Page 54: of Marine News Magazine (November 2020)

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Propeller Considerations for

Inland River Pushboats

By Donald MacPherson, Technical Director, and Adam Kaplan, Project Manager Propeller Tools, HydroComp

Images courtesy of HydroComp

Figure 1 – Pushboat hull nland river pushboats operate in a harsh environment. ence of the vessel.

Transiting our rivers, bays, lakes and inland waterways, The hull shape establishes the environment for the pro- these vessels push barges between hubs of commerce. Swift pellers, and the particular characteristics of a pushboat hull currents, trash and debris, heavy traf? c and narrow water- will greatly in? uence the selection of the basic style and

I ways are day-to-day realities for these vessels and operators. principal parameters of the propellers. Typical hull charac-

Pushboats have two typical modes of operation: steady- teristics of inland-river pushboats include a ? at nose (for state (long haul running) and transient-dynamic opera- pushing against the barges), a wide hull to provide space tions (backing, maneuvering and acceleration). Unlike for multiple side-by-side engines (for the substantial in- almost any other vessel type, pushboats have a larger pro- stalled power requirements), a shallow hull (for operation portion of dynamic operation which will affect the selec- in rivers and other shallow waterways), and an upturned tion of engine and propeller characteristics. stern to accommodate a large propeller diameter (to part- ner with the large engine power).

The vessel-propulsor-drive system Due to the shallow and wide stern, the in? ow into the

Each component of the system affects the others, so propeller is not ideal. The ? ow is strati? ed with slower wa- they must work together to achieve useful thrust-making ter closer to the hull. The non-uniform wake ? eld means performance. The propulsor—typically an open or ducted propeller will be seeing high variation in blade angle of propeller—is the central element of the system, taking en- attack against the water ? ow.

ergy from the drive and developing thrust within the in? u- Engines on inland river pushboats are still typically high-

November 2020

MN 54