SAW CUT LONGITUDINAL PATTERNS
Since Longitudinal frames are really developable surfaces that roll in two directions at a time they can be pre-formed by "Saw Cutting" or "Roll Forming" methods in one direction. This leaves the other direction of roll to easily follow the natural shape of the hull when fitting the longitudinal frames into the transverse framing system.
The drawing below shows a representation of two sheets of paper 24" x 65". It represents the full size patterns use for the "Bezier 28" Center Vertical Keel or CVK. Since the CVK is a longitudinal frame we can use it as the example.
The drawings break the CVK up into six (6) sections. They are labeled to assure the correct sequence bow to stern. Frame positions are also shown on these full size patterns. These positions will be transferred to aluminum sheet material used for fabrication the CVK, proving invaluable when setting up the frame work on the building Strongback. To shape any longitudinal, the CVK in this example, simple transfer the pattern to sheet material and cut in your vertical band saw.
Remember that the full size patterns alway come with CNC Cutting Files below.
How to fabricate the CVK
A two part method will be used to align and true the CVK.
The first part is a dimensioning process similar to the process used to true the transverse frames.
The below drawing illustrates the process. Dimensions are given using the fore point of the CVK, as a reference point, to the beginning of each individual section used to form the CVK. All of these dimensions must verify each other for the CVK to be at its designed profile.
The second part of the fairing process verifies the first. Sight down the length of the CVK. Look for any high or low spots, especially near the connections of the sections. The curve should look pleasing to the eye. In general if it does not look right, it probably isn't.
Below are Saw Cut longintudinals formed and fabricated for the Bezier 12.5 from the above method. First is the Sheerline and cockpit longitudinals followed by the Center Vertical Keel (CVK).
