600 UH-1N Twin Huey- ARF Bundle - Build and Impressions

[DCORSAIR]

Glad to see you might have it figured out, get some video when you can.
I have some Trex 600 ESP mechanics coming next week for mine, I didn't go with the Chaos 600 FBL.pro mechanics, I thought they had wider frames than the Trex 600?
Did you have any problems with yours?

[F106DeltaDart]

Completed a 6 minute test flight today, and everything has stayed intact so far! No strange vibrations to note. After my past few incidents, I kept the whole flight in ground effect so far. Downloaded the logs from the Brain and saw no significant vibrations from the data either. This weekend will be some more thorough testing proceeding into forward flight in the pattern.

[F106DeltaDart]

good looking 212, you've done a very nice job on it! It's big enough that you can start adding scale details which really make a difference in the look of it.
the devil is in the details! thanks for sharing!

Thanks! I love how the airframe looks, and there is definitely some ideas churning for more details. Just need to get my resonance issue sorted, and then it will be full bore on details!

With the new plywood down and headspeed lowered, that just left one more thing; doubling up the linkages. It took some digging through the parts bin and threading some new pushrods, but all of the push/pull linkages have been doubled up. If all goes well, it will be tested out tomorrow!

[Heli143]

good looking 212, you've done a very nice job on it! It's big enough that you can start adding scale details which really make a difference in the look of it.
the devil is in the details! thanks for sharing!

[F106DeltaDart]

1/4" birch should do the trick! Especially with Hysol, I can't imagine it going anywhere. What's your new headspeed?

Jon Ellis said he is running 1375, so I’ll shoot for somewhere in that range. In theory, increasing airframe stiffness and dropping headspeeds should help separate whatever modes are aggravating the airframe. Hoping for success this time around!

[Alpha]

1/4" birch should do the trick! Especially with Hysol, I can't imagine it going anywhere. What's your new headspeed?

[F106DeltaDart]

Happy Thanksgiving all! Just finished test fitting some new plywood. Bumped it up to 1/4” birch plywood. Much more rigid and stronger than the stock ply. Test fit is good, so I’ll get some Hysol on it tonight. Hopefully that moves whatever resonant mode that I’m hitting. Have also removed the boom supports and will drop headspeed a bit.

[F106DeltaDart]

Wow, that's crazy ! What in the world could have caused that ? You said "autorotated to a safe landing" si I assume it wasn't the landing that did all that damage ?

You are correct. I still am not sure, and I don’t like either theory I’ve come up with. The first is that my initial ground resonance issues had damaged the plywood at one of the mounting points, and it failed in flight, and caused the huge vibration. Or, that I have a fuselage resonance harmonic that is lining up the the rotor. Either way, there is a lot of work to go before it flies again.

[scootergenie]

Wow, that's crazy ! What in the world could have caused that ? You said "autorotated to a safe landing" si I assume it wasn't the landing that did all that damage ?

[F106DeltaDart]

A few photos after removing the mechanics. The plywood mounting surfaces are completely destroyed. This will be a long repair job.

[F106DeltaDart]

Last weekend, I test flew the mechanics more and ended up switching tail servos to a BK7006HV. This greatly improved the tail hold, and after a few more flights I was satisfied with the tuning and tracking of the mechanics. I moved them back over to the fuselage yesterday and did a few test takeoffs and landings, and no sign of ground resonance. Did a few patterns without issue as well. Just as I was about to call it a success, I heard a loud bang and huge vibrations followed. I cut throttle and auto rotated it to a safe landing. The plywood around where all 4 bolts are for mounting the mechanics was cracked and shattered. I’m baffled at this point. Still have to take it apart to investigate further, but I don’t have a solid root cause. Time to pull the mechanics out and start looking into the damage.

[F106DeltaDart]

To continue troubleshooting my ground resonance issue, I built a test rig and put a few flights on the mechanics today. Flew great, and had no ground resonance to speak of. I will be pulling the data logs in the FBL next to checks for any abnormal vibrations next.

[F106DeltaDart]

Well, I did the maiden flight today and things could have gone better. First hover was fine. Rotor was smooth, just needed gain tuning. On the second attempt, I got to light on gear and heard a loud bang. The H stabs, and 3 of 4 doors simultaneously departed the aircraft. I immediately hit throttle cut. When the blades came to a stop, the windshield was cracked, pieces were laying around in the scale cockpit, and fiberglass around the swashplate was chewed up. The whole center console in the cockpit has broken loose (probably contains a 1/2lb of ballast or so), and the mechanics were loose on their mountings. My theory is that that either the rear ball link on the swashplate let go, or that one of the mounting bolts actually pulled through the aluminum L mounting brackets. Both the forward swash linkages were also bent inward, likely from contact with the fiberglass. The event also delaminated several sections of plywood where the mechanics bolt on. I can get it fixed, but it bugs me that I don’t have a definitive “smoking gun”.

[Hardway]

love it!

[F106DeltaDart]

Balanced and fully assembled! Pilot and dog are awaiting drying glue mounting in the cockpit. Pretty much depleted my supply of lead for balancing.

[TiredIronGRB]

Going to be gorgeous!

[Hardway]

Fun! Nice job.

[F106DeltaDart]

Finally finished the setup today, but not until repeating it about 3 times. The bellcrank geometry amplifies small movements by a lot, so throws had to be turned WAY down, both physically and digitally. I had to move the ball links as far inboard on the servo horns as possible, and still had to turn down collective throw to 20% in the ikon software. Finally got it dialed in at +11 deg/-2 deg of pitch. Also had to make some changes on the tail gearbox attachment. It needed to be dremeled down in size to fit inside the Huey’s thin vertical fin. Mechanics are now bolted on the airframe, and will be planning for a maiden in the next few days!

[F106DeltaDart]

More progress on the mechanics. Got the tail boom installed and set up. I ended up making a few changes to the stock setup configuration. First off, the boom was not seating all the way stock as the torque tube was a bit long. This was also causing a gap in the scale tailboom joint to the fuselage. I shortened the torque tube by ~1/4” and it fits much better now.

The next change was the boom supports. The stock setup has them mounting on the screws that secure the L shaped mounting brackets. However, if you do that, the boom support block access to the screws for securing the mechanics to the airframe. Instead, I drilled 2 holes aft of the L bracket mounting, and mounted them there with some spare hardware. Works much better, and the mounting screws are easy to access now.

One last note is to be extra careful when snapping the ball link on to the stock tail rotor bellcrank. I applied a bit too much pressure, and snapped the end of the plastic bellcrank arm. A new Aluminum replacement is on the way. After that, it’s just FBL and ESC setup before a maiden flight.

[F106DeltaDart]

Any questions on your build, let me know.

Looks great, and will do! No major issues so far. Just time and waiting for some wire harnesses to arrive.