COG, Weights and more.

First off Im fairly new to R/C planes, but not to electronics or the Ardu-Family. So I started with a bixler, but as soon as she was done I ended up selling it (without it ever being flown) but I had it pretty tricked out, and it got my feet wet (btw I heard she flew great)

I had wanted a flying wing style for awhile, and this seemed to be the best thing out there.

I sprayed the outside with a very light coat of a protective material, although in hindsight I would have laminated instead. Originally I was going to use a 4000 mah battery for power since I have 2 brand new ones, but I also have 2 2200MAH that may work just as well with a Y connector.(Everything is 3S). I liked the idea the guy had about running 2 large batteries that he cut into the foam on either side of the cockpit....But For now 4000MAH is enough.(I also have a 1300 for FPV)

I have a camera for FPV that fits well into the slot in front with some slight modification.....But Now since I plan on using a canon with CHDK with a hole in the belly I decided that the batter should go as far forward as possible (For CG and other reasons) and put the camera in back. Today I picked up some 1/2 foam that Im going to use as a platform for the APM. Im guessing the back of the apm should go just in front of the spar is best? or should I move it forward?

I carved out a GPS sized square in the top of the canopy and used tiny screws to mount it so just the antenna goes up there, not the board. I did kinda the same thing with FPV and that antenna obviously goes all the way through the canopy.

As for weight I wasnt sure at first what to use, but I stopped by a tire shop and they have these new lead weights for balacing fancier wheels that stick to the inside. they come in a strip of 8I thing, and you can use just 1 or multiples. The adhesive  back is a huge bonus.

Anyways, If anyone has any input that might help me or any comments let me know. Ive included a pic of the inside of my canopy lid, and the weights (well 4 or 5 of them) They actually will kind of work around a curve  when you have a string of them.....since the adhesive stretches. Also one last thing.....Where are you putting you CG EXACTLY?



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  • 100KM

    The exact location of the APM is not that important.  It'll fly fine pretty much anywhere within the fuselage.

    If not too late, I would strongly encourage you to practice launching and LOS flight before packing it full of expensive gear.  If this is your first flying wing, the launch could be a steep learning curve.  The lighter, the easier to launch. 

    • I appreciate the help. I ended up making a mount out of block of foam board, and cut it so it its about an inch longer then the APM, and I cut some notches so it could go around the pieces of the planes cockpit that stick out, and still rest on both sides and the back edge butts up against the wing spar. I cut out some velcro and out it on each side where the piece lays on the ledge, and for good measure I added velcro to the end that buts up against the spar, and the spar itself. The APM is dead center in the middle and on the edge by the spar. Then I added some 2mm thick vibration damping soft foam on top of the tray, and finally added some tape to help keep the harder layer of foam together. I had to make 2 since I used some of that hobby glue (starts with a C) to glue the 2 pieces together, and it literally ate through the foam board like acid! 

      Anyways everything is wired up and mounted, Im just debating whether to use 2 2200 lipos or 1 4000.......or possibly 2 4000's. I have a 1500 mah for the fpv. Im also wondering whether or not to leave the stock motor as is for now, and add the other later once I get the hang of things. Spraying it with that plasti-coat did add some weight. But its so thin you can still see the hex pattern of the foam so Im not sure just how big of a difference it will make. I also cut out the hole for the cannon cameras lens in the bottom back, and am in the process of wiring it to the apm for snapping photos at the right time. ITs a very small point and shoot so it doesnt add much weight so thats a good thing. What do you think, should I add the bigger motor or do you think the stock will be able to handle it? Also what 10" blade are people using? Ive got ALLOT of 1045's from my quads. Your help is much appreciated   -Will

    • 100KM

      What will your flying weight be? Do you have details on the stock motor? (kv, size) I built mine from the bare airframe.

    • I will weigh it tomorrow but the stock setup is a 30amp Esc with 900kv Brushless Outrunner Motor. They dont specify the size but people who have taken it out say its roughly a 2530, but it looks to me that its about the same size as my sk3. I already ordered some APC 9x6 props but I could run the 1045 prop with this motor. Most people run the 1000KV but like I said I have a Brand new 3536 1400kv SK3 which is a sweet motor. Another thing is that there are allot of config files out there for people with some sort of skin adding a little weight to there phantom and setup just like mine is stock......I'm not sure what parameters I would need to tweak with upgraded motor. 

