Hi,

Does anyone here have any experience with the Nitro Planes Christen Eagle biplane?? I have finished mine up and am getting ready for the test flight. I would like some back up info on c.g. and control throws, as well as any flight characteristics/info that anyone can share with me.

Thanks!!
AV8TOR

Put your finger in front of the back cabane support for the top wing. It should balance in that area.

Yup like he said.

Also when you maiden it, let it run a little long on the runway to pick up more speed than you may usually use.

It has a relatively short coupled tail and it is easy to over control it as it comes up, ending up with an adverse roll when you can least deal with it.

Good advice on the takeoff roll. I use 60-70% expo on the rudder on these short coupled bipes. That tames down take off rolls considerably.

Ok guys, thanks. Shouldn't be much tougher than my Fokker Triplane I don't imagine. I was just wondering if the factory specs on control throws and c.g. were in the ballpark. Without adding weight, mine balances at about 160-165 mm rearward of the top wing center section leading edge. That is a touch rearward of the 150 mm they spec, but well ahead of the cabane. Think it will be alright there? Without doing all the measuring and calculating, it looks to be well forward.....

Just don't want it "snap happy" on the first flight.

AV8TOR

Seams like that would be a bit tail heavy to me. Nose heavy is always safer on a maiden, as you well know.

Yeah. Don't risk it.


At the least, try throwing the battery in the cowl, tied down with wire-ties to get the C.G. as recommended.

Later you can work it back to where you have it now.


The throws are always conservative IMHO.

Ok, I'll move it forward a bit and have at it. Thanks for the input guys.

AV8TOR

Looking forward to a good report on your maiden.

Ok, here goes...

I moved the c.g. forward to where the instructions say, and put all the controls at the high end of the recommended movements. (Except for the rudder, which I set to move 20mm more than spec'd, but added 60% expo.) The bottom wing incidence came out as recommended, but the top wing was +1 degrees positive while -1 degree is recommended. I decided to leave it at that, because normally on a positive stagger bipe one would like the top wing a touch positive so that it stalls before the bottom wing and causes a natural nose down moment once stalled.

It is powered by a souped up Homelite 30cc engine that turns an APC 16 x 8 prop at well over 9000 rpms. Final weight was 14 lbs.

Anyway, I just got back from doing the test flights, and it went great. For me at least, it seems like a ***** cat. No problems on take off, and the only problem on landing was that with the conservative c.g. and elevator throw, you had to work at it a bit to get the nose up and slow down for a nice landing. With this engine, it takes off before you reach half throttle, will cruise around easily at 1/4 throttle, and really moves out and has great vertical at full throttle.

After the first flight, I increased the aileron and elevator throws by 20%, and will probably increase them more yet as I get used to the plane. I will also start moving the c.g. back a little at a time. It does seem to want to climb and needed several clicks of down trim. The climbing seems to be speed related and not power related so I will probably shim the top wing to get the desired -1 degree of incidence to cure this tendency, and leave the engne thrust line alone.

I think the only caution I would have to mention, is to be careful and do your first snaps at high altitude. The first one I did surprised me and it did two snaps before I could release the controls. You might try partial snap control movements until you get used to the plane.

So, in closing, I like the plane a lot. It is very attractive and flies quite well. Stick with the factory recommended settings for the test flight, and you will do fine.

Thanks,
AV8TOR

Good report! Sounds like you have things well in tow.