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By flyingdawg
#383953
Fun and scared are not synonymous in my flying but maybe a lot of that has to do with my home flying site--the Sandia Mountains in Albuquerque. Anyone who was around back before all competitions started being held in mellow tow conditions heard the stories of the extreme thermals you can find on the Sandias. Some competition pilots refused to return after flying Sandia mid-day. Pushing out too far here can be a really bad thing. It's an incredible and beautiful place to fly but you had darn well better respect her or Mother Nature will spank you good.
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By Mavi Gogun
#383955
mbadley wrote:Really - of course pushing out for all you're worth and then slowing down too much, can result in a spin. I don't think I've ever had that problem with a thermal making my vario peg out. The forces that make your downwind wing stall out and start the spin are not present with the uplifting thermal force. So, when you feel that thermal tail off - well you pull in, natch. Same thing if you go over the falls, you pull in and get speed up again.

The other problem with being pushed out too much is the whip-stall. Those have a nasty habit of making topless gliders tumble (kingposted ones aren't totally invulnerable). So, it you are pushed out too much and things are getting very quiet - you would be wise to pull in.

I appreciate your advice and concern! Putting any glider into an attitude other than straight and level can result in risk and danger. (and, gasp,should we say it? FUN)
A combination of hedges, equivocations, and absolute proclamations here might be dangerous to the uninitiated. Were the advice to have gone unchallenged, some unknowing pilot might have followed course without qualification.

By nature thermals are unstable. Contrary to the above claim, spins are entirely possible in a thermal. The prospect of recovering sufficient speed to avoid a tuck/tumble when "going over the falls" depend on how violent the thermal, the transition, how extended the posture, and rate of pitch. A sharp, violent exit can result in a tumble, even if not fully extended. Too rapid a pitch adjustment can result in a tumble.

Is this bank and pitch angle appropriate for this thermal? If the answer is "I don't really know", then "put it on a wing tip and push out as far as you can" is not a good plan or sound advice. This judgment is developed over time, a natural progression from lighter thermal days to stronger, along the way discovering what bank angle can combine with what pitch to deliver control when getting dumped out of a thermal or smacking into turbulence.

It's a real challenge to keep a clear image of what it is like to be a relatively inexperienced pilot for those whom flying has become second nature. All the "but of course I don't mean"s often come too late, if at all. I highly recommend discussing what was proffered here with a mentor; specifically, ask about the threats of flying too slow or fully extended in thermals and what attitudes offer stability and recovery advantages.

There's nothing like being scared to suck the fun out of flying- except for, you know, getting hurt.
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By AIRTHUG
#383992
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...
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By Jason
#383994
im going to jump on the bandwagon here........


I almost never push out in thermals......unless Im scratching and need to fly as slowly as possible on the edge of stall...

other that that Im usually pulled in a little if anything, and my glider is trimmed on the farthest forward hole (t2c144 with 160 lb pilot+harness)
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By TjW
#383996
As far as staying flat vs getting in the core:
At Crestline, the lift is typically stopped by an inversion layer.
If you're flying flat turns, when you get close to the inversion layer, you'll run into all kinds of burbly garbage, while the inner core may (or may not) punch completely through the inversion layer and speed up.
If it doesn't, you still get the burbly garbage, of course.
So given equivalent climbs, I'll tend toward the tighter turn, because once in awhile, you'll punch through and get much higher than you originally thought possible.
Also, the tighter turn tends to be a better signal to other people what you're trying to do.
I've seen people flying low bank turns this direction, then that direction. If I'm above them, it's not much of a problem. But trying to climb through someone doing that is a trial. Yeah, I know the upper glider is supposed to give right of way to the lower glider, but I don't want to be a d--- about it by cutting him off.
Much easier when you can just come in opposite him at pretty close to the same bank angle.
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By Mavi Gogun
#384007
Jason wrote:other that that Im usually pulled in a little if anything, and my glider is trimmed on the farthest forward hole (t2c144 with 160 lb pilot+harness)
Great point of including how your glider is trimmed, giving context to the rest of your method. Trim, loading, model of glider- all make for a different story.

I do whatever the thermal demands. In weak lift, that might involve staying flat and shoving the glider around- you can often tell what sort of day it was by how much skin is missing from the base of my thumb. The other day I had the glider rapped up on a wing tip and the bar fairly extended- but still with plenty of energy in the wing.

I got distracted by mundane concerns while searching for lift one day, my mind wondering; some time later, the sound of the vario screaming demanded my attention, and I found myself banked over hard with the bar fully extended, nose high, racing UP in the fastest climb I've ever taken. While the wing was fully loaded, the peril was palpable- I eased the bar in to a place that I thought would afford a margin on scale with a mother-load thermal... reducing my climb rate only fractionally. Apparently, I thermal best when my consciousness is removed from the process- but the analytical side has to be around to hold the reins if I want to stay alive.