This assertion is only partly valid. Cracks in these members are not necessarily proof of inadequate scantlings or strength. In practice, cracks in A-brackets, spectacle frames and propeller shafts are far more commonly the result of:

• Fatigue loading: these members are subject to continuous cyclic loading from the propeller, vibration and wave action. Fatigue cracks initiate at stress raisers such as sharp corners, weld toes, keyways, fillet radii and corrosion pits even when the general scantlings are perfectly adequate.
• Stress concentration: poor detail design, sharp notches and abrupt changes of section concentrate stress locally and promote crack initiation.
• Vibration: excessive propeller-induced vibration and whirling of the shaft can cause cracking.
• Corrosion and erosion: pitting, cavitation damage and corrosion reduce the effective section and act as initiation points.
• Material defects: inclusions, poor weld quality and inadequate heat treatment.
• Misalignment and bearing wear.

However, the assertion has some validity: if cracks are widespread, recurring, or accompanied by permanent set or buckling, they may indicate that the scantlings are inadequate for the duty, or that the design strength margin is insufficient. The correct approach is to investigate the cause (fatigue, vibration, corrosion, or genuine under-design) rather than assume inadequate scantlings. A single crack is usually a local fatigue or detail problem; repeated cracking in the same region may point to a genuine strength deficiency. So the assertion is not universally true - it is valid only when cracking is systematic and not attributable to fatigue, vibration or corrosion.

This assertion is largely valid. Watertight integrity keeps water out of the hull, but the ability to shed water from the deck is equally important to seaworthiness. The reasons are:

• Freeing ports allow water shipped on deck to drain rapidly. If water is retained on deck, it adds weight high up, raising the centre of gravity and reducing stability (free surface and added weight effect), and can lead to a dangerous reduction in metacentric height.
• Retained deck water increases the effective displacement and can cause the vessel to become sluggish and unmanageable.
• In heavy weather, water trapped on deck can shift and cause a sudden loss of stability or capsize, particularly in vessels with low freeboard.
• Scuppers and freeing ports prevent accumulation of water that could enter the hull through openings, hatches and ventilators, thereby protecting watertight integrity itself.
• Blocked or inadequate freeing ports are a recognised cause of loss of stability and capsizing of fishing vessels and small craft.

Therefore, the provision of adequate, correctly sized and properly maintained freeing ports and scuppers is as critical to seaworthiness as watertight integrity. Both are essential; neither can compensate for the other. The assertion is valid.