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Old Nov 27, 2008, 05:24 AM
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Uppsala, Sweden
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FPV system in a 1:3,5 Shadow 200 model?

Hello!

I'm in the process of designing a model of the Shadow 200 in 1:3,5 scale. My intention is to install a FPV system sometime in the future. The camera will then be housed in the sensor pod beneath the fuselage.

However I'm not sure that the FPV system will fit. In the thread below I have some pictures of the design and I would appreciate if you FPV-gurus would give me your thoughts regarding a FPV-implementation in this model. Is it doable? Do I need to build a bigger model?

http://www.rcgroups.com/forums/showt...7#post11019095
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Old Nov 27, 2008, 06:36 AM
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1.2m wingspan wound be fine, but I read in your post you're approaching 1kg. I would definately increase the size of the model, but try to keep the weight same The FPV gear should fit, but I'm a bit skeptic if you can include the gimbal. Maybe something like this would need to do:
http://www.rangevideo.com/index.php?...products_id=73

I'd recommend something in the area of 2m. Offset the additional cost by buying a cheap motor and LiPos instead of the pictured ThunderPower But that's just personal preference I think.
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Old Nov 27, 2008, 07:17 AM
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Nice 3D renders! I'd aim for about 2-meter, or 80-inch wingspan, that's a good size, and make the wing detachable into two halves. Try to build as light as possible so the more equipment you can get up in the air.

Cheers,

Sander.
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Old Nov 27, 2008, 08:05 AM
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Thanks for the feedback!

First I need to know if the design can fly that's why I think I'll make a prototype in 1:3,5 scale. However it would be interesting to build a bigger a/c with three main detachable parts but I think that is for v2.0:
  1. Fuselage
  2. (right) wing, tailboom and tail
  3. (left) wing, tailboom and tail

My 3D CAD drawing is easily scalable for everything except servos etc so changing scale isn't a problem

The diameter of the pod sphere is 70mm in 1:3,5 scale so maybe this setup would fit inside?
http://www.rangevideo.com/index.php?...roducts_id=132

I think I'll have to model a similar setup just to be sure!
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Old Nov 27, 2008, 08:37 AM
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boopidoo, after giving this some thought, I'd be very interested in building a 2m model. The camera will fit effortlessly into a 7mm diameter pod. The thing is these pods you see at rangevideo are a great deal simpler in construction than a gimbal - which you have included. I'd suggest going with a pod any day.

By the way ... what are the 2 servos doing in the fuselage? You're not thinking about using those for the tail section, are you?

If you're serious about FPV, I highly recommend doing a 2m variant. The expensive part are the electronics, you can experiment with various chord lengths or wing setups. FPV gear will add another 60-100g and additionally reduce the flight time of a 1.2m model in half.

Regards,

Raphael
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Old Nov 27, 2008, 09:07 AM
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Yeah, you guessed right the servos are indeed intended for the tail section using flexible pushrods. However I have no idea how I should set these up. I guess it's similar to a V-tail setup.

When I've made the plans I could post a 1:2 scale version (~2m span).

My thoughts with the gimbal is that it shouldn't be impossible to make an improvised version that has a similar construction but that looks like a gimbal. For starters I guess a simple pod would be sufficient. I will model both just to try my idea.
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Old Nov 27, 2008, 10:50 AM
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I've modeled a similar setup for FPV and the pod should fit but I need to rethink my structural balsa beam and make some kind of mount for the panning servo.
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Old Nov 27, 2008, 10:55 AM
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Since your plane is front-heavy (as you mentioned) why don't you put the servos into the back and run wires back there? I have the servos for fin always inside the fin, for all my motorized models, simply for CG issues.

Is there any reason you want to put the pod at the bottom of the fuse other than at the front in the nose section? When flying FPV you'll always want to look out the front, my guess is the pod is located at the bottom in the original for surveillance purposes (which is typically top-down view).

Edit: Other things to consider in FPV platforms is to keep the distance between the video TX and the radio RX as large as possible. Also you'll want to place the video TX at a location where you can run the antenna horizontally (for high altitude flights) and vertically (for long range flights) without obstructions.
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Old Nov 27, 2008, 11:44 AM
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Thanks for the feedback!

Actually it's the opposite, the aircraft is prone to be tail-heavy which is why I need to put as much stuff in front of the CG as possible. This is because of the dual tailboom design I guess.

The only reason for the pod placement is that it's the same placement as on the original UAV. You're right that this is probably a poor placement and I might need to rethink this.

In the 1:3,5 scale I'm not really sure where to place the video TX. In a 1:3 and above I think the video TX could be placed in the nose in front of the battery, or maybe on a platform above/below it?
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Old Nov 27, 2008, 11:57 AM
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Wow, you're lucky. Tail-heavy planes are so easy to correct Just put your battery all the way forward. I'd also include the video TX just on top of the battery, either sticking out straight like a spear or vertically (depending on your 'mission'). That also takes care of interference between RX and video TX (assuming you run the RX antenna out the back). Keep in mind that the TX will require a bit of airflow over it otherwise it will just melt its way out of your depron plane.

I'd still put the tail servos in the tail, or at least into the wings and then run the controls down the carbon rods. If the plane comes out too tail-heavy, simply shorten the boom a bit (I bet by now you can tell I have no clue of aerodynamics ).
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Old Dec 01, 2008, 02:47 PM
I fly, therefor I´m...
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Tjenixen..!
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Old Dec 01, 2008, 07:02 PM
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nice work boopidoo.
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Old Dec 01, 2008, 09:24 PM
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Boop you may want to pick this guys brain for some tips/pointers. Very similar layout to what youre planning.

http://www.rcgroups.com/forums/showp...69&postcount=3
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Old Dec 02, 2008, 08:24 AM
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Uppsala, Sweden
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Thanks, I have a gimbal/sensor-ball construction under way but I think 1:3,5 scale might be a little small to make a decent construction. Will post results soon.

@Adam Neat
I like their design, kind of similar to the Shadow 400 UAV.
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Old Dec 02, 2008, 11:29 AM
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Madrid, Spain
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Hi, nice project!

Pushers always tend to be tail heavy, but FPV planes tend to be nose heavy, so you should be ok. If you put the camera in the nose I´d bet you will never be tail heavy with that long nose, and you always can move the battery to the nose too.


Trappy, putting the video tx in the nose is not a good idea IMO, because, where would you put the rc rx then, in the nose close to the tx or close the the motor/esc? There is no more options I think...

I´d put the video tx close to the motor and esc, and the rx in the nose, specially if you´re going to fly with 2,4ghz rc. But if you´re going to use 35/72mhz then you may have some problems routing the antena to the back and passing close to the esc, tx and motor. Another option would be trough the wing, but if it´s only 1,2m wingspan then a lot of antena would hang doing a 90 degrees turn, and that´s not good.


About the tail, if it´s going to be a A-Tail, it´s like a V-Tail, but with the opposite rudder movement.


Keep us posted

Andres
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