What were the consequences of the battle of Trafalgar?

Answer 1

The French Navy was required to build a new fleet and a new Navy.

Answer 2

For France it meant replacing the Franco-Spanish fleet before an invasion attempt on the UK could even be considered. How big an enterprise would this endeavor entail leads to a lot of speculation. Consider a few of the attendant problems that this high priority project would require based on the production of 45 ships of the line:

1. Obtain 450 mature oak trees, cut it, cure it, dry it, age it and deliver it to to the nearest shipyard at an enormous cost. Elapsed time about two years.
2. Recruit and train 2,000 additional shipwrights for the project and have them ready to go to work once the lumber has been cut and planed to begin building. Don't forget to order at least 180 good masts and the over 4,000 ships guns required.
3. Start building and expect each ship to take two years for construction even with an improved shipyard and the new shipwrights that you have trained.
4. Recruit and train your ships crews so that they are ready to launch their ships 4 years after you have started the build up.
5. Take a shake down cruise and practice at sea gunnery. Invade England.
6. Finance the project.

In the meantime the Royal Navy controlled the seas, and had been improving their ships, seamen, tactics and gunnery all of this time.