Kiran:

Theoretically your motor prop combination is fine for your model. For a 3D model you want less speed (read KV) and more torque (read thrust)

However, a certain minimum airspeed is always required to create lift. You may achieve this by using a 9*6 prop, but the reduced thrust will affect the 3D ability.

IMHO you are not achieving adequate airspeed (provided all other factors including incidence are correct)

If you have a tachometer, or can get access to one, you will get the story clear. You should be able to clock 14-15000 RPM at full throttle. Less means the motor does not have enough power to handle the 10*47 SF prop.

With the same motor you could also try a 9*47 SF prop. Although in theory it will give less thrust, the RPM drop under load (which I suspect is significant) will be less. Or, if you could do a trial with a more powerful motor it would be instructive.

For the 10*47 (which I feel is a good choice of prop) you would ideally be using a 1000 KV or thereabouts motor capable of 250 W. This will give you good 3D performance. A 2836-1100 KV from RCB or RCD will give you this.

Do check the incidence nonetheless. If you have an Android phone you could download the "Clinometer" app. Check the wing and motor thrust line w.r.t. the horizontal stab.

@kiran rc
From the pictures the chord looks like about 6", giving a wing area of about 180sqin, or 1.25sqft.
With AUW of 500g (17-18 oz), your model has:
Wing loading of over 14oz/sqft,
Wing cubic loading of over 12.
These are in 'Warbird' range. Ie, models which fly fast and have small control surfaces and small control throws
It seems to me that your model:
1. Is too heavy
2. Has inadequate power reserve for its high wing loading
3. Relative to 1 and 2 above, the control surfaces are grossly oversized

I saw that most Foamy Factory models of 30-33" span using 10" props of 3.8-4.7" pitch (ie, low and hence meant for slow flight) weigh under 200 gms!

(Did you use coro instead of depron and make a box fuselage instead of a profile one?)

Since it may not be possible to reduce the weight now, i suggest:
1. Check if your motor, Esc and battery can support full throttle on a 10x6 without overheating. Current draw may exceed 20 amps
2. Reduce throws on ailerons and elevator drastically to about 3mm each side.
3. Hand launch and be prepared to fly relatively fast, say above 60kmph (ie much faster than you would with a foamy 3D model)

The Rare Bear is 34" span, has 222 sqin wing area, has a symetrical aerofoil (not flat plate), weighs 490gms, has small control surfaces/ throws, uses a 10x6 on an Emax 2822 1200kv with a 1000mah 3s and flies more than twice as fast as my wife's 54" e-trainer. It's WL is 11.25 and WCL 9. Your model's WL is 14 and WCL 12.6. So it needs to fly even faster to remain airborne!

Best of luck. Have some fast flying fun and build another in depron for 3D.

Iyer sir, a 10*6 prop turning at 13,000 rpm will develop 2.06 Kg thrust, fly at 118 Kmph, and need 659 Watts of power.

From the pictures his model appears to be Depron

An 8 degree downthrust, or a 5 degree negative incidence will cause the exact effect he is observing

Kiran, is this model from a readymade kit or a scratch build?

I think originally it had an X-Frame fuse. And used a 110 W Himax motor. The AUW with a 3S 900 mah Lipo was 8.5 oz, or 241 grams.

Here's the build log:  http://www.rcgroups.com/forums/showthread.php?t=411019

The motor:  http://www.maxxprod.com/pdf/HC2808-xxxx.pdf

And yes, Iyer sir (aye aye sir)  ; the original WL was 4.9 oz/sq ft 

Thankyou Iyer and Sanjay sir

Quote from: sanjayrai55 on November 24, 2014, 06:14:46 PM
Kiran, is this model from a readymade kit or a scratch build?

Sir it is scratch built.