Spot the Defect – Materials in Boatbuilding 302 (AC 1.3)

Multiple Choice

What are the two conditions that cause wood infestation and decay?

• High temperature and sunlight

• Damp and poor ventilation

• Saltwater and UV exposure

• Low humidity and cold

Multiple Choice

What is the main sign of wood-boring insect infestation in a piece of boat timber?

• Cracks running along the grain

• Circular exit holes with fine dust

• Blue or black staining of the surface

• Raised grain after sanding

Multiple Choice

Why does infestation commonly occur in boats stored or used in damp conditions?

• Moisture helps larvae hatch and fungi to soften the wood

• Wet timber contains natural sugars that feed insects directly

• Saltwater repels insect predators

• High humidity prevents preservatives from evaporating

Multiple Choice

What is the most effective prevention method against infestation in stored timber?

• Stack boards tightly with no air gaps

• Coat with wax to retain moisture

• Apply varnish immediately after sawing

• Use seasoned, dry timber with good airflow

Multiple Choice

How does infestation typically affect timber used for structural components?

• Slight discolouration but no strength loss

• Weakening due to internal tunnelling by larvae

• Expansion of the wood, improving joint tightness

• Surface cracking caused by UV exposure

Multiple Choice

A section of oak in a deck structure shows dark, soft areas that crumble when pressed. What does this indicate?

• Resin starvation

• Fungal decay due to trapped moisture

• UV degradation of surface lignin

• Mechanical bruising during fitting

Multiple Choice

Why is timber decay a safety concern in boatbuilding?

• It changes the colour of decorative coatings

• It reduces structural strength and load-bearing ability

• It increases weight, improving stability

• It only affects surface appearance

Multiple Select

Which of the following statements about knots in timber are correct? You may select more than one answer.

• Live knots are generally stable and can be used in non-critical components.

• Dead knots significantly weaken timber and must be avoided in structural areas.

• Loose knots represent a void and severely compromise structural integrity.

• Loose knots are acceptable in all marine applications.

Multiple Choice

What mainly causes timber distortion?

• Uneven drying

• Resin content

• Colour change

• Tight grain

Multiple Choice

How can distortion affect boat construction?

• It makes joints tighter

• It causes poor fitting of parts

• It strengthens the frame

• It reduces water absorption

Multiple Choice

Which of the following best describes honeycombing as a seasoning defect in timber?

• Surface cracks caused by slow drying

• A network of internal cracks resulting from rapid or uneven drying

• Discoloration due to fungal growth

• Loss of surface finish due to UV exposure

Multiple Choice

What happens to knots when timber dries and shrinks?

• Knots tighten and strengthen the board.

• Knots often loosen and fall out, leaving holes or weak spots.

• Knots become waterproof.

• Knots dissolve into the grain.

Multiple Choice

What visible sign usually indicates early water damage?

• Grey discolouration and raised grain

• Increased hardness

• Smooth surface texture

• Lighter colour and gloss

Multiple Choice

What can happen if wet timber is sealed before it dries fully?

• It becomes stronger

• It traps moisture and promotes decay

• It prevents all future movement

• It improves varnish adhesion

Multiple Choice

Which maintenance action best prevents water damage?

• Leaving timber untreated for ventilation

• Applying marine-grade coatings and maintaining seal integrity

• Using unseasoned timber for flexibility

• Painting over existing damp areas

Multiple Choice

Which part of the wood structure does UV radiation mainly damage?

• Lignin near the surface

• The cellulose in the core

• The resin pockets only

• The sap channels

Multiple Choice

What is the most common visible sign of UV damage on timber?

• Blue or black fungal staining

• Grey or silvery surface colour

• Swelling at the end grain

• Raised pitch and resin spots

Multiple Choice

Which method best reduces UV-related surface degradation?

• Frequent power washing

• Applying UV-stable marine varnish or paint

• Storing timber in constant sunlight to harden it

• Using thinner coats for better drying

Multiple Choice

What is the main difference between oxidation and corrosion?

• Oxidation only affects wood; corrosion only affects metal

• Oxidation is a simple reaction with oxygen, while corrosion involves damage from the environment

• Corrosion strengthens metal; oxidation weakens it

• Corrosion only happens under water

Multiple Choice

Which of the following is an example of oxidation that does not cause major structural damage?

• Rust on a steel hull

• Dull grey layer on aluminium

• Pitting on a bronze propeller

• Cracking around stainless bolts

Multiple Choice

What makes corrosion more serious than normal oxidation?

• It forms a thin protective coating

• It is limited to dry conditions

• It continues to eat into the metal, causing loss of material

• It only affects decorative finishes

Multiple Choice

Why does aluminium resist corrosion better than steel?

• The oxide film on aluminium seals the surface.

• It never reacts with oxygen at all.

• It stays wet, which protects it.

• Steel contains more air pockets.

Multiple Choice

How are oxidation and corrosion linked?

• Oxidation begins the corrosion process.

• They are completely different reactions.

• Corrosion stops further oxidation.

• Oxidation only happens under paint.

Multiple Choice

Which of the following are effective prevention strategies for cavitation, fatigue, and cracks in marine metals?

• Use well-designed propellers, reduce vibration, use good-quality materials

• Increase engine speed, use thinner metals, avoid regular inspections

• Allow water traps, use poor welding, avoid spreading stress evenly

• Use non-absorbent gaskets, avoid cleaning, increase stress on joints

Multiple Choice

Which welding defect is characterized by small bubbles or holes trapped in a weld, and what is a common cause of this defect?

• Porosity; gas getting into the weld from dirty metal or poor gas flow

• Undercut; too much heat and fast welding

• Cracking; cooling the weld too slowly

• Lack of fusion; using the right heat and speed

Multiple Select

Which of the following are effective prevention methods for curing and mix faults in composites? You can select more than one answer.

• Accurately measure catalyst

• Mix components thoroughly

• Maintain correct workshop temperature and humidity

• Increase the amount of resin used

Multiple Choice

What is the most obvious sign that a laminate is under-cured?

• The surface feels tacky or sticky.

• The laminate is unusually hard and brittle.

• The colour has darkened evenly.

• The fibres are invisible.

Multiple Choice

If the resin mix was incorrect, how might the cured laminate appear?

• Glossy and smooth

• Cloudy or uneven in colour

• Flat and consistent

• Slightly textured but solid

Multiple Choice

What does a strong chemical or “sweet” smell from a cured panel often indicate?

• The laminate contains trapped solvent and is not fully cured.

• The laminate was polished too quickly.

• The mould surface was too clean.

• Extra catalyst was added correctly.

Multiple Choice

Which of the following problems develops when the laminate is left under-cured?

• It softens and deforms in warm conditions.

• It gains extra stiffness over time.

• It becomes waterproof immediately.

• It resists bonding to paint or gel coat.

Multiple Select

Which of the following are common causes of resin distribution faults in composite laminates?

• Inadequate or poor rolling-out technique during wet lay-up

• Incorrect measurement or application of resin

• Failure to effectively remove air during lamination

• Excessive use of catalyst

Multiple Choice

Which defect is characterized by radiating crack patterns from impact points, indicating localized stress concentration?

• Star crazing

• Delamination

• Pinholes

• Blistering

Open Ended

Summarize one key thing you learned today about identifying defects in boatbuilding materials and how it might be applied in real-world situations.