Thermal Q's
08-22-2007, 12:09 PM
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Thermal Q's
First, I found an excellent article on RCU for searching thermals:
http://www.rcuniverse.com/forum/m_39...tm.htm#3901498
Now the questions, I've never caught a thermal. The best I've done was catch some lift over a hot paved road. After reading this article:
I know it varies, but how big should I expect a thermal to be? 25yards? 100yards? a mile?
How tight a circle to fly once/if I find one? 50ft? 500ft? I know it depends in the thermal, but what should I expect?
How low do they start? I mean, after my high-start launch, if I drop below Xft altitude go ahead and come in, cause it's pointless.???
I did read the article thoroghly (SP?) and I found more on the internet with diagrams etc. So I have some indication of what they are supposed to look like and indications of lift. As far as experience or actually seeing it done, I have no idea.
As usual, thanks for the help! Oh, btw, I have a 2m Spirit.
http://www.rcuniverse.com/forum/m_39...tm.htm#3901498
Now the questions, I've never caught a thermal. The best I've done was catch some lift over a hot paved road. After reading this article:
I know it varies, but how big should I expect a thermal to be? 25yards? 100yards? a mile?
How tight a circle to fly once/if I find one? 50ft? 500ft? I know it depends in the thermal, but what should I expect?
How low do they start? I mean, after my high-start launch, if I drop below Xft altitude go ahead and come in, cause it's pointless.???
I did read the article thoroghly (SP?) and I found more on the internet with diagrams etc. So I have some indication of what they are supposed to look like and indications of lift. As far as experience or actually seeing it done, I have no idea.
As usual, thanks for the help! Oh, btw, I have a 2m Spirit.
08-22-2007, 01:05 PM
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RE: Thermal Q's
Its actually *much* easier than youre thinking it is.
Heres what I would do. Make sure your Spirit is in good working order, and youre getting good launches. Hopefully youre flying around noon to 2:00 PM, which is the time of day the thermals are working the most.
A thermal looks like a mushroom cloud. It starts as a bubble of warm air, like a bubble on the bottom of a pot of boiling water. It breaks loose, and begins rolling like a doughnut (inside rising faster than the edge, which can be sinking since its cooling) and climbing. As the thermals reach altitude, they can begin to join up, and suddenly theres lift everywhere. You want to be in the center of the doughnut. 50 feet is probably average size, though closer to the ground they can be quite small.
Heres what it feels like: Youre flying along, and suddenly your plane hangs a right turn with no input. Turn HARD left and go back there, because that was a thermal passing under your left wing. Your plane wants to turn away from lift. Anyway, turn back into the spot where that happend and circle. Remember the thermal is drifting down wind, so follow it.
I seem to have good success off of a high start like this: Launch, come off the high start, and turn 45 degrees cross wind and work across your field. If your plane turns on its own, turn back hard against it and circle.
Now, once youre in one, you'll sometimes notice your plane speed up, and the tailboom rise before the rest of the plane. Turn hard and begin pulling as much up as the plane can take. if you pull too much, you'll see it stall. Stay with the thermal and be ready to stay with it as it drifts down wind, probably behind you. The Spirit is a pretty good penetrator, so you can come back from a spot down wind, but dont get cocky.
You may need to make some subtle adjustments to your circle to stay in the thermal, so momentarily open one side of your circle to follow the thermal, but get right back into it. It pays to be aggressive when staying in lift.
And finally, learn the field you fly. If you know "Oh, that tree line always has something coming off of it" or "That tennis court 100 yards upwind always has a boomer coming off of it" Go for it. Really get in there and ride that lift, and see what you can do with it.
If you havent already, check out the Charles River website regarding the Spirit. They have some good tuning tips that will help you squeeze the last bits of performance out of your Spirit. You may want to put some dark wingtips on the bottom of your wing so its easier to see at altitude.
Heres what I would do. Make sure your Spirit is in good working order, and youre getting good launches. Hopefully youre flying around noon to 2:00 PM, which is the time of day the thermals are working the most.
A thermal looks like a mushroom cloud. It starts as a bubble of warm air, like a bubble on the bottom of a pot of boiling water. It breaks loose, and begins rolling like a doughnut (inside rising faster than the edge, which can be sinking since its cooling) and climbing. As the thermals reach altitude, they can begin to join up, and suddenly theres lift everywhere. You want to be in the center of the doughnut. 50 feet is probably average size, though closer to the ground they can be quite small.
Heres what it feels like: Youre flying along, and suddenly your plane hangs a right turn with no input. Turn HARD left and go back there, because that was a thermal passing under your left wing. Your plane wants to turn away from lift. Anyway, turn back into the spot where that happend and circle. Remember the thermal is drifting down wind, so follow it.
I seem to have good success off of a high start like this: Launch, come off the high start, and turn 45 degrees cross wind and work across your field. If your plane turns on its own, turn back hard against it and circle.
Now, once youre in one, you'll sometimes notice your plane speed up, and the tailboom rise before the rest of the plane. Turn hard and begin pulling as much up as the plane can take. if you pull too much, you'll see it stall. Stay with the thermal and be ready to stay with it as it drifts down wind, probably behind you. The Spirit is a pretty good penetrator, so you can come back from a spot down wind, but dont get cocky.
You may need to make some subtle adjustments to your circle to stay in the thermal, so momentarily open one side of your circle to follow the thermal, but get right back into it. It pays to be aggressive when staying in lift.
And finally, learn the field you fly. If you know "Oh, that tree line always has something coming off of it" or "That tennis court 100 yards upwind always has a boomer coming off of it" Go for it. Really get in there and ride that lift, and see what you can do with it.
