The Gull
Part II: Wrapping up construction and first flights.
In Part I of this two part series, I chronicled the inspiration, design and construction of my four meter gull wing glider which I affectionately refer to as simply The Gull. In this installment I will cover the rest of the build and the exciting journey of the first flights.
As most of the framing work was complete, I started covering the model in early May. I chose to cover the model with Oratex. I selected the natural white color for its silky translucent qualities. After covering the rudder I realized that the slight charring from the laser cutter showed through the fabric, so I removed the covering, carefully sanded all the ribs, and re-covered it.
Next, I covered the horizontal stabilizer and elevators. They looked nice, but I worried that the elevators were not stiff enough and could potentially flutter. Having lost a nice model to flutter before, I chose not to take any chances so I found myself removing covering once again. With the Oratex removed, I added 1/32 inch thick balsa sheeting to the top of the elevators. I installed the sheeting at an angle to increase torsional stiffness.
I couldn’t move forward on covering the fuselage without first making a canopy. Since my attempts at making a clear plastic canopy were a dismal failure, I chose to manufacture the canopy out of fiberglass instead. I protected the fuselage with plastic cling film and laid up five layers of fiberglass that had been precut to approximate the canopy’s outline.
Once the canopy had cured I removed it and did a final sanding of the fuselage. I glassed the forward half of the fuselage with two layers of two ounce fiberglass.
Next I coated the fuselage with Duratec to fill in any imperfections. Then the fuselage underwent several rounds of sanding, filling, and priming until I deemed the surface quality acceptable.
To open the cockpit area, I created a vinyl template and cut around it with a rotary tool. The abrasive cutting wheels from Perma-Grit are wonderful for tasks like this. I then trimmed the fiberglass canopy to fit.
On May 20 the fuselage was ready for installation of the tail surfaces. The vertical stabilizer was notched to accept the horizontal stabilizer and both were glued to the fuselage with epoxy thickened with flocked cotton. The wings were installed for this process and everything was laboriously measured to ensure perfect alignment. This process was anything but simple! Actually it was fairly humorous. The large, wacky shaped gull wings made it challenging to align other components. I used everything from precision ground 1–2–3 blocks to paper towel rolls to jig the wings and fuselage in position while installing the tail feathers. The plane is a bit too big for my shop, so I had to get creative while positioning it. After a lot of carefully stepping over the wings and tip-toeing around trying not to knock anything over, I finally decided everything was perfect and left the glue to cure.
With the tail surfaces installed, it was time to get to work on the control hardware. The elevator push rods and rudder pull-pull cables were installed through the laser-cut holes in the fuselage formers. The elevator and rudder servos were also installed at this time. The aft portion of the fuselage was finally ready to be covered with Oratex.
The ailerons were cut free from the wings. Balsa sheeting was installed on their top surfaces to stiffen them.
I also installed additional sheeting at the root section of the wing. Small triangular gussets were installed where each rib meets the trailing edge. The spoilers were made out of 1/8 inch thick balsa sheet. The wing tips are made out of 1/32 inch thick birch plywood template with 3/16 in thick soft balsa glued on top and bottom then sanded to shape. The aileron and spoiler servos were installed at this time. The wings were then covered. The ailerons were attached with CA hinges. The spoilers are hinged with Oratex. The right wing weighed 12.8 ounces before covering and 20.6 ounces after.
Now that everything was covered, it was time to begin painting. The entire fuselage was painted white with the exception of my AMA number which I had masked off so that the light would shine through it.
The paint went on beautifully but unfortunately began to wrinkle and crack as it dried. I suspect because I had taken it outside to paint and it was an exceptionally hot and humid Georgia day. Cracked paint continued to plague the project. Some parts of the fuselage had to be sanded down and repainted up to four times. Eventually I gave up and painted the fuselage inside my shop with the AC on and had no more problems. I love the translucent look of the covering so I masked off all the open sections of the wings and only painted the sheeted areas. The rudder was decorated with yellow scallops, which I plan on adding to the wings after flight testing is completed.
The plane sat around for a few weeks after painting. Things picked up at work and I had no way to tow the plane so I was in no rush to finish it. In September I had the opportunity to visit the Kill Devil Hills in North Carolina. I loved the idea of slope soaring near where the Wright Brothers took their first flight. With renewed enthusiasm I got back to work on The Gull. Final details like wing struts, tow release, and canopy screws were taken care of. The model was tail heavy, so about 12 ounces of nose weight was added. The finished all up weight was seven pounds and six ounces. For a big plane it sure is light!
Just when I thought I was ready, my radio died. I tried everything I could to troubleshoot the problem but it was to no avail. I decided it was time to upgrade anyway. I ordered a Graupner mz-16 and a couple of suitable receivers. Control Hobbies was kind enough to expedite my order to ensure I had it in time for my trip. The radio arrived just in time for me to pack up and hit the road. I read the manual while my dad drove. After ten long hours of driving we arrived in Kill Devil Hills to be met by cold and rainy weather. Thankfully we would be in town for a couple days and the weather was supposed to clear up. I installed the receiver and programmed the model in my hotel room. After a thorough airframe inspection and preflight check The Gull was finally ready to take to the skies.