      Another question. I noticed with the link you sent that they showed the over under hinge with one end flat.......But just cutting it down the middle seams to work ok as well?

      I also noticed hobby kink had this one back in stock......Which is pretty sweet I have to admit, especially if your going to use a GoPro, which I have.....But I havnt even maidened this one yet and besides, a GoPro is terrible for mapping, but nice for FPV Videos. But Id rather map an area then have a video I would watch once!

    • I weighed it out with just the fpv camera and no top today (so just motor and esc) and  it came out to 1.2lbs.

  • 100KM

    Hey Will,
    This may be a little late, but thought I would reply. It kinda makes me cringe to see ballast in a FPV plane because of all of the possible components to shift around. I guess sometimes you have to. CG is typically right on the spar for this wing. Start off on the forward edge. As you get it dialed in, you can move it back for less elevon trim. I found the behavior can change dramatically from moving the CG just the thickness of the spar. Some say they fly at the rear edge of the spar. When I tried, it was unflyable. APM did not like it that rearward either. Maybe it could have been tuned, but I stick with right on the spar center line.

    • I have 1 issue and 1 question (since your the only one paying attention to this group it would seem...... I noticed today one of my my flaps is ripped about 6 inches from the outer edge....And after seeing what super glue does to foam I decided to use a very, very sparing about of guerilla glue to re-attach, a I think Ill just try to cut the exess G glue foam away....but still Im worried. an ideas? and could you do me a favor and measure how far up and down it moves from the back edge up and down?

      Also I have this awsome 40 amp ESC and 3536 motor that 1400kv. I know thats allot of kv but its a turnigy sk3 so I love to use it.....

    • 100KM

      I never trust the foam hinges. They always eventually tear. It's easy to cut them loose and tape them. I used 3 sets of over/under hinges for each elevon. Then I ran a full length of Blenderm to seal the gap. I also sliced a groove and glued in a cf "spar" along the bottom forward edge of the elevon - touching the control horn. I did this because I had the cf laying around and the elevon felt very flimsy when I cut it loose. (I think it was 1x4mm cf.) Overkill perhaps, but I was building for heavy loads, long range, and landing in tall rough grass.

      My Phantom is not operational right now. Cannibalized the rx. I can tell you that I have the control rod on the outermost hole of the control horn and the middle of the servo arm.

      That motor on 3S would be probably over 40A with a 10x5 APC. It's a bit much for me, but some like lots of power. If I really wanted to use that motor, I'd probably fly it on 3S with a 9x4.5 to 9x6. I used to fly my SW with an NTM 1400kv on 3S and 9x6 APC. eCalc predicted ~35A. I consistently measured 50A on takeoff at 100% throttle. (heavy setup)

    • I play on running a 9x6 prop, and the blue series ESC is pretty beefy (Plus I have it already) What do you think? also, as for cutting and taping....could you explain that to as if I had never seen the plane? It's weird, I deal with Advanced computers and server all daylong....but when it comes to something simple I overthink it so much I get it wrong.

      Last thing.....Where do you get those hinges? and do you cut the tapered part of the wings hinge flat before installing? Thanks a bunch...-Will

    • 100KM

      Sorry Will.  I lost track of this after leaving town for a few days.

      A 9x6 with 1400kv on 3S should be plenty.  Most go for lower kv and a 10" prop.

      As far as hinges, I did a combination.  First, what's called a tension hinge here:

      Then I just ran Blenderm tape top and bottom along entire aileron.

      Either one alone is probably sufficient.  My flights were 2+hrs at a time, so I wanted to be sure.  I've used just the double tape (top and bottom) before and it never failed.  I've used Blenderm or extreme packing tape.  (the type with bi-directional weave)  I've also used plane packing tape on my lighter $Tree foam planes.

      As far as cutting the foam aileron, don't over think it.  I just eyeballed the thinnest point of the foam hinge and marked both ends and cut along a straight edge.

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