Saturday, February 16, 2019

Starting to cut wood.

You may not believe it, but I am making progress on the new boat.  It has been slow, because the boat is just my spare time project.  It is ski season; it is tax season; and there is snow to be shoveled as well as the usual life's tasks.  The frames will be built up from sections of solid wood, lapped and bonded; like putting together a jig saw puzzle.  I am not one to show every little detail, because I doubt that my methods are any better than most who are interested in building boats.  So, I'll start taking pictures when I have real completed frames and keel to show.

If I were going to build more than one boat, I would probably use particle board molds to define the shape and then install laminated ribs after planking was completed.

When you build a boat of your own design, there is no simple checking of plans to see what to do next.  Each step is being done for the first time.  So progress is a sequence of asking yourself, "How am I going to build that?  What material? In what dimensions?  What technique?  How will that affect subsequent steps?"  The challenge and risk keeps the build interesting.

A good day for working in the shop; new snow and a high of 17 degrees F.  We are having a snowy winter; in Colorado you never complain about moisture in any form; it is always needed.

Step 1:  Using the listed dimensions on the previous entry, plot out all the points to define the seven different exterior frame shapes and the two stems.  I use rosin paper because it is has the size and rigidity desired (although I recently became aware of a new product "Ram Board" which is even smoother and slightly more rigid).  Decide the desired thickness of frame members, and draw the interior shape of the frames and stems.  Calculate the board feet of lumber needed and buy it.  (1 3/4" by 1/2" cross section looked about right for frames; I used 1 1/2" by 3 1/2" for the stems.)

Step 2:  Find and buy the keel plank.  This needs to be a nice clear and straight piece, at least 7 1/4" wide and 12' long (or you can scarf it).  Layout a center line and transverse lines for the frames every 12" except for the middle of the board where the spacing should be 11 1/2".  All frames (1/2" thick) will be positioned on the tapered side of the transverse lines.  Thus, the actual spacing between frames will be 11 1/2" except in the center it would be 12" if we didn't make this 1/2" reduction.  You can rough cut the taper at both ends of this keel plank, but leave a little extra for the final fitting.

Step 3:  Using the full-size rosin paper drawings, trace each frame component onto your wood.  Then shape each frame component.  I use a table saw for straight cuts, a band saw for curves and a router for laps (joints are half thickness lapped, although gussets would work also).

The 1/2" thick frame member is surrounded by 1/2" thick plywood to provide support for the router base when trimming the half-thickness lapped ends.

Step 4:  Lay out the rosin paper drawings of a flat surface.  Cover them with painters' plastic (very thin and transparent) to prevent resin adhesion.  Mix a bonding consistency epoxy; coat the lapped joint pieces; and place them in the desired pattern.  Repeat this twice because you will need fourteen frames and two stems total.

The stem pieces are doweled and bonded together. The half-angle of the plumb bow is 21.8 degrees which I pre-cut.  The curved portion will have a changing angle, transitioning to an 18.4 degree deadrise which I will trim as a part of fairing.

Step 5:  After the epoxy sets, clean up the resin runs and blebs on the frames.  Time to add some detail to the frames and stems.  I will use a batten/stringer at sheer and each of the three chines and need to mark and cut notches to receive each of these longitudinal members.

Step 6:  Before assembling all these pieces, a method is required to precisely position all the frames-stems-keel.  I could build a strongback with supports to hold each frame in vertical, lateral, and fore & aft alignment; however, there is a simpler method.  Because this hull form was designed mathematically, the sheer is a mathematical curve described by an equation.  Because I use forms of this equation frequently in my boat designs, many years ago I used the calculus learned as part of my engineering training to integrate the equation.  The result is a usable but more complex equation which, by entering X-Y-Z values, can be used to calculate the length of that curve to all frame locations.