|Jun 03, 2012, 05:49 AM|
Do you evaluate air before launching and how you do it ?
As title says. When you go to the field and you are ready to launch, do you evaluate the air and where a thermal might be and if yes how do you do that. What do you take into account ?
|Jun 03, 2012, 05:36 PM|
Yes, I do. Looking and trying to read the air before launching -either electrical, bungee or DLG- is quality time to me.
Thinking and looking before launching can often make a big difference and it's cool to see if you can find the sweet spots on the time line of your flying day.
- birds (thermal indicator nr 1);
- windshifts (follow the wind and you'll hit rising air);
- sudden changes in temperature (sudden warming can indicate a forming thermal right over your head);
- air looking "thick" (dust in the air);
Taking into account, general knowledge like:
- where the sun hits the earth @ max effectivity (tarmac, sand, south facing slope);
- transitions in texture of the earths surface (wood/open, water/land etc);
- small ridges or tree lines or any bump at flat fields;
- woods from late afternoon until sunset.
|Jun 04, 2012, 10:13 AM|
United States, MA, Waltham
Joined Dec 2001
I find that lines of trees seem to break thermals free, plus there's a little bit of slope lift. However, I've also found that most of the time thermals move around and you can't just go to the same spot again and again.
If there's a prevailing wind, the wind you are experiencing will be a vector sum of the preailing wind and the effects of the thermal. That is, the thermal itself may be upwined of where the wind is going at the moment. However, thermals are pretty swirly so you may not know exactly where. Probably the ideal thing is to stand on something just slightly above a large field of long grass so you can read the thermals by how the grass is moving. This kind of thing may be mostly for low altitudes, though.
|Jun 05, 2012, 12:42 AM|
Every time I get below 100ft it seems that I can't hit any thermal to elevate back up, just gliding to land altitude and then motor on for high altitudes. When though I am really high (almost continuous loss of orientation) it seems that where ever I go glider is keeping up the altitude and of course gaining.
The field I am flying off, has a little slope to which sun rays heat almost 10 hours a day at temps,now at summer, of over 30 celsious. Over that area I always find some lift, but not at lower altitudes.
|Jun 05, 2012, 01:06 AM|
LI, New York, USA
Joined Mar 2003
Look for birds
look for gliders in lift
Note any wind direction change
look for temp changes
try to note any cycles that I can time
|Jun 05, 2012, 10:21 AM|
That is one of the parts of the hobby that is challenging. Sure, Folks can learn to fly and not crash. Even to blindly bump into a thermal. But reading the many signs or learning to look at your planes signals and respond to them is where the real skill lies. It also sure helps to learn which guys to poach thermals off of.
|Jun 05, 2012, 12:09 PM|
LI, New York, USA
Joined Mar 2003
Tips for success.
The key to long long flights is not catching a single huge thermal but being able to move from thermal to thermal as they die.
Get to know your flying field. Where are the thermal generators. They will usually be very wind direction dependent.
Try launching high then just cruise around watching the glider. If you find a thermal, work it for a little while, gain some height, then leave it and head off to where you think it came from and see if you can find another one behind it.
Work a thermal, gain some height, then leave it. Fly up wind a bit, then turn around and see if you can pick up that same thermal again. Remember it may not be in the same place as when you left it. It likely moved with the wind.
Put a ribbon on your antenna (72 MHz), on a stick or on a pole so that nothing interferes with the air flow. Don't launch, just watch the ribbon and establish what the prevailing wind direction is. Now, watch for the ribbon to change direction, say pulling 30 degrees to one side of the prevailing wind. If it holds there for a while, then returns to the prevailing direction you probably just witnessed the formation or the passing of a thermal. The bigger the shift the stronger or the closer the thermal.
The thermal may be exactly where the ribbon is pointing or it may be more up wind, say 90 degrees to the normal wind direction. This will fade out after a while. If it happens again, go launch and find the thermal. A small one will be close. A big one may be farther away.
If the ribbon reverses direction, then the thermal is forming directly up wind and is pulling so much air it is overcoming the prevailing wind. If you wait for a bit you may feel the air go calm and then get warm. You are standing in the center of the thermal.
When we fly hand launched glider contests we often set up a series of 10-20 foot poles with long streamers on them. The poles are set up around a launch area that is about 100 feet by 50 feet. Before the contest pilots launch they watch the ribbons. It is highly likely they are not all blowing in the same direction. This is a clear indicator of where you will find the lift.
