Stingray problems!
 

Hi Guys,

I flew for the first time on friday my Yellow Aircraft Stingray with Wren 44 Gold.

The flight was very uncomfortable with the model trying to severely pitch down continually throughout the flight, so much so that I ran out of 'up trim' on the transmitter. The model also lost a lot of height in turns and generally left me feeling with little confidence to ease back on the throttle. The control surfaces were absolutely neutral before the flight.

I bought the airframe second hand, unfortunately without the original instructions, so i was relying on the C of G point marked on the model. At this point the plane was slightly (but not overly) nose heavy. The guy who had the model before me used a Wren 54 and had found it necessary to put a huge RX battery in the nose to make the plane balance. With the smaller and lighter Wren 44, I had the opposite problem and have struggled to get my 2x 6v 2000 mah Nimh far back enough in the model.

My question is would the slightly nose heavy arrangement of the model cause such a severe problem in flight?

One other possible cause I thought could be a problem is the thrust line of the turbine. The model did not come with any sort of motor mount and therefore I made my own mount from aluminum. The motor is now mounted above the wing centre line and is probably not perfectly straight and inline. I wondered if this would make a significant difference to flight characteristics. I have attached some pictures.

any help and advice or even some Stingray instructions would be much appreciated.

Stephen

RE: Stingray problems!
 

I don't think the engine being slightly higher is going to make a huge difference if any. I have a kit and instructions at home and will check the CG tonight after work for you. Mine flew great and FAST!!! The plane will bleed off speed pretty good in turns, it is normal. Is there anymore info that you need?

Chris

RE: Stingray problems!
 

Hi chris,

Thanks for the quick response, the C of G position and reference to mounting the motor in the instructions would be very much appreciated.

Just out of curiosity, what motor did you have in yours, and whereabouts did you locate your RX battery?

thanks again

Stephen

RE: Stingray problems!
 

At neutral stick, you need quite a bit up "pitch up" trim on the elevons, probably 1/8 inch if memory serves.

If you took off with the elevons even with the trailing edge of the wing, that would explain the big pitch down "feel" you experienced.

EDIT your thrust line should be fine. CG is somewhat critical for good landing performance.

RE: Stingray problems!
 

Hi Matt,

Thanks for that, I will re set the elevons and have another go! Perfect weather here In the UK at the moment so will get out there this week.

Stephen

RE: Stingray problems!
 

Ahhhh yes, forgot about the elevons being high! The engine sits right on the rails using the following mount.

http://dreamworksrc.com/catalog/turb...all-p-298.html

Here is the build thread that i did on mine way back when! Should arm you with some good info. The turbine batterey was in the left wingroot area forward of the fuel tanks, the main battery was a 6C NiCad if I remember correctly was in the nose. My plane had a PST 600R installed.

http://www.rcuniverse.com/forum/m_58.../tm.htm#586665

Hope this helps you out!

RE: Stingray problems!
 

I crash my hotspot jet on its maiden flight due to neutral elevons (My fault) causing severe down pitch. The Jet call for 5 to 8 mm up elevons.

RE: Stingray problems!
 

My Stingray flew well with the ailerons in neutral. It sounds to me that he's dealing with a CG issue. I flew mine with a Wren 54 and ended up adding weight in the rear of the fuse to get it to fly perfect with no trim.
Steve

RE: Stingray problems!
 

Hi,

I didn't need to add any ballast anywhere with a P-60 installed. The trailing edges had quite a bit of up trim for neutral flight.

RE: Stingray problems!
 

Please inform final wheight of your Sting Ray.

I`m about to maiden mine in electric configuration and is 13 pounds with batteries installed.

Thanks

Juan

RE: Stingray problems!
 

I have a couple of delta with models and both need reflex TE to fly correctly, the Duckty needs a lot of reflex, I think that is your issue here.

Mike