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Thermal Duration
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- Created on Monday, 31 May 2004 17:00
- Last Updated on Saturday, 19 January 2008 10:50
A Beginners Guide to RC Soaring
Sailplane or Glider?
A glider is a ship you launch to good height that gently floats back to earth. A sailplane, on the other hand, is a ship you launch to good height and it goes on up from there!
Which one you experience largely depends on whether you have taken the time to set that new lead sled up correctly. Let’s start in the workshop.
You’ve just finished building your latest sailplane masterpiece and have installed your radio gear. All control surfaces seem to be working, your battery is charged and you’re ready for the field, right? Wrong!
There are some subtle and important steps you need to take to insure optimum performance. First of all, did you weigh your wings separately? Lateral balance not only makes your plane fly straight, it helps it perform better. Add small amounts of lead to make both wings weigh the same.
Your stabilizer should be parallel to wing leading edge and equidistant from stab tip to wingtip. Use your eyeball for the first part and a string to measure the last part. Line everything up first, then glue.
Have you set your control surface throws correctly? Look at the manufacturers recommended throws. Buy a gage and set these up--adjusting holes on the control horn or servo arm or with travel adjust on computer radios--so you don’t get more throw than you need. More throw means you’re more likely to over-control, with subsequent loss of performance and possibly even a crash. Less throw makes your flying smother.
If you are prone to over-control, dial in some dual rates with exponential on computer radios so that a large stick movement results in less control surface movement. If you don’t own a computer radio, you’ll just have to be VERY careful not to move the stick too far or too much.
While we're at it, center your servos, then center your control surfaces using clevis adjustment, not sub trim on your computer radio. Did you check for proper control surface movement? Viewing from the rear, stick forward, elevator down; stick back, elevator up. Stick right, rudder right; stick left, rudder left.
I am sure you balanced your ship, but let’s take a second look anyway. If you had to add lead in the nose, you might as well get a larger capacity battery that weighs more. Why not have more juice than lead? You’ll need it anyway for those longer flights you’re going to get after reading this!
While you’re into batteries, consider getting a larger capacity for your radio. Those small 600 mAh batteries are for wimps! New battery? Did you prime and cycle it for maximum performance? Old battery? Did you cycle and charge for the new season? Best to cycle three or four times to condition the battery for the new season. (NiMH batteries don’t need cycling but do need priming.)
Also, double check that balance point. Many newcomers incorrectly balance their plane because they read the ruler wrong or because they read the directions wrong! Use a good CG machine to do this. Don’t take chances with finger balancing or a homemade rig. The best rig I’ve seen comes from Laser Arts, makers of the Majestic. It’s simple, cheap and effective.
After that, make sure that tow hook is in FRONT of the CG. A good rule is 3/8 inch in front, but if you have an adjustable tow hook, you may move it back to within 1/8 for higher launches. You might want to wait on moving the hook until you have a few launches under your belt.
Now to the field.
At the Field
You’ve just arrived at the field with your spanking new Cloudbuster 900. You put in a lot of hours last winter building it into the perfect ship and now its time to test it out. Scary, isn’t it? Well here are a few tips to help insure your success.
Check everything carefully. Is everything nice and tight? No loose servos or batteries? You did follow the “Before You Get to the Field” instructions, didn’t you?
Always start with a range check, but before you turn on your transmitter, find out if anyone else is using your frequency!!! After assuring yourself that no one is using your frequency, turn on thetransmitter, then your receiver (reverse that order when turning everything off). Keep your antenna down and walk out onto the field about 200 feet. Facing the antenna away from the model, have a helper check to see that the control surfaces are moving. O.K.?
Go back to your ship and check for proper directional movement of control surfaces. Remember, look from rear to front. Stick forward, elevator down; stick back, elevator up. Stick right, rudder right; stick left, rudder left. Do all of the control surfaces line up with their stabilizers?
