Articles

• Thermalling (Part 1) | (Parts 2 & 3) | XC League
• Winter Flying | Spring Flying | Classic Days

Thermalling (Parts 2 & 3)

Thermalling Part I took us to the point where we had hooked a nice thermal and started riding it up to cloudbase. Surely not much more to say after that, is there? Well, those who attended Parts 2 and 3 (Feb 6th and Mar 5th Club Nights) were quickly reminded how complex the subject of thermalling is. Just like economics, the end result is simple (up or down), but the path is full of complex and invisible 'levers' and Dave Thomson's excellent talks focussed on those many little details that combine to decide Yes (up) or No (down).

Here is a taster of some of the topics covered:

• Visualisation - is a thermal a 'chimney' or a doughnut? Basic stuff but so important for seeing how to stay with the lift.
• Staying in the thermal - centering (not coring!) techniques
• Reading lift information - when is negative really a positive? The idea of relative lift and changes in thermal strength above the ridge.
• Decision time - when to plan your move to the next thermal
• Play time - when to relax during your climbout
• Approaching cloudbase - strategies for maximising distance
• Second thermal - Low save strategies
• Downwind decision-making - Factors in crossing ridges
• Leeside thermals - where to find them and how to use them

There was so much interesting and unexpected detail in these talks. The discussion on thermal path at ridge height was a revelation, with some very surprising outcomes. How many before this talk could honestly say they would stay with negative lift on a climbout?
And how can you spend 30 minutes discussing which side of the cloud to climb to? The fact that we did, and it was all fascinating stuff, shows the depth of detail covered and how much more there is still to consider and understand.

A very big thanks to Dave Thomson for his time and efforts - much appreciated by one and all.
Now we have the concepts, the strategies, the desire and the belief - Bring on some decent flying weather!

Thermalling (Part 1)

Despite the atrocious weather during the day, there was a good turnout for the club night on Jan 9th. It has been many weeks (or probably months!) since we have flown and so what better way to blow out the cobwebs and get us thinking about a new flying season than Dave Thomson talking us through the mysteries of thermalling. Pretty soon and before anyone could say 'flipchart' we were all imagining climbing out with the sweet beep-beep of the vario in our heads...And that was the main message, "Believe": Believe the thermals exist, believe you can catch one, believe you can work it all the way.

But this wasn't all faith healing - Dave's talk was filled with little tips and tricks to help get us away, along with an idea of progression towards that big climb. Unless you are incredibly lucky you can't just launch and start thermalling, so:
What is the best plan of action to get into position to catch one? (A: Maximise height to increase search area)
Where is the best place to look? (A: As far forward as possible)
By setting clear objectives like these, a picture starts to form of how to fly in each situation and suddenly the in-flight decisions are more straightforward.

This was all about developing a strategy and funny, how at times the simple and obvious is most difficult to see. How many of us put nice clean 180s to S-turn in a ridge thermal? Well, why not increase the turn each time to track back and actually follow the thermal drift? You could see the light going on in a number of heads with that one. OK, this hasn't made anyone a better pilot (yet) but we now have a better picture of what we are trying to do - the rest is practice, practice.

For more info on thermalling, see the Thermal Lore set of articles by Dennis Pagen. (Thanks Sean for this link)

XC League

The first Club Night of 2008 started with a brief introduction to the National XC Leagues.

The main intention of the league is to offer a simple way to encourage pilots to fly XC. By recording your distance, you have a measure to try to improve on. Of course there is a serious competition for those at the top, but for the rest of us all the talk of multipliers, Open Distance, Declared Triangles, FAI, etc. etc. is more or less irrelevant. Just go out and fly (and remember to switch your GPS on). The modern software is now so smart that, as long as you can download your tracklog using GPS Dump (available free), the system maximises the possibilities and tells you what you have flown. It then automatically tells every other relevant league (such as the Scottish League) which updates your flight details. How simple is that!

