Simple question? so I think!
Whats the diference between this two boats. Or is F18 the class and Inter 18 is a Nacra?
Hopefully I will be able to part of the F18 family, once a few funds come in. I already started doing my homework early and ahead of time. 
Inter 18 is a boat that conforms to the F18 Rules. Simple as that.
NACRA makes a F18 model also. The Inter 18 and NACRA F18 are both made by Performance Catamarans, but are different boats, different hull shapes. The Inter 18 was designed by Morelli and Melvin and produced by Performance. The NACRA F18 was designed and produced by Performance. Both boats were designed to fit within the Formula 18 Class. The Inter 18 design came first.
I think the Nacra F18 (second F18 in the line of Nacra Inter 18 and nacra F18) was designed by
Alan Comyn. But I could be mistaken here.
Wouter
Nacra's Inter 18 is out of production (I think). The carbon mast is no longer grandfathered in Formula 18 rules (I think). The Inter 18's carbon mast is taller than the Nacra F-18. The Inter 18's front beam is farther forward than the Nacra F-18. Should be a steal if you do not plan to race Formula 18.
Nacra F-18 is still in production and is designed to meet Formula 18 specs.
I have a similar question to the one at the top of the forum... what do you think the speed difference is between the Nacra F18 and the Inter 18, in terms of setting a handicap that would even out the performance difference? I ask because I am interested in getting a spinni boat of 18 feet, and think the Inters look like a good buy. However I realise there is a strong move to modern F18s - and I wonder if it is worth the extra money for the achieveable speed difference for an average club sailor, who is definately not a top flight F18 contender.
Thanks
Simon
No,
Such a sailor will not notice the speed difference. The difference is really small you must be sailing for the top 10 spots in a 100 boat fleet to notice it. For club races and fleets of 10-20 boats you'll end up 1st or 2nd anyway with sufficient skill. The difference is just that small. Besides most of it is due to age (old sails etc) anyway. That is something that even OD classes suffer from.
My advice and that truly does work best is to buy a relative cheap and well maintained F18 (probably an I-18) and sail/race it for a couple of season and ONLY when you skill has progressed to the level of a top sailors switch to one on the newer F18's. You'll get most fun out of ever single dollar and there is absolutely no point in spending more dollars then you have too, you really won't notice the difference. The difference between F18 and I-18 is magnified by some people. We could have the same argument about 4 year old tigers and new tigers even when they are the same design.
Work on you sailing skills first and on the make of your baot later.
Also take note that Carbon masts are not allowed on F18 boats ! I think a few of the I-18 were fitted with these.
Wouter
Thanks for the response Wouter. I didn't realise the difference was that narrow! Older boat and better sailing skills it is then!
Cheers
Simon