Guards on a steamboat were extensions of the main deck out from the boat’s main hull.
Guards were originally adopted for side-wheel steamboats to protect the paddle wheels and to provide a mounting point for the outer ends of the paddle wheel shafts.
[ The main deck planking extended out over the guards, and when a steamboat was fully loaded, and sunk deeply in the water, it often appeared that the edges of the guards marked the line of the hull.][
The size of the guards was governed, on a sidewheeler, by the width of the paddle-wheels and their housings.][ On early steamboats operating on the ]Mississippi
Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...
and Ohio
Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
rivers the overall width of the vessel, counting the guards, did not exceed more than about one-third of the hull width.[ However, by the 1850s, the width of the guards in extreme cases was more than twice the width of the hull.][
For example, the hull of the ''Jacob Strader'', a large vessel (905 tons) built in 1853 for the Cincinnati and Louisville Mail Line, was 27.5 feet wide, but measured over the guards the main deck was 69 feet across.][ While the ''Strader'' was an extreme case, it was common for guards to make the main deck 50 to 75 per cent wider than the hull.][
Guards were also used on sternwheelers, where, with the paddle wheel being mounted at the stern, they had no structural function on the vessel.][ On sternwheelers the guards gave additional room to store freight and fuel, allowed a passage between different parts of the boat, and provided a place for passengers to promenade.][
One problem with guards was that they could make the steamboat less stable, and with the type of boilers used on the Ohio-Mississippi boats, even a list of ten or twelve inches to one side could cause the boilers to malfunction, which, if prolonged, could result in an explosion.][ This was difficult to manage, especially when for example passengers would crowd along one side of a boat to observe an attraction.][
]
Notes
{{reflist
Steamboats
Ship design