Would appreciate some information on the age of sail in general if nothing more specific about the napoleonic wars and the repair of ships. The British navy captured a bunch of vessels and yet especially during this battle, they never were redeployed. Why? I don't know much about the repair of boats, but the British kept building more ships during the war. Wouldn't it be Cheaper to just fix these boats than build entirely new ones? Any info or direction to a repost would be helpful! Thanks.
I wrote about Trafalgar in this older post. Surprisingly, it's not a question that comes up a lot.
The basic answer to your question is that most of the captured allied prizes (allied here, of course, being the Franco-Spanish alliance) were destroyed in a storm after the battle, with some of the remaining being retaken by their own men (that is, they overwhelmed the prize crews and recaptured their ships). After the battle, some allied ships escaped to Cadiz, from which they sortied on 23 October in an effort to rescue some of the ships the British had captured. Collingwood, after Nelson's death in charge of the British fleet, was heading toward Gibraltar with his prizes, and had to cast off several of them to meet the enemy attack. Two of those were recaptured by French frigates, but several of the others were ether retaken or wrecked. The only four ships that survived to reach Britain were the Spanish ships Bahama, San Ildefonso and San Juan Nepomuceno and the French Swiftsure.
You're correct that the British did often buy captured ships into their own service, unless they were too badly damaged to be useful -- other navies did that as well, which is why there were two ships named Swiftsure at the battle -- the British Swiftsure built in 1804, which took the name of the Swiftsure, a British ship launched in 1787 and captured by the French in 1801.