Small beachcat design

[nacrajon]

Boat | NACRA 4.5 | NACRA 5 | NACRA F17
Length | 4.50 | 5.0m | 5.2
Width | 2.44m | 2.44m | 2.44
Weight | 120kg | 130kg | 156 kg
Sail area | 17.5m^2 | 19m^2 | 15.25m^2
Spinnaker | Option | No | 17/19m^2
People | 1-2 | 2 | 1
Design | Skeg | Skeg | Dagger
VYC Yardstick| 88 (no spin) | 81 | 72.5

What's the primary reason the F17 is 15.5 minutes faster around the buoys than a 4.5 in 100 minute race?

1. Waterline length
2. Only 15% heavier with both having one crew, but spinnaker makes up for it
3. Much faster to tack due to daggerboards
4. Dagger boards allow it to point higher
5. Higher aspect ratio sail
6. F17 has experienced sailors, 4.5 a beginners boat

[robherc]

I think #1 has a LOT to do with it (though maybe not a 25% boost!), and the longer waterline will help make up for a lot of weight difference with VERY minimal losses.
I'm guessing that 3, 5, and expecially 6 prob. had a lot to do with it too though

[Fanie]

Longer boats are faster than shorter ones.

[cleblanc]

Originally Posted by nacrajon

What's the primary reason the F17 is 15.5 minutes faster around the buoys than a 4.5 in 100 minute race?

1. Waterline length
2. Only 15% heavier with both having one crew, but spinnaker makes up for it
3. Much faster to tack due to daggerboards
4. Dagger boards allow it to point higher
5. Higher aspect ratio sail
6. F17 has experienced sailors, 4.5 a beginners boat

In this specific case, the waterline length has little impact on the speed around the course.

The main reason that the F-17 is faster around the race course is that it is design to be fast on the upwind legs and on the downwind legs, the Nacra 4.5 and 5 are design as recreational boats.

The high aspect ratio sails and daggerboards explain the improved upwind performance

Hull design and Spinnaker explain the downwind performance.

So points 5, 4 and 2

On a beam reach the Nacra 5 would probably have a similar speed.

You can look at the Texel rating page for some information on how the parameter are included into the handicap calculation

http://www.watersportverbond.nl/content.asp?me_id=468

The Portsmouth rating allows some modifiers

http://www.ussailing.org/portsmouth/...ications08.asp