If you havent already, check out the Charles River website regarding the Spirit. They have some good tuning tips that will help you squeeze the last bits of performance out of your Spirit. You may want to put some dark wingtips on the bottom of your wing so its easier to see at altitude.
08-22-2007, 01:26 PM
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RE: Thermal Q's
Trim your plane for hands off flight. Then keep your hands off. You will notice if it gets bumped, turn into the bump. People can thermal with light planes off a hand launch. Thermals start at the ground and spread out as they rise, kind of like an icecream cone. The higher you are the bigger the circle. I've stood my 2m on a wing tip and circled, its just a feel you develop.
Its quite a thrill once you catch a biggun!
As for how how high you can thermal, you need to make sure you have enough room to land safely.
Its quite a thrill once you catch a biggun!
As for how how high you can thermal, you need to make sure you have enough room to land safely.
08-22-2007, 05:55 PM
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RE: Thermal Q's
I have a Spirit 2M and its a wonderful thermal flyer. The trick I discovered was to get rid of all the extra weight in the nose. The construction directions have you adding weight in the nose to balance it on the spar. I found that once I removed all that weight, the CG was a little behind the spar, but the plane became much more responsive. I didn't need to worry about the nose dropping quickly, and have more time to see the wings get bumped by thermals.
If the plane does turn on its own, rather than try to force it back, I've found its much more productive to just continue the turn 270 degrees. That will put you almost into the center of whatever lift you experienced. You'll see the plane start to rise when it enters the thermal. Once you start circling, the plane will try to turn out of the thermal, and thats when you want to fight the turn to get back into the thermal. Eventually you'll find an altitude where the plane just doesn't want to come down. Thats when it gets fun.
Brad
If the plane does turn on its own, rather than try to force it back, I've found its much more productive to just continue the turn 270 degrees. That will put you almost into the center of whatever lift you experienced. You'll see the plane start to rise when it enters the thermal. Once you start circling, the plane will try to turn out of the thermal, and thats when you want to fight the turn to get back into the thermal. Eventually you'll find an altitude where the plane just doesn't want to come down. Thats when it gets fun.
Brad
08-22-2007, 09:18 PM
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RE: Thermal Q's
From what I read, thermals turn clockwise in the Northern Hemisphere (counter clockwise below the equator). While this in itself is very cool, what direction do I turn in the thermal? Or does it matter? Clockwise with the themal (perhaps considered downwind?) or counterclockwise against the thermal flow (riding into the lift?) ?
I hope to get my Rx in time for this weekend. If not I'm going to burrow the one out of my glow-trainer. I'm trying to learn all I can to have a fighting chance [>:]
I hope to get my Rx in time for this weekend. If not I'm going to burrow the one out of my glow-trainer. I'm trying to learn all I can to have a fighting chance [>:]
08-22-2007, 09:21 PM
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RE: Thermal Q's
Thanks, I'm definately going to make sure the nose is unloaded this time. It's been 12 years since she's been in the air!
I found a bunch of mods (listed above 2nd-3rd post, thank-you), but they will have to come later.
I found a bunch of mods (listed above 2nd-3rd post, thank-you), but they will have to come later.
08-22-2007, 09:53 PM
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RE: Thermal Q's
Thermal rotation is random. Just pick a rotation you're comfortable with and go for it.
If you go to YouTube there should be some handlaunch or discus-launched glider videos on there. Watch how they work light lift low and close to the ground.
If you go to YouTube there should be some handlaunch or discus-launched glider videos on there. Watch how they work light lift low and close to the ground.
08-23-2007, 09:35 AM
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RE: Thermal Q's
When you take the weight out of the nose of your plane it becomes less stable. Just remember that when you land that you probably will want to come in a little faster so as to avoid a stall. You may want to consider removing the weight a little at a time. Little steps are sometimes are better than big leaps.
Finding thermals is the great challenge. Up higher the thermals are typically wider but weaker. Watch the plane it will tell you when you are in a thermal. Thermals are going to float down wind. So you will need to follow this drifting motion. On days when there a lots of those low hanging puffy clouds moving slowly across the sky there will be thermals.
The more you fly your sailplane the better you get at finding thermals.
Have fun. bob
Finding thermals is the great challenge. Up higher the thermals are typically wider but weaker. Watch the plane it will tell you when you are in a thermal. Thermals are going to float down wind. So you will need to follow this drifting motion. On days when there a lots of those low hanging puffy clouds moving slowly across the sky there will be thermals.
The more you fly your sailplane the better you get at finding thermals.
Have fun. bob
08-23-2007, 12:49 PM
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RE: Thermal Q's
For trimming and weighting purposes, I started with the recommended CG. I took the plane to the field, and stuck with hand launches. I would throw the plane into the wind and then try to bring it around full circle. When the plane was nose heavy, this was very difficult. As I continued to remove weight, the circle became easier and easier. I quit removing weight when I could bring the plane around full circle or more, using almost no elevator. I also discovered that as I removed nose weight, the plane became less and less likely to drop the nose as it slows down. Its now weighted such that it will eventually drop the nose, which is essential for a stall recovery, but its going pretty slow when it happens.
I used the full circle criteria based on the logic that I wanted to be able to hook a small thermal close to the ground. Before doing this, If I didn't have a good 50 feet or so of altitude, I would pretty much have to give up hunting thermals. Now I can pretty much fly the length of the field at that height, which gives me that last little chance of keeping it going. The plane also responds much quicker to small thermals, due to the reduced stability.
Brad
I used the full circle criteria based on the logic that I wanted to be able to hook a small thermal close to the ground. Before doing this, If I didn't have a good 50 feet or so of altitude, I would pretty much have to give up hunting thermals. Now I can pretty much fly the length of the field at that height, which gives me that last little chance of keeping it going. The plane also responds much quicker to small thermals, due to the reduced stability.
