taken over by the navy during construction and beefed up to stand up to some serious combat as they were intended to sail with the convoys to take on merchant raiders in a stand up fight. They used the half built merchant hulls as they needed to look like merchant ships, but gave them better engines, more compartments and some side armour.
The original q-ships were armed merchantmen designed to take out submarines, but when they built the anti-raider ships they also gave them the Q designation.
Then you also get the DEMS as well in WW2 - Defence Equipped Merchant Ships, essential a merchant-ship with a gun or two mounted on it, usually on the stern . The Q-ships were Naval vessels and no cargo while the DEMS were merchant vessels with a navy gun crew on board and a full cargo.
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