A good launch with these gliders is 120 to 180 feet, so we are usually finding and working thermals that we find when were are fairly low in altitude. At this height they can be very small and narrow. It is not uncommon to pick up a thermal at 10 feet that is 5 feet wide and just forming. You turn in a very tight circle to stay in the core of the thermal. If the thermal continues to form and grow you can rise up till your plane is a dot in the sky.
Timing Thermals - Watch the changes and see if you can anticipate the changes. Are they regular? Thermals often run in cycles and sometimes they are very regular. I have been at contests where you could predict the cycle so well that when it was your turn to launch you could decide whether to chase the thermal down wind that the other planes were working, or go up wind and catch the one that was going to come through next. This is huge fun!
Back into the air - Using what you learned from the ribbon, launch and find the thermal. Work a thermal till it is down wind from you, but keep an eye on that ribbon. When it indicates another thermal, go see if you can find it.
Avoiding Sink - Get high, then find a thermal. Now leave it and come directly back toward yourself. Chances are you will fly directly into the sink that sits between you and the thermal. You will lose altitude quickly. Do it again but exit 45 degrees to one side or the other and see if you tend to drop less. You should.
Sometimes you hit that boomer where it seems the whole sky is up and you could stay up forever. Those are great but they can get a bit boring. Having to chase one after the other to keep the plane up is the real challenge. If you get an hour flight needing multiple thermals you will find a real sense of accomplishment.
Getting low - once you have the ability to find and work thermals up high, limit yourself in height. 15 second climb on an electric, or shorten the hi-start. Now go hunting. Thermals get bigger and stronger the higher you get. So finding them down low is much harder. Do the same things I said earlier, but start lower and stay lower. When you get to twice your launch height working that thermal, break off and start hunting again.
When you get good at that, 8 second climb or a 200 foot hi-start launch only and do it all again. If you can get a 10 10 minute flights off an 8 second climb or a short launch you are really becoming a thermal soaring pilot! This low level work will help you save that flight that is failing, where the big thermal died and you are about to land.
At no time during any of this practice do you use the motor to reclimb. Cheating! If you can't keep the Radian, or whatever you are flying, in the air based on thermal lift, then you land and start over again. Now you are becoming a real sailplane pilot.
I had my Spirit out one day. I launched from a hi-start and immediately found a great thermal. After 15 minutes I was getting low and called out that I was landing. On the approach I caught a blip at 30 feet and turned. Up I went for another 10 minutes. I did that two more times. What a ball! (Ed called not landing ... again. What a show off!)
Go play. Go practice and ALWAYS have a watch to time your flights. I have a switch on my radio that I flip on launch. This starts a count up timer. I can also have a count down start at the same time if I wish.
I also have one of these Talking timers. They are great, especially when you are flying alone.
The talking timer will announce the time as your flight progresses. And if you ever get into thermal duration contests where your time is for a specific period, like 10 minutes, you set this to count down. It announces every minute up to the last minute. Then every 10 seconds till the last 10 when it counts them off 10 to 0. On zero you touch the nose to the ground.
One caution. This thermal soaring thing is very addictive. No two flights are ever the same. You don't know how long you will be flying till after you land. I just love it!
BIRDS, THERMALS AND SOARING FLIGHT
From the full text of the classic FAA guide
|Jun 05, 2012, 01:04 PM|
When in Dallas, be very careful watching the buzzards... they've trained them to trick out-of-towners into launching into sink...
|Jun 05, 2012, 03:32 PM|
I am thinking of videotaping the procedure with the pole and ribbon, for everyone to know we are looking for. I am sure it will be equally exciting as flying.
Would a 12feet fishing pole do the job ?
Also, as you say, a low altitude thermal may be impossible to work out with a glider at 2+meters wing, as the span is bigger than the thermal itself. We might see wings rocking or other signs that indicate thermal, but won't be able to take advantage of it.
Do you recommend someone starts with a dlg, before going bigger and higher ? But then I should find no wind conditions, something rare here.
|Jun 05, 2012, 03:35 PM|
LI, New York, USA
Joined Mar 2003
Yes a 12 foot pole would be great.
What is really great is when you have 4 poles set in a square about 100 feet or more on a side with 5-10 foot streamers on them. Really light stuff.
What surprises you is that they don't all blow the same way and at times they can actually all point toward the center if a thermal passes through the square. DLG contes are often run with these 4 poles at the corners of the launch/landing area. The DLG pilots watch the streamers for indication of lift so they know where to launch, and when.
If you watch the streamers over a period of an hour or two you start to see the thermal cycles.
Another thing that works well is bubble machines. The freeflight guys sometimes use these, or so I have been told.
