Wood Boat Construction: Frames, Planking, Fasteners, etc.

The Bones of a Canoe
The Bones of a Canoe

I purchased the December 2010 issue of Wooden Boat magazine the other day at West Marine. As a brokerage we sometimes used to advertise in it especially when we had a wood boat for sale. These days that is pretty rare. I have been thinking about wood boats a bit more recently, so here is an article on the basics of wood boat construction. When talking about wooden boat construction, there is a basic set of questions and associated terminology that are wholly different from those of glass techniques. This article goes through the two basic questions and lists possible answers for each.

What are her bones?
The first question relates to the platform which gives the hull structure. The framing as it’s called is either steam-bent, sawn, or composite. Most small to medium size employ steam-bent bones which means the wooden ribs are soaked and then bent via heat to form the dinosaur like backbones of the hull. They are clamped in place and when cooled spring back only slightly. Steam-bending frames prevents them from fighting to spring free of fasteners and minimizes the risk of cupping or cracking in the future.

Wooden Boat Magazine December 2010
Wooden Boat Magazine December 2010

Sawn frames are made up of one or more piece of wood cut to the needed shape. They are more common in large wooden boat construction when steam bending would be too difficult to handle. It is a more complex method and takes more time to get right because you have to cut and measure. Finally, composite frames usually steel is a final way to provide a framing structure. Wood purists might not want to purchase a composite constructed boat. The worry with steel is rust which will eventually happen. With all these methods (steam-bent, sawn, or composite), the real key to quality is the builder skill not so much the technique.

What kind of planking does she have?
Carvel, Lapstrake, strip, and cold molded are the common choices. Carvel construction is the most traditional and describes a method in which wood planks are only fastened to the framing without any overlapping. It makes repairs easy as you only have to remove the fastening to the framing. Fasteners could be monel, bronze, and stainless steel in order of quality. A common example of carvel construction is double planked, mahogany over cedar with steam-bent oak frames. Another common planking wood is long leaf yellow pine. Tar paper is used between the two layers of planking. Afterwards, the seams are caulked.

Carvel vs Lapstrake Planking

Lapstrake planking is similar to carvel except that the planks overlap and are fastened to each other. This technique is usually used on smaller vessels. The “lap” adds extra strength acting like a stringer to stiffen the hull but leaves a gap that collects dirt and debris. Strip planking melds old and new world wood techniques when set in epoxy. All the basics are the same as carvel except that the strips are narrower and are fastened athwartships to each other. Construction is faster, less expensive, and requires less skill than carvel because you do not have to shape the planks. Finally cold molding involves laminating veneer over a mold. One way is to combine this technique with strip planking and mold veneers over the strip planked hull. The veneer is laminated in place with epoxy.

If you have approached a wood boat or if you have one and people approach you, you will recognize the common terminology above. Mostly the important factors are the builder skill and wood quality not so much the techniques used.

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