Building a Cedar Strip Canoe: The Details: Lofting the Plans

This hubpage will start a new series of pages documenting the details (as diligently as I can) of building my next cedar strip canoe. If you plan to build a canoe I woud advise purchasing a book. It will contain much more information that I intend to provide here. I can not guarantee new information will flow onto these pages very quickly but as I proceed I will add new pages, The descriptions will be my own words and experiences (and mistakes) as I proceed with the build.

I decided to build another canoe of a different, more modern design. I chose the Freedom, which is a modern with an efficient asymmetric hull. This means the hull has a sharper taper from the center toward the bow than it does from the center towards the stern. The slimmer forward profile helps increase speed while the wider aft section helps improve tracking. So goes the theory. My goal is build this canoe somewhat lighter than my last, although I still want it to be rugged enough for canoe camping and wildernes trips. I am thinking 55 lbs is a good target.

So the first step was to choose a design, which I have done. It was selected from the various designs provided in Canoe Craft, however I will shorten it by about a foot.The next step is transfer the numbers in the tables onto paper so that the shape of the hull can be traced onto ply wood for the forms. This process is called Lofting.

Lofting:

I will describe what I did, but another description is available at the link below. On a large sheet of paper layout a grid of 2 inch X 2 inch squares. About 18 horizontal and 10 vertical. Mark a baseline and a centerline. The horizontal lines are water lines (WL) and the vertical lines are buttress (butt). Since the hull is symetrical side to side only one half of the hull needs to be plotted to define it's shape. Once the first half of the hull is traced for a particular station, the outline plan for that station can be flipped about the vertical center line to trace the other half. Station lines tend to get crowded together near the bottom so it would be a good idea to draw half of the stations on the right of the center line and the other half on the left. Or use more than one sheet of paper.

A good description of the lofting process can be found on: http://www.bearmountainboats.com/offset_lofting.htm

An example of a plot for station 8 is shown. Measure from the center line along each horizontal water line for the "WL" values in the offset tables, then make a mark. Measure each vertical buttress line for the "butt" values in the offset tables, then make a mark. For the sheer draw a horizontal line at the distance from the baseline given in the table of heights. Then use the distance given in the table of half-breadths to mark the sheer along that line. The stem plots are created the same way by just using the WL gridlines.

My plan for the next step is to trace the half hulls on poster board to create templates for tansferring the hull outlines to partical board which will be used for the station molds. At the bottom of each station there needs to be a portion that will hold the station moulds above the strong back and which will allow the stations to be attached to the station blocks on the strongback. I plan to use about a 4 inch extension on each mold.

Shown is the strong back from my last project. It has the station blocks attached.