been cleaned and dried, you should make a careful necessary. All frame member sections should be
inspection to determine the extent of damage. joined with a scarfjoint if at all possible. A scarf with
Physical damage may extend far from the
a 12:1 pitch is best. A scarf with this pitch, glued with
obviously stove-in areas. A boat may have been
epoxy and secured by boat nails, bolts, or rivets, will
squeezed in a collision situation, and although there is
be nearly as strong as the original member. If you use
obvious damage on one side, equal stresses have been
epoxy glue, you can allow some gap in the joint since
suffered on the other side. By calculating the direction
epoxy has better strength in tension than regular
that forces were exerted on the hull, you can estimate
marine glues. A good scarf can be made by
the points where stresses were transmitted. Look in
overlapping the members to be joined and shaping
those areas for loosened fastenings or cracks in the
both ends with one cut of a saw at a steep angle. Heavy
wood.
timbers must be sawed and carefully planed to shape.
When a rib or strake cannot be easily reached, the scarf
If decay is present, either as the cause of failure or
angle will probably have to be chiseled into it. The end
incidental to it, you must plan to remove not only the
of the new section then is carefully fitted to this angle.
rotted wood, but also the wood into which the decay
organisms are assumed to have spread. The rule in
Since epoxy has strength in tension, rougher faces of
doing this is to remove sound wood for 2 feet along
joints can be used than was possible with older glues.
the grain from the soft wood and for 2 inches across
The easiest way to lay out a replacement part is to
the grain from the soft wood. Plywood should be
use the old part as a template. If the old part is too
removed for a 2-foot radius from the rotten area. If this
badly damaged, you may be able to construct a
is not done, decay can spread back into the repaired
template of scrap materials or lay out the new part by
area.
careful measurements. Experienced boatwrights have
When you remove a damaged plank, plan to take
a number of techniques to form duplicate replacement
out a generous length. The new plank should butt to
parts, but for emergency repairs you can probably
the end of the old one between frames, using a butt
settle for any method that will fill the hole or provide
block; you should saw the ends to meet that
adequate reinforcement. Plastic patch materials
requirement. If the plank is fastened with screws,
permit simple, quick repairs that formerly were not
chisel away the putty or the bung plugs and remove
possible.
the screws. If boat nails are used, cut off the heads with
a cold chisel. When the plank is pulled off, either pull
the nail or drive it into the frame. To remove rivets,
FERROCEMENT BOATS
cut off the upset head and punch them out. (Rivets are
usually found in lap stroke hulls, which are best sent
Ferrocement is a material finding increased use as
to an expert for repair.) If the plank is fastened with
a low-cost material for hull construction. It is a
drifts, pry them out by leverage on the plank, or allow
combination of steel-reinforced mesh and portland
the plank to break at the rib, then pull the drift or drive
cement binding. The reinforcement material ranges
it flush.
from several layers of chicken wire to a few layers of
specially woven steel wire. Ferrocement hulls may
To repair a sprung frame or rib where the exterior
planking is sound, construct a sister frame and fasten
also have some structural steel or steel pipe
it along the old frame. The sister frame should extend
reinforcement or framing.
well to either side of the damaged area. Planks may be
Repairable damage to ferrocement hulls probably
refastened to the sister frame.
will be in the form of punctures or structural damage
If a frame has rotted, or is badly damaged, it must
from collisions or groundings. Other failure of these
be replaced. To replace a curved frame section, it is
hulls will be caused by poor design, materials, or
easiest and best to laminate the replacement part on a
workmanship. Hull failure from these causes is not
template; or, if the exterior of the boat is sound, the
economically repairable since the seaworthiness of the
section could be built up in place. On Vee hulls, the
entire craft is questionable.
lower ribs should go from keel to chine, and the side To repair punctured areas not over about 1 foot in
ribs from the chine to the sheer strake. The ends should greatest diameter, use the plastic patching kit and
be joined as were the original members. Curved rib basically the same techniques described later in this
sections can be joined to the ends of the old rib if
chapter for repairing fiberglass hulls.
4-5
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