If you want to make really strong light boards it's not too hard to make them out of uni carbon and foam.
I've made wooden blades before. You can make them from ply but ply does not like the rolling stresses experienced so you need to make sure the outer layers of glass take the load.
I've found making from foam and carbon much easier and if made the way I did, gives a very true board.
I personally consider the carbon boards a much better investment of my time than making from timber.
I have photos on my web site that show how it is done.
I used a vacuum pump however you may be able to get away without one. It cost me around $75 Aus per board and they are very very light and incredibley strong.
Regards,
Phill