A stiff ship is one with a very large GM caused by KG being too small. This occurs if too much weight is placed low down within the ship. The ship will be excessively stable, righting moments will be so large as to cause the ship to return to the upright very quickly when heeled. Roll period will be short.
A very large GM should be avoided for the following reasons:
- The ship will return to the upright very quickly whereby the motion will be jerky causing excessive strain on cargo lashings and possible cargo shift.
- Loose gear will be thrown about.
- It is uncomfortable for crew and injury may result from the ship’s quick motion.
- Structural damage to the ship may occur due to racking.
A tender ship is one with a very small GM caused by KG being too large. This occurs if too much weight is placed high up within the ship. The ship will have insufficient stability, righting moments will be very small when heeled causing the ship to be sluggish and slow to return to the upright. Roll period will be long. (A tender ship is still a stable ship i.e. M is above G.)
A very small GM should be avoided for the following reasons: