Take a foamboard length center section wing which is a rectangle when viewed from above. Now imageine another one half the length BUT instead of the trailing edge being straight so you have another rectangle, bring the trailing edge forward to about 75 percent, perhaps more. See what that looks like from the top? Leave the leading edge straight and when you go to cut the length of the folded over top piece, cut that at an angle to match the trailing edge. Leave the spar section the same thickness, we'll use that for a progressively thicker airfoil. Make two of these, remember one for each side, and decide if your wing will be flat OR if you want poly-hedrahl like the FT Old Fogey has. Put one of the wingtips up to a straight table edge so that it's even with the table, block the narrow tip up to 2 inches and then use the vertical side of the table to sand any overlapping wing vertical with the table. Now you can but the wingtip up to the center section of the wing and it will mate flat with 2 inches of elevation at the tip. Do this for both sides. You can follow the angle made by this and cut a thin plywood doubler to fit against the spars of both pieces to re-inforce the joint and hot glue all that mess together. Now you've got a wing thats flat in the center with wingtips that are 2 inches up. That will give you a bunch of stability and you can fly the glider with rudder, elevator and throttle. If you want to use ailerons, leave the wing flat all the way across OR just add about half an inch at the tips. This will give you less stability but will leave ailerons active. More dihedral less response to ailerons but more response to rudder.
Thats just the wing. Make a tail surface thats 15-20 percent area of the wing with 10 percent of that area elevator surface. Make a Rudder that 10 percent of wing area. Make a fuse to hold these pieces in their appropriate place along with a power assembly, radio, battery and servos and move the pieces around on it till it looks about right and the balance is correct, CG somewhere around the peak of the wing or slightly in front. Mount that stuff permanent with hopefully an area in the battery compartment to move that around with, make it fly.
The Palo Altos club has a website with calculators to figure out the correct proportions for all this stuff. Use mr google to find it and start reading. It'll take a while. One things for sure. If you put something together, go away for a couple days and next time you look at it you say 'Man, that don't look right' it probably isn't. Too many times I see motors about 2 feet away from a wing and tails 5 feet back to balance when a 6 inch nose and a 2 foot tail would do. Not that you couldn't fly one that way, but the farther away the parts are from the center of balance the more of a barbell effeect you will get. Think of holding a barbel with both hands close to the weights. Easy to control right? Now, put your hands together in the center of the bar and try moving the thing around. Wow do those weights have a mind of their own out there at the end of the bar. You don't want that.
Can I cofuse you any more? Want me to keep going?