Brad
08-23-2007, 01:25 PM
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RE: Thermal Q's
ORIGINAL: bkdavy
For trimming and weighting purposes, I started with the recommended CG. I took the plane to the field, and stuck with hand launches. I would throw the plane into the wind and then try to bring it around full circle. When the plane was nose heavy, this was very difficult. As I continued to remove weight, the circle became easier and easier. I quit removing weight when I could bring the plane around full circle or more, using almost no elevator. I also discovered that as I removed nose weight, the plane became less and less likely to drop the nose as it slows down. Its now weighted such that it will eventually drop the nose, which is essential for a stall recovery, but its going pretty slow when it happens.
I used the full circle criteria based on the logic that I wanted to be able to hook a small thermal close to the ground. Before doing this, If I didn't have a good 50 feet or so of altitude, I would pretty much have to give up hunting thermals. Now I can pretty much fly the length of the field at that height, which gives me that last little chance of keeping it going. The plane also responds much quicker to small thermals, due to the reduced stability.
Brad
For trimming and weighting purposes, I started with the recommended CG. I took the plane to the field, and stuck with hand launches. I would throw the plane into the wind and then try to bring it around full circle. When the plane was nose heavy, this was very difficult. As I continued to remove weight, the circle became easier and easier. I quit removing weight when I could bring the plane around full circle or more, using almost no elevator. I also discovered that as I removed nose weight, the plane became less and less likely to drop the nose as it slows down. Its now weighted such that it will eventually drop the nose, which is essential for a stall recovery, but its going pretty slow when it happens.
I used the full circle criteria based on the logic that I wanted to be able to hook a small thermal close to the ground. Before doing this, If I didn't have a good 50 feet or so of altitude, I would pretty much have to give up hunting thermals. Now I can pretty much fly the length of the field at that height, which gives me that last little chance of keeping it going. The plane also responds much quicker to small thermals, due to the reduced stability.
Brad
That sounds like some pretty good advice. I'm saving all this stuff to a file so I can run through it again when I can put the plane in the air. I'm still hoping for this weekend, but my Rx is in Illinois right now. NOOOoo!
As I remember, mine lost altitude faster than that. I know it was nose heavy, my complete inexperience at the time told me to err on the nose heavy side. And boy did I! Now with balance experiences on my trainer the last 2-3 months should help out considerably.
I did look on Youtube and Google video for some thermal action. I've studied several videos, but I can't seem to detect the "symptoms" of a thermal just before they circle. I'm still working at it though. It'd be nice if I knew someone that soared.
08-23-2007, 04:38 PM
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RE: Thermal Q's
The "symptoms" of a thermal are simply a change in the flight of the plane. It could be a wing tip up (or down), or the tail (up or down) or some combination of both. Thats why trimming the plane to fly straight and level hands off is so important.
Once the plane is trimmed and in the air, you let go of it. Let it fly. If it starts to turn on its own (eg banks slightly) then you have either grazed a rising air current with the wing or a sinking air current with the down wing. If you continue the turn 270 degrees, you will either fly into the rising air or out of the sinking air. Both good things to do. As you steady on your final course, watch the plane closely. It will rise or fall. If it rises, you're in lift. Start your circles. If it falls, you're in sink. Keep flying to get out of it.
Once you start circling, keep the circles as tight as you can without stalling. Watch the plane closely as you circle. If it trys to turn opposite your circle, you're probably just outside the thermal, so fight it back into the thermal. Eventually you'll find the boundaries of that thermal. And remember, thermals will move down wind. So let the plane move downwind with it. Its not magic. Its just being attuned to your plane, your field, and the air.
Sometimes to find the rising air, you have to think about the situation. The Manual that comes with the Spirit has some great advice on finding thermals. For example, you normally want to fly up wind to explore new air. But there are times when its worthwile to fly downwind. If air is moving across the ground where you're standing, chances are there is a column of rising air somewhere downwind. Your mission is to find it. Parking lots, plowed fields, cars, and roofs can all be great sources of heat that will drive thermal currents. Depending on where you fly, sailplanes can often get away with flying outside the boundaries, because they don't make any noise. Nobody will even know you're flying there unless they look up.
Look for birds circling. They are great at finding the rising air. I watched a hawk a couple weeks ago launch himself out of a tree and then perform some pretty tight circles about 25 feet off the ground very close to the tree line. In about 2 minutes, he had risen several hundred feet without ever flapping his wings. Wish I'd had my glider that day - I could have hand launched into some real boomers.
I think of thermal soaring like fishing. Its a great reward when you hook the big one. But it takes a lot of casting sometimes to find the right spot.
Brad
Once the plane is trimmed and in the air, you let go of it. Let it fly. If it starts to turn on its own (eg banks slightly) then you have either grazed a rising air current with the wing or a sinking air current with the down wing. If you continue the turn 270 degrees, you will either fly into the rising air or out of the sinking air. Both good things to do. As you steady on your final course, watch the plane closely. It will rise or fall. If it rises, you're in lift. Start your circles. If it falls, you're in sink. Keep flying to get out of it.
Once you start circling, keep the circles as tight as you can without stalling. Watch the plane closely as you circle. If it trys to turn opposite your circle, you're probably just outside the thermal, so fight it back into the thermal. Eventually you'll find the boundaries of that thermal. And remember, thermals will move down wind. So let the plane move downwind with it. Its not magic. Its just being attuned to your plane, your field, and the air.
