Has anyone assembled this fixed-wing UAV airframe (Hugin 2.6m)?

I recently bought the "ARF combo" version of one of these:  https://www.fpvmodel.com/hugin-ii-electric-powered-uav-2-6m-platfor...

So I got two large boxes a couple days ago with airframe components, motor, ESC, servos, and about 15 different flavors of screws, nuts, etc.  – and NO diagram or assembly instructions! Some I can figure out, but a lot I can't. And I'm not even sure everything I need is even in there (e.g. motor mount). 

Has anyone gotten one of these airframes flying?  If so, could you post close-up pics of anything involving screws or other fasteners?

Seems like a nice airframe, but it may cost me a lot of time to puzzle through the assembly, and I'm afraid of messing something up.

  Thanks

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Hi Grant, I just received my Hugin 2. This is a hard build, but I've done something like it on a smaller version of the MQ-9 Reaper. It's been a few months since you first posted this. How far have you come along? Currently all my parts are laid out and I'm organizing all the pieces and figuring where they all go. I'll start with the servos, wiring and control horns on the wings. Once those are done I'll start on the fuselage, landing gear, servos and wiring. finally do the tail section. It should go smoothly. I'll be using the dragon link just for the maiden flight. Once that is successful, then I'll add the FPV, Vector, and 2nd camera gimbal. Let me know how yours is going?

I'm getting close. This was my first build beyond a simple foamy, so kind of ambitious, but I think I'm past the trouble spots. It took me some time to puzzle through some things, and I ended up redrilling the aluminum pieces for the main landing gear. Also replaced the thumbscrews that hold the wings on with slightly beefier Allen-head bolts. I still haven't decided whether to epoxy the three tail surfaces together or just trust that the little screws will hold them together. And I still don't have a motor mount, so will probably fabricate something from plywood. And I'm waiting for bullet connectors and EC5 connectors that I need for the ESC and motor and that didn't come with kit.
I'm hoping to be ready to fly it by the end of March, if all goes well.

How is the build quality of the Hugin? I was looking at another product from FPV Model - the MUGIN - but was not able to find much information from others that have actually built one.   If you need help building your plane, let me know.  I've been building RC models since 1984 and would be happy to help if I can.  

I was interested in the Mugin for a long range project.  It can supposedly fly for 6 hours using a DLE170 two cylinder gas engine.  

The Hugin quality is decent. Minus build plans and some shipping damage, I would purchase another one, but find a direct seller for a cheaper price. Mine is almost complete, working on the tail section and booms now. Whats the process and measurements for attaching the booms to the wings? I have a basic electronic setup for the test flight and if successful, I'll add the Dragon Link, Vector, Cameras.

Update:  After many long delays (most related to other projects I'm tied up with), I am getting close to having the Hugin 2.6m flight-ready.  BUT ...

With it now fully assembled, including electronics, and sitting on a table, I'm unsettled by the following things:

1) It seems very tail heavy.  I have to put a large (1.3kg) 6S 10000mAH battery all the way forward in the payload bay to get the CG even close to where I think it should be (about a third of the way back from the wing root chord). I haven't calculated the exact CG yet (I bought three cheap kitchen scales - one for each wheel -- to work that out), but if it's still a little too far back even now, I'll have to add ballast to the nose, and the gross takeoff weight will increase even further from the current 13.5 lbs (6.1 kg).  I don't know what I could do to instead lighten the downward tail moment, especially given how fragile the tail already seems (see below). The electronics don't weigh much, and the motor isn't going anywhere.

2) The tail seems very flimsy. If I push down on the tail with enough force to raise the nose wheel (as you would to rotate on takeoff), the slender carbon tube booms bend noticeably. Also, the three pieces of the hybrid A-tail  are held together with small screws through thin plywood, and the joints flex easily.  Of course, the required downward force on the tail is also related to the fact that the main landing gear is well behind the CG, even in a tail-heavy configuration.

3) I'm not experienced with this kind of airframe, but the tail control surfaces seem small given the amount of force needed to raise the nosewheel.  I'm wondering whether there will be enough control authority to rotate for takeoff until well after exceeding stall speed. Again, this is just a hunch, but if it's correct, this could also mean inadequate elevator authority to flare for landing (though this is perhaps less of an issue than takeoff if the CG is near the aerodynamic center of lift).

Other thoughts: 

4) Assembly and dissassembly is a pain.  The wings are secured to the fuselage with thumbscrews that are too close to the underside of the wing.  I replaced them with Allen screws, but you can't really get in there with a tool to speed up screwing/unscrewing them, so you have to do it painstakingly with an Allen key, and it takes several minutes for each screw.  Also, the tail booms attach to the underside of the wings, and you need to be able to make the servo connections at that mount point.  I have not found there to be enough room to hide the connectors inside the mount point, so I have to let them dangle outside in the wind.  And again, there's those very fragile-seeming joints between the three tail pieces.  You really have to be careful not to stress them when attaching the booms.

