About the BR1 Sailplane
After being away from model aircraft for over twenty years, I decided to get back into the hobby in March of
2007. I started with
radio control aircraft in 1977 and got out of it around 1987. During that time I
had built several model aircraft from kits. Now I wanted to do something that I had never done before in my
aero-modeling experience — design and built a radio controlled model aircraft
completely from scratch.
The idea for my first scratch model was to build a two meter sailplane. The main reason for this is to keep
the cost down for this project because I am starting with no building equipment, radio gear, parts, or materials.
As time went on I began draw ideas on paper and thinking what shape this little model aircraft would look like.
I am a strong believer in the basic reason an aircraft flies though the air is simply because of its shape and if I
could get that shape right I would have a model aircraft that really flies.
Putting on paper an actual design became much more difficult than I thought because I would put something on
paper then begin to second-guess myself. I went to the internet for help and that’s where I found the Airfield
Models website. The website gave me ideas and also some confidence that I was on the right track. The
website was also sponsoring a model aircraft building contest too so I decided to enter the contest.
During the shape design phase I wanted to build a sailplane with a very efficient and clean wing so I decided to
do two things. First, make a wing with low
dihedral over much of its span for efficiency, and at the tips
bring up the dihedral more for stability and turning assistance. The wing would also have a slight taper sweep
for additional direction stability. With this setup, I knew that the ship would most likely need ailerons for
roll performance but instead I wanted to keep the
airfoil as clean as possible so I put into the design small
spoilerons to aid in roll control.
Now to design the airfoil shape which was very hard for me to decide. After looking at many airfoil shapes
and studying a little on airfoil design I actually free hand drew my own airfoil profile with what I had learned.
I called the design the R1 which came out to have a 9.4 percent thickness and it also has an undercamber shape to
it for efficiency. The tail feathers I drew up for function and style and made their surface area sizes and
moments from the wing by best guess. The fuselage was again freehand drawn for function and style.
Now to begin the construction process. When the design was finalized I taped together sheets of graph paper
and drew actual size plan templates for the wing, fuselage and tail feathers. From there on out I built and
designed the actual structure as I went with the things I knew and learned of model aircraft construction. I
wanted to keep the model as light as possible and had a target airframe weight of 16 ounces.
CA was the primary
glue. Epoxy glue was used in areas of high stress. The little ship took shape
after much cutting, sanding and fabricating over the course of a month. Much to my delight I thought that this
thing may really fly. The ship is covered with
MonoKote using sky blue for the fuselage and a transparent
yellow and orange scheme on the wings for high visibility. The tail feathers are covered in transparent
yellow. The completed airframe came in (without radio gear) at 16.3 ounces!
The radio I selected was the Futaba 9C Super which provides massive capability for programming flight control
coordination. Four micro servos are installed for control of the elevator, rudder, left spoileron and right
spoileron. The weight ready-to-fly came to 23 ounces with the radio gear installed! Airborne telemetry
equipment from Eagle Tree Systems was also installed. This moved the flying weight to 27 ounces. The
ship was now ready to fly.
It was a day in early May that I went out to a local school's soccer field to perform a hand toss flight to see
if the sailplane would indeed fly. After assembling the ship and placing ballast for a best estimate of the
proper center of gravity it was time to fly. With a big lump in my throat, I lifted the craft up over my head
and did a last chance flight control check. I then tossed the sailplane straight ahead and a little high of
me. What happened next was amazing and I’ll never forget it. The sailplane flew and flew and flew for
about 180 feet before landing in the grass!
The pitch control of the craft was absolutely superb and the roll seemed OK. The rudder seemed to work fine
in the yaw axis. After a few more hand tossed flights, I noticed that the roll control response was much less
than to be desired. To fix this problem (which I had somewhat expected) I increased the spoileron throw and
mixed more rudder throw in with roll inputs. This along with a change in the center of gravity fixed most of
the problem. Roll response is much better now.
In the end I really enjoyed the entire design and construction process even though at times I was a little
frustrated. But that goes with the endeavor. It is such a gratifying feeling to know that the sailplane
I am flying at my AMA club’s field, I designed, fabricated and built myself. Lastly the sailplane needed a
name so I decided to use the initials in my name plus the number 1 for my first scratch built model aircraft, thus
the sailplane is called the BR1.