Hi all,
  I have built a powerful hexacopter with tarot 680 frame coupled with Avionic 880Kv motors (http://www.rcbazaar.com/product.aspx?productid=4744). Now, I need suggestion in choosing a propeller which best suits my need. Consider that my only requirement is high payload lifting(2.5 Kg), should I buy slowfly or DD or Electric propellers?. As per the datasheet from the manufacturer, I decided to buy 11 X 4.7 props, but my frame can accommodate up to 13X4.5 props. Of course, I will get high payload capacity with large propellers, but the motor manufacturer didn't recommend it.To summarize these,
1.) which one is preferable for high payload lifting---- Slowfly, DD or Electric propellers?
2.) Is it okay to use large propellers that it is recommended by the motor manufacturer?

Thanks in advance.

It is better to use slow fly props because they are efficient compared to others as they are efficient compared to others. Electric props are meant to be used with high speed motors and they have less thrust compared to slowfly at same speed.

1: Slowfly works best on lower kv motors. However, speed can be decided by the pitch of the propeller. Speed is directly proportional to pitch.
2: 12inch slowly(either 12x3.8 or 12x6) would be perfect. 13 inch would also work but the motor can turn warm.

Thank you, Balakrishna Reddy and Kiran for your valuable suggestions. I decided to go with slowfly-12" propellers. I hope it will lift at least 2Kg payload.

To answer number 1, what is your battery size. If its a 3S i would prefer slowfly propellers, if its a 4S or higher i would recomed electric propellers all the way.

to answer number 2, I would not recommend going above the motor manufacturer ratings as it could cause your motors to overheat and end-up destroying the magnets or burn the coils (incase of this motor the data provided is incomplete).

As RCB hasn't provided a max wattage for this motor, suggesting a bigger prop is not an easy task.

to be on the safe side, this motor looks like atleast a 500W motor.

according to my calculation 13x3 propeller (assuming a 3S setup) would be pushing the limits.
all the best  

@ajith_kumar,
Hi,
What's the AUW?
I.e, airframe with battery plus 2.5kg payload?
Regards

What is the flight time you are expecting?The total weight, including the payload would be around 5 kg. Estimated thrust of 6 motors will be around 9kg. This would lift off the multirotor but this calculation is for 100% throttle.

Thank you sidd, K K Iyer, Kiran for your replies.
@sidd1994: Yes, I planned to use 12" props instead 13"
@K K Iyer: Definitely, AUW would be around 4-4.5 Kg.
@Kiran: I actually don't expect more flight time. 5mins is enough.

I will be using this UAV for testing indoor navigation algorithm. So, I am not expecting it to have high flight time like commercial drones. This is a prototype.I have to mount some heavy-weight sensors and actuators. So, I couldn't compromise on weight.