I've run a few tests with this result:
During combat, a ship is designated as "unarmed" if its minimum beam range is equal to zero.
If a ship is designated as unarmed, then its beam type and torpedo type will still be displayed correctly, but without the numbers and strengths.
For example, instead of
"6 Phaser Banks ... 40"
the game would only display
"Phaser Banks"
So if you're giving a ship torpedo launchers, but not beam weapons, then make sure that its minimum beam range is set to something greater than zero
