Chaps,
Belle is absolutely spot on. An aircraft's L/D ratio (i.e. glide angle) is not affected by weight. However, for a given aerodynamic configuration, as the aircraft weight increases the speed at which the best L/D is achieved also increases.
This is precisely why we glider pilots carry hundreds of pounds of water ballast in our high-performance sailplanes on good cross-country soaring days. We are able to fly at higher inter-thermal speeds more efficiently.