thanks, I think I will write Mark Biggers an e-mail.
So far, after reading the class rules and all other info, I found the following :
(I'm write this up so you can check up wether I understood it right, please correct me if I'm wrong)
-1- Class rules say nothing about any dimension or specification of the boat. They do declare the F17 to be a One-design class and state :
A certain degree of latitude in the Class Rules permits
skippers to rig their boats to their personal liking for convenience in
sailing. However, the Class Rules do not permit any alterations that will
make a standard factory boat less competitive than other boats.
(P.s. Just as a side comment but does the quoted rule allow any and all modifications that will make the boat more competitive ? Sorry I couldn't resist !

)
In this respect teh F17 class differs from the I-17 class. However the class rules seem to rule on most aspects anyway. Example : like the maximum purchase allowed on the mainsheet or downhaul (8:1) and how many grommets may be put into the trampoline. The freedom to modify is then limited to the parts on which on rules exist. This includes most blocks and lines and you may alter how some control lines are run.
-2- within the Nacra F17 class you may use the original (long) I-17 daggerboards or cut them down (or have them cut down) to the following specs :
http://www.nacraclass.com/northamerica/dagger_mod.jpg-3- If you are heavier than 210 lbs (in swimsuit) then you may use a larger spinnaker. The two sizes are not specifief in the class rules. The leaflet specifies TBA for the big bouy spi and gives 167 sq. ft (=15.5 sq .mtr.) for the small boy spi size. (leaflet can be found at :
http://cathouse1.com/F17.htm ). The leaflet refers us to the class rules but these do not specify the big bouy spi size as I stated earlier.
-4- The leaflet (
http://cathouse1.com/F17.htm ) then specifies :
mast height = 30" 4' = 9.25 mtr.
mainsail area + mast = 170 sq.ft. = 15.8 sq. mtr.
Boat weight is not specified
I'm unable to find a similar leaflet for the orginal I-17 and the I-17R ; however Texel measured the I-17R with :
mainsail luff length = 8.53 mtr => suggesting a 9 mtr mast = 29" 4'
mainsail area + mast = 16.44 sq. mtr. = 177 sq. ft.
From this it appears that a sligtly taller mast is used on the F17 but with a slightly smaller mainsail area; lowered by 0.6 sq. mtr. = 6.5 sq.ft. That or the same rig is used on both boats. That or someone (maybe me) fouled up on the conversion or the measuring of the I-17R.
-5- private comments suggest that the hulls were not made significantly lighter with respect to the I-17R in order to allow the single forestay setup to be used when so desired. This loads up the bows more and thus taking material out is not wise. The single forestay setup has the advantage that it allows better gybing under spinnaker.
-6- The F17 class has a weight equalization system allowing the heavy sailors to carry a bigger spi and progressively forcing lighter sailors to carry corrector weights.
That is what I have been able to find on the net and on the
www.nacraclass.com website and the site of mark biggers and cathouse
http://cathouse1.com/Please correct me if I got something wrong.
Somebody asked me why I'm doing this. Well I often describe the F17 as being the same as an I-17R with a new and larger spinnaker design for heavy sailors and modified rudders/daggerboards. I want to make sure that my comments are (or remain) truthful.
Wouter