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Camber and other curves, How do we draw them?

Camber and other curves, how do we draw them?

In most of our drawings, we refer to "camber". This means a curve going through three points, an arc of a circle. It is a very simple curve that can be drawn with a batten or PVC pipe.

(Picture courtesy of Justin Pipkorn)

Camber is used in different places: for the molds (= stations = frames = bulkheads) or for other parts of the boat like the sole (cockpit floor) or seat tops.

Let's look at some examples:
In this drawing of a floor frame, we show that the bottom side has camber: 1-1/8" ( 28 mm).

To draw that curve:
- First draw the part with straight lines
-Mark the middle of the bottom side.
- Mark a point 1-1/8" offset from the middle.
- Draw a curve between the three points: the two end points and the offset middle point.
- That's all there is to it!

This is a seat top panel for a bow rider. All sides are straight except for the one along the hull: it has camber. The procedure is the same than for the floor frame above:

- Draw the complete outline with straight lines.
- Along the hull side edge, mark the middle.
- Offset that point 5".
- Draw a curve between the three points.

Next, the deck camber.
In the case of a station, we may not show the two sides of a part. This is customary in boat design: boats are supposed to be symmetrical, why complicate the drawing with unnecessary lines? The drawing shows a typical forward frame of a power boat with a small deck. All dimensions not relevant to this discussion were removed for clarity. Note that all dimensions are always taken from the baseline and the centerline.

Step one:
Draw the outline for the frame, two sides, without the deck.

Step two:
Mark the height of the center, draw the curve of the deck.

Last example, a transom with motorwell.
Step one:
Draw the outline without deck.

Step two:
Ddraw the deck curve.

Step three:
Draw the motorwell cut.
Taking it one step at a time makes it simple.

  •  Unless marked otherwise, camber is always measured from the middle of a line.
  • Cambered curves may be an approximation of the exact shape but the curves are always within 1/8" of the true curves.
  • We try to restrict our hull lines to second or third degree polynomials and this produces very fair cross section curves: conicals or plain arcs.

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