Capture or purchase a Class 1 battleship. Go to the store and purchase cannon ammunition, sailcloth, planks, etc. up to the maximum payload capacity of 4500 lbs. Next, go to the shipyard. Highlight "Battleship", then buy any other ship desirde. Class 2 super fast frigates or corvettes with 24 lb. cannons are recommended. You will now notice that you still have your entire battleship cargo, even though the payload capacity of the frigates and corvettes is less than half of the battleship's payload capacity. Choose your original cargo wisely, as once you swap ships you cannot purchase any more cargo until you are under your new ship's maximum payload capacity.