Sometimes to find the rising air, you have to think about the situation. The Manual that comes with the Spirit has some great advice on finding thermals. For example, you normally want to fly up wind to explore new air. But there are times when its worthwile to fly downwind. If air is moving across the ground where you're standing, chances are there is a column of rising air somewhere downwind. Your mission is to find it. Parking lots, plowed fields, cars, and roofs can all be great sources of heat that will drive thermal currents. Depending on where you fly, sailplanes can often get away with flying outside the boundaries, because they don't make any noise. Nobody will even know you're flying there unless they look up.
Look for birds circling. They are great at finding the rising air. I watched a hawk a couple weeks ago launch himself out of a tree and then perform some pretty tight circles about 25 feet off the ground very close to the tree line. In about 2 minutes, he had risen several hundred feet without ever flapping his wings. Wish I'd had my glider that day - I could have hand launched into some real boomers.
I think of thermal soaring like fishing. Its a great reward when you hook the big one. But it takes a lot of casting sometimes to find the right spot.
Brad
08-24-2007, 02:00 PM
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RE: Thermal Q's
Man! I really appreciate the tons of info and help here. I've learned a lot and it's given me more things and keywords to Google that led to diagrams and more info.
I think I've learned enough to give me a fighting chance this weekend (weather permitting) with my Spirit. I won't have a chance to do some of the mods to the plane by then, but I will later. At least I know what to expect now (I think), and an idea of thermal/circling size should help out greatly.
My Rx didn't come in
so I hope to borrow or steal one from somewhere temporarily.
I'll let you know how it goes. Thanks again!
I think I've learned enough to give me a fighting chance this weekend (weather permitting) with my Spirit. I won't have a chance to do some of the mods to the plane by then, but I will later. At least I know what to expect now (I think), and an idea of thermal/circling size should help out greatly.
My Rx didn't come in
so I hope to borrow or steal one from somewhere temporarily.I'll let you know how it goes. Thanks again!
08-24-2007, 06:56 PM
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RE: Thermal Q's
Best of luck with it. Boy, it's been a while since I wrote the stuff in that link.
As you're quickly learning there's no one right or wrong way for the most part other than learning to "go with the flow" and avoid horsing the model around unless you're in lift. Learning to REALLLY observe the model's actions is also paramount. You need to sharpen your visual perspective of what the model is doing until you can shave with it...
Some folks can walk and soar at the same time. For me I loose too much perspective from the moving background and model so I tend to come off the launch winch or highstart and run out of the way and then settle down and get to work observing what my model is doing.
Outside of that it's all about stick time and practice. Lots of stick time will expose you to all the variations the weather has to offer.
Generally the closer to the ground the smaller and usually weaker the thermals are. But if you can circle tightly enough with good control over the model's speed and gain some height you can progresively open up the turn as you move up further into the fatter portion of the thermal. Again observing the planes climb and sinking will tell you in a hurry if you are circling too open or if you're not centered. Don't be afraid to move the circle around by tightening the turn a little here or opening it up a little there for a portion of the turn to move the center.
As you're quickly learning there's no one right or wrong way for the most part other than learning to "go with the flow" and avoid horsing the model around unless you're in lift. Learning to REALLLY observe the model's actions is also paramount. You need to sharpen your visual perspective of what the model is doing until you can shave with it...
Some folks can walk and soar at the same time. For me I loose too much perspective from the moving background and model so I tend to come off the launch winch or highstart and run out of the way and then settle down and get to work observing what my model is doing.
Outside of that it's all about stick time and practice. Lots of stick time will expose you to all the variations the weather has to offer.
Generally the closer to the ground the smaller and usually weaker the thermals are. But if you can circle tightly enough with good control over the model's speed and gain some height you can progresively open up the turn as you move up further into the fatter portion of the thermal. Again observing the planes climb and sinking will tell you in a hurry if you are circling too open or if you're not centered. Don't be afraid to move the circle around by tightening the turn a little here or opening it up a little there for a portion of the turn to move the center.
08-25-2007, 09:56 PM
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RE: Thermal Q's
Thanks BMatthews, I got it. I didn't realized you wrote that stuff. It's good material.
Tomorrow's the day, weather permitting. I got the model working once again and balanced.
It looks like I had some OLD Futaba servos in there. The connectors were the wrong gender and a wierd pin spacing, so I removed them. I installed some standard size Airtronics I had and burrowed a mini Rx. I also too the opportunity to relocate the servos about eight inches forward to lose some nose weight. New pushrods and some fancy routing. Whew! It looks good. I was able to remove about an ounce from the nose, not as much as I had hoped. Oh, well.
Tomorrow's the day, weather permitting. I got the model working once again and balanced.
It looks like I had some OLD Futaba servos in there. The connectors were the wrong gender and a wierd pin spacing, so I removed them. I installed some standard size Airtronics I had and burrowed a mini Rx. I also too the opportunity to relocate the servos about eight inches forward to lose some nose weight. New pushrods and some fancy routing. Whew! It looks good. I was able to remove about an ounce from the nose, not as much as I had hoped. Oh, well.
08-27-2007, 09:12 AM
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RE: Thermal Q's
If anyone is waiting in anticipation:
I took my glider out and hand launched it a few times. Got it trimmed out after adding another .5oz to the nose for a total of 2oz. Ouch!
The wind was frequently gusty up to probably 10mph..... But I was there with all my stuff and it was a beautiful day. The first high start launch went straight up to about 100ft and stalled (on the high start). That was interesting, I don't think that's even happened before. The second lauch I tried to keep the nose down with elevator. 150ft and pathetic. I decided it was too windy for the setup, so I should move the hook to the front hole (from the middle hole). The #$*&! hook broke off. So that was all. Yay.
I'm going to try and drill out the t-nuts and install larger nuts and hook. I'll post any updates if anyone is interested.
