HI
i m tejas,
            i want to ask a query that is it compulsory that every model should glide freely
             without any electronics used in it ?
                                                                                               regards,

Hi Tejas

It is  not mandatory that every model should glide... However, the model is made to fly only with motive power by way of thrust, what happens if the motive power fails or gets depleted? ... The model just simply fall out of the sky.

Actually, most sort of profiles will glide if there is sufficient thrust to create lift from the profile. The higher the obstructive nature of the profile,its weight and its attitude (read angle of attack), the lower the lift and the higher the stall velocity. If the profile goes below the stall velocity, the profile will actually fall (stall) because the air around it cannot support it. Certain types of profile generate higher lift than others. If the profile goes below its stall velocity, the profile starts falling like a deadweight. As it falls, it gains velocity. At some point the velocity would have gained enough to overcome the stall speed and then it starts gliding. This is what is considered a 'stall'. At velocities close to its stall velocity, the model becomes highly uncontrollable. This is the one factor why it is better to have the model glide... that is in a RC model, its glideability becomes of paramount importance in very tricky situations.

Saju

Quote from: TEJASCOOL007 on August 11, 2009, 10:29:35 PM

HI
i m tejas,
            i want to ask a query that is it compulsory that every model should glide freely
             without any electronics used in it ?
                                                                                               regards,

For a beginner yes it should have a good glide without power so that you have time to react.
sai

Considering that Saju's explanation for a beginner might have been a bit heavy.
To put is simply, every fixed wing aircraft will glide at a certain speed (aka velocity). So if you have required speed you can glide or if you have height (altitude) you can convert that to speed for the aircaft to glide   

Going by newbe standards, there are few things that I would also look at
1) The CG of the aircraft. The model should be slightly nose heavy - tail heavy ones will not glide
2) The shape of the wings should be agreeable to glide - tear drop shape with a good aspect ratio are a better bet than bet.

Pankaj