Backdrafting.(Station.wagon.effect) - Four winns 348 vista Owner's Manual

K. Backdrafting (Station Wagon Effect)
Backdrafting or the "station wagon effect" is caused .
by.air.movement.over.or.around.a.boat.creating.a.low.
pressure.area.or.suction.area.around.the.stern.that.
can.increase.CO.level.on.the.boat..Backdrafting.can.
be.affected.by.relative.wind.direction.,.boat.speed,.
and.boat.trim.angle..See.Figure.B-9.Backdrafting.-..
Airflows Over Boat and Behind Transom".
Under.certain.speed.and.operating.conditions.the.low.
pressure.area.may.form.in.other.regions.and.permit.
carbon.monoxide.to.enter.the.hull.through.openings.
that.are.not.on.the.back.of.the.boat..Boat.factors.
which.may.affect.CO.concentration:
Figure B-9: Backdrafting - Air flows over boat
and behind transom.
1.. Intentional.or.unintentional.excessive.trim.angle.
causing.high.bow.angle..See.Figure.B-10.
2.. Excessive.or.unequally.distributed.weight.
Figure B-10: Inefficient trim angles.
3. Canvas Configurations - Under various conditio-
ns,.adding.or.removing.canvas.may.raise.or.lower.CO.
levels..See.Figures.B-9,.B-10.&.B-12
Boating Safety - Section B
Exhaust Fumes!
Hull exhaust from your boat can cause
excessive accumulation of poisonous carbon
monoxide gas within cockpit areas when using
protective weather coverings (while underway
or while stationary). Provide adequate
ventilation when the canvas top, side curtains
and/or back (aft) curtains are in their closed
protective positions.
4.. Opening.and.closing.ports,.hatches,.doors,.and.
windows.may.raise.or.lower.CO.levels.on.board.a.
boat. When airflow is moving forward inside the boat,
CO.may.be.entering.the.boat..See.Figures.B-11..
and.B-12.
Figure B-11: Desired air flow through the boat.
Figure B-12: The effect of canvas configurations.
5.. Operating.a.boat.at.slow.speeds.with.a.following.
wind.should.be.avoided..Consider.changing.
direction,.adjusting.speed,.or.both...
See.Figures.B-13.
Figure B-13: Operating at Slow Speed
with Following Wind
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