So get involved and enter your flights. As a member of SHPF, all flights starting in Scotland also qualify for the Scottish league, the only one where paragliders compete on even terms against hangliders! As a further incentive to participate, the Scottish League will also accept a 5km distance flight (10km min for XC League). For more info (or find out how to measure a flat triangle!) see British Paragliding Comps (click the XC Leagues tab on the page) or for National HG leagues see UKNXCL.

LATEST NEWS! At the time of publishing (Jan 2008), Scottish flying is very well represented in the National XC Leagues. Two of the top four pilots are SHPF members, and our own Dave Thomson is currently leading the way in winter flying and with the longest flight to date.

Winter Flying

This is a slightly modified version of a previous article written by Dave Thomson and published in the LLSC Bulletin in December 2001. It has been published again due to the number of recent requests from pilots asking for information on winter conditions.

Another season has gone by, with some excellent flying, more records broken, and another group of newly qualified Club Pilots joining the ranks of Scottish pilots. At this time of year we all go into the phase of desperately hoping for some flying, but more often than not it doesn't happen ! One thing that is really apparent is the number of days that are wasted by going out to the hill and either not flying or having flights that are something less than enjoyable, so it struck me it might be worth looking at some of the differences between summer and winter conditions. We all know that the sun doesn't come up high enough in winter to produce reliable thermals, but what differences could we expect for a soaring flight ? The biggest differences are, of course, air temperature and hence density.

Maybe its all pretty obvious, but it maybe there are a few tips which may be helpful. Let's start with the first decision of a typical winter day - whether to go flying. If its snowing or pouring, Christmas shopping comes on the agenda, however what about when you look out the window first thing and there appears to be very little wind and a clear sky. In winter, the wind gradient tends to be much greater, so the trees (or whatever) you rely on during the summer to judge whether to go, are much less reliable in winter. By the time the upper wind gets down to ground level you're probably on your way ! Solution - rely more on the weather forecast than a look out the window. (As a guide, if Heather says 15 mph or more, don't bother thinking about it, between 12 and 15 its worth further consideration, and less than 12 we know that its a fair chance.)

So you get to the hill that you reckon is facing "into wind", if its not blowing a gale, you find that more often than not, it's blowing across rather than up the hill. With dense air and insufficient heat in the sun to warm it up, the air has a much greater tendency to flow along valleys rather than up hills. This is the opposite to a thermic day in summer, where the air can be flowing up all sides of a hill. This effect is less noticeable on longer ridges,- so that's another factor to consider in your choice of site.

Another point to watch is "horizontal rotor" - If the wind is not straight up the hill, then features, such as gullies, trees etc., in an upwind direction along the hill, can cause turbulence which roll along the hill for surprising distances.

If you do find somewhere that seems flyable, what differences can you expect ? - if there is enough wind to stay up, then look out for the high wind gradient, especially when you get to hilltop height. Very often, the horizontal wind flow is slowed by the hill at lower levels, but as soon as you climb above the top you get into the "true wind" and you can experience much higher windspeed, with a turbulent shear layer between the two.

The cold moist air very often leads to low cloud base, so another hazard is orographic cloud (sometimes below hill height), very often forming quite quickly in the late afternoon, as the air cools. Its bad enough flying in cloud well above the ground, but getting lost in cloud, knowing that there is a large hill somewhere around is not an situation you'll want to experience !

On a day where it is flat calm at the top, don't assume that it will be at the bottom. I've seen days where we've forward launched at the top, and glided down to find ourselves landing backwards in strong wind blowing along the valley !

So that's some of the issues and hazards of winter flying - and that's just the days where it looks flyable ! As always, it's important not to let our enthusiasm to fly overrule our judgement on marginal days. However, if we take account of the differences in conditions, winter flying can be incredibly beautiful, so lets hope we get some suitable weather to keep us current before next spring.

David Thomson