Sunday, March 27, 2011

Long Hours

This post may not be up to my usual standards, it's very late and I'm tired, but I had a few things I wanted to show off. I spent almost every waking hour today in the wind tunnel, working on something that to my knowledge is unique in the past five years of the UD Aerodesign Team--a second aircraft. After a long week of work, we finally have it flyable, and I have to go to bed soon so I can get up in the morning and go to the field, but I wanted to share some images I took today.

UD Aerodesign Team aircraft, awaiting transport to the field tomorrow
In the image above, the prototype that I showed images of last week is on the right in pieces, ready be packed for transport to the field. The new plane (called V2 because we've been too busy to be creative about names) is assembled on the right. V2 incorporates several lessons learned in the construction of the prototype, and its very existence is owed to some new techniques we've been practicing this year. 

The most critical new technique is the fuselage molding, which we've been doing with assistance in the form of advice and facilities from Industrial Fiberglass Specialties here in Datyon. I talked in my last post here on Engineer in Progress about what a difference this makes in terms of the time and materials, and the plane above is the payoff. Thanks to more experience with the techniques involved in making fuselages from the mold, the new fuselage weighs almost half a pound less than the original, yet still incorporates several structural modifications to reinforce areas that the prototype demonstrated weaknesses in. Making new fuselages is in fact so easy that the fuselage team went ahead and started work on laying up a third fuselage, which will probably be combined with other componetns we have around to produce a third (!) aircraft to our design, with further refinements from the flights and construction of V2.

The really tricky part of V2 was the wings and tail. Normally, we hot-wire cut the wing and tailplane foam cores on a CNC foam-cutter, enabling great accuracy and precise adherence to our designs. However, the construction of V2 was hampered by the fact that the foam-cuter broke between the cutting of wings for V1 and the cutting of wings for V2, requiring that the surfaces instead be hand cut with a wire bow. Josh Nieman, the club president, spent over six hours working to produce the wings and tails for V2, going through an entire 4 foot by 8 foot sheet of 2-inch insulation board in the process. The resulting wings, while not quite up to our normal standards, are still very good, and the implementation of some suggestions from Greg at Industrial Fiberglass enabled us to trim 17% off the weight of the wings by reducing excess epoxy used in our layup--this is demonstrated vividly in the different color of V2's wings compared to V1 as seen below:

Prototype is at the top of the image, V2 at the bottom
V2's wings and tail were laid up using epoxy with the same dye concentration as the prototype. The pinkish tint of V2's wings and the increased visibility of its carbon-fiber reinforcement is due entirely to the reduction in the total amount of epoxy on the wing. The imperfections of the wing are not visible from this angle and distance--the trailing edges are a bit wonky due to cutting difficulties. However, the wings for V3 (which should end up being the competition plane) will be CNC-cut as like the prototype wings were, and thus should have all the improvements of V2's techniques implemented with precision cores like the protoype used.

The testing of new techniques to see what works like with the fuselage and the wings is something we didn't have a chance to do last year, since we only had one plane and one set of wings, and making full use of this ability throughout the plane should make our team more competitive at Tuscon--I know I feel that V2 is a better plane on the whole than the prototype so far. Tomorrow, we find out for sure when V2 (hopefully) makes its first flight attempts, which means for now it's time to get some shut-eye.

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