Godfrey Wenness writes in XC Mag that a tail wind component isn't the most important part of a PG pilot's XC potential. Why not? Well, he says, you only spend 50% of your time gliding, the rest of the time you are climbing and looking for lift, so you don't drift. Er...
Difficult to tell a world record holder he's got it so obviously wrong. I mean, for mountain flying, where you might hang in ridge lift waiting for a thermal to trigger, you might say he's right. But Australian flatland flying round Manilla? Eh?
Now, I should show a least a little modesty since he's done loads of 300km flights or whatever and my longest is 75km OR (and yes I'm on a HG). But even so: if I look at the stats in SeeYou, I managed over 60-65% straight lining, 35kph average XC speed, and my thermals generally bend with the wind. Indeed, the thermal drift and cloud development were exactly the main reasons for my flight direction choice. And for the section shown, my downwind departure leg from this thermal was 10kph faster than my return leg. The thermal drift is 10kph: so in fact one might guess that my return leg should have 20kph slower than this. But it wasn't - why?
The first is fairly obviously related to speed to fly theory: flying upwind I fly faster to improve glide, and vice versa down. The second is psychological: coming home I was well high (1800m) and arriving in home ground where I've previously got back from around 1000m (below ridge height) and in any case didn't need another thermal to get home.
But hold on: let's split the flight in half (I've dropped a leg made after I flew back over the TO at 65km into the flight). To go from TO out to my furthest point, I took 1h for around 32km: 32kph XC speed. Coming back - against the 10kph wind - took me just over 50mins! So I covered the return leg at 40kph, 25% faster than my outward leg, despite a headwind for a large part of the flight plus I arrived >600m above take off (that's around a 5 min climb on that day).
Why? Pure psychology, I'm sure. It's easier to head for home, there are no decisions to make, you've already flown the thermals, everything is in just joining dots. So maybe he's right, a tailwind can be irrelevant...
Nevertheless, all other things being equal, even if you are flying the best machine you can get, a tailwind has to be rather handy, for example 10kph should add something around 10km per hour of flight (oh it might be 8 but why quibble? Try adding 8kph to the best glide or the race glide speed of a PG!). And the thermals do drift with it, so you get the effect even if you are climbing, Godfrey ;-)
9:52:34 PM 
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