Grouchy_Old_Coot
06-06-2006, 12:51 PM
The following are two excepts out of the USDA Wood Handbook.
It is available for free at: http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm (http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm)
(I tried to past the cover image - I can't get the darn thing to post!)
Other Structures and Products
(Page 13-8)
Wood boats present certain problems that are not encountered
in other uses of wood. The parts especially subject to
decay are the stem, knighthead, transom, and frameheads,
which can be reached by rainwater from above or condensation
from below. Frayed surfaces are more likely to decay
than are exposed surfaces, and in salt water service, hull
members just below the weather deck are more vulnerable
than those below the waterline. Recommendations for avoiding
decay include (a) using only heartwood of durable species,
free of infection, and preferably below 20% moisture
content; (b) providing and maintaining ventilation in the
hull and all compartments; (c) keeping water out as much as
is practicable, especially fresh water; and (d) where it is
necessary to use sapwood or nondurable heartwood, impregnating
the wood with an approved preservative and treating
the fully cut, shaped, and bored wood before installation by
soaking it for a short time in preservative solution. Where
such mild soaking treatment is used, the wood most subject
to decay should also be flooded with an approved preservative
at intervals of 2 or 3 years. During this treatment, the
wood should be dry so that joints are relatively loose.
Protection of Boats
(Page 13-15)
Wood barges have been constructed with planking or sheathing
pressure-treated with creosote to protect the hull from
marine borers, and the results have been favorable. Although
coal-tar creosote is an effective preservative for protecting
wood against marine borers in areas of moderate borer hazard,
it has disadvantages in many types of boats. Creosote adds
considerably to the weight of the boat hull, and its odor is
objectionable to boat crews. In addition, antifouling paints
are difficult to apply over creosoted wood.
Some copper bottom paints protect boat hulls against marine-
borer attack, but the protection continues only while the
coating remains unbroken. Because it is difficult to maintain
an unbroken coating of antifouling paint, the U.S. Navy has
found it desirable to impregnate the hull planking of some
wood boats with certain copper-containing preservatives.
Such preservatives, when applied with high retentions (24 to
32 kg/m3 (1.5 to 2.0 lb/ft3)), have some effectiveness against
marine borers and should help to protect the hull of a boat
during intervals between renewals of the antifouling coating.
These copper preservatives do not provide protection equivalent
to that furnished by coal-tar creosote; their effectiveness
in protecting boats is therefore best assured if the boats are
dry docked at regular and frequent intervals and the antifouling
coating maintained. However, the leach-resistant wood
preservatives containing copper arsenates have shown superior
performance (at a retention of 40 kg/m3 (2.5 lb/ft3)) to
creosote in tests conducted in areas of severe borer hazard.
Plywood as well as plank hulls can be protected against
marine borers by preservative treatment. The plywood hull
presents a surface that can be covered successfully with a
protective membrane of reinforced plastic laminate. Such
coverings should not be attempted on wood that has been
treated with a preservative carried in oil, because the bond
will be unsatisfactory.
It is a great book and has tons of info on wood, its uses and how to preserve it.
It is available for free at: http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm (http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm)
(I tried to past the cover image - I can't get the darn thing to post!)
Other Structures and Products
(Page 13-8)
Wood boats present certain problems that are not encountered
in other uses of wood. The parts especially subject to
decay are the stem, knighthead, transom, and frameheads,
which can be reached by rainwater from above or condensation
from below. Frayed surfaces are more likely to decay
than are exposed surfaces, and in salt water service, hull
members just below the weather deck are more vulnerable
than those below the waterline. Recommendations for avoiding
decay include (a) using only heartwood of durable species,
free of infection, and preferably below 20% moisture
content; (b) providing and maintaining ventilation in the
hull and all compartments; (c) keeping water out as much as
is practicable, especially fresh water; and (d) where it is
necessary to use sapwood or nondurable heartwood, impregnating
the wood with an approved preservative and treating
the fully cut, shaped, and bored wood before installation by
soaking it for a short time in preservative solution. Where
such mild soaking treatment is used, the wood most subject
to decay should also be flooded with an approved preservative
at intervals of 2 or 3 years. During this treatment, the
wood should be dry so that joints are relatively loose.
Protection of Boats
(Page 13-15)
Wood barges have been constructed with planking or sheathing
pressure-treated with creosote to protect the hull from
marine borers, and the results have been favorable. Although
coal-tar creosote is an effective preservative for protecting
wood against marine borers in areas of moderate borer hazard,
it has disadvantages in many types of boats. Creosote adds
considerably to the weight of the boat hull, and its odor is
objectionable to boat crews. In addition, antifouling paints
are difficult to apply over creosoted wood.
Some copper bottom paints protect boat hulls against marine-
borer attack, but the protection continues only while the
coating remains unbroken. Because it is difficult to maintain
an unbroken coating of antifouling paint, the U.S. Navy has
found it desirable to impregnate the hull planking of some
wood boats with certain copper-containing preservatives.
Such preservatives, when applied with high retentions (24 to
32 kg/m3 (1.5 to 2.0 lb/ft3)), have some effectiveness against
marine borers and should help to protect the hull of a boat
during intervals between renewals of the antifouling coating.
These copper preservatives do not provide protection equivalent
to that furnished by coal-tar creosote; their effectiveness
in protecting boats is therefore best assured if the boats are
dry docked at regular and frequent intervals and the antifouling
coating maintained. However, the leach-resistant wood
preservatives containing copper arsenates have shown superior
performance (at a retention of 40 kg/m3 (2.5 lb/ft3)) to
creosote in tests conducted in areas of severe borer hazard.
Plywood as well as plank hulls can be protected against
marine borers by preservative treatment. The plywood hull
presents a surface that can be covered successfully with a
protective membrane of reinforced plastic laminate. Such
coverings should not be attempted on wood that has been
treated with a preservative carried in oil, because the bond
will be unsatisfactory.
It is a great book and has tons of info on wood, its uses and how to preserve it.