mbadley wrote:don't worry about angle of attack as much as bank angle. Put as much bank as your thermal will hold and slow down (push out) as much as possible. Pull in a bit on the downwind side to get around QUICKLY. Staying in the BEST meat of the thermal is more important than turning perfectly coordinated circles. When you're centered - just put one tip towards the ground, push out for all you're worth and watch your vario scream UP, UP, and AWAY at you.
I'm not here to say my way is "the" way... but this is
not at all how I thermal.
First, I try to bank as shallow as I can, but as steep as necessary. What I mean by that is- often you can do flatter turns in a weaker portion of the thermal, or tighter-steeper turns in an inner core (note I said 'an' inner core- there can be more than one!). How do you know which is better? Well, experience helps LOL But to get there, use the averager on your vario. Do 5 or more flatter 360's in the weaker outer part, and then try to turn tightly in a core... sometimes the differential between the core and that slower outer part of the thermal is enough to justify the steeper bank and tighter turns... sometimes it's about the same result, or better even, to concede the core and relax doing the bigger turns. After a long time of trying both in a wide variety of thermals... you'll start to get a feel for it, and at that point you sort of know when to widen up and when to tighten up. And- thermals often shift gears on you as you climb... so I might widen and tighten several times within one single climb!
I agree flying slowly = climbing efficiently. I disagree about pushing out. In a turn, our wingloading increases. As wingloading increases, stall speed increases. The steeper we bank, the more G's we're pulling... so in a really tight, steep banked turn, your stall speed - that is, the angle of attack at which the airflow separates rather than flowing over the wing and generating lift - comes sooner than you might expect. Add to this that we fly flexible wings; as wingloading increases, the airframe can flex more, and the sail can washout more... when a really heavy pilot flies a small glider, they need to adjust the hang point FORWARD for this reason. Intuition usually leads us to think the fat guy will be zooming around on that tiny glider, so move the hang point aft... but no... because of stall speed and changes in wing twist, he needs it trimmed faster or he'll be stalled all the time (or dangerously close to stall all the time).
On a single surface or lower performance double surface, any wing that provides a reasonably strong amount of pitch pressure feedback, I find letting the bar find it's own trim happy place gives me the most efficient climb for whatever bank. If I'm trying to stand it up on a wingtip in a tight little stick thermal, I might be pushing out a TEENY bit, at most.
On a high performance glider with much lighter bar pressures (less twist, less sweep)... the wing sometimes needs a little more help finding that happy trim position. I still wouldn't describe this as "pushing out" as I would just being an active pilot because this type of glider doesn't do it for me as much.
So, flying slowly = climbing efficiently, yes. BUT! Flying slowly reduces control, and keeping the glider accurately positioned where you want it trumps any small sink rate or turn diameter advantages. Also, a stall in a hang glider is not a binary thing- it's not a yes or no, on or off thing. It's a gradual onset, with plenty of "mush zone" between a fully flying wing and a drop-the-nose stalled one. Pushing out, especially at a steep bank angle, might FEEL like you're doing a great job of tightening up in the core... and "coordinating" pitch with the steep bank... but the wing is usually somewhere in that mush zone, and not flying efficiently at all. I find relaxing on the bar and keeping the WHOLE wing flying efficiently is almost always the best climbing strategy.
I would confidently describe myself as a pretty good climber... and I think anyone that's flown with me- especially in the Santa Cruz Flats Race competitions, when I'm really really trying hard- would vouch for that. I'm again not trying to say anyone is
right or
wrong... but I've found this way to work better for me than many others... so you might consider giving it a try...
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Three additional notes:
* As I travel around and fly with people all over... I find that many, many, MANY of them seem to turn a little too wide for the lift they are working. This may mean flying too fast, or not banked enough... or probably a combination of both... if I'm not exactly sure how tight I should be turning, I like to error toward tighter. A slightly slower climb inside the thermal trumps falling out of the thermal and turning in the sink on the edges, right? Once established and centered well, I can try turning slightly flatter and feel out the thermal to see what's "out there".
* Besides all these efficiency issues I talked about, there are some SIGNIFICANT pitch stability (SAFETY) issues with pushing out. Moving the aircraft's CG aft destabilizes it in pitch... doing so within a thermal, where you might fall out and possibly get pitched down a bit... not a wise combo
* If you've flown with me (or watched my videos), you might see me pushing out in climbs at times. There is a BIG difference between pushing out and holding it there, trying to make the glider fly slower, and using pitch to adjust placement within a thermal. A brief push out can accelerate heading change and adjust where you are in the thermal. Doing this either requires planning ahead, and pulling in to gain some extra airspeed/energy first- to fuel the heading change acceleration- or you can expect to need to pull in or even dive slightly afterwards, to replace the energy (airspeed) spent...
Shut up and fly.