Short answer - yes, you're crazy.
Longer answer - if you are going to need outside funding doing two at a time is going to be challenge and, if you find investors who will back you, they will probably apply either a significant valuation discount or otherwise impose penalties, restrictions or high performance requirements.
If you don't need outside money (or can make it far enough to borrow rather than raise equity) AND you are really confident about your skills and capacity, go for it. Remember, however, that most people who are running multiple businesses simultaneously have the resources to be steering the ships but not handling much day-to-day executive or management duties. Mark Cuban, Richard Branson and Donald Trump keep very talented people around them to run their companies - they are the brand and the keeper of the vision but not the management.
Good luck - sounds like fun whatever you decide.