5) At this point, I have no idea what to expect in terms of stall and cruise speeds.  I'm guessing stall could approach 20mph or even more (the airfoil doesn't have a lot of camber), and I might have a real tiger by the tail once it gets airborne.  I had been hoping for something that could carry a largish payload but still be relatively gentle to fly.  Fortunately, I'll have a PixHawk2 on board to provide stabilization (and eventually autonomous flight), so hopefully that helps shift the margin in my favor -- if everything works!

In retrospect, I believe I might have bitten off more than I can chew by committing to such a large airframe, especially one that seems not to be in wide circulation, and if I were to start over, I'd scale back to something smaller and more established.

That said there's little choice now but to at least try to make it fly.  If it crashes, I'll salvage the motor and electronics and try to do something else with them.

Looking forward to hearing others' experience, if anyone out there has some to share.

Grant, you've probably flown the plane by now, how was your experience? 

I have the inverted V-tail version of this vehicle with a dozen flights on it. Runtime is about 30 mins with 6s 10Ah batteries. Top speed with 12x8 APC prop is 76 mph without wind. Landing and takeoff speed are 40-43 mph, which is really fast and uses all of our runway. All speeds were measured with radar. 

The CG is about half way between the spar and leading edge. In flight, the vehicle likes to bounce around on roll and pitch axes. We upgraded the tail tubes to 25 mm diameter and this made the plane much more stable.- ted

Ps. the slender carbon tubes that you referred to are plastic, at least on my model. It's ok - we thought they were carbon too, until we took a knife to one! 



Grant Petty said:

2) The tail seems very flimsy. If I push down on the tail with enough force to raise the nose wheel (as you would to rotate on takeoff), the slender carbon tube booms bend noticeably. Also, the three pieces of the hybrid A-tail  are held together with small screws through thin plywood, and the joints flex easily.  Of course, the required downward force on the tail is also related to the fact that the main landing gear is well behind the CG, even in a tail-heavy configuration.

Ted,

We've only flown it once! For me, a relatively new RC pilot, it was a "holding the tiger by its tail" kind of moment, and I was glad to have a more experienced pilot at the controls. As you noted, the aircraft is fast and needs a lot of runway, which I normally don't have (I had the privilege of flying it out of the Embry-Riddle RC strip in Arizona last fall, which is much better than anything I have access to hear in Madison, WI).

What I noticed above all is that the tail structure was indeed kind of wobbly in flight and that there didn't really seem to be good rudder authority, especially at lower speeds. It's interesting that the tail booms might be plastic instead of carbon, as that would explain my surprise at how flexible they were! Replacing these with a larger diameter carbon fiber tube was already high on my list of things to do before trying to fly it again. Apart from that, having a good place for takeoffs/landings remains my biggest obstacle, something I didn't anticipate when I first took on this project.

I'm also contemplating moving the main landing gear closer to the CG so that the nose can lift easier on the takeoff roll. But maybe experts will advise me against that.


Grant, glad your maiden went well. This plane is definitely not for beginners. 

Moving the main wheels closer to the CG is OK, if you're sure about your CG location. The gear should always be in front of the CG by some margin to encourage the nose to fall upon landing. You may decide to move the CG further forward down the road, so I would keep the main gear in front of the CG by at least an inch. 

Below are pics and source files for our tail boom upgrade. We used 25mm OD, 23mm ID carbon tubes. Also some prefab split clamps from any online retailers. The screw threads in our wing at the boom mount are M4 and most other threads are M3.- ted

Hey guys, I know it's been almost a year since your last discussion on this, but I have the 3.0m version of the Hugin II, and I have flown the 2.2m version of the Hugin. With the 2.2m version, the boom-to-wing mounts deteriorated after about 15 flights to the point where the elevator couldn't counteract the flimsiness. I added block of wood and epoxy from the factory mounts to the trailing edge under the boom. That stiffened everything up and helped with the pitch authority/other random oscillations in flight. For the Hugin II (have not had the first flight yet), I installed a tension wire from the A-Tail-to-boom joints to help strengthen flimsy tail section. I also added a metal bracket to the boom wing joints to strengthen that section as well, basically adding a 3rd load point that goes through the wing to support the 2 mounts the kit comes with. I'm going to be running it with a 4s 40Ah battery, 100A Hobbywing ESC and a Turnigy 5055B 600kv 1500W motor with a 15x10 prop. It currently weighs 13 lbs and I'm trying to get 2 hours of flight per battery. I can upload pictures of my modifications if you are still having issues. 

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