Since Brooke Henderson got her first major this past weekend, I thought it might be interesting to take a quick look at that unusual driver swing of hers. This isn't something everybody should try, but understanding why it works might help you improve your own drives.
This video shows her at normal speed, then slowed down. It's less than two minutes long, so you can watch it several times if you need to.
First off, they said Brooke's driver is 47 inches long in this broadcast, 48 inches long this past weekend. It doesn't matter that much; what does matter is WHY Brooke uses a long shaft. She grips down on the shaft two or three inches (she does that with all her clubs) but this allows her to still get the kind of distance off the tee that she would if she held a normal driver at full length while also getting a bit more control.
I'll add an extra thought: The extra shaft at the butt end of the club can help counterweight the club at bit. That would make the clubhead feel a bit lighter, and might help her get a little more clubhead speed.
Kay Cockerill notes that she has a one-piece takeaway. I know I talk this into the ground, but a one-piece takeaway can do more than almost anything else to give you a good swing. If you start your swing well, it's much easier to finish it well. My primary post on how to make a one-piece takeaway is right here, if you need it.
Brooke overswings. So does John Daly. So do a number of good players. Overswinging isn't a problem as long as you can control the club at the top of your backswing. That means you need a stable body position throughout your swing. That's important.
On the way down, Brooke seriously re-routes the club. She really flattens her swing plane on her way down. Kay talks about this in the video. Stop it at the 1:20 mark and you'll see just how much her hands have dropped, way below her trailing shoulder.
Look at how close her trailing elbow is to her side! That's how she manages to pull this off. Brooke is almost making a baseball bat swing, and she's letting her trailing side brace her arm so she can keep the club in position as she turns through the ball. This is mostly a body swing, and her arms don't really swing away from her body much until the ball is long gone.
This swing is so flat that it can be troublesome unless you're hitting the ball off a tee. For comparison, here's a wedge swing from the same tournament. Notice that this swing is more arm-oriented and much more upright. Otherwise she'd hit a lot of fat shots.
Brooke's driver swing is really unique. However, gripping down a bit on the shaft (for better control) and making a one-piece takeaway (to get the club started back on plane) are two things you can definitely copy from the newest Women's PGA champion.