Thread Tools
Nov 14, 2019, 12:03 PM
Aerodynamically Enhanced
XionUAV's Avatar
Here's my version of the Dragon getting close for an LOS test flight. VTX is a 1.3GHz 400mw from RMRC. Antenna is a VAS unit that came with the VTX. Works great for tail mounting. Painted the area around the front of the GoPro lens flat black to reduce possible glare. Will probably also use ND filters for bright days. Mounted a tail wheel and wing skids. Should be good for asphalt road landings.

Receiver is an EzUHF. I have a few different versions of 433MHz links but like the fact that the EzUHF module fits in the Taranis so no messing with external boxes on this one. Normally I mount the RX antenna(s) closer to the nose to get the most separation between TX and RX antennas but there just isn't a better place to mount this RX since it's diversity. A single antenna RX would be easier to mount but hopefully this will work ok. The main thing is to keep as much separation as possible between the 1.3GHz VTX and the GPS antenna since a strong 1.3GHz signal can swamp the GPS.

Initial battery placement shows a 3000MaH 4S 20C/25C will have the back of the battery about even with the spar. I'd rather use a 4000MaH but currently have a bunch of the 3000MaH or much larger with high C-ratings. In other words much heavier. The only 4000MaH I have on hand is a 10C for some multi-rotors. Would probably work ok if the current draw was kept low but flying slow wasn't the point of this build. Two 2200MaH 20C in parallel fits ok but is fiddly so it looks like HK will get an order for a couple of Zippy 4000MaH 20C or thereabouts. I really like the Nano Tech line but not sure it's worth the extra $$ for this plane. Zippy has been a good battery as long as they aren't abused. There's a Zippy Compact 3700MaH 25C that's about 40g lighter than the 4000MaH so that's what I might go with.

With the back of the battery around the spar that means the 405 FC will go behind the spar. I'd prefer to have it closer to the CG but it is what it is. So after the test flight, if it survives, then I'll get everything else installed and hooked up.

One thing that still bugs me that I'm going to have to mod just for peace of mind is the airflow. The little tray in the tail is a nice idea but anyone who's used a VTX at more than 25mw knows that really good airflow is mandatory for not cooking the thing. That's why I mounted mine on top and made the mount with a space under it. So having the air scoop in the middle of the plane is pointless. It needs to be up front with some ducts to the GoPro. This would also allow the air to flow over the batteries then to the rest of the electronics before exiting the tail. Minor details but still logical.

This will be a short-range plane for me up to about 5 miles. Most flights will probably be no more than 20 minutes. Of course that also depends on the battery and throttle management.
Sign up now
to remove ads between posts
Nov 17, 2019, 03:02 AM
Aerodynamically Enhanced
XionUAV's Avatar
Drone Camps RC's review could have been waaay shorter but it shows something interesting.

My measurement indicates the seam near the front of the wing is exactly 45mm from the leading edge. It appears this guy has his CG at 48mm. At more than about half throttle his plane porpoises badly. I'm going to launch at 40mm just to be safe on the first flight. Thanks Andrew.

Speaking of Sir. Newton, one comment stated that "Andrew Newton suggested a CG of 40mm." Drone Camps RC's reply was, "Mine worked fine."

Yeah I don't think the plane doing "The Wave" under power should be considered 'working fine.'

BEST RC PLANE for $122? - REPTILE DRAGON 1200mm - REVIEW, CRASHES, 20 MIN FLIGHTS (20 min 49 sec)
Nov 19, 2019, 02:18 AM
TheWizard
IndyFPV's Avatar
Quote:
Originally Posted by XionUAV
Drone Camps RC's review could have been waaay shorter but it shows something interesting.

My measurement indicates the seam near the front of the wing is exactly 45mm from the leading edge. It appears this guy has his CG at 48mm. At more than about half throttle his plane porpoises badly. I'm going to launch at 40mm just to be safe on the first flight. Thanks Andrew.

Speaking of Sir. Newton, one comment stated that "Andrew Newton suggested a CG of 40mm." Drone Camps RC's reply was, "Mine worked fine."

