I have owned a Nacra 18 Sq., Nacra 5.5 Uni and currently own the Inter 17R. I have not sailed the Nacra 5.5 Sloop. If you look at the Portsmouth numbers, the Nacra 5.5 Sloop, Nacra 18 Sq. and Inter 17 R are all pretty similar, but they have different ways of getting there. The sloop gets it using a 2 man rig with a big jib and generating good speed upwind and downwind with the slot effect created by main and jib. The 18 Sq. gets its speed with a large mainsail and wide beam. Like all unirig boats, it is less exciting downwind, but goes upwind very well. The I-17R get it's speed from a modern rig and mainsail plus the spinnaker downwind. In my opinion, this is the most exciting and fun boat to sail. If your interest is in the I-17 without spinnaker, it is the slowest of the three. Another of the advantages to the Inter is the way it handles and steers. It has a near-nuetral helm and tacks extremely quickly. I loved the 18 Sq. for its wide beam and forgiving nature in going fast upwind. I loved the N 5.5 Uni for the great class racing here in Michigan and its ease of trailering, set-up and take-down. It is also a great upwind boat, although more challenging than the 18 Square. Best of all has been the single-handed I-17R with it's high aspect Technora mainsail and the spinnaker. This boat gets around the race course very quickly and changes the focus from being an upwind boat (which it is) to being a downwind boat because of the fun and excitement, although short-lived, going downwind. After sailing single-handed boats since the mid-eighties, I can't believe how quickly the downwind legs are over!<br><br>Les Gallagher
<br>Inter 17R USA 104
<br>"little yellow boat"