Ventucky,

Yep, original Nacra 20. I owned one for a time and have a Tybee 500 under my belt on the boat so am aware of the rear beam slap. It would be a good mod to our fleet to race the rear beam a few inches, but honestly it wasn't usually that bad if you kept one hull out of the water. In the race I'm talking about we were on the Chesapeake Bay in some of the nastiest sea state I've been in; the waves were spaced about 8-10' apart. This was driven by 3 kts of current plus wind driven through a fairly narrow channel (4-5 minutes to gybe across at 17kts of ground speed under jib+main). We had rear beam slap on the Infusion a few times as well even with the extra stern volume and raised rear beam. In that particular set of circumstances the extra 2' of hull length was noticeably faster. Usually this isn't a problem for the 20's as the bay is generally lighter air and flat which suits this design quite nicely.

Of the F18's I've sailed the Scorpion and Falcon are the least likely to have this issue. The Cirrus probably fits that category as well; all are relatively high volume designs and the Scorpion has hulls 4" taller than the Infusion PLUS an elevated rear beam. Very comfortable and fast in breeze.

My experience is generally speaking the Atlantic doesn't have a lot of what I call short chop, mostly rollers. There are places this isn't true-Jacksonville at the St. John's River inlet, Cape Fear, Hatteras, Hyannis, St. Barths, approximately 1400nm east of Newport, RI in a deep low with sustained 40 and gusts to 50. In these spots you have chop/breakers on top of rollers and it can get nasty.

I'm sure even the free range organic Pacific can deliver similar in some spots..

I'm going to agree with Sam here.... The kick from the rear beam slap worries me less than having a 2' shorter boat in chop. I've been in short steep waves on both platforms and I'd pick the I-20 over most F-18's all day. That said however, the I-20 design is long in the tooth and with F-18 development, isn't as fast comparatively as it used to be. For reference, SCHRS only rates the I-20 0.03 faster than the F-18. If given the choice, I'd probably pick the boats Sam mentioned as well as the Edge over the I-20 though; big full rounded bows instead of the wide flat deck.

Part of the reason the beam slap is bad on the I-20 is the trampoline. I've seen a couple of boats that had a "trap door" flap cut in the tramp to let water through when a wave hit.

Like I said, that was my only complaint on the boat... Other that that, it was a Cadillac ride if there ever was one...

Probably why the class did so well with Mission Bay in San Diego...

Yep the I20 is a hard boat to beat in predominantly light air venues. We've been sailing a mixed fleet of F18's/I20's and the real kicker is the heavier teams on the F18 (over 370lbs) are just generally not competitive with the 20's, which isn't fun after a while .

We actually use the SCHRS rating for the Nacra 20 One Design which is also incorrect (the correct value is 0.957, there is an error with the jib size in the SCHRS table). Anyway this computes to 2m41s an hour, which isn't trivial given that in many conditions a top F18 team can beat a top Nacra 20 team.

Anyway the N20 modified with a lifted rear beam and updated sail plan is still a real weapon. They are long in the tooth though and the F20c is a very nice replacement.

I suffered a really mysterious rear beam slap on a new-to-me I20 (my third). I couldn't believe I was struggling with the rear beam slapping the chop on a lake. I finally figured out I had left both drain plugs out when Karl went to retrieve our (now floating) sandwiches from the hull.

We need to get a sponsor or two or there's no way we're going to make it. Also, the $2,000 entry fee is too damn much.
As far as the Carbon 20 against the F18's go...both have their conditions that they like best but the Carbon 20 is simply a monster that loves everything. We've found when the F18's are tight spin reaching (where the N20 could never hang), we still had faster speed with main and jib. A huge part of that is being that we are semi foiling and can carry the apparent wind longer when we drive off. Heavier on the tiller but it handles the big stuff better than the N20 did (just my opinion after 14 GT300's and 2 Tybee 500's). The beam on it is so high off the water, I think we only slapped it less than 5 times already. And it takes a LOT to do it. The achillies heel has been rudder arms and spin poles. The carbon spin pole should fix that. We were doing 26 knots jib reaching and punched the back of a wave due to my poor driving and the pole collapsed like an empty beer can with a horse stepping on it. With that, we had to lower the jib and stow it on the trampoline with the spinnaker and run uni rigged for the next 50 miles. It dropped our speed back to 17 knots.

I raced in and finished 4 Worrell 1000 s and ground crewed for one. My extremely low budget average cost, trying to make chicken salad from chicken ****, was about $7,000 not counting boat parts. There was a Sports Illustrated article that contrasted our scrape it together team with a/the top sponsor team. I usually picked up a new suit of sails each race as well so that would bump it to $10k. This was 1999-2002. 1998 I ground crewed out of an RV with 5 of us staying in it and it SUCKED, the only good thing about it was John McLaughlin, who I endured it for. The other racer was one of the biggest **** of miseries to ever draw a breath and you would not want to be trapped in an RV with him.
Parts costs will vary greatly on the intenseness of the weather and the weak points of the boats, and don't kid yourself there WILL be weak points, likely lots of them for untested platforms. Complete rudder systems w/ spare castings, spare spin pole, and the various blocks, shackles, and screws are a must.
My advice, don't scrimp unless that is the only way to do the race for you. The more prepared you are (think more $$$ you spend) the more enjoyment you will get out of the race.

Todd Hart
Team Cat Fever