"Beer can" grain hoppers

[CShaveRR]

Canadian carbuilders stuck with the cylindrical carbodies much longer than ACF did--companies like Marine Industries were building these cars into the 1980s, while the last cylindrical Center Flow was built in the mid- to late 1960s.  These were supplanted by cars with more of an "inverted tear-drop" profile.  Lately the design without a center sill appears to be falling into disfavor, and what you're seeing are cars like the Trinity 5161-cubic-foot car with curved sides and a center sill.  Even ACF's successor is now selling a "Through-sill" car that looks a lot like a Center Flow, but with an obvious difference.

Advantages to the cylindrical design included greater volume for the length of the car, and a profile that allowed better utilization of the space at the top.  The tear-drop shape further refined this.

Besides Alberta, Saskatchewan owns a bunch of the cylindrical grain cars, as does (did?) the Canadian government.  CN's and CP's cylindrical cars were mostly smaller, and have found favor for the transportation of potash (though both railroads are now carrying the potash in bigger cars that used to be used for grain stateside).

[GP-9_Man11786]

The main advantage of this design is that the car has no center sill. A common problem with conventional covered hoppers is that the cargo would hang up on the center sill during unloading. The cylindrical unibody design eliminated this problem. These cars are generally made by ACF and for the most part look like regular hoppers with slanted ends. However they are made with the "beer can" design as well. In fact Atlas O makes a nice model of the beer can style.

[Murphy Siding]

     Every now and then ,during harvest season, I see odd-ball grain hoppers shaped like a beer can.  Generally, they are Canadian.  In fact, I saw some today that had Alberta witten in big letters on them.  Why are they this shape?  Is there any advantage?