Now you are ready for the next step. It is helpful at this point if you have a buddy to assist. Pick up the sailplane and run forward with it about 15-20 feet. The idea is to get the plane up to flying speed. When you have enough speed, toss the plane out in front of you, keeping it as level as possible. Whether you or a friend does the toss, be ready to input some control surface movement to compensate for dives, stalls or veering left or right. Some guys will run farther and let the ship “bounce” up and down in their hand to get some idea of what the plane is going to do when released.
Ideally, your ship will glide straight out ahead of you and gently come to earth about 50 feet later, with little or no control surface input. If not, you may have to check your CG, lateral balance, or compensate by adjusting your trims. If you throw the plane hard and it pitches up immediately, you probably have too much nose weight.
Once the toss proves satisfactory, it’s time for the true test. Launch! But first, check to see if your tow hook is in the proper position, hang the plane upside down from the tow ring. It should hang slightly tail down. If it hangs tail up and wants to slide off the ring, you’ll need to move the hook forward. (Note: if one wing hangs down more than two inches lower than the other, see the previous section on lateral balance.
When you do launch, toss the plane hard on launch to get it up to airspeed. Don’t just let it go from your hand. You may want an “old timer” to take her up for the first time, but if you do it yourself, try to launch and fly hands-off as much as possible. Remember, you’re not looking for thermals at this point. You are just trying to get a good feel for the flight characteristics and trim needs for this particular model. Fact is, you should launch and land that new ship 20 or 30 times before you really start thermal hunting.
One thing you don’t want to do in this sport is hurry things up. Take your time. Explore your ship slowly and you will be rewarded with better piloting skills. Practice makes perfect.
Check out the “Trimming” instructions from here.
Trimming Your Lead Sled
Little at a time method.
Try several flights with no wind (early morning or evening). On each flight, try a few tight thermal turns at altitude with slow speed (some up elevator slows your ship in turns). Remove ¼ ounce lead on each flight until plane becomes unstable or tip stalls in turns (Note: dial in additional down trim as you remove weight). Pay attention to slow speed handling and pitch characteristics When plane gets mushy, tip stalls a lot or starts slow oscillated pitching, add back in a ¼ ounce lead and call it good.
Note: you will probably need to add nose weight under windy conditions, try ½ ounce at first
OR
Start with the dive test – launch and trim for slow flight (up trim). Come around and fly perpendicular to yourself. Perform a shallow dive, about 30º then let go of stick.
- Gradual pull out = O.K.
- Immediate pull up into a climb = too much up trim holding too much nose weight. Land and remove nose weight, then re-launch, re-trim and do the dive test again. Repeat until the pullout is very gradual.
Teaching point; if your ship is flying too fast, move CG rearward by removing nose weight; if your plane porpoises a lot, you probably need to remove nose weight. During the dive test, if the dive angle increases – tuck under – add nose weight.
When it is flying more smoothly, go to early morning test.
Early morning test
Again, this involves several flights under no wind conditions. Launch (no zoom) and fly straight ahead, hands off as much as possible. Trim the rudder to fly perfectly straight. When she sinks far enough, turn straight back and land. Time each flight and change the elevator trim to optimize the flight times. Once you have determined the optimum trim setting (close to stall), remove 1/8 ounce of nose weight and start the process all over again. Your flight times will increase throughout this process. Eventually, though, she becomes unstable and you have to give so much input to keep it straight and level that flight times start to decrease again. When this happens, put ¼ ounce weight back in the nose and your good to go.
Note: if you’re having to fight for control of your plane all the time (as with porpoising), you’ve either got too much nose weight (probably the case) or too little. Either way, you’re going to have to adjust the nose weight to get smooth control.
Flying for Fun
Unless you are a competition pilot with a flat wing, full house sailplane, you’re probably just out to have a little fun soaring. Here’s how to enhance your experience.
Let your sailplane do the flying. The number one problem with beginners is overcontrol. Too much up elevator will cause a stall, leading to difficulty in trying to regain control to get the plane flying smoothly again. Near the ground, this problem spells BIG trouble. Move that stick in small increments. (Usually, just letting go of the controls will right your ship, without any input from you.)
