“Lofting” the Lines
Special to Eskimotom.com
For the stitch and designs, lines aren't lofted in the traditional boat building sense. A majority of my canoe and kayak designs are created from two pieces of plywood. Lofting these plans entail recreating the "Plank" lines shown on the plans but in full size.
Begin by first measuring and cutting 4 x 8 sheets in half lengthwise. Make sure to mark the factory edges as they are square and your lengthwise cut may not necessarily be true. The next step is scarfing together the four lengthwise pieces to give you two pieces with finished dimension of 24” x 192.” When scarfing, it's useful to use a stretched out length of line to make sure the factory square lines remain so during gluing.
The plans found in Chris Kulczycki books and the CLC plans call for measuring and cutting individual fore and aft pieces then scarfing these together. There typically will be issues of mis-alignment as the pieces slide easily during gluing if proper precautions are not taken. With my process of gluing up the blanks first and then laying out and cutting the full length planks there can be no misalignment in gluing. Also matching panels on both sides of the hull are cut out at once so one side will match the other. Alignment issues for each panel is eliminated minimizing chances of having a set of bad panels.
Laying out the Lines
You will need a Square. The bigger the better as long as it's accurate. You can check the accuracy of a square by drawing a line with it squared to the factory edge on the bottom of the sheet, that is, the edge closest to you. Flip it and draw a second line. Are they parallel? If the lines match up your square is accurate. If not, now is the time to accept the fact you needed a new square any way. Some folks have sheet rock squares which are nice because they are so long. A small combination square is really too small to be of any use.
You may want to consider which side of the panels you want to make the pencil marks. Note the color of the plywood, one side is a slightly different tint. It is possible to layout the lines and have them fall inside the boat’s hull and also to mark the lines so the color will match inside or out. For kayaks this is nice because you don’t have to erase the vertical lines unless you want as they won’t easily be seen once the deck is on. Canoes on the other hand have both sides showing. Regardless, don’t use a pen. Use a sharp pencil for accuracy. Don’t press down hard with your pencil as it will indent the plywood. The ideal pencil is the mechanical pencil which will deliver a consistent width line throughout the whole process without having to stop and sharpen it.
Measure and mark vertical station lines 12 inches apart. It is helpful to lightly mark each with its respective distance from the left edge i.e. 12-24-36-48 etc., on the top and bottom of each line. The next step is to consult the plans and make a mark for each plank measurement. I prefer to mark out all the verticals first and the work on the bow and stern ends last as they can be a little bit tricky.
Next get out your long batten and connect the dots for each plank outline. A batten is simply a long, narrow strip of wood used to guide the drawing of curved lines. Longer battens can be made from clear, knot free scrap lumber. The edges need to remain straight and smooth. If you don’t wish to make one, consider shopping your local big box home store for a piece of trim or edging 8 feet long. To hold battens in place small nails could be used to serve as guides. I use small heavy objects such as my wood planes; tin cans filled with sand, etc., to “spring” or hold the battens in place when I draw the line. If you have a helper on call, now is a good time to get their assistance. One person can hold the batten in place verifying its alignment with the other person concentrates on drawing the curve.
In general I start from the bottom and work up. It is easy using the bottom as a baseline counting up to each dot you created and mark it. There are areas which can be confusing, especially where dots and the corresponding line are close together. It is easy to mistake the upper line of one plank with the dots outlining the bottom of the plank above it. Take your time. If it gets too confusing consider using small pieces of masking tape marked with the plank number along the dots you have made to see if it makes sense and follow up with the batten and pencil when you “see” the plank outline. Note that there are occasions where two dimensions are the same height along two verticals. This does not mean that there is a straight line between them as there will likely be a subtle curve between them created by heights further along the batten. When the outline is finished remember to indicate the plank number, the bow and stern of each plank as well as which way is up and which down.
Historically scarf and butt joints were staggered so that any potential weakness associate with the joint would not fall next to another potentially weak joint. On hulls of solo canoes and kayaks with epoxy and glass it is not significant for strength. Visually however, it is much more attractive to keep the joints staggered. Unfortunately to get the most boat from the least amount of work and material, this is not always possible. On smaller boats like the Trout Lily at 13 feet, I offset the planks before drawing the lines and cutting them out so the scarfs are as far apart as they can be placed.
Do you have suggestions or comments?
