Born to Fly — 2011/11
DLG: It's not your grandpa's Sailplane!
Jim T. Graham | [email protected]
I have become a huge fan of sailplanes, but not just any sailplane. I am all about the discus launch glider (DLG).
I saw my first DLG flight at the Clover Creek competition in between rounds and then started noticing them hiding in trailers of my favorite 3-D pilots. A DLG is a sailplane that you throw discus-style.
Being a newbie at this form of RC has been tons of fun and loaded with questions. I thought it might be informative for me, as well as you, if I asked a DLG expert some of my newbie questions.
I had a long talk with DLG veteran Bruce Davidson. Bruce is well-known in the DLG circles and also hosts his own DLG contest called—wait for it—The Bruce. If you are into sailplanes and DLG or if you have been thinking about it, you might find some answers to your questions in this interview.
JG: When did you start flying and what kind of airplane did you start out flying?
BD: I started flying in the 1970s. I started out in sailplanes. In the park near where I grew up they flew sailplanes. At that time they were just balsa and MonoKote. You have to guess what my first sailplane was.
JG: A Gentle Lady?
BD: Exactly. That was a test to see if you were a sailplaner or not! I built it on an old door in my mom and dad's house. When I got it done I went to the Louisville Area Soaring Society. They still fly in that same park. The person who taught me to fly was Ed Wilson and I still see him out there.
I took a little bit of time off when I was in the military. I flew some during that time and that was the only time I flew power because that was the only option. I picked sailplanes right back up when I got out.
JG: I got into DLG by watching a pilot at the Clover Creek competition fly one. Do you think DLG is gaining in popularity, and if so why?
BD: It's absolutely gaining in popularity and that is evident by looking at the attendance in the clubs. I originally flew hand-launched gliders. Back then you were lucky to find a contest here and there. There was a great big one in California that is still in existence: the International Hand Launch Glider Festival.
Switching over from the hand launch to the discus launch was what allowed it to pick up steam. The javelin launch was a very physical way to throw an airplane. That had huge rewards for guys who were young and athletic and put in the time. At that time I was that guy; I'm not that guy now.
The advent of the discus launch made it more accessible to more pilots. That has helped its gain in popularity as well as the availability of models.
JG: For our readers who don't know, a discus-launched glider is a 9- to 11-ounce sailplane with an average wingspan limited to 1.5 meters. The airplane is held by tabs on the wingtip and rotated around the pilot by hand before release. So it's like throwing a discus. What are your DLG launch tips?
BD: I usually try to take two steps when I throw. It helps me orientate into the wind so I know what direction I'm going. It also gives me time to wind up. You have to think about it like releasing a spring. What you want to do is reach back and twist to coil that spring up. I do that in the run-up.
JG: I try to keep the airplane as far behind me as I can so I can get as much "fling" on it as possible. Is that right?
BD: You want to keep it on toe. The longer you're in contact with the airplane, the longer the arc is, and that means more time to accelerate. That is where I build my speed. The two things I think about are to reach back as far as I can and to accelerate the entire time.
You can't just muscle it at the last minute. It will make it yaw and put some tough stresses on the airplane. You want it to accelerate in a very fluid manner through the entire process. Another key thing is to follow through.
JG: I think of it like hitting a golf ball.
BD: Golf is a really good example. Your power comes from the core; you line up, accelerate, and follow through. There is a lot of footwork that goes on that you should never think about.
JG: Right before you release, it looks like you're keeping that back leg planted as you spin around to release the airplane, allowing your body to rotate.
BD: That would be the footwork part of it that I recommend you never think about (laughter). That's good advice. I would urge you not to think about your feet.
JG: Does anyone spin around twice? I try this occasionally.
BD: There are a bunch of people that have tried that route before but there doesn't seem to be an advantage to it.
JG: If there is no one at my field I will tend to wander around as I throw and fly my airplane. Is that typical?
BD: Most guys walk. Some guys don't move a bit. We all have a tendency to move toward our airplane. The thing about flying sailplanes is you go where the lift is. In a contest there are times when I will run to the other side of the field instead of flying.