Also, if you overcontrol, you’ll never know when your plane passes through a thermal. Again, let the plane do most—but not all--of the flying. If you read “At the Field,” you will find that it is important to get a good feel for the flight characteristics of your model. You can’t do that when you are constantly yanking the stick. Also, you should have already trimmed your rudder for perfectly straight flight. If you move rudder very much, you won’t be able to see the signal your plane makes when it hits a thermal.
Fly a pattern search. When you’re off launch, turn to the left or right and fly at about a 45° angle until you find thermal activity. If you are getting uncomfortably far out, turn into the wind and come back. Don’t turn with the wind, as you will lose ground and fly in air you’ve already flown in. Stay out in front of yourself, unless you’ve found that elusive thermal and follow it downwind to gain altitude.
When you see your plane coming down significantly, you have a choice. Either find a thermal quick or join the landing pattern. My advice for beginners, join the landing pattern. In fact, you should practice landings more than anything else, and this should be a separate activity from hunting for thermals.
Landing – Coming to Jesus
Landing can be a scary time for sailplane pilots, especially if you’re new to the sport. If you’re at this point, try these tips:
Don’t bother using spoilers or flaps, if you have them. These will just confuse the issue (and possibly cause a crash). Deploy spoilers and you’ll dive; deploy flaps and you’ll balloon or stall. Wait to use these until you have some flying experience and can quickly compensate for these effects. (A computer radio can be programmed to automatically compensate for these effects.)
Be careful when using up elevator to slow down. You can easily stall this way and, close to ground, that usually means a crash. When landing, avoid using the elevator.
Mentally create your landing pattern and practice it as often as you can, This should be a separate operation from flying for fun and hunting thermals. That’s because your mind should be focused on this one task to get good at it.
Start by entering the pattern at about 50 feet up for a good safety margin. Put in one or two clicks of down trim. This will speed things up but increased speed means better control. Going slower may give you more time to react, but it also creates more opportunity for accidents like stalling. Come to your left or right, as you prefer, and sink to about 20 feet. At this point, you should be about 100 feet out to your side. When you get about 40 feet behind you, start a gentle turn to the left (or right). When your ship gets about 20 feet out from your side, make another gentle turn toward you. (See the illustration) Watch that up elevator!
If you are too high on approach, you can turn downwind slightly and come around from the other side of you. You can also zig-zag behind you on final approach to bleed off altitude and energy. If you are too low, shorten the approach by spending less time between turns. Practice, practice, practice!
Keep the wings straight and level, then let her settle in. You can give slight up elevator when she is about a foot above ground. This will slow the model. (Remember, when you are looking at the nose of your plane coming toward you, move the stick in the direction the wing is dipping. This is opposite of when you are looking at the tail of your plane in front of you.) If it rolls right past you and seems not to want to land, just let it go. It’s better to walk a distance to your plane than to pick up the pieces at your feet. Next time, fly a little further past yourself before making the turns.
When it’s windy, don’t fly past yourself. Make your first turn when your ship is at a right angle to you or even in front slightly. That’s because the wind will carry it downwind by the time your make your final approach.
Have fun with MRCSS!
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- Created on Friday, 14 March 2003 16:00
- Last Updated on Friday, 14 March 2003 16:00
Introduction To Thermal Duration (TD) Contests
By Bill Rakozy
President, MRCSS 2003
Thermal Duration (TD) soaring can be relaxing, rewarding and challenging all at the same time. In fact, many RC soaring pilots just stop at this juncture, which is a great place to be. Over time however, many a fun-fly pilot have honed their flying skills to the point where it’s enjoyable to pit their flying skills against one another, just for the fun of it. Like golf, once you learn to hit the ball fairly well, you want to compare your “score” with others! That’s where TD soaring contests comes into play.
Contests are well established in the world of TD soaring and there are many opportunities available across the US. Local soaring clubs like MRCSS sponsor contests on a regular basis. In fact, in 2003 the MRCSS flying calendar supports half a dozen weekend competitive events. Our contests are very low key and fun to be a part of. Actually, I like to think of our soaring contests as “learning events”. In reality, TD soaring is a contest against yourself most the time. You know what must be done, but can you do it?
