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Thermalling clockwise or anti clockwise?

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Bruce Austin29/08/2013 14:46:24
242 forum posts
1 photos

Hi Guys

I am just getting started into the real air.

I have been flying on a Model simulator for the past twelve months to get a feel for the "stick" and to arrive at the decision to get involved with this (new to me) hobby.

I have been welcomed as a visitor to the High Wycombe & Dstrict Model Aircraft Club, and what a great bunch they are.

My primary interest is in Electric Powered gliders.

I am about to take delivery of a Bixler 2, to get my hand in, and to work toward the A Achievement certificate.

I might need to use a different model with an Undercarriage for the A certificat, but that is another matter.

So, finally to my question.

IS THERE A CORRECT DIRECTION FOR FLYING UP IN THERMALS?

I have observed that water draining out of a wash hand basing always goes in the same direction, and so was just wondering if thermals tend to also go in the same direction. South of the equator the water drains in the opposite direction, for those that were not aware. interesting, eh?

By the way, i subscribe to our RCM&E mag, and it has been such a wonderful help to me in understanding just a few of the complexities within our hobby.

Regards

Bruce

Chris Bott - Moderator29/08/2013 17:18:03
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Hi Bruce welcome to the forum, and what a great question. I wonder if there is a difference.

To be honest, I'm never sure whether or not I'm centred on a thermal. If one wing rises, I try to turn towards that direction, and I think I end up criss crossing the thermal. If I go up in a nice round spiral then I'm doing very well indeed! So to actually choose a direction would be something else.

Those in the know though, may know different?

pete taylor29/08/2013 18:02:19
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Hi Bruce, and welcome again!

I'm no expert, but I have been flying thermal soarers for quite some time (Ye Gods...can it really be 35 years this summer???) Anyway, for all practical purposes it appears not to make a jot of difference. I'm sure someone out there will correct me (Lord, how we all do love a pedant!) but Chris is quite right, just find yourself a thermal by whatever means you can and milk it for all it's worth. The whole game is really a bit like fly fishing I always think - only in the air... and I've found myself holding my breath and contorting in all directions when willing a model around a tiny bubble of lift!

To centre on a thermal isn't too tricky, you need to watch closely and see on which side of the circle the model goes up, and which side it goes down (if at all) then gently elongate your turning circle in the direction of the upward part - cos that's where the lift is better. What you will find is that once you've got the centre nailed the model will speed up quite noticably.

One thing that I would whole-heartedly recommend for any budding thermal soaring is Dave Thornburg's Old Buzzards Soaring Book. It's not new, and possibly maligned in some quarters, but it's a real insight into what goes on in the "river of air" and a fascinating and very funny read.

Good luck with the thermal hunting

Pete

Greybeard29/08/2013 19:02:36
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I would go along with what Chris and Pete have said but with the proviso that if you follow someone else into a thermal then you adopt their direction of rotation.

Phil Cooke29/08/2013 19:08:37
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There is no functional or performance reason why turning left circles is better or worse than turning right circles in the rising air, assuming of course your model is built and trimmed correctly/evenly and your control inputs each way are comparable.

There is of course a thermalling etiquette though - in that the first person in said thermal (the finder!) can turn either way to best suit his needs, then anyone else 'joining' the thermal should turn the same way - this helps avoid collisions and helps maintain order in the small volume of airspace.

Rick Tee30/08/2013 05:47:14
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Posted by Bruce Austin on 29/08/2013 14:46:24:

I have observed that water draining out of a wash hand basing always goes in the same direction, and so was just wondering if thermals tend to also go in the same direction. South of the equator the water drains in the opposite direction, for those that were not aware. interesting, eh?

Myth.

Frank Skilbeck30/08/2013 08:04:27
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I think there should be a full investigation into this in the mag,.......................... April issue wink

David Ashby - Moderator30/08/2013 09:21:43
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Yep, get writing Frank smile

Josip Vrandecic -Mes30/08/2013 10:24:27
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2993 forum posts
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Hi Bruce , Northern hemisphere- right circles ,Southern hemisphere- left circles...