Life's rules #196 - Don't fly your glider in gusty wind, you can't tell if it's a thermal anyways.
I took my glider out and hand launched it a few times. Got it trimmed out after adding another .5oz to the nose for a total of 2oz. Ouch!
The wind was frequently gusty up to probably 10mph..... But I was there with all my stuff and it was a beautiful day. The first high start launch went straight up to about 100ft and stalled (on the high start). That was interesting, I don't think that's even happened before. The second lauch I tried to keep the nose down with elevator. 150ft and pathetic. I decided it was too windy for the setup, so I should move the hook to the front hole (from the middle hole). The #$*&! hook broke off. So that was all. Yay.
I'm going to try and drill out the t-nuts and install larger nuts and hook. I'll post any updates if anyone is interested.
Life's rules #196 - Don't fly your glider in gusty wind, you can't tell if it's a thermal anyways.
08-29-2007, 10:27 PM
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RE: Thermal Q's
ORIGINAL: spiral_72
Life's rules #196 - Don't fly your glider in gusty wind, you can't tell if it's a thermal anyways.
Life's rules #196 - Don't fly your glider in gusty wind, you can't tell if it's a thermal anyways.
High Starts tend to work better with a little breeze too. Wait until you get a good strong hook on that Spirit and learn to zoom your launches. I hope your wing joiner is built right!
08-31-2007, 09:59 AM
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RE: Thermal Q's
ORIGINAL: JasonS
Those gusts may be caused by thermals! Some of the biggest boomers I've hit have been on days with a fair breeze. Plus you can sometimes use "standing waves" of roiling air to sorta "slope" soar on. Or get "slope" lift off of any tree lines around. Some fields are only really good with a little breeze.
High Starts tend to work better with a little breeze too. Wait until you get a good strong hook on that Spirit and learn to zoom your launches. I hope your wing joiner is built right!
ORIGINAL: spiral_72
Life's rules #196 - Don't fly your glider in gusty wind, you can't tell if it's a thermal anyways.
Life's rules #196 - Don't fly your glider in gusty wind, you can't tell if it's a thermal anyways.
High Starts tend to work better with a little breeze too. Wait until you get a good strong hook on that Spirit and learn to zoom your launches. I hope your wing joiner is built right!
I bought some hardware for another hook. It's 1/4"-20 and t-nuts. I'll have to heat it to bend I'm sure. Maybe I need to use something bigger.... Maybe 3/8"??? Just kidding.
The gusting was causing my launch to be interesting to say the least. I think the wind was actually changing directions rapidly. Or, either it was wind followed with a low pressure area. I think that's a better description...... and I think you're right, I was standing in a thermal. It just wasn't to high-start friendly. She'd climb like a rocket, then the nose would drop and sink.... no FALL very rapidly. It was very tough to keep control. I'll try it again asap.
09-10-2007, 11:44 AM
#19
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RE: Thermal Q's
I went out with my Spirit for several house yesterday. The wind was gusty with sometimes ~12mph winds.
My high start give me only 250ft launched, I think mainly bec of high grass. I got a couple hits in flight that lifted the wing, but I wasn't able to find lift. I did however find sink and of course the lift must have been there too. I got probably 3-4 3 minute flights and 3-4 2 minute flights with about 10 hand launches ranging from 10sec to 45 seconds.
My plane is trimmed fairly well. I put some expo in the rudder bec it was rediculous sensitive. I might do the same with the elevator. I don't remember that 10+ years ago. I did end up putting all the weight back in it that was there originally. That's pretty discouraging considering I spent the better part of a day relocating the servos and new control rods.
For minimum sink rate, how fast should the plane be moving? I know that's relative, but with a "zero" as stall speed and "10" as a flat out dive, I was puttin' along at about a 1. Just over stall. Is this correct?
Also with every failed thermal chase I lost about 50ft of altitude. Am I controlling to much or is that expected? I think I'm going to change the control horns and tame down the throws a bit too. Maybe I can remove the expo then.
I've got another field in mind for next time. Hopefully I will get better launches.
My high start give me only 250ft launched, I think mainly bec of high grass. I got a couple hits in flight that lifted the wing, but I wasn't able to find lift. I did however find sink and of course the lift must have been there too. I got probably 3-4 3 minute flights and 3-4 2 minute flights with about 10 hand launches ranging from 10sec to 45 seconds.
My plane is trimmed fairly well. I put some expo in the rudder bec it was rediculous sensitive. I might do the same with the elevator. I don't remember that 10+ years ago. I did end up putting all the weight back in it that was there originally. That's pretty discouraging considering I spent the better part of a day relocating the servos and new control rods.
For minimum sink rate, how fast should the plane be moving? I know that's relative, but with a "zero" as stall speed and "10" as a flat out dive, I was puttin' along at about a 1. Just over stall. Is this correct?
Also with every failed thermal chase I lost about 50ft of altitude. Am I controlling to much or is that expected? I think I'm going to change the control horns and tame down the throws a bit too. Maybe I can remove the expo then.
I've got another field in mind for next time. Hopefully I will get better launches.
09-17-2007, 09:46 AM
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RE: Thermal Q's
Spiral...thought I would throw in a few cents worth <grin>.
I returned to RC last year after several years away and it's great. I fly electrics now but still have my trusty hi-start. Concerning trimming -- I trim my planes in flight with just enough elevator to keep them from stalling. Both my planes have sufficient wash out built in so I avoid tip stalling and a possible spin. I think your comment about possibly over-controlling is on the mark. I had to work on that myself.
