Calculation Methods

The definition of deflection (turn) angle as well as channel widening in a turn is displayed at the drawing below.

Widening is used together with turn type configuration. “Draw Channel” function implements selected turn type configuration always even if widening is zero. In all turn type configuration widening may be placed in 3 different ways.

In example drawing widening placed 1/2 outer and 1/2 inner curve. Turn geometry is constructed of 4 lines:

1. Transition start point to (2) 2nd segment radius extension line
2. 2nd segment radius extension line connects to (3) curve middle segment extension. This line must tangent outer curve.
3. curve middle segment extension connects to (4) 5th segment radius extension line. This line must tangent outer curve.
4. 5th segment radius extension line connects to (5) Transition endpoint.

In example drawing below widening is placed to inner side of curve. Outer and inner side geometry is constructed of 3 lines:

1. Transition start point connects to (2) 2nd segment radius extension line
2. 2nd segment radius extension line connects to (3) 4th segment radius extension line. This line must tangent on outer curve.
3. 4th segment radius extension line connects to (4) Transition endpoint.

Apex turn type has 2 variant (please see example drawing below).

Outside curve apex geometry rule: extension line of transition start point and end transition point (start of curve) connects to form an apex triangle.

• 2 point Apex: Curve Start Point (A) connects to Curve Endpoint (B)
• 4 point Apex: Curve Start Point (A) connects to 2nd Segment (A') that connects to 4th Segment (B') and finally to Curve Endpoint (B)

Widening inside curve: Full widening in start of curve and in the end of curve.

Widening outside curve: Full widening in start of curve and in the end of curve.

Following rules are used to analyze horizontal geometry:

• Straight segments (line) in a horizontal geometry should be at least five times the length of design ship.
• Minimum radius Rmin is defined by deflection angle at horizontal geometry. Following default values are used:
• Turn angle (delta)= 0° to 30°, Rmin = 5*L
• Turn angle (delta) > 30°, Rmin = 10*L
• L = design ship length (length between perpendiculars)
• Maximum width. Maximum channel width < 3.0km.