This is due to the rotation of the globe.face 1

Cheers

Joe

Jamie sawyer30/08/2013 10:33:53
390 forum posts
99 photos

I know slope soaring is a different thing but if I were you and as you are new to the whole thing I would possibly suggest that you try and get to a small slope on a light wind day. You may not have the availability of a slope, not sure but at least if you are up a few hundred feet with the wind hitting the hill straight on then you can at least learn .....first to read your gliders response when it enters some lift and with a bit of practice on the a slope you will end up scratching about barely staying a loft. This is very good practice as a basic foundation in my eyes first. If you just launch of a field and get up with the electric motor the glider will be directly above you and as a novice you probalbly wont be aware that your even in lift when you hit it. You will learn to read the clouds and watch what the birds do to. The wild life in the air can be a good clue some times. I had my thermal glider up a hill last week in a 10 mile/hr wind and was scratching about and loving the hunt for the lift. Every now and then I'd find a sweet spot in the air and I'd gain 100 feet just crabbing back and forth with the nose into the wind. Crabbing as in flying left and right , not turning the nose any more that 30 % out of the wind. If you do a full turn some times in a small pocket of lift it can have an adverse affect and you will actually loose more lift than you wished for. If you find a good thermal then where there is warm air rising at the edges there could be cold air falling all around the thermal. The ground can be a good advantage to read where you may find thermals to. A freshly plughed feald where the soil is black can attract heat from the sun thus creating lift...

Jamie

Jamie sawyer30/08/2013 10:35:31
390 forum posts
99 photos

**LINK**

Here is a link to info. The internet will give you good resources for information.

Good luck

Jamie

Mike Etheridge 130/08/2013 11:22:57
1520 forum posts
415 photos

Very rarely do we get thermals at our flying field at Bartons point at Sheerness in Kent. Most of the time sea breezes influence the wind strength and direction and probably cancel out any thermals. However just the other week when the trade wind was Southerly / South Westerly I noticed that a great number of sea gulls were 'thermalling' above us. I had my Twinstar 2 handy and sent it up to circle with the birds and it was the birds that determined the direction of the turns. A couple of club members also sent up their power gliders to fly with the birds. It was good fun and the gulls seemed agile enough to avoid the planes.

MJE

Edited By Mike Etheridge 1 on 30/08/2013 11:25:39

avtur30/08/2013 12:31:08
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883 forum posts
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If flying solo it doesn't mater ... if flying with others it is easier/safer if everyone goes in the same direction ...

Mike Etheridge 130/08/2013 12:44:50
1520 forum posts
415 photos

Just to confirm the turns made by the birds were left hand as Josip suggests,and our club rules state that all model aircraft should be flown in the same direction as Avtur has stated, to avoid mid-air collisions .

MJE

Edited By Mike Etheridge 1 on 30/08/2013 13:13:46

Down Under30/08/2013 13:05:15
67 forum posts

Hi All

For once I can actually make a useful contribution here. I used to fly paragliders, and we were always looking for those elusive thermals. In fact, the duration of our flights were often deteremined by how well we could read the country side for thermal trigger points.

The fact is, most thermals do not rotate clock wise or anti clockwise. Picture a column of air. Warm air rises up through the middle (thermal) and descends down the outside of the column (down draught) as cool air. To enter the thermal, you first have to pass through the descending air on the outside of the column before you get to the thermal inside.

A good indicator that we had found a thermal was either side of the wing lifting. The same applies for paragliders and models alike. Here are a couple of scenarios:

1) You manage to enter the thermal dead centre. In a paraglider the wing would remain stable, but you would feel a descending / falling sensation, followed by a sudden and some times violent ascent as you hit the middle of the thermal. Our vario (flight computer) tells us when we have past through the strongest part of the thermal, at which point we then make a decision as to which way to turn. If you are first into the thermal, the choice is yours, otherwise you follow the same direction as every body else.

With a model, looking up from the ground, it would be harder to tell that you have passed into a thermal as you have neither the sensation nor the flight computer telling you. The biggest / most visual sign will be the wings of the glider rocking as it passes into the middle of the thermal. Wait a couple of seconds, then begin coring the thermal (circling in the thermal). I guess same ettiquette applies. If you model is alone or you are first to enter the thermal, circling direction is up to you.

2) You enter the thermal offset or to the side. This is easier to see from the ground that you have found a thermal but needs to be treated differently. Again, the same applies to paraglider as to a model. Lets say you find a thermal and pass throught it on its right. Your inside wing (left wing) will lift as it catches the thermal while the right wing will fall as it stays in the down draught. This has the affect of turning the paraglider / model OUT of the thermal.

