author
1Instructables6,656Views4Comments

Tell us about yourself!

Complete Your Profile

Achievements

Make It Fly Challenge
Contest Winner Second Prize in the Make It Fly Challenge
Show 1 More »
  • DIY Heavy Lift Fixed Wing RC Aircraft

    You seem to know a lot, why not share the knowledge and make an instructable yourself? Would be nice to see all your suggestions put into practice :) Do share the link when you do so!

    View Instructable »
  • DIY Heavy Lift Fixed Wing RC Aircraft

    1) The idea of this project was to minimize interface drag hence the v-tail. I understand having the servos/receiver exposed would compensate for whatever drag we could have saved with the v-tail. But for the same reasoning I went with a monoplane - lower interface drag. A biplane requires the wings to be vertically separated by approximately the length of the chord hence would also require a strong and well engineered pylon to support the top wing or wires to maintain structural strength. 2) A concave wing does not offer greater surface area since what the oncoming air sees is the wetted surface area of the wing which is project surface area. Apart from that, it also very difficult to hot wire cut a concave airfoil and ensure it is strong enough/able to accommodate structures that can ...

    see more »

    1) The idea of this project was to minimize interface drag hence the v-tail. I understand having the servos/receiver exposed would compensate for whatever drag we could have saved with the v-tail. But for the same reasoning I went with a monoplane - lower interface drag. A biplane requires the wings to be vertically separated by approximately the length of the chord hence would also require a strong and well engineered pylon to support the top wing or wires to maintain structural strength. 2) A concave wing does not offer greater surface area since what the oncoming air sees is the wetted surface area of the wing which is project surface area. Apart from that, it also very difficult to hot wire cut a concave airfoil and ensure it is strong enough/able to accommodate structures that can reinforce it.3) As a part of the mission statement of this project, also to ensure a level playing field for all the students, we were given a fixed set of electronics. With those constraints in mind, we had to design an aircraft capable lifting the highest payload. 4) A polyhedral design requires much more complexity in terms of construction due to the fact that a single spar cannot be used and has to be cut and angled and reinforced so that the wing does not collapse. This did not seem a viable option considering we were trying to save weight and add simplicity to the design of the wing core. I also did the stability and control analysis on MATLAB and determined I needed ailerons that extended the entire span of the wing in order for me to make turns inside the Carrier Dome with a safety margin. Polyhedral wings usually do not feature ailerons and only use rudder to make turns and due to the adverse yaw effects of an V tail would not help roll the aircraft, in fact have the opposite effect! I did consider the fact that an inverted V tail would take care of this adverse yaw effects, however I did not want the tail to strike the ground and rip off during take off and landing.5) Inspiration for Junker ailerons and fixed LE slats were taken from the Zenair 801. This aircraft is one of the best STOL aircrafts in the market and I have flown in one and was sure of its abilities and decided to go replicate its design. Its efficiency did show up in the experimental results as it was able to carry a heavier payload as opposed to just the wing without the LE slats and Junker Ailerons, while it did take a few tries to get the separation distance and slat design right. 6) As for the reynolds number, the Zenair 801 and the model seem to fly at similar reynolds numbers where it did seem giving the LE slats and Junker Ailerons a try a reasonable idea. Besides having detached ailerons would increase drag, it would also increase lift as these can be treated as separate airfoils. Detached ailerons also face undisturbed oncoming wind and are not engulfed by the thick boundary layer wherein, they are ineffective. Do refer to the pictures below. 7) I agree structurally a fully ribbed slat seems like an overkill, however due to the nature of balsa and its elasticity, it would try to return to its original unbent shape if not anchored/glued at sufficient points. Each balsa slat only weighed 0.3g so it did not seems that bad an idea to have 12 at the cost of it not distorting and warping. As mentioned above, a concave airfoil is not easy to cut with a hot wire hence foam was not an option (I did try it!).8) The day I was cutting the wings, the laser cutter at my university was closed and was booked for the next couple of days. In the spirit of DIY and making, with some trial and error I found cardboard worked just as well :)9) XPS foam is denser than regular thermocol and hence requires you to pull the hot wire and wait till the center catches up. I tried to run the wire hotter and held with more tension, however the wire would just snap. As for your comment regarding the negative template, I think having a positive template works just as well and little reading on RC forums will lead you to the same answer, its a matter of preference and what works best for you. 10) As for the numbering technique. Great idea, however that is standard practise while hot wire cutting if being done manually and somewhat common sense hence did not find it necessary to mention. As for rigidity, balsa strips on the LE and TE seem like an overkill since the wing was rigid enough to begin with (also the reason why I chose XPS over regular foam) I hope this reasoning is sufficient to clear your questions/doubts about the design and design process. If you have more questions/suggestions, I can share my senior design thesis with you and that should clear up more misconceptions. Thank you for the compliments and have a good day!

    View Instructable »
  • sahevaantaneja's instructable DIY Heavy Lift Fixed Wing RC Aircraft's weekly stats: 10 days ago
    • DIY Heavy Lift Fixed Wing RC Aircraft
      453 views
      10 favorites
      4 comments
  • sahevaantaneja's entry DIY Heavy Lift Fixed Wing RC Aircraft is a finalist in the Make It Fly Challenge contest 13 days ago