I have a 2014 Cannondale Scalpel Carbon 2. It's an amazing XC race bike but some courses are so gnarly that I'd love to have a bit more trail. The head tube angle is so steep. I would like to make it just a bit slacker without having to buy the new 2017 model. Is there any way to do this? I am new to biking and bike mechanics so I hope I got all the terminology correct.
If you get a fork with longer travel, it'll result in a less-steep head tube angle, and a higher BB. I'd say it's worth trying, but in your case there is a major complication: the Lefty fork. So you have two options:
Get another Lefty with longer travel. And I don't think they sell those separately, so that's probably impossible.
Get a normal fork. And this will means replacing the parts that are designed to work with the Lefty: the front wheel, the stem, and the headset (you'll have to get a special reducer headset to make it fit in the over-sized headtube.) This is definitely doable, but you'll be better off just buying another bike.