I am going to try and build a Red Oak Board Bow. My question is what do I use to finish it. Polyurethane? Fiberglass Resin without the mesh?
Do I need to back the bow with anything?

There are many finishes you can use and one of them is poly. I prefer Tru-Oil, a gun stock finish.
  It will depend of the board you get as to whether you will need to back it.  If the grain is good on the back and sides(few if any runoffs)then a backing is not necessary. Find the best board you can. We can help you decide if a backing is necessary.

wipe on any Poly with a paper towel two or three coats and it will look like a piece of furniture.  I like to use "AGED OAK " gel stain first on red oak it puts a dark brown in the pores and look great I think. ;-)

Thanks guys Im sure I will be back with alot more questions.

2 words..... Tru-Oil

I hav'nt built broad bows for a long time but when I did I always backed them.
  My finish is fairly simple I stain the color I want.Then I use wax with a hair dryed.The wax melts right into the wood pour's or cells.Wipe off excess,do this 1 OR 2 times a year or when needed.
 This gets rid of your hunting scratchs and makes your bow look new each time you use the hair dryed on it.And you can't get anymore water sealed than this.

I think all board bows should be backed.last year I sealed a bow for soneone with super glue.I never used it to bach a bow but seams to me.It would be a good backing for board bows.
 Has anyone out there done this.PM me and let me know.Plus leave BROKER ARROW a message.
 A broken arrow my indain name given is CROOKET ARROW.Another story why my user name is ROY STEELE my real name.