Formula Windsurfing (or just plain "Formula" racing as it's done in PWA
and Euro/So. American Championships) is "unlimited" except by a few rules.
Max. Sail size is 12.5 m2.
Max. Board width is 100.5 cm.
Max. Fin span (soon to change I've heard) 70 cm.
Everything else is pretty much you can sail anything you can afford, so racing formula at high levels is expensive.
Formula Experience is a Juniors and Youth program that limits alot more things.
Just a few are:
The board must be from the "registered" FE list (reg. with ISAF) and the FE boards do not change each year. They usually have a 4 year
"static" life span where the same boards are used, There ae new boards each year, but they come from the same molds for 4 years.
Depending on your age, the max. sail sizes are 11.0 of over 16 years old, and 8.5 m2 for under 16 years old. (I may have the ages or sial sizes mixed up here, but there is a definite rule that the smaller younger kids are restricted to 8.5 m2)
No 100% carbon masts are allowed. There is an approved list of masts that are normally 75-90% carbon, making them less expensive (but heavier).
Only aluminum booms are allowed. No full carbon booms! Once again the idea is to make the cost of racing FE less expensive.
Here's the link to the FE Class rules:
So there you have it!
Formula is "unlimited" and costly!
Formula Experience limits sail sizes, boards, masts, booms, and I think maybe stock fins are required.
FE's main focus is to limit the cost and provide a "level playing field" as far as the equipment goes.
Hope this helps,