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fit and vent a fuel tank
John de Frayssinet (editor of
Yachting Life)In this age of plastics, it is gratifying to see such
an abundant use of wood on many modern craft. While the price of glass
fibre resin continues to rise, the cost of prime hardwood rises more
so.
The cost of building a boat using
teak or oak frames has become virtually prohibitive. And yet, only a small
proportion of hardwood types have ever been used by the industry. Many
species of hardwood still remain un-felled and their properties unknown.
The reason for this is simple enough. The boatbuilder has for a long time
had available to him a large choice of timber, all with well known
characteristics. These timbers have stood the test of time, and it would
be foolhardy for the builder or new owner to experiment with some new type
of wood when building a yacht which is expected to remain sound for many
years.
The construction of a wooden boat
encompasses many timber requirements. The hull planking must be easily
bent, and be resistant to water and borers, Frames must have much greater
rigidity and mechanical strength. Exterior trims must be able to be
finished attractively but be resistant to water, while interior woodwork
must be capable of working to a fine finish.
The greatest problem these days is
to find any wood at all that has been well seasoned. Very few boatyards
carry large stocks of hardwood, air dried for many years, and even fewer
are prepared to sell any quantity to outside buyers. Unseasoned timber is
quite useless for boatbuilding. While seasoning takes place, wood
undergoes contraction, as the moisture content is gradually reduced. If
this contraction continues once the wood is in place on the boat, warping
and opening of joints is inevitable. A lot of timber is now kiln dried and
the moisture content driven down to an acceptable level. However, the
quality of this wood is without a doubt reduced, and movement occurs much
more readily in different moisture conditions. It is not always easy for
the amateur to distinguish well seasoned timber, and often he must take
the word of his supplier as gospel.
For many years, I fondly imagined
Mahogany and Teak trees proudly growing in some South American or African
forest In fact, many of the timber names used by the trade only describe a
type of wood. As supplies become limited, different species can be
marketed under familiar names, provided they closely resemble the original
specification. However, in recent years the disparity has enlarged.
Most mortals these days are only interested in buying
timber for trims. Rightly or wrongly we still think that a boat only
becomes boaty when there is a reasonable amount of nice timber
embellishing the otherwise clinical glass fibre. As the cubic footage
involved is usually small it is still possible to use choice timber. The
use of marine plies has reduced our requirements even further.
When a large area of timber is
required, plywood, correctly used is preferable to solid wood as it
does not suffer from any discernable expansion and contraction Also, its
use in bulkheads is advisable as a laminated timber has a much higher
strength to weight ratio.
The greatest expense in
boat-building is labour, so if at all possible, it is well worth spending
a little extra money on the right choice of wood and save a lot of trouble
later on.
TEAK
Without any doubt teak is the
prime timber for most aspects of boat construction. The high resin content
makes the wood feel like a lump of lard, It is almost totally resistant to
seawater and a yacht built in this material will outlive all of us. The
resin content does make it difficult to varnish and glue together.
Exterior bright work has a tendency to be sloughed off unless early
varnish coats are very well thinned and the wood degreased. Conventional
waterproof glues are unreliable, sometimes even after degreasing with
carbon-tetrachloride. A resorcinol glue should be always used. However,
these are dark brown or red in colour and often begin to show through
joints after a year or so.
teak interior of a Nicholson 45 refitted by the author ('Jealousy' ex Yeoman 18)
Teak is without doubt best for all
exterior woodwork. Unless you are keen on playing around with varnish it
is quite unnecessary to seal it. Left to weather in salt water, the wood
gradually becomes white in colour. Items such as rubbing strakes and toe
rails are certainly best left in bare teak, as constant abrasion will ruin
the varnish anyway.
Under no circumstance should
exterior teak ever be oiled. This produces an excellent medium for fungal
growth, which while it will not attack the wood will leave it a foul black
colour in damp climates.
For all our latest super non- slip
paints, a teak deck, for those who can afford it, still gives by far the
best service and looks absolutely wonderful. When constant abrasion is
expected on unsealed teak, it is important to buy riftsawn timber,
otherwise the softer grain will be worn away.
Many yachts are also finished
inside with teak. The colour is attractive, but generally, with solid
timber, there is little attractive grain.
