What I did was use my tiller's hiller-furrower attachment to form raised beds. If you don't have access to one, then the form seems like a good plan.

But, why not construct the form from (2)-14' + (2)-4' 2x8s instead of plywood? Unless you laminate several layers together, the sides will bow-out from the weight of the soil and plywood only comes in 8 ft lengths.

Either way you might think about adding a brace in the middle, just a board nailed over the top to keep those 14 ft sides from spreading. Good luck.

g'day mailman,

check our hay bale presentation out with pic's on our site, the bales become part of the bed as weed barrier and no formal sides needed ever.

len

Here is a link that might be useful: lens garden page

I don't have sides on mine and they are really nice. Also, if you want to till something in a bit or mow/chop, you can easily.

Mine are about 6 or 7 inches higher.

Got any pics Wayne?

You can use green .5" x 1" meshed plastic screen(from HD) as permanent retaines. You have to cut it though. It come 40" wide. All you have to do is to drive a stick every 2ft or so (from outside). Burry the plastic just couple of inches first, drive sticks, fill. You can spary paint the sticks green to blend in.Let some weeds grow on the retainer wall to firm it.