Hoverfly Here I go again....

[Webheadfred]

Well... Maybe it's a build thing. I just like building.

After some disappointing performance with the big X8 I made some observations and I'm making a change. While watching my x8 fly, she flew beautifully on manual but I could never get the GPS to hold worth a darn on PH. So I watched it carefully as I was bringing her in and noticed quite a bit of flex in the arms as she hovered at eye level. I also noticed that she was a bit front heavy from the camera gimbal position so, I assumed the front motors were working a little harder than the back to maintain level. My wiring harness was a quagmire as I didn't give it too much thought as far as position as long as it was 'in there' and electrically sound. I fit all 8 40a Turnigy Plush ESC's in the main body of my Rusty's frame along with the wiring harness so I imagine there was quite a bit of magnetic field wreaking havoc with the magnetometer, even though I had an external one. So here goes....

I rebuilt it into a Hex. Same Avroto 2814 motors. Instead of 11x47 props, I'm planing on using 12x38's. I built it from the wiring harness up, being careful for symmetry in the harness and twisting the positive and negative wires. I moved the ESC's to the more reasonable length arms on specific mounts to keep them firmly in place. On the X8, I was 41" MTM and on this hex, I'll be 31" MTM. It's perfectly balances front to back and side to side with the camera gimbal and camera on. I'm planning on placing the battery on top for ease of access and more centered CG. I'm using stiffer carbon fiber arms and the entire build is much stiffer than the previous X8. I'm thinking that by going to a flat hex versus an x8, I'll regain about 15% efficiency than a coaxial configuration, I'll be lighter by two motors and I'll draw less current from the battery. I should get a little more flight time (hopefully).

It should be finished and ready to fly this afternoon or tomorrow afternoon (if it stops snowing) and I have a question. With the HFP and GPS, will the flight characteristics be similar as far as hovering and maneuvering versus the X8? I'm still a novice with this RC stuff and if anyone has any suggestions, I'd appreciate it... Thanks.

 

[ChrisViperM]

Can't help you with the HFP....but I wish you lots of success


Chris

 

[Stacky]

I dont have the GPS board but my Hexa flies as well as my X8 does. the main difference for me is simply orientation, the X8 is easier. Also I get 15% shorter flight times from the X8 than the Hexa using the same batteries. The X8 handles the wind better. On a calm day you cant really tell the difference.

 

[Webheadfred]

Thanks Stacky. I've found that in gusty wind, my X8 would climb a little. I really liked how it handled manually, I just couldn't get it right with the GPS and I'm sure it was my wiring and my arms. This Hex is WAY more stiff. I'll keep my fingers crossed. I know the wife-unit laughs at me always rebuilding. Oh well...

 

[Webheadfred]

First Flight

Hmmmm was this a lesson.... I have to learn all over again.

First of all it's now a hex with shorter arms. It's 31" MTM now. I can carry it by one arm if I have to. I've moved the 5000mha battery to a plate above the HFP & GPS for easier access and for an additional batter in the future, and for a higher CG, thinking it would make the HFP work less to keep her flying. It's all quite stiff.

I reduced the gain to get the new hex dialed in properly. My old gains were 91 or so and I started this one at 60.

Quick burst to verify the props are turning correctly (I've checked this about 5 times already but it cant hurt) and lift off....

The conditions, somewhat gusty 10-15 mph swirling wind. Overcast and humid, about 58º F. I lift off and I could barely control it as it was vibrating so much. I thought I had an issue and I had to land in the grass. Reduced gain to 40. A lot better but needed more. Reduced down to 30 and she was flying smooth. Good I thought. But let me tell you... the 'feel' of this smaller hex is entirely different. With the higher CG, I find it very sensitive. Previously, with the lower weight, I guess gravity would help keep it level. Not in this case, I needed to get right on it to keep control. I didn't even attempt auto level as it was entirely too windy. It is much more sensitive to the wind but I think AL will help me here. I flew at eye level and the arms are working as I expected. No flex whatsoever. It did bring to view a slight out of balance prop. I was a little bit surprised as I was able to see it in flight and sure enough, on the balancer, it was out. I suppose I need to be a little more accurate there. I was surprised as well, that I was able to get at least a minute longer in flight than on the X8. Same 11x47 APC slo-flier and two less motors. I weighed her all-up last night and it was 3.77kg. I had more power left but had a couple dicy landings due to the winds so I didn't want to press my luck.