If I landed at one end of the field but on the other side of the field where there was lift, then it might be more efficient for me to run across that field and launch into that thermal. Sometimes it is better to run, sometimes it is better to launch from where you are.
Wandering is perfectly acceptable. That is why we usually have a caller. He will tell you where the thermals are; he will tell you if you are walking into traffic, etc.
JG: I have caught a few thermals since I have started. I try not to scrub off speed by making too many turns but I'm not sure what to do when I feel as though I'm in lift. I'm afraid if I make abrupt turns to get in the thermal I will kill all of my momentum. What do you do when you see the nose of the airplane go up?
BD: That's a great question because you really hit on what sailplanes are about. It's about being efficient. Every time we move a control surface, we cause drag and that makes your airplane fall out of the sky faster.
Typically in that scenario if your nose goes up you probably hit the thermal nose-on. That is the easiest way to tell where the lift is. When your sailplane goes off level it tells you something about what you flew through and tells you what you need to do. So if your nose goes up then your airplane is trying to go up; but it's a sailplane and that's not going to happen.
The next thing that will happen is you're going to stall. You have to apply some down-elevator so you can keep flying nice and level. I would fly through that thing. When you get through it you will see your tail go up. Your airplane gets a little more lively and it bobbles around and speeds up a little bit.
If you pay attention to the speed of your airplane, you can tell when you get to the other side of it. Then I would come back to it and initiate a turn.
JG: What kind of turn would you make to get back into it?
BD: That depends. If it's really windy then I would do a hard turn. If it's a nice, calm day then I would do an easy turn.
At this point I would know exactly where the thermal is. I wouldn't have to be in a hurry to get to it. Now that I have already flown through it, I have an image in my mind where it is. You want to watch that fuselage and keep it nice and level. If you are in lift then you can leave it pointing up a little bit. At this point it's like having a motor on the front.
JG: The thermal is always moving, so am I using wind direction to tell me where it's going or where it's going to be?
BD: As you do the turn, think about it in quarters. I try to slice my turn into four pieces of a pizza. I would ask myself is this piece better or is another better. Every quarter where it's better you open up your turn. This will allow you to follow that thermal.
Also, ask that better-or-worse question and open to the better quarter. That makes it easier to read it and see it. It's important to watch for that feedback. Did it go faster? Did it go down? Did I stall? If it gets faster on one side then open your turn up to that side. There is a lot of subtle information that the airplane is giving you. All this will help you follow the lift.
JG: The other day I was only 10 feet off the ground and the sailplane just started going up. It went up and up to the point it was a little scary!
BD: When you are coming in on an approach and then, bang, you feel some lift ... those are the best. There is nothing better than catching them low.
JG: I'm still looking for another one. I guess that's part of the draw. How low is low for you?
BD: Oh, 10 feet off the ground maybe. You know a lot of times when it's that low you can feel the thermal. So that's another challenge and a big step in flying contests. You need to know where the lift is and launch straight to it.
Guys at your stage will be like, "Yeah, I got a thermal and I'm taking this baby out of here!" Then you get real far out, but once you know how to fly a thermal and know how to identify it, the fun part is how many times you can get to the same thermal. You try to get to the best part, the part we call the sweet spot.
There is a spot where all four sides are going up just as well. You find that speed mode, which is raising the trailing edge on your ailerons. Now it's going to fly fast. You could come ripping home at 60 mph, grab a catch, and throw to the same lift. This is what I practice a lot. Sometimes it will get farther away than you can get home if you don't find it. That's a really fun thermal. We call it a "Hero or a Zero."
JG: I saw where you said it is better to throw at the horizon instead of throwing up to the sky. Tell me about that.
BD: Yes it is, if our airplane is properly trimmed in speed mode. Usually a DLG will have two or three settings that affect the trailing edge of your wing. In speed mode, your ailerons rise up and fly faster. In thermal mode, your trailing edge is lowered and you fly the slowest. In that speed mode, coming off a throw it should fly nice and straight and level. So we do a launch preset.
Normally a launch preset is just a little bit of up-elevator. It's just enough to give us a quick rotation to roughly 45° and then we can release that preset. A lot of guys put it on a momentary switch. I have it on the switch closest to my index finger. That allows me to flip it on and flip it off.