Now, once I'm trimmed out, I concentrate on keeping my thumbs "quiet" and focus on my plane. Turns, especially aileron turns, are "expensive" in terms of altitude, especially while hunting. While searching, I often turn with my rudder or ruddervators on my v-tail. Once, I've found a thermal, I have to get a bit more aggressive with the turning, including my ailerons, to get in there and catch my ride.
I fly in farm country off a small private grass strip airfield. It's fairly tight for sailplanes with tall trees on three sides and two "plane grabbers" out in the open. To find thermals, I have to work the whole field.
I'm watching the wind today and hope to get out this afternoon
Highride
I returned to RC last year after several years away and it's great. I fly electrics now but still have my trusty hi-start. Concerning trimming -- I trim my planes in flight with just enough elevator to keep them from stalling. Both my planes have sufficient wash out built in so I avoid tip stalling and a possible spin. I think your comment about possibly over-controlling is on the mark. I had to work on that myself.
Now, once I'm trimmed out, I concentrate on keeping my thumbs "quiet" and focus on my plane. Turns, especially aileron turns, are "expensive" in terms of altitude, especially while hunting. While searching, I often turn with my rudder or ruddervators on my v-tail. Once, I've found a thermal, I have to get a bit more aggressive with the turning, including my ailerons, to get in there and catch my ride.
I fly in farm country off a small private grass strip airfield. It's fairly tight for sailplanes with tall trees on three sides and two "plane grabbers" out in the open. To find thermals, I have to work the whole field.
I'm watching the wind today and hope to get out this afternoon
Highride
01-29-2008, 10:42 PM
#21
RE: Thermal Q's
I think this is a good discussion that deserves to be revived. I am going to add my 2 cents here.
And how is our new thermal pilot doing after all these months?
Learning to Thermal
by Ed Anderson
aeajr on the forums
A thermal is a column of warm rising air that occurs when one section of the
ground warms faster then other sections. As the air raises it draws in
more air. Think of a very slow moving tornado.
Not exactly correct but close enough for first approximation.
What do thermals look like?
http://www.flyaboveall.com/mountainp...rmalclinic.htm
Here is a great video on thermals. I highly recommend it!
The Secrets of Thermal Soaring
http://www.radiocarbonart.com/Pages/...ermalmain.html
Almost any plane can thermal, but the lighter the wing loading the better.
Under 12 ounces/sq ft is really good and under 8 is great! The typical
small electric plane has wing loadings in this area so they
often thermal well.
Flat bottom or under cambered wings tend to do better than symmetrical or
semi-symmetrical wings but if the lift is strong, you can thermal anything.
In fact we sometimes have to pull out of thermals because the lift is so
strong that the plane can be pulled into the sky and out of sight. I have
seen it happen.
For some people this may sound boring, but I relate it to fishing. You may
cast out many times with no bites. Still, the process is relaxing and
pleasurable.
Finally you get a strike and the fight begins.
You go on each fishing trip looking forward to the catch, but knowing that
you will enjoy the process even if you come home with nothing. To
nonfishermen this sounds odd. They just don't understand. Likewise with
thermaling.
TIPS ON FINDING THERMALS
The best conditions are calm air, hot sun and low humidity. Some big dark
areas surrounded by lighter areas will help to create thermals, so look to
see if there is anything like that on or around your field. A freshly
plowed field is good. A parking lot works great! A large building with a
black roof is awesome.
However I have caught thermals at 35 degrees F in 15 mph winds. They can be
weak and they move fast, but the are there!
Here are some thoughts on the hunt!
Get your plane up high, the higher the better. Get it well up wind from you
as we are going to glide and drift with the river of air.
If you have a motor, cut the motor and trim the plane for nice level flight.
Now, focus on watching the plane and keeping it on a nice steady glide.
Steady as she goes. Try to keep your hands off the sticks as much as
possible.
Let the plane ride with and across the river of air, giving it only
occasional input to keep it going in the general direction you want to go,
but don't be a stickler about it. Let it drift like a fly on the surface of
the river, waiting for a trout.
If you listen with your eyes, it will speak to you, but you have to listen
patiently.
Glide across the wind, not into it and not with it. Sort of a 45 -60 degree
left for a while then a 45 to 60 degrees to the right. Nice and slow and
easy. You want to cover the sky and search the moving river of air, like a
bird looking for food.
As you are flying watch the wing tips the nose and the tail. If a wing
seems to bump up, or if the plane seems to become buoyant, floating up for a
moment, it could be a gust, or you might have just brushed a thermal. Go
immediately into a slow turn in the direction of the wing that rose. If
you think you went right through it, fly on for a moment then turn to
circle back into it. It will be moving toward you.
Try to make a circle, but not too tight or you will lose too much altitude.
Try for about a 75-100 foot diameter at first. Complete a couple of turns
and see if the plane seems to be rising. If it is, just stay with the turn
but give it a little up (back) stick. Not a lot, just a little. Maybe two
to four clicks on the up trim. Just a little. We don't want to scare the
thermal, we want to bond with it.
Try to observe if the plane is rising steadily, or if it seems to rise and
fall that means you are not centered in the thermal, so work your way more
toward the side of the circle where the plane rises.
Remember that thermals move with the wind, so you are not trying to stay in
one place in relation to the ground. The air is like a river and you are
trying to stay in a little whirlpool that is moving with the river.
If you go into the turn and make a couple of turns with no success, then
just resume the search pattern I mentioned. Angles across the wind. Not
into it and now with it.
A sailplane in lift
http://www.rcgroups.com/articles/lif...r/ava/Ava2.wmv
If you are getting out too far, work your way back the same
way, angles to the wind.
Unless you hit a boomer, you are not going to immediately know you are in
lift, so you have to watch the plane. Sometimes it becomes apparent because
you realize that your not sinking but appear to be holding altitude. The
only way to do that is to be in lift.