Yeah I don't think the plane doing "The Wave" under power should be considered 'working fine.'

https://www.youtube.com/watch?v=Krq_uh6OTJ4

Yeah, that guy really has no idea what hes talking about when it comes to fixed wing.

I think the porpoising was from a poorly tuned stabilizer. He hadnt really tuned the gains.

Andrew is right that for slower flight as he is doing in his vid, 40mm is probably ideal.

I have mine at 45mm, right on the gap, and it feels about right to me, maybe a bit forward honestly. No bad tendencies.
Nov 19, 2019, 11:36 PM
Aerodynamically Enhanced
XionUAV's Avatar
Finally got a chance to toss the Dragon. Here's what I found.

The Sunnysky 2216 1800kv motors are waaay too much on 4S. Might be ok on 3S but I'll be swapping them out for SS 2212 1400kv to tame it down a little. During the entire session I never went above 1/2 throttle. Would probably even fly fine with 1250kv. No reason it shouldn't cruise comfortably at 60 mph if aerodynamics are kept reasonably clean. 7" props would be an interesting test but I'll leave that for someone else to try.

Started with the CG about 3mm in front of the seam. That should have been around 42mm. The 3000mAh Nano Tech 4S was quite a ways forward in the tray. The back was at the 40 mark on the tray or about 50mm in front of the spar. For level flight I had to add down trim. Elevons were about 2mm down. Moved the battery forward more to about 35 on the tray and level flight was about 1mm down. So a CG of 40mm or maybe even a little less would be neutral trim. GoPro was a Hero4. Didn't want to risk the new-to-me Hero7 just yet.

Given that the 3000mAh 3S was so far forward I'm going to try a larger battery later. And while I previously said that two batteries was too fiddly, now I'm thinking two 20C or other small-ish 2200mAh 4S might be a good option for fit. Much easier to install and remove shorter batteries. It should leave a little more room for the FC closer to the CG as well.

Reptile Dragon Hat Cam Nov 19 2019 (3 min 51 sec)

Second video is from the GoPro. Looks pretty good. I was keeping the plane close so lots of turning. No long straights to show stability but overall it is really stable, which others have already noted.

Reptile Dragon GoPro (4 min 34 sec)

Planks like lots of aileron, very mild up elevator and very, very little down elevator. My best guess for expo and travel ended up sluggish on the ailerons and too sensitive on the elevator. Plus the temporary FrSky/Futaba control link had a weird glitch once in a while where I'd bank, nothing would happen then it would suddenly turn. Never seen that before. Permanent control link will be an EzUHF system.

For a plank it flies great. For a serious FPV plane I would like a little more pitch stability. Obviously an active tail could be added and I'd almost be tempted to graft in a V-tail on another one. But for now I'll try a small static horizontal stabilizer on top of the tail to see how that might dampen pitch movement.

Overall I'm very happy with it. Now we'll see if there's still bare ground when I finally get the 405 installed. Decided to go with Ardupilot.
Last edited by XionUAV; Nov 23, 2019 at 10:11 AM.
Nov 21, 2019, 02:59 AM
Registered User
tumarol's Avatar
Hi,

i got the dragon yesterday. I could not read anything about the recommended throws (for aileron + elevon) in the manual.

Please tell me which throws you are flying at the dragon.

Thank you from bavaria.

Gerhard
Nov 21, 2019, 09:09 AM
Aerodynamically Enhanced
XionUAV's Avatar
Quote:
Originally Posted by tumarol
Hi,

i got the dragon yesterday. I could not read anything about the recommended throws (for aileron + elevon) in the manual.

Please tell me which throws you are flying at the dragon.

Thank you from bavaria.

Gerhard
Since I've only flown mine once so far I can only give my initial setup that will probably change as more flights are made. However, we have snow coming here next week so more flights for my Dragon may not happen for a while.

I'm using Emax ES08MA II metal gear servos with the 3 hole servo arm. Control rod in the middle hole on the servo arm and outer hole on control horn. For aileron programming I have 100% travel with 50% expo. For up elevator I've limited the travel to about 5mm up and about 3mm to 4mm down with about 70% expo.