You're going to get more power if you can do a flat rotation and throw straight at the horizon. So you flip the preset switch, do your spin release, and as soon as it gets to the right angle, you flip that switch off and finish the climb and then push off over the top. So it's important to have a well-tuned launch preset.
JG: Can you DLG when it's 90° at night and 104° in the daytime? Are there still thermals out there?
BD: The thermals are really weak. When you walk outside and see big clouds that are like cotton candy, then you know that thermals made those clouds and it's going to be a good day. The best thermal days are when we have a big temperature difference from day to night. So you want it to be cool at night and warm during the days. Thermals are there during the summer, but it's much more challenging because they are lighter and dissolve quicker.
JG: Do you try to visualize the thermal in your mind or are you working off feel?
BD: There are a whole lot of things going on. A good learning tool is visualizing how the air works. Air behaves like water. If there is a tree line, you can visualize how the air hits that and gets pushed up into the air and tumbles over the top.
JG: Like a wave?
BD: Just like a wave. If a thermal comes down this swirling air, it hits those trees and gets thrown up into the sky. So that is a really good visualization practice. When I encounter a thermal, I always visualize it as a tornado. That's your most typical shape, but thermals can also be blobby donuts as well.
That's why catching them low is so tough. They are smaller at the bottom. So when you are really high it seems like you can just eat up the sky and fly anywhere you want and not come down. Up that high you have these great big thermals. Visualization really does help.
JG: What kind of sailplanes do you fly?
BD: I fly the Sirius and Polaris by Momentum Models in Sweden. There are a bunch of great models out there. I like the Sirius. It's all carbon fiber and really strong. It works for me. I need a model that doesn't break when I throw it.
Once you get to the competition-level sailplanes, there is not a big difference in performance. Sometimes a model might give up lightness to fly better in strong winds. Some might give up strong-wind performance to do better in light air. There are different design directions because you can't really predict what conditions will be.
Most DLG sailplanes are designed to do well in all conditions. When the wind is high, you can add more lead for ballast. Most models weigh approximately 11 ounces, so if I add 2½ ounces, that is a big percentage increase in weight. It allows me to throw harder and fly faster. The Sirius is a good all-around airplane. They are all so close I can't strongly recommend one over another.
Get something that is available. By the time you get a contest DLG sailplane flying, you're going to have a $1,000 in it no matter which one you buy. Your best bet for an entry-level airplane is to find a used one. Most of these guys who fly contests get a ding in them here and there; they aren't as clean as they once were and they don't want to fly a contest with a beater. So you can pick it up and get flying right now. The Blaster is up there with the $900 models. It's affordable and available.
Really, it's about how much you practice. So just get something you can get up there with. DLG has a pretty steep learning curve. So if it's already beat up you won't be emotionally attached to it.
JG: Is there anything you would like to say to future DLG pilots?
BD: The best thing you can do is to fly with someone else who is experienced. You're going to learn so much faster and get to that enjoyment level so much faster if you can get good instruction from someone who's already out there doing it.
Don't be a fair-weather flier. In the springtime you will go out there and the weather is great with big puffy clouds and it is "all-you-can-eat" thermals, but there is so much satisfaction in a blustery day when it's overcast and gray, blowing 10 mph. You can get out there and realize the air is just as active on a crappy day when you would normally sit on a couch. It's awesome to go out on a bad day and throw the airplane and get 3- and 4-minute flights all day long. It's like a great day of fishing, you just keep catching them!
Living here on the thermal farm is a beautiful thing. When I decide that it's time to fly, I pick my model up, pick my transmitter up, and walk out. There is no other support equipment needed. What's really neat is DLG pilots are passionate about what they do. They love the challenge, they love the thermals, and they like to think about when they first started and all the things that they learned.
I think that you will find the DLG community is fantastic. Everybody on the field is really there to help. Everyone wants you to succeed and find the joy that they find in soaring.
MA
Sources
- The Bruce F3K — www.thebrucef3k.com
- Momentum Model Technologies — www.momentum-mt.se
Transcribed from original scans by AI. Minor OCR errors may remain.
