I’ve busted my ass twice now on this small dip at my local trail, about 3-4ft decline then back up, and am looking for some pointers. I’m about to put a brake set on my 24" Nimbus but I’d like to get the technicals down. If I try to go real slow down the hill I get bumped off about half way down. Also, too slow means the trip back up the dip is TOUGH. If I try to ride it out the Uni goes flying. I see people bombing these massive downhills in clips and there’s got to be a trick to it.
Any help would be appreciated!
I hear ya, that is my problem too. The quick transition from going steep down to steep up gets me every time. Hopefully this thread produces some good results 
I only use my brake on long drawn out down hills to save my legs on shorter technical slopes I prefer to use my legs to manage my speed and hold on tight with one hand and use the other for balance, this way I can also stop and hop off drops or change line, regain my balance etc.
On a short up down as you describe I would probably not resist the pedals at all and go with it building up momentum for the up slope, the faster you go the more stable you are to a certain extent anyway 
Also if you are getting bumped off is your tyre pressure a bit hard and are you standing up enough so as to use your legs as suspension?
Speed comes with technique and confidence which you get in time, I have only been riding for 5 months but have picked it up quickly and put in a lot of MUni time so am only recently pushing my speed which is not only enjoyable but actually makes going over rough terrain and drops easier (although will cost you more if you make a mistake). Some of the downhill vids show epically fast people which I use as my intensive to et faster.
If you haven’t already get so leg armour, wrist guards and helmet and go for it, you will be surprised the confidence you get from being protected a bit.
Finally remember to laugh when you hit the ground get up go back to the top of that section and hit it again, on the saddle or in the dirt is it all fun 
Dips like that look worse than they are. If you’re too tentative, you’ll come off the back every time. You have to get past the fear and keep your weight over the wheel. The rest sort of happens on its own. Just hold on tight to the handle and go.
That is down to your fore and aft lean/weight distribution
You will be leaning back coming down if you are resisting or maybe almost upright if you are spinning the cranks to fly down the hill and gain speed for the up, either way when you hit the transition to up hill you are going to be pitched forward so you need to lean the Uni back to compensate and maybe pull up on your handle, this will also allow you to really push hard on the pedals and capitalise on your momentum, at the same time I would probably lift myself off my seat slightly as I hit the transition, eventually fully standing and slogging up the hill if I ran out of momentum
No different to the sudden rear lean you would do hitting a curb or root accept your not going to bump over but carry on going up
High gear with brake
I do lots of deep water bar crossings (some are four or more feet deep). I find shifting into high gear and bombing through at 9-12 mph against the brake works best when they are on down hill sections. Faster is smoother than slow. Clipless helps maintain peddal contact when they are rough or rocky.
JM
Part One: Ride down to the bottom of the hill at a normal speed, then come to a complete stop and dismount before the drainage.
If can’t stop before an obstacle, you are out of control, so this just should help you gauge your level of control. Practice this until you get it.
If you are getting bumped off when you try to go slow, then you are already out of control, so you need to work on “micro managing” that slope from the start. A brake might help, but only if you can use a brake well, otherwise it could make it harder. Long cranks would help, as would good technique.
Part Two: Do repeats on that dip, starting at the bottom of the hill, until you can get it.
Part Three, put it all together.
I try to control being “out of control”. It’s similar to falling for miles and landing on your feet at the end powering through the brake.
I do a ride where I muni for 4.5 miles down hill and descend 2000 feet in 25 minutes powering through the brake more than 4 miles of it.
http://app.strava.com/rides/9933005
JM
Yeah, that’s a big part of how I use a brake, peddaling into a mild to moderate downhill while riding the brake for resistance.
But it seems like he’s talking about a steep hill that requires significant pedal back pressure for control, so I’m thinking he needs to work on crank based control before adding a brake.
He’s riding a 24 which is a really small wheel, probably 150mm cranks, so that should be plenty.
@Dartmech: Are you sitting on the seat when you go down the hill?
So basically when you hit the bottom of the ditch, your uni would momentarily pause as your upper body transitions from leaning back to leaning forward. Follow this by a good pull up on your saddle to get your wheel moving again?
I think the answer is pretty much the same as for all else unicycle-related: practice. 
I’ve got a very similar terrain trap on one of my usual trails, that even throws off a lot of bikes. The first time I got it, I was so excited that I wasn’t paying attention and UPD’d shortly after the dip, and then a biker totally lost it on the dip while I was watching and nearly took me out. The spectacle of watching me ride the dip then UPD probably didn’t help him any with his focus. 
professionally built single-track is designed with a mountain bike (that can coast) in mind. On a trail with “good flow”, a bike should gain just enough speed down the dip to make to the top on the other side without too much pedaling. Riding MUni, the fun begins when you can make it up that next hill, so you can go down the one after that.
Brakes (preferably disc) are for long sustained downhill.
I’m not completely on the seat… I try to slow down significantly right before I start going down so I’m not flying down, I think I’m running 165 cranks (dual hole KH supplied with the UDC build). As I think more about the situation, I slow, get a tad wobbly because of my already moderately fatigued legs then try to creep down the slope while maintaining a few inches between me and the seat. But when a sudden drop of about 5-6 inches comes along during the decent that’s usually when I hit the seat and pop off. Thats why I was thinking if I just flew down I wouldn’t notice these “bumps” as much.
My set up is 24" with tire pressure pretty low to absorb the roots and things, seat lower then normal riding so I can stand when I need and get some clearance.
I’m going to just try and take 'er slow until I can build up speed each time. I’m not expecting to use the brake on this particular trail because I agree brakes are best for continuous downhills.
I’ve got full leg armor, gloves, wrist guards, helmet, etc. Murphy’s law I left the elbow pads off this last ride and skinned it on my last fall down my favorite dip.
I’ve heard some say to run the cranks on the smaller holes for these things but I would hate to loose the power going up hills.
Practice on just the “crux move” which seems to be throwing you, then once you can get it without trouble, work the downhill in, you’ll get it. Fatigue and distraction are the two things that make me UPD, that and not seeing a root or rock 
There also may be a way to hit a different line…