Longevity
Timber is the oldest boatbuilding material known to man. Egyptian boats have survived for over 4,000 in the desert sanda and plenty of small craft survive for over 100 years in cold waters. Essentially they need regular maintenance and protection from the elements.
Types of timber degradation
1/ Dry rot (Merulius Lacrymans)
the most dreaded disease in a wooden boat because it can spread fast. Rate of extension can be up to 8mm (5/16”) per day if temperature and moisture levels are right. And like other forms of rot, it quickly extends into neighbouring scantlings as the fungus grows. Can be hidden beneath paintwork yet, when a spike is pushed in, it can dissappear up to the handle.
good ventilation is vital because a stream of air takes away the humidity and inhibits the spread of rot.
All affected timber must be taken out and burned. it must be replaced with new timber. Copious quantities of rot-preventing fluid applied by brush or sprayand regular inspection to check for any re-occurance, is exxential
2/ Wet rot (Coniophora Cerebella)
has much in common with dry rot in that it thrives in poorly ventilated, moist, warm conditions. It is generally considered to be dormant in freezing conditions.Symptoms - cracks in the wood; timber undulates with the grain. Frequently occurs where twi pieces of timber butt up without sufficient bedding in the jointso moisture can lodge in the grain end. Prevalent in cheap (or medium) plywoodwhich has hidden voida. The edges and underside of ply decking is particularly vulnerable areas and the bottoms of plywood bulkheads wher bilges are badly ventilated.
3/ Ship worm (Teredo Navalis)
Found mainly (but not exclusively) in warm waters. More likely to be found near calcureous coasts (calcium carbonate - chalk). Toredo larvae settle onto exposed surface and burrows inward. It can get behind copper sheathing or behing GRP sheathing by finding tiny fissures - crack in GRP - dad overlap of copper - badly fitted seacocks. Underwater anti-fouling can provide some protection but a scratch or graze can provide a point of access.
Once inside the timber the worm runs with the grain. It doesn’t com back to the surfaceand a spike has to be used to find them. A worm can be up to 6ft long and tunnels will be 1/2” or less. The worm cannot be seen on the surfacebut a number of unexplained leaks is a good sign. If Teredo is suspected a wood chiselis the quickest way to settle the issue. Teredo tunnels are lined with a chalky deposit. Once a tunnel has been discovered one can expect infestation over a wide are. teredo can be the death of a vessel if it has got into the keel or sternpost.
4/ Termites (Termes Termitem)
Wood worm (also called ‘white ant’) - tropical. Attacks upperworks of wood vessels. First signs can be wooden beams sagging because they have been eaten away from the inside. Most frequently attacked if the vessel is laid up ashore on wooden chocks. If the vessel is laying alongside for a period with a gangplank then termites can have a go.the first signs if infestation could well be the collapse of the gangplank!Termites are about 5mm long, are very destructive and attack in their millions. Spike testing confirms the trouble which shows itself outwardly by many small holes and fine wood dust.
4/ Gribble (Limnoria Terebrans)
Marine borer widely found in temperate and warm water - muddy or brackish. Crustaceon compared with the wood louse. Makes a mass of small, shallow holesin exposed, submerged timber. The trouble is easy to seeand once exposed timber has been attacked action is required. As with other worms etc... good anti-fouling or sheathing protects providing the barrier is not breached.
5/ Galvanic corrosion and fastening softness
Two different metals immersed in a liquid create an electric current. Impure water (sea water) is an electrolyte.