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
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
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
5/ Galvanic corrosion and fastening softness
Two different metals immersed in a liquid create an electric current.
Impure water (sea water) is an electrolyte.