I assume you want something a beginner could fly when you are done??? First thing I would look at is a flat bottom airfoil. For the rest of us that use standard measurement you indicated a wing with a 47.25 inch span and a 7.9 inch chord. Do you intend to incorporate dihedral in this wing? It would be more stable for a beginner if you did and it will be required if you do not install ailerons. I have a habit of using the TLAR (That Looks About Right) meathod and coming up with planes that fly. Assuming you base your design off of traditional high wing trainer type aircraft proportional to this wing and use light weight building materials such as balsa and/or foam, a [link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLM4010A]Efligt power 10[/link] brushless electric motor will fly it. Keep the [link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLB18003S]battery[/link] weight low and aim for 16oz/sqft of wing area or less. Your wing area is about 2.5 sqft so this gives you about 40 oz to build your plane with or 2.5 lbs(lighter would be better).

Remember that physics only explains why it flys and engineering is what makes it fly Take a traditional paper airplane and then make a copy of it with only one ply of paper (no folding over edges) and give em both a toss...

The point of that is to say take a look at some proven structural designs to ensure your students efforts don't fold up under the stresses of flight.