Chain girth is a specific measurement taken on a hull to understand its shape. According to the provided reference, chain girth is measured as a straight line from a given elevation on the hull near the waterline vertically from a specified fore-and-aft position and diagonally as viewed from the bow to a point on the hull near the keel.
Understanding Chain Girth Measurement
The definition highlights the key components of measuring chain girth:
- Starting Point: The measurement begins at a designated height or "elevation" on the hull, typically located near the waterline.
- Fore-and-Aft Position: A specific longitudinal position along the hull is chosen for the measurement.
- Viewing Angle: The measurement is taken diagonally when viewed from the bow (front) of the vessel.
- Ending Point: The straight line extends downwards from the starting point near the waterline to a point on the hull located near the keel (the main structural member running along the bottom of the hull).
This method captures a specific diagonal distance across the hull section at a particular fore-and-aft location.
Chain Girth vs. Skin Girth
It's important to differentiate chain girth from other hull measurements. The reference explicitly states:
- Chain Girth: Measured as a straight, diagonal line as described above.
- Skin Girth: Measured by following the actual surface contour of the hull. This means skin girth traces the curve of the hull from the starting point to the ending point, rather than a straight line.
Key Difference Summary:
| Measurement Type | Method | Path Followed |
|---|---|---|
| Chain Girth | Straight line (vertical + diagonal) | Direct straight line |
| Skin Girth | Following the hull's surface contour | Curved path |
Therefore, chain girth provides a direct, linear measure across a hull section, distinct from the curved measurement that follows the hull's "skin."