Most TD contests require two flying skills, which must be executed fairly well if you are going to be competitive. The first is staying aloft, until you are ready to come down. The second is landing with accuracy. Staying aloft requires good launching techniques so that you come off the winch or hi-start as high off the ground as possible, with some idea of where you are going to begin searching for thermal activity or “lift”. Otherwise, you will looking for a place to land in 2-3 minutes. A “timer” starts the clock the moment you separate from the tow ring; and stops the clock the moment any part of the aircraft comes in contact with the ground.
Flight Task
In a TD contest, you are given two assignments: (1) a flight task and (2) a landing task. You’ll be awarded one point for each second of flying time. If you fly beyond the assigned task, you lose points. For instance, if you are given a 6-minute flight task, you will be awarded one point for every second in the air, up to 360 seconds (points). 6 minutes x 60 sec/min)= 360 points. If you fly 6 minutes and 15 seconds, your score would be 360 points (-) 15 sec or 345 points total (plus) your landing points if any. Flight tasks require a good flight plan while in the air. It takes practice to know how long it will take to come back to the landing area at the exact moment your assigned flight task is complete.
Landing Task
There are many different ways to award landing points. A very common method is to fix a “landing tape” to the ground with a nail in one end. The free end can scribe a 360-degree circle. If the nose of your aircraft is anywhere in this circle, the tape will read how many points you earned. Obviously, the shorter the tape used, the more difficult the landing task.
If your nose is resting in the 6” center bull’s eye circle, it is worth 100 additional points added to your flight time. (That’s like flying 100 seconds longer than the other guy!) Other landing requirements are: the plane must be upright when it comes to rest and not loose any of its parts (canopy, tail section, etc.) to receive landing points.
Flight Rounds
A contest event usually gives a person the opportunity to launch and fly the “task” between 3-8 times (called “Rounds”) in a day. It all depends upon the size of the group and how fast things are moving. The CD (Contest Director’s) usually determines how long the day will run and when the contest if officially over.
Preparing To Compete
So, if you have been flying for a few months, or a few years, and feel “the call” to participate in a club contest, how can you prepare yourself to do the best you can? This article can’t possibly begin to cover all the individual items, which you must address, but I’ll mention a few which come to mind. Your best bet is to find someone who is more experienced than yourself, and spend a lot of time flying with them. Ask lots of questions. Practice “flying under control” every chance you can.
Getting your plane ready to fly!
Will it hand launch and fly into the wind in a straight line (no wing warp)?
Is the elevator trim set to land slightly nose down, but not too steep?
Is your CG (Center of Gravity) at or slightly behind where the kit plan calls for it?
Have you given it 10-15 test flights to check the trims and you feel confident flying?
Rx (Receiver) battery freshly charged?
TX (Transmitter) battery indicating full strength on the Tx screen?
Here is my pre-flight check list which keeps me out of trouble:
- Select Model (On my Tx screen)
- Crystal OK? (Tx and Rx on the same frequency?)
- Antenna Up
- Wipe Tx Up (All switches in their proper position)
- Switch On (Both Sailplane and Tx)
- Spoilers Down (Launch pre-sets in the correct position)
- Up/Down/Left/Right (Is everything moving freely and in the correct direction.)
- Tow Hook (Attach tow ring on planes tow-hook)
- Pulse Winch Pedal (Be ready to take corrective action in the event of a “pop-off”.
Note: I have this checklist taped to my transmitter and read through it EACH TIME I launch. This pre-flight checklist served me well at the recent LSF/AMA NATS as I was flying two different airplanes, on two different frequencies, using two different “model set-ups” on my computer Tx, all on the same day. No problems to report.
LSF “Fast Track”
I’m convinced that each and every individual who discovered “soaring” and either built or purchased their first sailplane, all walk the same path to success. No one gets a free pass to the head of the line. While some seem to run the path to soaring success, most of us take one small step at a time. It’s called learning. Learning by doing; learning by reading; learning by watching others; learning by asking more experienced pilots and builders how it’s done; and learning by making lots of mistakes. Mistakes are all part of the walk to soaring success. At the recent 2003 LSF/AMA NATS, I heard other who watched Joe Wurts some 20 years ago, do some fairly dumb things while flying his airplane. However, Joe kept pressing forward and today his flying skills are legendary.
