Originally Posted by
Ka6crpe
Mr.Buzzy and Nitpicker330, you are both correct.
The glide distance remains the same because the glide ratio remains the same, as long as the speed is increased. If you keep the speed the same as for the lighter weight then the glide distance will decrease.
I wish I could post my glider's polar curve up here to demonstrate.
Yup.
Suffices to say that L/D is primarily a function of AoA. Weight itself is not a factor influencing the max L/D value. As Long as you keep Alpha at max L/D the Lift/Drag Ratio (=Glide Ratio) and thus the distance achieved from a given altitude will remain unchanged.
The only things which we ignore in this case are the Re- Number effect on L/D when the Speed changes due to different weight and as has been mentioned compressibility effects once >M0,8.
In reality these two factors can be ignored since the relatively small speed difference will have no appreciable effect on L/D and thus distance achieved.