Remember also that thermal can vary in size and intensity. Some are fairly
narrow and some are so large that it seems a whole region of the sky is in
lift. I rode one area recently for 45 minutes where it seemed about 1/4 of
the field was in lift. You didn't really have to circle. You could just fly
back and forth and the plane would rise beautifully. Those are really nice,
when you find them.
It is a hunter's game, if you are up for it.
Good luck pilot! May your hunt go well!
Resources
What do Thermals Look Like
http://kohlin.com/air/soar-faq.htm#589882
http://www.rc-soar.com/tech/thermals.htm
http://www.apogeerockets.com/educati...br /> ls.asp
Finding Elusive Thermals
http://f4bscale.worldonline.co.uk/Thermals.htm
Thermaling on a windy day
[url]http://www.moneysmith.net/Soaring/soaring9.html#ref97[/
url]
The Soaring Methods of Birds
http://www.apogeerockets.com/educati...ng_methods.asp
Search Patterns
[url]http://www.quicktechhobby.com/articles/thermal_surfing%
20part%202.htm[/
url]
If you are a new glider pilot, this is a great resource:
http://forums.flyesl.com/topic.asp?TOPIC_ID=224
And how is our new thermal pilot doing after all these months?
Learning to Thermal
by Ed Anderson
aeajr on the forums
A thermal is a column of warm rising air that occurs when one section of the
ground warms faster then other sections. As the air raises it draws in
more air. Think of a very slow moving tornado.
Not exactly correct but close enough for first approximation.
What do thermals look like?
http://www.flyaboveall.com/mountainp...rmalclinic.htm
Here is a great video on thermals. I highly recommend it!
The Secrets of Thermal Soaring
http://www.radiocarbonart.com/Pages/...ermalmain.html
Almost any plane can thermal, but the lighter the wing loading the better.
Under 12 ounces/sq ft is really good and under 8 is great! The typical
small electric plane has wing loadings in this area so they
often thermal well.
Flat bottom or under cambered wings tend to do better than symmetrical or
semi-symmetrical wings but if the lift is strong, you can thermal anything.
In fact we sometimes have to pull out of thermals because the lift is so
strong that the plane can be pulled into the sky and out of sight. I have
seen it happen.
For some people this may sound boring, but I relate it to fishing. You may
cast out many times with no bites. Still, the process is relaxing and
pleasurable.
Finally you get a strike and the fight begins.
You go on each fishing trip looking forward to the catch, but knowing that
you will enjoy the process even if you come home with nothing. To
nonfishermen this sounds odd. They just don't understand. Likewise with
thermaling.
TIPS ON FINDING THERMALS
The best conditions are calm air, hot sun and low humidity. Some big dark
areas surrounded by lighter areas will help to create thermals, so look to
see if there is anything like that on or around your field. A freshly
plowed field is good. A parking lot works great! A large building with a
black roof is awesome.
However I have caught thermals at 35 degrees F in 15 mph winds. They can be
weak and they move fast, but the are there!
Here are some thoughts on the hunt!
Get your plane up high, the higher the better. Get it well up wind from you
as we are going to glide and drift with the river of air.
If you have a motor, cut the motor and trim the plane for nice level flight.
Now, focus on watching the plane and keeping it on a nice steady glide.
Steady as she goes. Try to keep your hands off the sticks as much as
possible.
Let the plane ride with and across the river of air, giving it only
occasional input to keep it going in the general direction you want to go,
but don't be a stickler about it. Let it drift like a fly on the surface of
the river, waiting for a trout.
If you listen with your eyes, it will speak to you, but you have to listen
patiently.
Glide across the wind, not into it and not with it. Sort of a 45 -60 degree
left for a while then a 45 to 60 degrees to the right. Nice and slow and
easy. You want to cover the sky and search the moving river of air, like a
bird looking for food.
As you are flying watch the wing tips the nose and the tail. If a wing
seems to bump up, or if the plane seems to become buoyant, floating up for a
moment, it could be a gust, or you might have just brushed a thermal. Go
immediately into a slow turn in the direction of the wing that rose. If
you think you went right through it, fly on for a moment then turn to
circle back into it. It will be moving toward you.
Try to make a circle, but not too tight or you will lose too much altitude.
Try for about a 75-100 foot diameter at first. Complete a couple of turns
and see if the plane seems to be rising. If it is, just stay with the turn
but give it a little up (back) stick. Not a lot, just a little. Maybe two
to four clicks on the up trim. Just a little. We don't want to scare the
thermal, we want to bond with it.
Try to observe if the plane is rising steadily, or if it seems to rise and
fall that means you are not centered in the thermal, so work your way more
toward the side of the circle where the plane rises.
Remember that thermals move with the wind, so you are not trying to stay in
one place in relation to the ground. The air is like a river and you are
trying to stay in a little whirlpool that is moving with the river.
If you go into the turn and make a couple of turns with no success, then
just resume the search pattern I mentioned. Angles across the wind. Not
into it and now with it.
A sailplane in lift
http://www.rcgroups.com/articles/lif...r/ava/Ava2.wmv
If you are getting out too far, work your way back the same
way, angles to the wind.
Unless you hit a boomer, you are not going to immediately know you are in
lift, so you have to watch the plane. Sometimes it becomes apparent because
you realize that your not sinking but appear to be holding altitude. The
only way to do that is to be in lift.
Remember also that thermal can vary in size and intensity. Some are fairly
narrow and some are so large that it seems a whole region of the sky is in
lift. I rode one area recently for 45 minutes where it seemed about 1/4 of
the field was in lift. You didn't really have to circle. You could just fly
back and forth and the plane would rise beautifully. Those are really nice,
when you find them.