I'll have to re-find that thread about reducing a Futaba 8FG to lower endpoints than 30 as I think it needs a little less gain. That'll be another day...

I'll put more up later but it's the anniversary with the wife-unit and if I wasn't willing to press my luck flying, I certainly don't want to press it with her as she tolerates my hobby. :tennis:

 

[Webheadfred]

I am really having a hard time flying this xHex. I have it stable as far as twitching but any slight breeze blows it off level. I am constantly fighting to keep it level and on station even with AL. It's very sensitive in the roll and pitch axis when flying. I have dual rate in and it helps but I'm on the sticks so much, it's hard to even flip a switch... Maybe I just need more practice. The Co-axial's were so much more stable. Any thoughts?

 

[octocine]

Did you try putting foam over the sensor? This seemed to really help stabilize mine, especially in wind. Good luck....

 

[Webheadfred]

I have the foam over the sensor. I think the CG is a little high. I've always put the battery low on the frame. Now, it's above the frame. In fact, it's probably 3" above the main body where the arms connect. The HFP is mounted to The body with the GPS above that. I may try lowering the CG and go from there. The last two X8's and my Y6 were so easy to fly. Nice and smooth. This one is very sensitive to the slightest input or breeze. I'm also noticing more impact of the ground effect of the props over a coaxial setup. Hmmm...I was hoping it would be better.

 

[Webheadfred]

Update. I was right. The CG was way too high. I suppose I've seen other multi's with the battery on top and thought it would be easier access. It was. It also sucked as far as flying. So, off came the gear and the camera mount and a thorough rethink on the CG. I moved the battery underneath the main body and wiring harness. The gear and camera mount is under that. I was afraid to fly as the wind was 15mph and gusty. Oh well, I have to be able to fly in that so off I went. It was 100x better. I mean it was night and day. It was really windy and swirly but I managed to get a nice level flight and had full control. I didn't really mess with the gain on this flight as I think I'll get a better feel for it in the morning when it's calm. I'll also trim out the AL and check the AH, and PH. My fingers are crossed.

 

[SMP]

Ahhh I've seen those builds with the batteries stacked overhead and thought about trying to balance a bucket of water on a broomstick... Been lurking your build. Glad to see it worked out!!

 

[Webheadfred]

Yeah.. I suppose those other builds, there's so much weight in the camera equipment, that the battery weight is insignificant. My battery was 577g which weighed nearly as much as the RusticWave gimbal and GoPro underneath.

I got up and flew today. I have AL trimmed so good that it's almost like position hold. AH is perfect. PH hold within tolerance. Interestingly, since I've moved the battery to under the frame, I've been able to raise the gain nearly 40 points on the transmitter. Nothing else changed except the CG and I've needed to raise the gain. The camera is charged for the next flight. Hopefully a video is next.

 

[SMP]

Aye, seems that with the retracts the batteries on the Skyjib are getting higher and higher. Currently mounted between two arms. Thanks for the CG pain avoidance

 

[Webheadfred]

The Hex is flying beautifully. I have a question though that some of y'all with a little more experience may have some insight. The AH is nearly flawless. The AL is perfect. The PH is, well, lets put it this way... This is the first time I could use the PH and AH and completely rotate the hex, 720 degrees stopping at various points, raise and lower the altitude and slew without the craft going haywire. I'm really happy about this. It's fun to fly again! So here goes....

I have absolutely no vibration dampening. None. My APC11x4.7 are balanced nicely and double checked. I've never checked the Avroto 2814's but running them on a boom and holding them, I feel no vibration. What I have done, I think Stacky suggested it, was really clamp everything down. Every is TIGHT. No play, No wiggle. So what I'm seeing is when I lift off, everything seems very smooth. As I get through the battery, the jitters start to set in. Could it be the lower voltage of the battery causing jitters? Could I have my advance set too high? I know in the setup client, it says it could cause jitters if it's too high. Would this present itself as the battery draws lower? I'm running the servos on a CC 6 volt bec with the signal from the HFP. I suppose next, I'll add some dampening material and try backing off the roll advance. Anyone else have any thoughts? Thanks...