The next day brought more rain, so we visited the Wright Brothers National Memorial. This was a fantastic experience that I highly recommend to any aviation enthusiast. The rain subsided later in the day, but was replaced by ferocious wind. Perhaps this would be exciting for a more seasoned slope flier, but I’m a slope soaring novice at best so the idea of doing a maiden flight in such strong conditions did not appeal to me. We visited Jockey’s Ridge to scope out the flying site. I always get a bit nervous before a first flight, but now I was starting to get really concerned. I was far from home, with an unfamiliar radio, at an unfamiliar flying site, with an untested aircraft. My dad and I agreed this was not the day to attempt a flight.
The next day the wind raged on even stronger and we were occupied at a family event. That day gave me an opportunity to assess the pros and cons of the situation. I knew I would be taking a big risk if I attempted to fly the plane. I have very little slope soaring experience and the 20 knot conditions were not dying down. On the other hand, test flying near where the Wright Brothers did their test flights really appealed to me. Also, this would likely be my only opportunity to fly The Gull for many weeks, since there are no slopes back home and I don’t know any tow pilots.
I decided to go for it. I wanted to take advantage of this once in a lifetime opportunity.
September 24 was the big day. We waited as long as possible, but the wind maintained 20 knots with powerful gusts. At least my GoPro would be onboard to provide a bit of ballast. I assembled the plane in the parking lot. A handful of onlookers came by to check it out and wish me luck. A security guard noticed the crowd and came by to investigate. He was very friendly and had no problem with my giant model once he determined it didn’t have a prop. He said any kind of unpowered flying is welcome on the dunes, but nothing with a motor. I had another glider with me that I planned to use to practice sloping, but the motor up front didn’t fly with security. I knew my DLG didn’t stand a chance in such strong wind, but I took it anyway as a last resort.
With the plane assembled, my dad and I did a final preflight inspection before beginning our hike out to the dunes. I carried The Gull and my dad followed with my transmitter case and DLG. We chose a hill that looked promising and climbed to the top. I could barely hold on to The Gull as the wind tried to pull it out of my hands. We ended up walking around the dunes for nearly an hour searching for the best spot. Some locals were out flying kites and having a great time, but I couldn’t find a place where the wind seemed to be blowing directly up the hill. Eventually I decided to launch my DLG to see what would happen. The wind easily overpowered it and it ungracefully landed at my feet. We wandered around a bit more searching for a spot with suitable topography and a favorable wind direction. Around 6:00 PM we settled on a low, shallow, hill. It seemed like a good place for some test tosses to see how The Gull would glide.
The first flight was pretty smooth, besides a strong pitch down tendency. This was my fault. I had dialed in a lot of down trim earlier because when I held the plane in the wind it seemed to pitch up. Turns out that wasn’t a CG or trim issue, it just wanted to fly away. I corrected in flight by pulling back on the elevator and letting the plane follow its natural glide path. I didn’t attempt to turn except for a strong rudder kick near the end to straighten up for landing. I was headed towards the one bit of shrubbery in the entire area, so I deployed full spoilers and set the plane down smoothly, albeit a bit fast.
I was shocked by how slippery the plane felt in the air. The unnecessary down trim made it much faster than I expected. We carried it back up the small hill for another test glide, this time with a neutral pitch trim setting. The second flight was very short, but it offered me much more insight into how the plane behaves. My dad threw the plane straight and level. I pulled up slightly then started a left hand turn to feel out the controls. The Gull flew slower this time and felt more floaty. Pitch authority was excellent and the rudder seemed to respond well, but the ailerons felt a bit sluggish. The air was very turbulent and the plane was bobbing around quite a bit. I hoped I could find some lift, but either the hill was too shallow or I don’t know how to read the air when sloping because I quickly started to lose altitude. I attempted to make a right turn back into the wind and once again felt like the aileron response was a bit slow. The rudder yawed the plane very well but now I was slipping and losing altitude fast. The landing had quite a lateral component but the plane was fine and I was happy for it to be back on the ground safely. The entire flight was only about 15 seconds but it felt much longer.
I carried the plane back for a third flight. As we were preparing to launch, a strong gust picked up the left wing and caused the right wingtip to jam into the ground. It made a bad sound. We inspected the airframe thoroughly. The only damage was some broken ribs near the root of the right wing. The spar seemed fine. I foolishly decided to carry on with the third test flight. Right as my dad launched it, the right wing twisted and the plane aggressively banked to the right. I attempted to counter this with left aileron input, but there was no stopping the inevitable. The right wingtip jammed into the sand once again, this time cracking the main spar and crunching some more ribs in the process.
Unfortunately the flights were poorly documented. We hoped to get three camera angles. I had a RunCam on my hat, a GoPro on the plane, and my dad planned to film with his phone after launching the plane. The RunCam died before the first launch, and the flights were all short so my dad didn’t have time to start filming after throwing the plane. At least we have the onboard camera footage. I included a video of the short but exciting second flight below.
We collected our things and hiked back to the parking lot where I could unscrew the struts and remove the wings, one of them which was now floppy. It had been a whirlwind of an evening. Obviously it was a bummer that I damaged the wing, but I knew since I built it I could fix it. I was excited that I finally got to see the plane in the air after waiting so long. The experience was fun and memorable. I got to experience a bit of what the Wright Brothers felt. Success and adversity often go hand in hand. I have repaired the wing and look forward to flying The Gull again in the spring.
©2021 Thomas Martino
Resources
Read the next article in this issue, return to the previous article in this issue or go to the table of contents. A PDF version of this article, or the entire issue, is available upon request.
