Gliders come in all sizes from tiny to really large... so you won't find general info like you are asking since that info varies depending on which specific ones you look at and each one will vary considerably.
Here is a link to Esprit model. Esprit Tech/Model 1.321.729.4287 - Powered by Network Solutions. This page has listings for sail plane power systems by wing span. You don`t necessarily have to buy from them, but their listings might give you enough information to get you pointed in the direction you want to go.
If this is no help to you, let us know, and we`ll try another avenue.