As I mentioned earlier, planks can be very pitchy so very small elevator movements can create strong pitch movements in the aircraft. That's why proper CG is so critical. For a maiden you might want the travel to be slightly more. But after you fly it a few times you'll figure out what works best for you.

Good luck with it!

EDIT: I just setup EzUHF for the Dragon's second test flight with the new motors and measured the actual throws as setup in the Taranis. Aileron travel isn't 100%. I have it limited to 80% which is about 12mm up and down. Elevator is limited to 50% which is about 7mm to 8mm. 50% expo on aileron and 80% on elevator. I might crank up the expo on the elevator even more because in flight you don't want much elevator travel but need it for a decent flare on landing.
Last edited by XionUAV; Nov 22, 2019 at 09:36 AM.
Nov 21, 2019, 09:39 AM
Aerodynamically Enhanced
XionUAV's Avatar
Didn't have two SS 2212 1400kv on hand so decided to install SS 2212 1250kv to test.

A while ago I was in a discussion with some guys about how ESC's create more heat at part throttle vs. full throttle. That sounded odd to me but information from several professional sources supported this theory. The ESC's have to work harder limiting the current flow to the motor at part throttle vs. WOT. The only way to verify this would be a controlled test with ESC temp sensors so until that happens I'll just accept it as a possibility.

So if 1250kv gives enough thrust for launch then they might actually be a good option. Going to a 7" prop with this motor would also be an option. I'll order a couple SS V3 2212 1400kv just in case 1250kv isn't enough because I do like the 6x6E and EP props. Need a couple for my stock anyway.

Going to setup the EzUHF and try another test flight in the next few days if the weather holds.
Last edited by XionUAV; Nov 22, 2019 at 10:42 AM.
Nov 22, 2019, 08:50 PM
Registered User
Quote:
Originally Posted by XionUAV
Didn't have two SS 2212 1400kv on hand so decided to install SS 2212 1250kv to test.

A while ago I was in a discussion with some guys about how ESC's create more heat at part throttle vs. full throttle. That sounded odd to me but information from several professional sources supported this theory. The ESC's have to work harder limiting the current flow to the motor at part throttle vs. WOT. The only way to verify this would be a controlled test with ESC temp sensors so until that happens I'll just accept it as a possibility.

So if 1250kv gives enough thrust for launch then they might actually be a good option. Going to a 7" prop with this motor would also be an option. I'll order a couple SS V3 2212 1400kv just in case 1250kv isn't enough because I do like the 6x6E and EP props. Need a couple for my stock anyway.

Going to setup the EzUHF and try another test flight in the next few days if the weather holds.

I run 2216 1250KV on my S1100 w/ 8x4.5 props. Super efficient.
Nov 22, 2019, 09:37 PM
Registered User
tumarol's Avatar
Quote:
Originally Posted by XionUAV
Since I've only flown mine once so far I can only give my initial setup that will probably change as more flights are made. However, we have snow coming here next week so more flights for my Dragon may not happen for a while.

I'm using Emax ES08MA II metal gear servos with the 3 hole servo arm. Control rod in the middle hole on the servo arm and outer hole on control horn. For aileron programming I have 100% travel with 50% expo. For up elevator I've limited the travel to about 5mm up and about 3mm to 4mm down with about 70% expo.

As I mentioned earlier, planks can be very pitchy so very small elevator movements can create strong pitch movements in the aircraft. That's why proper CG is so critical. For a maiden you might want the travel to be slightly more. But after you fly it a few times you'll figure out what works best for you.

Good luck with it!

EDIT: I just setup EzUHF for the Dragon's second test flight with the new motors and measured the actual throws as setup in the Taranis. Aileron travel isn't 100%. I have it limited to 80% which is about 12mm up and down. Elevator is limited to 50% which is about 7mm to 8mm. 50% expo on aileron and 80% on elevator. I might crank up the expo on the elevator even more because in flight you don't want much elevator travel but need it for a decent flare on landing.
Thank you very much for the detailed Information!

Regards Gerhard
Nov 23, 2019, 10:13 AM
Aerodynamically Enhanced
XionUAV's Avatar
You're very welcome.

