Unhappy with my soft field take offs

rudder authority to counter the roll

Rudder for yaw, and ailerons for roll. .

Torque is a smaller effect on GA aircraft. Detectable, but all other things have to be in pretty good balance for the torque affect of an O-235 or O-320 to be a detracting factor in a takeoff. I sure would not accept the excuse that the pilot could not maintain control of the 172 because of the effects of torque!

400 HP on the front of a 172 would be enough that torque would require considerable application of control to counter. I would use the rudder (and steering) to keep it straight on the runway, and ailerons, (with co ordinated application of rudder, if the directional control was still favourable), to counteract any wing drop at low speed once in flight.

I was not thinking of a crosswind, but rather the torque roll from full power at stalling speed (JasonC alludes to this above). Lower powered aircraft will have sufficient rudder authority to counter the roll, but a pilot can be surprised by the amount of rudder required - hence the need to practise.

Extra skill is acquired through pushing the envelope under controlled conditions.

During any operations on the runway, the only time you'll get close to a rudder or aileron application limit is during crosswind operations in excess of the demonstrated capability of the aircraft. It would be rather poor pilot decision making to attempt a necessary soft field takeoff in a crosswind so extreme.

Strong crosswinds (winds in general) are usually accompanied by gusts. Those gusts really work against a soft field technique, even when aligned with the runway. Yes, a headwind will get you up in less distance, but the lull between gusts, will have you settle back. The natural pilot reaction to the "up and down" will be corresponding pitch control inputs, which at the slower speed will become even more extreme and less precise. Doable, but difficult.

Yes, I agree that practicing the technique on a regular basis is excellent, and some crosswind is okay, but the capability of the aircraft will become limiting, and flying in those corners of capability requires extra skill.

Of course soft field technique is not just for short grass strips, it's also useful for getting off a slush covered hard runway.

As with most things it's worth practising in controlled circumstances, i.e. try it on hard runways at progressively lower speeds and greater flap settings to get used to the feel and to anticipate the roll-off and the amount of rudder available.

may be off-topic because it's not stick & rudder technique, but ... be careful on short soft runways and check that they didn't get too wet and too long grass. Also consider the wind - an indicated crosswind at the place of the windsock may easily turn into an average tailwind component along the runway. Take care of the density altitude. Don't operate too close to the performance limits of the AFM if it contains any data about soft field take-off length at all. As a young lad I made it barely over a fence (centimeterwise) beyond which a flock of sheep was grazing ...

The advice I was given by experienced pilots post-PPL, and which conflicted with what instructors had taught me, was that in the takeoff roll the first 10 knots are the hardest to get.

Hence when backtracking a short strip get all your final checks done during the backtrack, get right to the end of the strip and turn it through 180 degrees at the quickest safe taxi speed possible and apply full power as you come out of the turn.

Opinions vary on 'popping' the flaps. I can see the logic on a very soft strip of applying a force that will encourage it to leap into the air, but also appreciate the risk of loss of control. I have never done it, but have sat next to someone who did it and it appeared very effective. Presumably it depends hugely on the properties of the individual aircraft, and is less practical with electric flaps.

In my experience, at low speed the rudder is even more effective in picking up a wing than the ailerons.

Yeah, that's another discussion.

However, in the context of a soft field takeoff, you're going to use the ailerons to keep the wings level, or as nearly so as you desire (possible crosswind), and you're going to use the rudder to maintain the runway centerline, as you accelerate close to the ground. Hopefully, these can be co-ordinated control inputs, but in any case, roll and lateral displacement must be controlled.

Staying low to the ground is not so much to be in ground effect, though that effect is an added bonus, but it is more because you probably broke ground hanging on the stall, and accelerating close to the ground will be more safe than climbing away in a nearly stalled plane, which is now even less able to accelerate, because you're trying to climb too!

Concur with what's been said here. Don't apply full brakes with full power on a soft surface - keep the aircraft rolling as much as possible. If possible, even do your runup checks on the move and if that's not possible, on the firmest surface you can find - which may not necessarily be near the hold.

As far as accelerating in ground effect is concerned - I think ground effect is effective up to half the wingspan or so. In a high-wing aircraft you'll be out of ground effect very quickly unless you really hug the ground. Ever notice the difference in the flare/float between, say, a C172 and a PA28? So don't think of 'ground effect' as the reason for staying low early on. The main reason for staying low after lift-off is to reach a safe climb speed. Vx is quite a few knots higher than Vs0 after all.

Are you using the rudder together with the ailerons if the aircraft rolls at low speed? In my experience, at low speed the rudder is even more effective in picking up a wing than the ailerons.

Well I don't need to worry in the P46T. Not enough rudder authority to do a soft field takeoff without demonstrating an inverted landing. Although you do do the ground effect approach for a hot and high departure but still using 85kts as your Vr.