Taken from another post around here. Special thanks to user adam_one for finding or drawing up these sketches.

What we have here is a good general proportion sketch for a basic model layout. The two sketches show an upper and side view. My own feelings are that the tail moment spec should be noted as 2 to 3 chord lengths but what is shown there is fine. If you go for the 6 chord wingspan option then I seriously recomend the 3x tail moment. It was also noted in the original thread that these proportions also hold true for a low wing model but that for a trainer or second model the dihedral should be increased to roughly 1.5x that shown. For a more sporty model the dihedral can be minimized but for a true low wing design some dihedral will make it track better, perhaps 2 or 3 degrees. Mid wing designs with true aerobatic aspirations won't need any dihedral at all.

Other comments off the top of my head are that for a symetrical or very low camber airfoil (AKA semi-symetrical) the lower end of the stabilizer size range is fine. For a flat bottomed, and especially a thicker flat bottomed, airfoil the stab should be kept up at the 20% point and combined with the longer 2.4x (or 3x) chord for better longitudinal stability.

Other than these little items the proportions in these two sketches look pretty durn good if you want a basic fly around model or even a trainer. If you start stretching things (like going to a higher aspect ratio then it all falls apart so don't stray too far from what you see here).

Be sure to post up your plans if you try a new design based on these. Cheers....

PS: The original pics and more explanation can be found at adam_one's website at http://sky.prohosting.com/air2/ . Check it out, he's got some great stuff there. Thanks adam_one!