I prefer working with teak to any
other wood. It is straight grained and very rarely plays nasty tricks on
you like splitting. Being quite soft it is easy to work but as a tendency
to blunt power tools. The dust is laden with resin and does not therefore
fly around and get up your nose.
IROKO
This is now used as a substitute
for both oak and teak. Its colour is similar to teak but the grain is much
more prominent and difficult to finish to a smooth surface. It is almost
as hard as oak and approaches the rigidity of that wood. Many yachts these
days are framed and planked with Iroko. While good service can be
expected, it is necessary to keep the wood well painted. Iroko is not an
easy timber to work, being very hard and brittle but with a lot of care
excellent results can be achieved.
MAHOGANY
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This is easily distinguishable by
its rich red colour and attractive grain. Again this is a wood that must
be very well protected. Many yachts are planked with mahogany but
generally speaking, they will have a shorter life unless really well cared
for. I know of nothing more attractive than a varnished mahogany carvel
hull, but so much work is involved in maintaining it. If water is allowed
to enter under the sealer a very nasty black stain occurs which is very
difficult to remove.
Some types of mahogany now being sold are very much
harder. In some cases it is almost impossible to put a screw into it, so
care must be taken in its selection. The attractive grain makes working
difficult. Planing a cross-grained plank can be soul destroying.
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the glory of traditional mahogany
(saloon of 'Lelantina')
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AFROMOSIA
This is very similar to mahogany but has a straighter
grain and is slightly less red in colour. The dust from sanding can be
extremely unpleasant and is actually dangerous.
CEDAR
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interior of 'She Too' under refit |
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A soft wood but one which is extremely resistant to
seawater. Some racing boats have been built in this timber as it is
extremely light and fairly strong. However, under normal circumstances I
would not recommend its use except where little abrasion can be expected,
as it is very soft. When varnished the appearance is very similar to teak.
The photo is of a 1/2 ton yacht finished in cedar still under
construction.
As with most softwoods of good quality, cedar is easy
to work and is very straight grained.
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PINE
This must always be well protected but can be a
suitable timber for planking, although I personally would never use it.
One or two boat yards have used pine as an interior timber to great
effect. It makes a very nice change to the more conventional darker woods.
If knot-free timber can be obtained it is quite easy to work.
BRAZILIAN TEAK
This is one of the more recent timbers gaining
preference in boatbuilding. It carries many of the properties of teak but
does not contain such a high resin content. It is lighter but stronger and
very much harder and is reputed to be highly resistant to rot and marine
borers.
OBECHI
This wood is more commonly known to modellers but can
be used effectively as a laminated timber for deck beams. It has a very
high strength to weight ratio but is prone to rot.
ASH
This is a very strong timber which will allow a high
degree of flexibility and was used in early aircraft as structure.
However, upon exposure to water it becomes ‘sleepy’ and loses much of its
strength. It is, however, ideal for sail battens and is a lovely straight
grained timber to work.
DEAL
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While this is the most readily
available timber and is used widely by the building and joining industry I
can think of few more unsuitable woods to put in any boat. Much of it is
totally unseasoned and even
better examples are poor in strength and durability. Perhaps one could use
it for hidden battens but I would have to be very short of money to
contemplate it.
If totally encapsulated in GRP
it can be used for floor bearers |
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BALSA WOOD
Believe it or not this is in fact
a hardwood and some parts of the tree have a high strength to weight ratio
and are quite resistant to rot. The most common use for this timber is as
end grain sheets to produce a glass fibre sandwich. When used in this way
it produces a very rigid structure that is low in weight.
PLY
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Many other types of
timber can be used mostly for decorative purposes below decks.
At one time, Swan yachts made extensive use of Koto wood,
giving a very attractive light finish. Should you decide to
try a less conventional timber, by all means do, after you
have taken advice from an experienced shipwright.
Plywood is now used
exten sively and
again care must be taken that it is marked as marine
ply. It is possible to use exterior grades but I would doubt
that this is wise in the long run. Teak faced ply is now a
crazy price. Many manufacturers use such a thin veneer that I
am very reluctant to use it. Unlike solid teak, it is
inadvisable to use teak face ply outside without varnishing,
as much of the protective resin is removed during manufacture.
Marine ply is
found in craft large and small and can be the basis of
complete construction.
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