Figure B7: The effect of boats moored along side.
K. Backdrafting (Station Wagon Effect)
Figure B9: Inefficient trim angles.
Backdrafting or the “station wagon effect” is caused by
air movement over or around a boat creating a low pres-
sure area or suction area around the stern that can in-
crease CO level on the boat. Backdrafting can be af-
fected by relative wind direction , boat speed, and boat
trim angle. See Figure B8 Backdrafting -Airflows Over
Boat and Behind Transom”.
Canvas Configurations - Under various conditions,
adding or removing canvas may raise or lower CO
levels. See Figures B8, B9 & B11.
Hull exhaust from your boat can cause exces-
sive accumulation of poisonous carbon monox-
ide gas within cockpit areas when using protec-
tive 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.
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:
Opening and closing ports, hatches, doors, and win-
dows 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 B10 and B11.
Figure B8: Backdrafting - Air flows over boat and
Figure B10: Desired air flow through the boat.
Intentional or unintentional excessive trim angle
causing high bow angle. See Figure B9.
Excessive or unequally distributed weight.
Figure B11: The effect of canvas configurations.
Operating a boat at slow speeds with a following
wind should be avoided. Consider changing direc-
tion, adjusting speed, or both. See Figures B12.
Sundowner™ Owner’s Manual
|Categories||Four Winns Manuals, Four Winns Sundowner Manuals, Outboard Marine Corporation Manuals|
|Tags||Four Winns Sundowner 205, Four Winns Sundowner 225, Four Winns Sundowner 245, Four Winns Sundowner 285|
|Model Year||2003, 2004, 2005, 2006, 2007, 2008|
|Document Type||Owner's Manual|
|Product Brand||Boats and Cruisers, Four Winns. For support contact your dealer at http://www.fourwinns.com/locate-dealer.aspx|
|Document File Type|
|Wikipedia's Page||Outboard Marine Corporation|
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