<< WEEK 1

2004-06-28, Monday
Luis Torres
Julia Lee

We spent Monday morning at Lake Lagunita flying (and crashing) an R/C plane with Axel. Many of us got a chance to be at the controls, but the fun ended with a servo problem. We returned to the Green Earth Science building where we split up into groups of two to briefly research the effects of particular glider parts. Then we gathered together to share our findings, ending with a question and answer session with Axel.

2004-06-29, Tuesday
Nicki Lui
Jessa Lee

Today we gathered in the meeting room and were told that we were needed to finish and test our models today. So each group took up materials and began building from their drafts of their models. The first flight tests were quite exciting, everybody wondering if their designs had sufficiently compromised appearance with aerodynamics to enable the models to fly. Each group encountered different problems and spent some time adjusting and fixing up their aircraft. Then we went out to lunch in Tresidder as a quick break from our building. When we came back from lunch, we began working on our models again. Some groups finished up and made final adjustments to their models, while other groups worked on building a second design. Then, when time was up, each group brought their gliders to the meeting room to present the design for critique by the whole team. We learned a lot from the presentations. The team heard all the experience and problems that each group faced while trying to make their model fly, gaining experience. The team learned different ways of working with new materials as well. The following summarizes the designs and ideas gathered during the meeting.

BEST IDEAS:

Slight dihedral

Not too light (best 8-10 g for small models)

Adjustable control surfaces (wires)

Aluminum foil flaps

Membrane, no tension in back of membrane

Pterosaur form (dimensions more important than exact look)

Control symmetry (canât be perfect, so make it correctable)

Increase wingspan (2-3 ft)

GOALS TO EXPLORE:

1. sweep, dihedral, anhedral, control shape of tail/wings (just balsa)
2. membrane: tension, strings
3. mixture/combo

DEADLINE: need shopping list and detailed designs by tomorrow.

06-30, Wednesday
Erica McCay
Clark Willison

Arriving at 10 am as usual,the team was excited for another day. Well into the second week, many different small gliders had been built, as well as many lessons learned. Now it was time for a larger challenge - 3 foot wing span. In two groups of four and one group of five, the students set off to design their pterosaur-like gliders. Each group had a different task: group one worked on membrane design, group two worked on wing sweep and dihedral, and group three worked on control surfaces. The morning was spent making detailed drawings and choosing materials for the gliders. The shopping lists were sent with Axel while the rest of the team stopped for a lunch break. Work resumed even before Axel's return as students calculated the weight, CG, CL etc for their gliders. Once Axel arrived, the team was ready to embark on the next step—building. Each group’s design was unique from the others. Group one used mono coat for the wings, group two created three gliders with different sweeps and variable dihedrals, and group three used metal pins to test the different positions of wing and tail joints. As usual, four o'clock approached and students stayed late, trying to finish up one more thing before letting the gliders sit for the night.

2004-07-01, Thursday
PJ Thompson
Cameron Tacklind

Glider Completion:

The previous day, Team Pterosaur had decided that they needed to further investigate specific characteristics of pterosaur flight. From the smaller models constructed before, students decided that the three primary issues still plaguing their transition from a glider to a pterosaur were membrane design, control surface interaction, and wing position during flight. With these three categories in mind, students divided into three teams. Each team was responsible for building a pterosaur/glider model with an approximate wingspan of 3ft.

Today the membrane team worked trying to emulate the actinofibrils that existed in the pterosaur’s wing. This team tried to emulate how the pterosaur would use these fine hair like structures embedded in their membrane to dynamically control tension in the wing membrane. The group used monokote (as used on many RC models) as the membrane material and simulated the actinofibrils using fishing wire. The leading edge bone representation was made from pieces of reinforced balsa wood that could flex in the lateral axis. In addition, the group used a thin metal wire, placed along the leading edge of the wing, to tension the actinofibrils in turn tensioning the membrane. This group worked today on placing the actionfibrils between two layers of monokote and then meticulously ironing the monokote to itself to form a pterosaur-like wing membrane. The finished product had many wrinkles and the group discovered that monokote was not elastic enough to be a realistic representation of a pterosaur membrane. However once assembled with a standard body and tail, this group’s pterosaur served as a good example of how an actinofibril membrane pterosaur wing might have looked like. The glider did not fly well even with weights on the front but as will be explained later, professor Ilan Kroo explained to the team how this pterosaur model was currently configured to fly upside down.

The control surfaces team worked with modulating primarily the wing dihedral and the v-tail control surfaces. Using steel wire this group created adjustability in the various joints they created and therefore made their design flexible to investigation of several different flight configurations. This team built a body that began to look very large during construction and many were worried about its weight distribution. However once all the pieces were manufactured the glider weighed in at just about 40 grams. After assembly, the group placed weights in strategic locations in order to balance out the position of the CG relative to the CL. The glider from this group had the largest wingspan of any glider made so far and was seemingly the most ambitious yet to be developed. This group’s glider was very successful in many of its tests and with the help of Ilan Kroo, they were able to optimize the shape of their pterosaur glider to the best possible shape given their degrees of movement.

The wing configuration group took a slightly different approach in investigating different wing flights configurations. Instead of using steel wire as the control surfaces group did, the configuration group used thin aluminum sheets to adjust the dihedral angle in the wings. Unlike the two other groups, they created several models of their pterosaur glider to test. This group took on one of the most undefined challenges which is the question of what angle dihedral did the wings have and what sweep did the pterosaur wings have. This team’s glider was marginally successful, more so than the membrane glider but slightly less successfully than the control surfaces group.

Afternoon Lecture:

In the afternoon, students received a very special visit from the Professor of Aero/Astro and Stanford, Dr. Ilan Kroo. Mr. Kroo came to spend several hours with the students talking more in-depth about different characteristics and principles of flight in both regular gliders and the perceived ones in pterosaurs. He began by explaining the fallacy in the assumption that Bernoulli’s principle is the primary reason for airplane flight. He explained that it has to do partially with deflection and other factors of airplane wing shape. Mr. Kroo brought with him a styrofoam glider which he demonstrated. He explained how the sweep and twist/curvature in the wing made it much more of a stable and efficient glider. At the same time he demonstrated how you could take a simple piece of paper and by adding weights and a small control surface, the paper could glide very efficiently. Mr. Kroo talked in great length about how the twist in the pterosaur wing is vital and about the principle behind wash-out/wash-in and how that relates to the twist in a wing.

WEEK 3 >>