I have been watching lots of replay videos lately. Between supernats and now Daytona. And see a very wide range of when/how people duck.
I have always kind of treated it like a crotch rocket. Duck coming on to the straight. Pop up, brake, turn in.
But it seems that a lot of people just duck till they hit limiter then pop up. What do you do?
Until just before braking point
I think ducking on the straights is more psychological than aerodynamic, though it may have some tiny aero/weight distribution benefit.
In which case I say duck however long or short you want. I’ve seen plenty of drivers sitting up pull away from others who are ducking.
Funny you say that. As I often only find myself doing it when I’m alone.
All depends how tall you are, lol. I block enough air it can be a big difference. I recline my seats now to get myself out of the air.
In @Terence_Dove’s book, he mentions that there was a study that tucking could save up to .09 seconds a lap at the track where they did the study, but that it was a full tuck. It really depends on the speed and length of straightaway. As TJ said, there’s probably a more psychological impact than an aerodynamic advantage, at least in sprint karting.
Im pretty sure that situationally it matters. Draft is a thing. Even in dinky rentals. But, to, me it’s mostly mental. Giddy-up!
To get any aero benefit you really have to bury your helmet into your crutch.
I’m 6’0, and I’m a world formula at a road course I’d gain about .8 mph. I geared for drafting but lost the draft, so I wasn’t even hitting the rev limiter. Draft gave me about 3mph
Is there more effect in tucking by moving your weight forward, thus releasing some strain on the rear and allowing the engine to spin up faster? maybe more when used directly out of a corner onto a straight…
You see folks hopping in their seats in low hp stuff. I can’t tell if it helps.
That’s one theory that’s always been thrown around.
Maybe I’ll make a video on this in the summer and test it.
This has been done on standing starts (most of my experience is in street racing) for years and years. Just trying it, in the low hp classes it does seem to help a little (maybe placebo?). It definitely doesnt hurt. There are a lot of other good tricks standing start people use that are much more important, though.
The ol foot on the front tire while you rev up pre flag drop? I have never done that.
Also amusing in rental races: backing the field up as you prepare to hit main straight if you have pole in the warmup lap.
I don’t duck, I lean (slightly) forward to activate my DRS down the straights and pop up just before a turn . . .
There is a great video somewhere of Kip Foster at the last Supernats Australians could actually travel for, so maybe 2019? He was racing masters.
On the straight he would slide his bum forward in the seat, making him able to get his whole body lower and out of the airflow. Then he would pop up just before the sweeper into the finish line.
You could watch his feet changing positioning on the pedals, really impressive.
Did it help? No idea, he was in a class of his own all weekend.
I’m pretty sure it does help, both. How much depends on your physique but air resistance is definitely a factor. Well, definitely my opinion at least.
When I was skydiving back in the day aero was everything, we’d wear different material suits to each other on formation dives - heavy weights would wear a more cotton type suit whereas the lighter guys would wear slick suits, the idea being to fall at the same speed as each other. Flatten out your body from arching you fall slower than the others, reduce your mass by tucking arms in or even standing up straight you fall faster. Translate that into karting if you present less body mass to the airflow you’re creating with forward speed, less resistance against that airflow means higher forward speed. It’s not much, but it’s there.
You can bounce, tuck and duck all day long and it’s not going to do you any good if you’re still chasin multiple tenths on the guy running P1. 
Very true. Sometimes it’s just not worth the effort. That said if I’m massively short of pace compared to P1 but ducking and hopping helps me get on the bumper of P5, I’ll do it. Otherwise what’s the point of even starting.
I can almost guarantee it’s not helping anyone on a Sprint track.