved but the fiberglassing would definitely have made a difference.

My next boat will be either strip-planked or cold molded or some of both, and I must say that Pardey's book made the process of building a traditional boat of that size seem at best a daunting task.

The skill and knowledge required makes it seem (at least to me) a very difficult project with out at least access to an experienced boatbuilder for consulting and/or direction. I don't have the time to spend several years learning all of those techniques ( over 50 years old) and usually I would just jump right in and figure it all out. My better judgement here tells me it would be a much better project with access to some experienced consultant at key intervals...just my take on it for now.

Although all of my experience is in stitch and glue boatbuilding I am constantly reading and trying to educate myself on the methods of traditional boatbuilding and have no plans to stop learning about it any time soon.

I also am quite interested in hearing all about the many many successes of epoxy built boats and also what are the real facts when a failure is found. I live in an extremely hot enviornment and have decided the well built cold molded or strip-planked boat will require the least manitenance and stand up the best.
I will also make the necesssry efforts to protect the finish of my boat and make damn sure the ventilation is adequate.

I know of two boats close by built with epoxy, one my own and the other by a really good professional in my area. I will be keeping a watch on both to see how they withstand this hot climate.

I may have come to some mistaken conclusions but thats where I'm at for now.

RB

[ 07-10-2004, 02:35 AM: Message edited by: RodB ]

[Andrew Craig-Bennett]

I'm not aware of cold moulding having a poor reputation in the UK. Quite the reverse, in fact -not only was hot moulding pioneered here by Fairey Marine (I have one of their dinghies) but Clare Lallow were an outstanding builder of resorcinol bound cold moulded hulls in the Sixties - before the Gougeon Brothers and epoxy were so much as heard of. Many British offshore racers of the 70's era were coild moulded, including a couple of Ted Heath's "Morning Clouds". The Fairey hot moulded boats have an outstanding reputation for durability, and the resorcinol cold moulded boats have done very well too. However these boats are built of veneers, not veneer over strip as in the modern methods, and were correspondingly labour intensive.

[mmd]

When one thinks of constructing a boat of a given material, one must consider that each material has its own characteristics, strengths, and weaknesses. These characteristics must be accommodated by the boatbuilder via using different tools, different methods, and different environments for each material. It is quite apparent that one cannot build an aluminum boat using steel welding methods, even though on the surface it seems to be the same technology and tools. Similarly, although traditional carvel boatbuilding and wood-composite boatbuilding seem to be very similar, they are quite distinct technologies and require different methods of building, including the building environment.

Carvel construction requires that the wood used has a relatively high moisture content so that the timbers are somewhat flexible during building and so that the physical swelling of the wood as it transitions from building ways to water is minimal. Since the average atmospheric humidity on most coasts is just about the same as desired wood moisture content for building traditional boats, enclosed shops were a requirement only for worker comfort and not a necessity for the boat under construction. If a bit of rain or snow occasionally landed on the work-in-progress, it didn’t cause any problems.

Cold-moulding a hull is a totally different technology. It is much more akin to fiberglass boatbuilding than traditional wood in that it requires a structural material that must be clean, dry, and dimensionally stable during and after construction. Preferably the wood for cold-moulding should be around 7 – 12% moisture content. To keep the lumber stock and the boat being built at this level, a building with a controlled environment is needed in almost every locale that boats are built if high quality standards of construction is desired. As well, the resins used in cold-moulding are temperature-specific so working temperatures need to be controlled, and that is hard to do outdoors in most places.

To put it another way, building with resin & wood is similar to building in resin & glass fibre, and you don’t see many GRP boats being built outdoors in temperate climates. For good quality wood composite structures, a controlled environment is necessary, and that can only be achieved indoors. I know that hundreds and thousands of boats have been successfully cold-moulded in backyards and on beaches, but it’s sort of like premarital sex without condoms – the odds are in your favour that nothing will go wrong, but when it does go wrong the results can be catastrophic. It is better to be safe than sorry.

As for cold-moulding resins failing at high temperatures, well, if you use the wrong product for the intended use, you sometimes have problems. If you know that you are going to spend some time in hot tropical waters, it would be reasonable to contact the manufacturer of the resin you intend to use and have their tech department assist you in selecting the proper resin and instruct you in how to use it properly. After all, if you are going to drop fifty grand or more and a few thousand manhours on a cruising boat, the time & effort spent to do it right is miniscule in comparison. If you’re going to the tropics, don’t paint the boat black; don’t have dark mahogany cabin trunks, don’t skimp on UV additives. Think about how you intend to use your boat and build it accordingly – it’s not rocket science, just chemistry.

As for longevity, how long should a boat last in it’s original structure? Sure, there are traditionally-built boats out there that are 50, 75, 100 years old, but an existing hundred-year-old boat is a statistical anomaly; thousands of boats just like it have mouldered away to nothing in that time. And the ones that have lasted usually have very little of their original structure left. (Can you imagine a Model T owner bragging about his car if it had the “care & maintenance” that a classic Herreshoff has? “Sure, it’s all original! Why, she’s only had the frame strengthened, she’s got all new sheet metal on the body, the upholstery has been all replaced, the engine has been rebuilt twice, and she’s on her third canvas roof. Yep, she’s all original!!”) So reasonably, you want a boat that will last your lifetime of use and maybe a bit more; say, thirty to fifty years. Cold-moulding technology has not been around as a proven method for quite that length of time yet, but it is closing in on it and I think that there are plenty of examples of these types of boats out there that are going to prove the longevity of the method. And I don’t doubt that there will be a few that are built with care and proper methods that will be given the care and reasonable use to last a century.

[Tomcat]

At a practical level cold molded boats do need to be built inside. I would recomend Hub Miller's fabulous book, which starts with the required shelters, and how to build them, and moves on from there. The shelters required aren't any much different than the kind of shelter one sees for any boat building project. If you are contemplating the size of boat that requires it's own shelter and can't be built in the basement, you have a large project in hand, and while it may yield to building outdoors, will drag on indefinetly without some shelter.

If you are thinking of cold molded as in veneers over frames and stringers as the Gougeons and Guzzwell perfected, you are largely considering a method for which the material has disappeared. It must be out there somewhere, but getting it will cost you 5-9 times what the identical veneer costs in a plywood panel. So before considering too much longer a particular method, see if you can find the veneer required at a tolerable price. Or can saw it yourself. In the last ten years I haven't seen any of it for sale. Sure you might find it at 2 buck a square foot, but at that price a sheat of 3/4" ply would cost $576. The dean company used to sell it at 1/10 that price.

[Paul Pless]

This topic interests me from a maitenance perspective. How do coldmolded hulls hold up to having their paint stripped and their bottoms scraped? I'm guessing that a heatgun and/or chemical strippers are out of the question. Does this leave only handscrapping or sanding to remove old paint? I've also heard that coldmolded boats that use a sturation technique are relatively impervious to teredos; is this true? Can a coldmolded boats bottom be copper plated? How would the copper be attached?

many more dumb questions to follow.... :D

[Andrew Craig-Bennett]

The ones I know are in two groups. Some get scraped and stripped just like ordinary boats. The others had a sheathing applied when new (often Cascover - nylon cloth in resorcinol glue) and have to be treated gently.

[Ross M]

I too thought that cold-molding was considered problematic in the UK, based on an authoritative and logical comment about 2/3 down this thread:

Haven: Cold-Molded versus Carvel (http://media5.hypernet.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic&f=1&t=001716&p=)

smile.gif

Ross

[ 07-11-2004, 07:47 PM: Message edited by: Ross McDonough ]