Main cabin windows are typically non-opening (fixed) for
several reasons. Cost appears to be the primary motivation since
fixed windows are much less expensive than their opening
counterparts. Modern "european style" boats are designed with
compound curves and large edge radii which are very difficult to fit
with openings which do not leak. Sailboats are somewhat justified
in their use of slanted side walls for aerodynamics, however, these
windows are now exposed to excessive solar radiation so "sunscreens"
are subsequently fitted to keep cabin temperatures tolerable.
Sunscreens not only add to the total cost but require frequent removal
to clean the windows' outer surfaces. They wear out, after
several years, from exposure to ultraviolet radiation and constant
fabric flexing by buffeting winds. Sunscreens also reduce
visibility from within and are an esthetic eyesore.
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Plastics (Lucite®, Lexan®,
Plexiglass® etc.) are used for most boat windows because
they are much less expensive than glass and reduce weight. Glass,
whether fixed or opening, is mounted in frames. Frames add
rigidity and provide a large area for sealants to prevent leaks.
Plastic windows are typically glued-on using the "direct glazing"
process. This permits the semi-flexible plastic to conform to
curved surfaces. Unless the plastic window is thermo-formed
(pre-bent using heat) to the final curved shape before direct glazing,
there will always be residual stresses which force the sealant to also
function as an adhesive. Contrary to manufacturers' claims, few
direct-glazing compounds are capable of sealing and retaining
highly stressed bent plastic windows for a reasonable amount of
time. UV radiation also degrades the sealants' adhesive
properties. Repeated expansion- and contraction-forces,
from the differences in coefficients of thermal expansion between
fiberglass and the window's plastic, not only subject the
adhesive/sealant to significant shear stresses but the plastic window
is forced to endure similar loads - often resulting is warping or
rippling. Leakage is a common problem!
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An abundance of deck hatches are often added in an effort to
compensate for the lack of opening cabin windows. The sailing
catamaran above has 3 hatch obstacles to overcome during every fore-aft
transit of the side deck. Stubbing bare toes on these hurts!
Tripping can send a person overboard. Falling into an open hatch
is very painful too. The large power catamaran at right has 12
such hatches; 3 obstruct passage along each side deck, 4 clutter the
front deck over the two beds and 2 more are placed above the raked
forward windshield. This may suffice on a clear, sunny day but
none
should be open during a shower or storm. Then what???
Operating the air conditioning or suffering in the clammy stagnant
interior are the only options.
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Boats, like houses, cars and airplanes, require ventilation
for the comfort of passengers and to avoid problems with condensation,
mildew and mold. The chart at right quantifies basic flows
of 1/3 -1/2 cubic meters of air per minute (10-15 CFM), required for
each passenger, and the minimum vent diameter to achieve this.
Closed windows and portholes have an effective area of 0, hence the air
flow is zero!
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There is one unique (patented) hatch available which
provides some ventilation (13.3 CFM in a 6 knot breeze) at the
almost-closed "venting" position. These "Sea Breeze" hatches are
manufactured by Bomar division of Pompanette LLC and function quite
well. The slots visible in the picture at right permit air to
flow when partially closed.
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The labyrinth, formed by the combination of proprietary
extruded profiles and the complex gaskets, separates water and permits
adequate air flow under most conditions. When dogged closed,
these gaskets compress to form a 100% water-tight seal. These are
the hatches specified for SEDATION
4. There are only 2 hatches on the vessel, one over each
queen size bed, which serve as emergency escapes and star-gazing
viewports too.
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SEDATION 4 has four large (7" x 17"
openings) screened portholes on the forward bulkhead, two for each
bed. These are shielded from rain by an 8" overhang of the 5°
sloped roof. There is an integral rain gutter molded-in to the roofs' surface, near the front edge,
that also re-directs light rain
and drizzle. The portholes are placed high for optimum protection
from the elements. A "storm screen" can be fitted into C-channel
on the underside of the overhang, then attaches to the front deck for
further rainproofing during nasty weather. Ventilation is
assured, therefore, in even the worst conditions. An additional
six (7" x 17") portholes are located strategically along the 10°
sloped upper walls of each hull. These "hooded" portholes provide
light and additional ventilation throughout the entire length of the
yacht.
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Air flow requires both an inlet and and outlet. Aboard
SEDATION 4 there are
2 vertical-sliding windows at the outer corners of the main cabin aft
wall. The upper sections can be slid-down
in 1"
increments and locked into position for security. These are
shielded from rain, by the 14" overhang of the salon roof, providing
231 in² of exhaust area under any conditions.
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Large, screened, sliding windows surround the main
cabin. The top-hinged windshields open-up to a horizontal
position for copious ventilation with unobstructed visibility.
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