If you see a mass of birds all darting around the same area in the sky, chances are a lot of bugs have been sucked into a thermal. The birds are feeding, and marking the lift.
|Jun 06, 2012, 05:06 PM|
Today it was just amazing...!
All of what you instructed happened.
Initially I went out for the final trimming flight, but receiver failed at the range check (orange rx - first and last time used it) so I was grounded. Fortunately, I brought with me the fishing rod and settled for an observation quality time.
The weather was hot (32deg celsius), with NNE winds at 8knots, as they were on LGAV Metar report (4miles far from the field) with some scattered clouds high above.
I installed the rod on a fench, reaching almost 15feet, and confirmed that prevailing wind was indeed NNE (typical for the field). At that time, little to no birds was flying around and it seemed quite and inactive. I was trying to figure out what was happening according to what I felt and what I saw the wind sock do, when I noticed that every couple of minutes, wind grew strong and then after a while died down, and then again grew strong with a change in direction (45deg).
After a while, downwind of where I was standing, a hidden buzzard took off, immediately going into a thermal and as he rise, he left it, just flying 150feet to the west and went on rising but without circling exactly, it was more of doing a figure 8, for another couple of minutes, then flown off upwind, where it seemed there was no thermal. He then picked up speed going to another position of the field, where a big one was present and it really became a dot, until I lost sight of it. Then another buzzard took off heading where the first one was, but after just gaining some altitude, it left to come downwind of where I was standing and hit another big thermal.
After that, I focused on the wind sock, trying to time the cycles and just before the end of my visit in the field, I was able to accurately predict how the wind will change. It was a great thermal day as it was indicated by many factors. Buzzards went in thermal, wind did what it was supposed to do, swallows went high to feed (while it was quite, they started to tweet and went up high to find the bugs) i.l could tell the presence of a thermal, just by hearing how they tweet and not seeing them, some butterflys flew past me at great speed and went vertically up but after 45feet they went vertically down (sink) showing me, the boundaries of the thermal that was in front of me
After todays observations, I got a clue of where are the sweet spots that are popping thermals out in this field, so next time I ll go there to find some. You can see it in the pics
Amazing day, even without stick time. I took footage of all of the above, but it is 18mins long and it needs some editing
Thanks again for all that valuable info.
|Jun 07, 2012, 12:43 PM|
Joined Jan 2008
Now, find a copy of the book, "The Old Buzzard's Soaring Book", by Dave Thornburg. Your command of English is excellent, and Dave's writing skills are also very good, so I think you will find it an easy read. Look for it on Amazon.com, if nowhere else.
In it, you will find reinforcement of many of the ideas already here in your thread, plus maybe a few more, along with tactics and strategies for getting the most out of the available air.
|Jun 07, 2012, 01:56 PM|
Today, it was totally the opposite...!
After changing the rx to an AR7000, went out to the field. Pinned on the fench the fishing rod (which is still there as I forgot it, hope I ll find it tomorrow) and was noticing the winds, waiting the best moment to launch. Winds were at 9 knots NNE. Birds at the field were quiet and grounded and the prevailing wind was strong without dying down or changing directions at any time (bad sign).
I launched and managed to put 40mins of powerless flight (in sections) most time continuously on air 18mins, the other two were 10mins each. I couldn't tell if up high I was in thermal as sometimes it seemed like I was hovering but not gaining altitude. Also no buzzards or seagulls today and clouds were not present also.
A problem I have now is, that it seems that when I turn tail into wind (downwind) I loose so much altitude and I feel like not having elevator authority. The same happens when I turn to work a thermal. Also there are times, mostly when going downwind, that rudder and aileron doesn't work at all, they don't turn the glider.
Today I also let the glider drift with the wind and many times it wanted to circle, but when I got into control, I could't find a thermal, but managed to retain altitude.
I ll go check on the book now.
|Jun 07, 2012, 02:42 PM|
When it seems like you don't have any elevator/rudder/aileron authority, then your airspeed is probably very low. If it's windy and you turn downwind, the plane "appears" to start moving very fast. It IS moving fast relative to the ground, but it's NOT moving fast relative to the air that it's in. When you turn downwind and your ground speed increases, you're likely to pull back on the stick in an effort to slow the plane down. This will reduce your airspeed to the point where the controls become sluggish or worse, you stall. The plane will still appear to be flying because of the wind and the high ground speed, but it's hardly flying at all because of the low airspeed.
You'll want to work on resisting the urge to pull back on the stick (more than usual) when turning downwind.
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