Building a UAV for photo mapping - Packing it all in

The first image shows the recommended distribution of components for the electric version of the Cularis. (Click for higher resolution). In this configuration, the plane balances at the CGO with 3 weights (supplied in the kit) fixed under the tail plane. The component weight budget is

  • Motor/Prop Assemply 225gm
  • Multiplex ESC 34gm
  • Fight Battery 149gm
  • 7Ch Rx 30gm
  • Rx Battery 112gm
  • Cularis cable set 50gm
  • 6 servos 70gm

This gives a total of 670gm. The manufactures claim an all up weight of 1680gm with a wing loading of 30.5g/dm2.

In this image, I have added the Pentax A30 camera and a PicoPilot with PicoGPS. The camera is about 8mm wider than the center opening in the fuselage, so I will have cut back the sides for it to fit. I will also machine out a stepped hole in the base for the extended lens to sit in and see through. If I try to locate the camera further back, then I will have to machine out the two servo openings as well.

The addional weight is

  • Pentax A30 with battery and SD Card 150gm
  • Pico Pilot and GPS 63gm

However, I think the real problem is not the weight but the COG. A simplified calculation of the moments of the camera, the autopilot and the new position of the Tx about the COG, suggest that I will have to add about 70gm to the tail in order to bring the plane back into balance. So the total additional weight will be in the order of 283gm. This will increase the all up weight to 1963gm with a 16% increase in wing loading to 35.6g/dm2.

Although it may be standard practice, I am not really happy about have separate Fight and RX batteries. There are two things to charge and check before each flight and it just seems more elegant to have a single power source with a switch mode SportsBEC. With some searching, I found a DuraMax UltraPro 3s 3600mA Li-po with a flat form factor. The dimensions are 145mm x 50mm x 16.2mm. With a small amount of machining, this will fit in the space previously occupied by the Rx battery. The weight at 280gmplus a Sports BEC is only 35gm more than the previous batteryconfiguration. The real gain is in the balance, as the new heavierbattery is behind the COG.

By moving the Rx and autopilot back as shown, the balance weight reduces to 25gm, so in all this solution is a little lighter than the previous one and I get more battery power

Conclusions and Questions

  1. With some careful cutting, I can fit the camera and PicoPilot into the Cularis airframe.
  2. What will happen to the performance of the plane with a 16% increase in wing loading?
  3. Is it a good idea to use a single battery with a SportsBEC? How about noise on the 5V power for the autopilot and GPS?

Building a UAV for phot mapping - Previous Posts

  1. The Goal
  2. Camera Selection
  3. Packing it all in

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  • Great post!

  • Chris

    Sorry, I did not see the search bar as it got a bit lost up in the top right hand corner.
  • 3D Robotics

    The search bar should be at the right of the black strip at the top right of page, opposite of where your name is. Not there on your screen?

  • Paul, We have not mounted a camera on this particular bird yet, but will be doing so over the next week or two, and will post more photos for you to check out.

    Also, regarding your newer UAV post, it is not totally necessary for you to fly an autopilot to cover the 2km2 you are trying to do. With a simple video downlink and video goggles, you can dramatically increase the range you would get from flying normal RC, and the Co-Pilot can do alot to help you level the plane out so it is making nice photos at Nadir.

    Anyway, stay in touch, and we are very happy to help you process and publish your images as soon as you have them.

  • Jeff

    Many thanks for posting the photo's. It's quite useful to know that the wings could fall off BEFORE loading the plane with camera, autopilot and other expensive stuff. I will check out RC groups as you suggest.

    I also like the idea of moving the elevator and rudder servos to the rear. It not only moves weight to the back, but frees up the cabin area for more cutting if necessary.

    Have you any photos with the camera mounted yet?

  • Also notice that we moved the servos to the back.

    This implementation still flys a bit nose heavy, so we are working on adding some weight to the back. In the end this bird should also fly our downlink gear as well.
  • Paul, I recently posted some images of the latest Cularis we are building. Check here ... There has been some serious problems with the wings (check RC Groups for info), so see our solution with dowels holding them in.

    We are intending to fly this one with a Nokia N95 and a Canon SD1000.

  • Chris

    A Multiplex ESC with BEC come with the motor kit for the Cularis, but the instructions tell you to disable the BEC and use a battery instead as it does not give sufficient power for the 6 servos. I have now found several high current switch mode BEC - I just ordered the SportsBEC as I found it first.

    The date thing when editing the blogs is most confusing. It would seem that an edit should have the option of leaving the original post date. I have changed the dates on my edited blogs so that at least they are in the right order.

    By the way, is there a search facility on this site. I wanted to reference a post I saw a little time ago, but I could not find it.
  • This is my concern. I have already ordered the SportsBEC so I will try it out with the Rx efore deciding which route to take.
  • I think another point of using separate Rx battery is to reduce interference. In some cases, the noise generated by the motor may go into the Rx through the BEC of the ESC.
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