In order to fly a timed task and land with accuracy, I believe it will take the rest of your lifetime to perfect those flying skills. That’s what keeps me coming back for more! It is difficult to “out grow” the sport of RC soaring and it’s seldom boring. The more airtime you log, the more comfortable you will begin to feel with your plane under all wind conditions; you will be spending more time flying and less time fixing; and you will arrive at a brand new flying level, regardless of where you begin “your walk”.
It’s my firm belief that regular participation in the League of Silent Flight (LSF) skills development program, is the best (fastest) way to improve your flying skills in the shortest amount of time. And the best part of LSF is you get to progress at your own pace! You determine how fast you want to “walk the road to success”.
To achieve Level 1, you must focus all your flying attention and skills to “ flying under control”. Beginning pilots usually launch and just come down whenever it happens. And they’re usually delighted when they land someplace on the flying field which doesn’t require crossing the highway or drainage ditch! It’s not uncommon for a club member to stay at this level of flying proficiency for years at a time. However, there is another way.
To achieve LSF Level 1, for the first time in your brief flying career, you will be “required” to land in a 3-meter circle and have someone be your witness. In fact, you will be required to land (with a witness), 5 different times before you can begin working on LSF Level II. Level II requires you land 10 times in a 1.5 meter circle. By the time you have completed both Levels I and II, your flying skills will have improved dramatically and your enjoyment of this sport will be at a new and accelerating level of knowledge and interest in this hobby! You will look forward to any and all contests opportunities, instead of trying to convince everyone around you that “contests aren’t for me”.
I hope this brief introduction to TD Contest Soaring will encourage you to fly our weekend contests and become involved in the LSF program. Contact Bill Rakozy, your LSF Club Coordinator at This email address is being protected from spambots. You need JavaScript enabled to view it. and he will get you going for only $2.00. (The best $2 bucks you will ever spend in this hobby!)
Visit the LSF Web Site at: www.silentflight.org
This website contains all the information you will need to get you fired up! Read it all and then get started working on your LSF Level 1 tasks. Also check out the LSF link on our home page to see who in our club is involved in LSF and more importantly, who is advancing in their flying skills!
But above all, enjoy your walk down the road to soaring success!
- Details
- Created on Saturday, 31 May 2003 17:00
- Last Updated on Saturday, 19 January 2008 12:43
- Written by Webmaster
The Path to Improvement in Thermal Soaring
By Bill Kuhl
Introduction
After my first year of sailplane flying, I thought I was a fairly competent RC sailplane pilot. The second year of flying, my flying improved significantly also, in fact every year I seem to improve some. This made me realize this is a hobby that will provide continuous challenges. The first couple years, I often blamed the conditions for difficulty in thermaling, as my skills improved I found success staying up in lift in more conditions. With sailplane flying, fishing, and many other things, luck should be a decreasing factor in your success as you improve.
The objective of this article is to discuss attitude and approach to improving thermal flying skills, not so much technical details covered in many other sources. It is about breaking down the elements and practicing smaller parts before trying to perfect everything at once. Hopefully I can offer a couple of tips that have helped me.
In writing this article, I came up with several points that were important to me.
Attitude
Your success or failure has more to do with controllable factors than by luck, good or bad. Seemingly small factors added together can give big results. The skills will not be learned overnight, if they could be it would not be such a challenging, interesting hobby.Adjusting Your Attitude
It is only natural to think that the small things really dont matter, how could a slight difference in the curve of a wing make a difference? In an activity that is so much about efficiency, all the little things together can make a huge difference. One of the biggest attitudes to overcome is that your skills dont need improvement. Contest flying should prove to you that there is room for improvement.
The fair weather attitude is one I admittedly have problems with, practicing only on days with light wind and plenty of sunshine, will not make you a competent contest pilot. Besides, when you try to fly on the slope in 30 mph winds, it will be a traumatic experience when landing without some windy weather experience.