Most people would naturally try and turn the paraglider / model left back into the thermal. While strictly speaking there is nothing wrong with this, you actually lose forward momentum / speed as you are fighting forces trying to turn you out of the thermal. The more efficient approach is to let the paraglider / model follow its path out to the right and because you are not fighting the natural forces already being exerted on the aircraft, you will actually maintain or gain forward momentum which you can use to your advantage. As the paraglider / model is pushed out to the right (with the left wing being lifted), you are better to follow through and circle round to the right, as you come back round let the model straighten up so you can enter the thermal with some speed. The idea of speed here is to pass as quickly as possible through the down draught and minimise your height loss. So your circle to the right becomes elliptical as you come around and re-enter the thermal. (Would be so much easier to draw a diagram, but I hope you get the picture).

Of course, if you passed a thermal on its left, then opposite would apply.

In short Bruce, there is no 'correct' direction determined by the air. Only the direction called by you. If you are first in, or alone, the choice is yours. If you are second or joing a group, the correct direction has already been pre-determined and is best followed in the interest of avoiding a mid-air...

Hope this helps.

 

 

Edited By Down Under on 30/08/2013 13:09:47

Bruce Austin30/08/2013 19:54:58
242 forum posts
1 photos

WOW! and aggain WOW!

As a newbie, I am just overwhelmed at the responses, and the guidance from all you guys.

A very special WOW to "Down Under" for the amount of time and detail that you have gone into in the explanations.

You must have had many interesting experiences with the paragliders. What model glidersare you flying?

I found and find your explanations so amazingly clear, and simple to understand. Thank you so much for the extraordinary amount of time that you spent on describing the techniques.

My club Instructor has invited me to come along to sample the slope soaring and to provide some training in those techniques.

My simulator provides various scenarios for pursuing this aspect of our hobby, and I have already had some fun combing the ridges and slopes, so I am already "hungry" for the real thing.

Cheers guys

GO WITH THE FLOW

Bruce

Mark Agate30/08/2013 21:48:04
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144 forum posts
38 photos

Take a look at what came up on the BBC News website today: **LINK**

This one's clearly going anticlockwise, so the mantra would be "Circle left for lift!". I used to thermal soar with a couple of friends many years ago, and strangely enough we decided this was always the best way to go to stay centered in a thermal.

andyh30/08/2013 22:31:26
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421 forum posts
22 photos

my £0.02 ...

I fly paragliders & used to fly hanggliders, & have had one memorable 250k O&R glider flight with a mate who is a Lasham instructor., which I flew a fair bit of, including thermalling

as has been said above, your turn direction is generally dictated by your detection of, & turn in, to the thermal (ie inside wing up, turn against)

in the full-size world, if you enter a thermal with another aircraft already in it, you should turn in the same direction (at least if it's above you). some ridge sites have 'house' rules that you should only thermal in one direction below a certain height (often 1,000' above ridge height. in some competitions they have the same rule but reverse the turn on alternate days to be fair to people who prefer to thermal in different directions

I know the British rigid-wing hang-glider record holder, who flew from Wiltshire until he ran out of land in Norfolk (he then flew a few miles out over the sea to add to his turn-point distance) , & he says he thermals one way 85% of the time, based on his GPS tracks. so I think the long & short of it is that you're best off turning wihchever way works for you

I would like to add that I have great admiration for RC thermal fliers who can core a thermal based purely on remote observation. I can't imagine trying to core into lift with out a vario screaming at me, plus an averager (plus, if I'm honest, my GPS-vario showing me where the last core was)

-andy

Bruce Austin30/08/2013 22:33:50
242 forum posts
1 photos

WOW! and aggain WOW!

As a newbie, I am just overwhelmed at the responses, and the guidance from all you guys.

A very special WOW to "Down Under" for the amount of time and detail that you have gone into in the explanations.

You must have had many interesting experiences with the paragliders. What model glidersare you flying?

I found and find your explanations so amazingly clear, and simple to understand. Thank you so much for the extraordinary amount of time that you spent on describing the techniques.

My club Instructor has invited me to come along to sample the slope soaring and to provide some training in those techniques.

My simulator provides various scenarios for pursuing this aspect of our hobby, and I have already had some fun combing the ridges and slopes, so I am already "hungry" for the real thing.

Cheers guys

GO WITH THE FLOW

Bruce

Down Under30/08/2013 23:55:44
67 forum posts

I'm hear you Andy. Without my vario, I doubt my flights would have been half as long....

To answer your question Bruce, I used to fly a classic Gentle Lady years ago. It was also the first rc model I ever owned. We are talking some 20 years ago. I just recently bought another more out of nostolgia. I intend to put an electric motor in it so I can get up to thermal hunting height 'quick smart'.

Happy (thermal) hunting!

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