Helmsmen

Helmsmen can be recruited by spending Rank Points. 1 Helmsman will increase your defense by 1 point. Each Rank Point spent will recruit 2 Helmsmen. So spending a full levels worth of rank points can hire 10 Helmsmen (5 Rank points x 2 = 10), increasing your defense by 10.

Note that Helmsmen will also help defend your ship from enemy Raiding attempts.