I am trying to build an electric aircraft which will have the maximum flight times..

I will be having a maximum payload of 400 gms excluding battery ..

Please guide me for selecting a model which will be robust at winds and can fly at higher altitudes..
I am currently flying a balsa plane of wingspan 96", which is a pusher model and sadly it gives a flight-time of only 20mins with a 4s 5000mah battery..
But it is quite robust at heavy wind conditions..

The website marcus UAV is using the model Zephyr which is a flying wing..
http://www.marcusuav.com/zephyrairframe.htm

Is it that a flying wing is much more efficient that any other models..??




Please suggest me a DIY model which will give me the maximum flight times and can fly at high altitudes and heavy wind conditions..

I am also trying to make an efficient aircraft to train on as the flying field is far from my home and I do not posses the means to charge my batteries at the field. You can take a look at the "nova" featured in "mygeekshow". It is also a pusher but is made from foam, so is very light and durable.

if u have time.. buy profili n dev fuse n design it.. very easy to use n awesome software..
for efficiency of airframe.. there are alot of param.
if u r using HobbyKing batteries.  n motor n esc..  20mins is good

if u want effeciency.. n ready to pay for it then. go for axi motors,  castle creation or jeti spin esc, yuntang or thunderpower or flightpower or hyperion batteries... u will see the incredable difference.. 

secondly choice of airframe has to be perfect.. key feature u have to look for are..

aspect ratio.. sometimes a plane might look smaller compared to other but has a better aspect ratio.. this usually happens with cresent n elleptical plan form wings..  if u can get shumman's planform or van dam planform  airplane. .u have hit the bullzie..  reaper  is an example of van dam planform.. with aspect ratio of 14.. !!!!

wingloading -u cant expect a a brick giving u effeciency..  choose ur electronics wisely.. sometimes a 3000mah may give better performance than 5000mah.. u see the weight difference all most 250grams..

trade secret- for effeciency keep ur throws. on the frame low.. especially pitching...

avoid using high kv motors.. they draw alot of current..
..

@ shadman_alam
+1