Preflighting the Twinstar

Preflight testing of the Twinstar this morning, planning on a maiden today after some Honey-do's.

She has Sky Power 40A ESCs. The 480 Plus motors are rated for max 450 watts, but they caution running more than 400 watts sustained. I am running a switching voltage regulator instead of the BECs.

Ran the motors using the 3S 2200 mAh. I got about 7 min, 350 peak watts, around 35 peak amps. On the 4S 3300 mAh it peaks at over 700 watts, 37 amps! On time testing I got 15 min with some cells dipping to 3.4 V.

I need that flight time, so I set up a throttle curve and at a top curve endpoint of 50% produced around 430 watts, around 27 amps. At 50% of that throttle curve it produced around 230 watts and 12 amps, and gave me that 15 min runtime. The 3S 2650 mAh gave me about 10 solid min before.

So I plan to fly her 4S 3300 mAh set at 10 min with 5 min bingo, using a throttle curve to bring the power down so I don't blow the motors. I can fly the 3S 2650 mAh if necessary but would need to remember to remove the throttle curve. Not likely to do that.

More on the maiden later today!

Great Planes Twinstar EP Ready to Maiden!

Well, that's embarrassing... So I am watching the cat play with a white piece of plastic down in my shop... Wait a minute. Let me see that. Sonofabitch. It's the plastic Nose Gear bracket thingy. (Apologies to Great Planes...).

So I installed the nose gear and the nose cone, on the Twinstar EP, put a fresh 3S 2200 mAh battery in, checked CG (fine), and ran the motors at 50%.  Got almost 7 min, but it took them down to 3.5V. I need to see how it does with a 2650 mAh, or I will need to get the recommended 3800 mAh.

Trimmed that...

 

Bench test. Power to spare.  50% Throttle, 3S 2200 mAh, got close to 7 min but went down to 3.5V/cell.

I find their lack of faith... disturbing.

But for a nose block, the Twinstar is done.

The motor mount arrived from HeadsUpRC today, allowing me to complete the install of the port side motor and nacelle. All that is missing now, on The Plane of Missing Parts, is the nose wheel block, coming from Great Planes/Tower Hobbies. Once that is in, she will be complete within a few minutes, ready to CG and maiden.

After installing the port motor I ran them on a 3S briefly. Plenty of voltage/power. I wiIl need to see how much time I get on fresh 2200mAh. I am looking for 7-10 min of sport flying. I believe she is rated for a 5000 mAh or something ginormous. I already have a lot of connectors and adapters in there adding weight, but could easily change the EC3 one I have to EC5 and series in a pair of 2650 mAhs.

Twinstar Making Headway

Awaiting the motor mount and the nose wheel block. After that, CG and maiden.

The Plane of Missing Parts

Does twice make a trend?

As my Great Planes Twinstar project has unwound I found I was missing a motor mount, now graciously on its way from HeadsUp RC, and today I found that the Nose Wheel Block, the white nylon part that secures the nose gear to the airframe, is also missing. I keep all the bags and boxes, checked, not there. I went through the trash, not there. I crawled around on my knees and belly looking on the floor and under the work benches, not there. I called Great Planes/Tower Hobbies and a replacement is on its way.

UPDATE:  They never sent me the part, which is okay because I found the missing one. Cat stole it. No, seriously.

Between these minor annoyances and the problems I had with the RCGF 10cc engine, I wonder if I need to tune my RC mojo.

I finished the wings, but for the left motor for want of the mount.

And installed the rudder/steering servo, and the elevator servo.

And finally the tail.

I am stopping here for today. Next time installing the control rods for the empennage and steering, the latter once the nose wheel block arrives. Looks like another week before she will be flight ready.

In the meantime I await the RCGF 10cc.

Eflite Stearman Maiden

Beautiful day, virtually windless. Perfect time to take the Eflite Stearman up for her maiden flight. The takeoff and first flight was hairy. Despite being on CG she flew a tad tail heavy, her DR and Expo were off (too low), and it took some sick skills to get her back down.

Over a couple of flights I found her happy place, she rolls like a pig, buy otherwise handles predictably. I enjoyed the flights and flew three long 3S 2650 mAh packs.

RCGF 10cc Update: Try, try again.

UPDATE: Its running fine!  Read the UPDATE.

At my last posting on the RCGF 10cc engine with an update, I was having the ups and downs of our hobby, trying to get a new engine to run. If it wasn't for the exceptional one-on-one service from Joe Nelson at RCFG-USA, I would have abandoned this long ago. After this, Joe and I are going to be drinking buddies! I haven't had such personal attention from a dealer, someone who is more disappointed about this than I am.

So... this morning I ran out to RC Buyers Warehouse in Nashua (if they don't have it, you don't need it), and picked up a Hanger 9 Power Pro HD Starter. I McGyvered an EC5 connection to the alligators on the starter and ran it off a pair of 3S 2650 mAh Lipos in series (~24V).  I used this to try to start the RCGF 10cc (more on that in a moment). I didn't mean to run it in series,but I fogot I didn't have a parallel cable and used the series thinking it was a parallel cable...  Since it worked well, I decided to unsolder the gators and installed an EC5. This evening I made up a series connector and tested it at ~12V 5300 mAh. Runs fine.

Now about the engine. I used the starter this morning, and I could not get the engine to start. I ran some experiments that showed that the vacuum was sufficient to feed the pump and fuel was coming out of it just fine. It was filling the pump outlet line to the carb; fuel was getting to the carb. Was wasn't it starting? Check spark, all fine. I decided to remove the engine and check the carb. I tried blowing in the inlet with the throttle open, and I couldn't. Don't know if I should be able to with the needle valve not being metered. I took it apart and removed the needle valve, used Gumout to clean it. With the needle valve removed I could blow through it fine. I put it all together and tried running it again, still no joy.

Joe Nelson (RCGF-USA) and I chatted and he got some calls with issues like mine, and spoke to some skilled pilots, and he realized that those of us having problems weren't using starters. As we thought, hand starting didn't develop enough vacuum. With the starter it clearly moved the fuel. The other guy who used a starter once he was told to had his start the first time, his problem solved. I have no doubt I needed the starter, but is there something wrong with this motor? Why? Joe got it running before he sent it back.  I am out of ideas.

Well Joe has a new engine coming to me with a return label for this one. He's going to see if he can get it running. I've uninstalled the engine and ignition, cleaned it and packed it to return, waiting for the new one.

I hope there isn't something wrong with me and my setup. We'll know if I can't get this one running.

I am optimistic the engine will be fine. I am not optimistic that I can get it running...