Having a perfectly tuned DLG is paramount to utilizing all aspects of its advanced construction. Doing basic flight tuning is necessary after you get your glider built. It should also be performed over time as your technique improves and if any changes or repairs have been made. Recently, I was greeted with an abnormal break in the weather which is typical in northern Florida in the early part of the year. I took this opportunity to get out and make sure that all my gliders were flying in tip-top shape.
I headed out to this area in my neighborhood that is essentially a giant retention “pond”. I use pond loosely because the area is so big it never fills with water. The developers used the fill from this area to build up the surrounding neighborhood and left me with a great place to fly my smaller park flyers. The location has a great advantage, below the treeline the wind is greatly reduced.
Basic DLG Flight Tuning
I started with my HobbyKing 1m DLG. After doing some glass work to the fuse the weight was at 160 grams. I set-up this glider has a FrSky receiver with a vario/altimeter. I wanted to see how high I was throwing and then time how long the flight lasted. What I’m doing here is basically trying to figure out the minimum sink. On a glider with just rudder and elevator, like my 1m DLG, I’m essentially trying to find the optimum placement of CG and get the trim of the elevator right.
Having a no wind situation is the best time to do this. Here we establish a baseline and can adjust it to other conditions. The added bonus on this day was that with the overcast sky there was no thermal activity to alter flight times. The end goal was to find an optimal position for the CG that allowed the plane to be controllable and set the elevator trim such that the plane slows down as much as possible, again while keeping the plane flyable.
Adjusting the glider’s CG is pretty easy to do in a small DLG. All I was doing was moving the vario unit forwards and backwards. Even adding an extra wrapping of electrical tape around the nose or tail-boom can adjust the CG a millimeter or two in either direction.
After after about 30 minutes of throwing I was averaging 45 second flights. Remember, this is completely dead air. I’d throw, level out, go to one tree line, turn back towards the other and repeat. My best flight was 51 seconds. The best height I could achieve 26.5 meters.
Tuning the E-flite UMX WhipIt DLG
Since the HobbyKing 1m composite DLG is just rudder and elevator I moved on to my E-flite UMX WhipIt next. This is my second WhipIt. With this WhipIt I took the time to do some modifications right off-the-bat to make it lighter and a bit stronger. This involved removing the decals from the wings and adding packing tape to the wing along the leading edge and around the root where the plastic is located. After these modifications the weight came out to 47g.
Now, the WhipIt is much lighter than the 1m DLG. This light weight means that there was no way I would be able to launch the glider as high. I don’t have a vario in this setup so I couldn’t say how high I was throwing it. The times reflected this. The average flight time was around 33 seconds. I ended moving the battery around some. The best flight I had was one that went to 40 seconds.
Quick Side Story
The last DLG I pulled out was my Storm prototype. I ABSOLUTELY LOVE THIS PLANE! Unfortunately I recently had a spat of bad events with it. First one of the aileron servos showed that it was going out. I’ve never actually built a high-end DLG and was super scared about the repair. I’m still not very sure that I’ve put the new one in as best as I could have done.
That dwarfs what happened next. I was out trying to do some practice in some windy conditions. I hooked up on some lift coming off the hill that is our club’s flying site. With the wind I was quickly out over a pasture which borders our field. The fields are separated by a barb-wire fence. Well, I realized that I was probably at the limit of what I should be attempting with the plane. The plane had what I thought was enough altitude so I moved into speed/reflex mode to get the best penetration back upwind. From my vantage point, about 100m up wind from the fence it looked like I was just going to be clear. I knew I wasn’t going to land in my imaginary landing area. I ended up coming up short by a handful of centimeters.
The damage wasn’t horrible. On one side of the wing there was a break in the carbon and some delamination. The foam was compressed just bit. On the other side the barb-wire put a few small cuts through the fiberglass and into the foam.
Luckily I have an awesome friend. A great DLG pilot and all around nice guy, Dave Forbes, was able to help me fix my idiocy. He’s built a number bagged wing gliders including some nice 1 meter DLGs. He had everything needed to fix the wing. Needless to say, I was kind of nervous that the plane would not perform as well it had previously. The first time out I was able to fly the heck out of it. I did realize right away that I need to put in some tuning in dead air conditions to fix up the CG and trim.
Tuning Up My Storm
Back to tuning my DLGs! After the WhipIt I grabbed the Storm. For the first flights I tried to match the heights I was throwing with my 1m. I was really interested in how much the larger span would affect the flight time. Doing this I was able to get consistent times between 1:15 and 1:20. After about 15 throws to get this average time I decided to go ahead with the tuning. I ended up putting in a lot of elevator trim in all of my flight modes. For a while I was able get flights just under 2 minutes. I may have to wait for another day like this and re-adjust the pull-strings. Tinkering a little more, especially with launch and zoom modes, I was able to get the glider to hit 2 minutes on 8 out of 10 flights.
Since the 1.5m Storm stayed up for much longer than the others I was doing a different circuit. On the last few flights I was heading over the tennis courts. On my last flight I noticed a bit of a bump. I took a turn and wondered if it was just a no sink situation or a slight bubble of thermal lift. That second turn kept the Storm at its same altitude. I was starting to get nervous. The light poles were still there and I wasn’t going up. After a third turn I decided to call it and head back. When I finally landed I had to look at the timer. The flight was 3:15! Awesome for almost no lift.
Summing It Up
This whole post was written to share with you how I used another droll day to tune up my DLGs. Next time you look outside and see it all overcast without the hint of lift take the time to see if you can get in some throws to test your setup. I think that once you do you’ll find that when in other flight conditions that your workload will be a bit lighter!