It is a hunter's game, if you are up for it.
Good luck pilot! May your hunt go well!
Resources
What do Thermals Look Like
http://kohlin.com/air/soar-faq.htm#589882
http://www.rc-soar.com/tech/thermals.htm
http://www.apogeerockets.com/educati...br /> ls.asp
Finding Elusive Thermals
http://f4bscale.worldonline.co.uk/Thermals.htm
Thermaling on a windy day
[url]http://www.moneysmith.net/Soaring/soaring9.html#ref97[/
url]
The Soaring Methods of Birds
http://www.apogeerockets.com/educati...ng_methods.asp
Search Patterns
[url]http://www.quicktechhobby.com/articles/thermal_surfing%
20part%202.htm[/
url]
If you are a new glider pilot, this is a great resource:
http://forums.flyesl.com/topic.asp?TOPIC_ID=224
01-30-2008, 07:53 AM
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RE: Thermal Q's
Ed Very well said All new sailplane people need to read this many times and as you fly you will find all the signs of up air....Oldtimes reading this will point out some of the tricks of finding that air go up that we have just taken for granted.....May the Wind alway be good ...Mr. Kite
01-30-2008, 10:58 AM
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RE: Thermal Q's
Best way to learn about thermals:
Read info such as the links in Ed's reply and in other soaring books and articles. Then, if possible, get yourself a full scale sailplane instructor and take a few flights in a full scale sailplane. This will allow you to feel and see the real true affects of thermals and sink. You'll feel the strong, upward push on your butt from strong rising air, the sinking feeling in the pit of your stomach from a downdraft, and other results of vertical or rising air (i.e. a rising wing, a rising tail, a rising nose.
Look at and hear the sound of the variometer when you are in rising or falling air. If flying out west on Rockey Mountain slopes, experience the
feeling of a 800 to 1000 ft/min rising air thermal. What a blast! Of course you can also sink at that rate. In the eastern US such as Florida, 200ft/min to 500 ft/min is considered good; however, your sink rate is usually much less than those found out west. These are all average figures because, just as in model sailplanes, there are many variables that can affect thermal or sink rates.
Give a full sailplane flight a try; it's great fun and will help you to increase your model sailplane flying skills!
Take a look at the Soaring Society of America's "Soaring Flight Manual." It has much information that can be used by a model pilot.
Sailplane
Ernie Diaz
Read info such as the links in Ed's reply and in other soaring books and articles. Then, if possible, get yourself a full scale sailplane instructor and take a few flights in a full scale sailplane. This will allow you to feel and see the real true affects of thermals and sink. You'll feel the strong, upward push on your butt from strong rising air, the sinking feeling in the pit of your stomach from a downdraft, and other results of vertical or rising air (i.e. a rising wing, a rising tail, a rising nose.
Look at and hear the sound of the variometer when you are in rising or falling air. If flying out west on Rockey Mountain slopes, experience the
feeling of a 800 to 1000 ft/min rising air thermal. What a blast! Of course you can also sink at that rate. In the eastern US such as Florida, 200ft/min to 500 ft/min is considered good; however, your sink rate is usually much less than those found out west. These are all average figures because, just as in model sailplanes, there are many variables that can affect thermal or sink rates.
Give a full sailplane flight a try; it's great fun and will help you to increase your model sailplane flying skills!
Take a look at the Soaring Society of America's "Soaring Flight Manual." It has much information that can be used by a model pilot.
Sailplane
Ernie Diaz
04-28-2008, 02:59 PM
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RE: Thermal Q's
I've revisited all the helpful info given here. After much ummmm, difficulty I've got my sailplane back in the air. She flies just like I remember.
I've made a lot of changes to the weight and CG, but the biggest difference come when I lifted the trailing edge of the wing 1/4".
I actually found a thermal! A poster above stated "it's not as hard as you think". I'm not sure about that
but it's definitely not as hard as I thought to find a thermal. Maybe I got lucky, but there was an area in the sky she just refused to fly. It "bumped" my plane off. I was able to circle around the perimeter of where I was supposed to be. I did extend my flight using it's lift, but I never did get hooked onto the thermal.
Is it easier to find a thermal with no wind? Or does it matter?
Is there still Thermal activity at 6pm when I get to the field and unload my stuff, or is it useless by this point?
Do you suppose a 2-lane road could generate enough rising air to lift a 2m glider? or maybe just to extend the flight time? The reason I ask is, as a kid I caught lift that extended my flight off a road, but Saturday there didn't seem to be any available over the road. I just wondered if it's a waste of altitude to try.
I've made a lot of changes to the weight and CG, but the biggest difference come when I lifted the trailing edge of the wing 1/4".
I actually found a thermal! A poster above stated "it's not as hard as you think". I'm not sure about that
but it's definitely not as hard as I thought to find a thermal. Maybe I got lucky, but there was an area in the sky she just refused to fly. It "bumped" my plane off. I was able to circle around the perimeter of where I was supposed to be. I did extend my flight using it's lift, but I never did get hooked onto the thermal.Is it easier to find a thermal with no wind? Or does it matter?
Is there still Thermal activity at 6pm when I get to the field and unload my stuff, or is it useless by this point?
Do you suppose a 2-lane road could generate enough rising air to lift a 2m glider? or maybe just to extend the flight time? The reason I ask is, as a kid I caught lift that extended my flight off a road, but Saturday there didn't seem to be any available over the road. I just wondered if it's a waste of altitude to try.
04-28-2008, 03:25 PM
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RE: Thermal Q's
That was some very good information. Thank you. I especially enjoyed the video. That's the first time I've ever seen a sailplane in lift.