I really like this plane and hope it gets some respect from the FPV community. I seriously doubt it will become super popular just because planks are more fiddly to set up than tailed aircraft but I applaud Reptile for manufacturing a unique and very cool little airplane that so far flies great.

Unfortunately we have major snow coming this week so my scheduled test flight today with the EzUHF and new motors will probably bit it for a while. In the meantime the rest of you guys with decent weather will have to take up the slack.

Hey Jake Bullit, curious since you started this thread did you ever buy one?
Nov 23, 2019, 03:14 PM
Fly,crash,glue,repeat!
Jake Bullit's Avatar
Thread OP
Sadly, not yet. But it's at the top of my list next time I buy a new plane.

Sent from my SM-G960F using Tapatalk
Nov 23, 2019, 10:43 PM
Aerodynamically Enhanced
XionUAV's Avatar
Second test flight today trying out the SS 2212 1250kv motors and 4S with EzUHF and Taranis. Still with the Hero4 to get an accurate read on stability. A few longer, straight runs in this video.

1250kv and 4S is a good combination for strong cruising using the 6x6 props. Plenty of thrust for launch and it would cruise at half throttle fine. I'm guessing around 45mph at half and maybe 55mph to 60mph at 3/4 or so. We'll see when the FC is installed.

Another nag I found today after watching the video is I think the camera needs more down angle. On many of the straight runs you can see that the horizon is in the center of the screen. Generally you want about 2/3 ground and 1/3 sky. Some even prefer 3/4 to 1/4. Tilting the GoPro down more would require major surgery to the nose. The angle bugs me enough that I'll probably end up whacking off the nose and make a 3D printed replacement or at least a wedge. An action camera like a Mobius or Runcam 2 would be much easier to tilt downward.

Also think the motors might need some down-angle. An Increase in throttle would cause a mild climb. One more thing to try.

And it does wag its tail a bit. Still thinking of making it longer. One of my landings was crap because a crosswind skewed the plane and of course there was no rudder to correct it. That might not be a bad mod. I'll live without it but still not a bad mod.

Gerhard, my expo in the Taranis is different than it was in the Futaba. Travel is about the same with aileron at 12mm and elevator at 7mm to 8mm. Originally I said around 5mm but that's too low. 80% expo on the Futaba was good but way too much on the Taranis. Now aileron and elevator are both limited to 70% travel with aileron expo 50% and elevator 60%.

Was impressed with the EzUHF. Very smooth and worked great.

Edit: Forgot to mention that the elevons were neutral at 0 trim and produced a mostly level attitude with the CG at 38mm. Had the battery all the way forward against the back of the GoPro to get that CG. In-flight trim may change slightly when the motors are angled down but the angle will be very small so we'll see.

Dragon 2nd Flight Edit (4 min 36 sec)
Last edited by XionUAV; Nov 24, 2019 at 02:36 PM.
Nov 24, 2019, 02:40 PM
Aerodynamically Enhanced
XionUAV's Avatar
Did a quick hat-cam video of 1/2 and full throttle passes with the 1250kv motors, 4S and 6x6 APC props for ground reference.

Reptile Dragon 1250kv Passes (1 min 20 sec)
Nov 27, 2019, 10:17 AM
Aerodynamically Enhanced
XionUAV's Avatar
Anyone else doing anything with the Dragon? We're getting about a foot of snow here.
Nov 27, 2019, 10:36 AM
Registered User

Dragon


I have just received my Dragon! Came in good condition, no damage! Kit is very good design, but it's about 570g, not 430g as adv


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
New Product [New Arrival]Reptile S800 V2 SKY SHADOW 820mm Wingspan FPV Flying Wing RC Airplane BG Tobey FPV Aircraft 686 Feb 02, 2020 08:59 AM
New Product Reptile S800 V2 SKY SHADOW 820mm Wingspan Gray FPV EPP Flying Wing Racer PNP With FPV D Gains FPV Aircraft 1 Aug 10, 2017 10:31 AM
Build Log EasyGlider Wing on a Wing Dragon: Testing a new FPV rig uninsane FPV Talk 2 Nov 08, 2010 03:43 AM