If you have power plane experience, following thermals will take some change in your flight paths over the field. As Dave Thornburg stated, thermals dont care about field boundaries, tree lines, and such. In Thornburgs video I thought he made it seem like thermals travel in a straight line downwind. Paul Naton in his Secrets of Thermal Flying video showed graphics of how the path of a thermal downwind can take many twists and turns in the path downwind. This appears closer to real world conditions in my opinion.
Practicing the Parts
Selecting, building, and trimming a sailplane has been covered in many articles; what is important, is to have a good flying sailplane. If the sailplane is fighting warps or the center of gravity is incorrect, the performance suffers greatly. A sailplane that thermals easily, will give you more practice.
The areas I practice; revolve around finding the strongest lift and making the most of the lift by smooth flying. Through practice learn to recognize the ground signs, and fly in marginal lift conditions to practice smooth flying.
Practice Recognizing Ground Signs
Many articles have been written about using the shifts in wind and changes in temperature to locate thermals. These are often subtle signs, especially changes in temperature.
With repeated practice over time you become more sensitive to changes in temperature and wind speed and direction. Try to correlate wind dropping, and finding lift directly upwind. Notice when it all of a sudden it gets much warmer right where you are standing.
What makes spotting lift tough, is that while you are trying to figure out where the lift and sink might be, you also have to fly the sailplane. You have to become so comfortable flying the sailplane, that your brain can think about other things.
At first you might want to have devices to help with this, such as thermal flags. Besides a thermal flag, I purchased an accurate wind speed indicator and a heatsensitive thermal indicator like the free flighters use. What I found, was that the temperature changes were pretty small, normally only a few tenths of a degree. Wind speeds changes were more dramatic, often jumping up and down several miles per hour within a short time period. Eventually you get to the point where you feel it is getting warm or you feel the changes in wind speed, or direction on your body.
Recognizing Changes in Speed
Along with ground signs, develop your skills in detecting lift by watching your airplane. Recognize the changes in speed. With hours of practice the little changes in speed were more noticeable to me. Observing the sailplane suddenly pickup speed was a very clear indicator to me that it was in lift. Not as obvious was when the sailplane was slowing down, it was most likely in sink. Recognize when the plane is working hard to penetrate the wind, this is really killing performance. If the plane is inside the thermal it shouldnt have to work so hard trying to penetrate.Practicing, Smooth Flying
With a limited amount of energy, not wasting it is very important. You might think your flying is smooth, but practicing flying in margin lift conditions may prove there is room for improvement. Recognize that any control inputs you are using are creating drag. Think about your flying in terms of energy. The plane is flying with only so much kinetic energy; unnecessary movements such as extra control movements, stalling, or sharp turns, will bleed of the kinetic energy very quickly. The smaller the plane, the worse this will be.
Tight thermal circles turns take a huge amount of energy, if the plane is not circling in lift, the potential energy of altitude is being lost. This means it is best to have a high degree of certainty that you are entering lift, if you hit weak lift, adjust quickly to find stronger lift, or straighten out to fly out of sink.
Learning to Fly Smooth Ways to Practice
Fly in conditions of lighter lift; I often fly later afternoon, early evening. With practice I am climbing in lift later in the day consistently.
Practice flying with an under-powered electric slow-flight plane and try for as long a duration as possible. I noticed that a slow-flight plane of mine would barely climb when other people were flying it (beginners and glow-powered pilots). Most of my flights were of considerably longer duration and of higher altitude because I was using less and smaller control inputs.
Practice flying smooth by flying from small slopes; to stay up on a small slope takes very smooth flying, recognizing when the lift is decreasing or increasing. When the plane is climbing in lift, that is the time to turn. When you are in the core of the thermal, this is when you can experiment with turning tighter to see if the plane goes up even faster. Keep working to have the plane climbing around the entire circle.
Circle in the lightest lift as long as possible. Often with my hand launch I will try to locate lift until I catch the plane, then quickly throw back where lift was spotted and proceed to climb out. When the plane is circling 15 feet high chances of climbing out are not very good, but you can easily see what is going on with your plane.