Sure Johnnie:
this tip I picked up from David O'Brian one of our International USA team members, He's really heavy into RC/RG and boost gliders.
this method is mostly used for glider wing airfoils with or without under camber, but can also be used for symmetric airfoiled fins with some care and "practice" ..
My plate glass slab is 12 x 24 inches and 1/2" thick. Place the slab on a table top with something under it like thin corrugated cardboard or the like.. I use a 1/8" polypropylene mat the same size as the glass from tandy leather supply. Funny how all our hobbies lead back to Rocketry
This mat or cardboard helps keep the glass from moving around while your sanding. Apply a strip of 1" wide double faced masking tape on the forward top surface of the glass even with the edge and longer than the part to be shaped. I usually run my hand and or fingers over the upper surface of the tape to reduce the amount of tac. Remember the thighter the adhesive on the tape hold the wood the more difficult it will be to remove after the part is sanded. Lay the shaped fin or wing slab of wood on the tape making sure the leading edge is even with the edge of the glass. Press it down on the tape to insure it doesn't move while you are sanding. After marking the high point "Center ridge - bout 1/3 of the width" use a sanding block with 120grit or heavier sandpaper and two hands to remove the excess wood to the line, rounding the forward "leading" edge as you go.. Carefully with a putty knife or very thin spatcula pop the wing or fin off the tape, reposition with the tailing edge of the wing even with the edge of the glass, press the wing onto the tape then feather sand the trailing edge of the wing from the high ridge to nearly a knife point at the tailing edge. To keep the wing or fin as even as possible use a long sanding block, I personally use 11" long 1" square blocks or 15" alum. T sanding blocks i'm sure you've seen in the hobby shops. If making a fin, flip the fin over and repeat on the other side.
Once happy with the taper, finish sand the entire wing or fin with 320 and/or 600 grit, pop it off the tape and start the next piece. I usually get 2 wings or fins complete before the d/f tape must be replaced.
What purpose does the glass serve? First; because it is dead flat you are assured the part will not be bowed or warped as you are
attempting to sand the shape. Second; the glass edge resists the sandpaper so it can be used as a tool rest to help insure you are making even passes. That is a point I almost forgot.. make long single direction passes over the entire length of the wing or fin NOT BACK AND FORTH. with as even down pressure as you can. inspect the shape often from both ends.
Please note, you will ruin the first two or three parts you try to airfoil, and/or snap one or two off removing them from the D/F tape.. this is a finess operation. I've been very happy with the results, Hope you will also.