Nacra17 rating for upcoming regatta

Slip to Ship in Ocean Springs

I've done some searching here and on out on the interweb. Is there any consensus on a D-PN we could use? I know this question is ridiculous given the methodology for determining D-PN but we still have a regatta next weekend with C foil N17. What do you recommend?
I would like to use SCHRS but I'm not sure there is enough willingness/understanding. I suspect we are heading that direction maybe this is a good reason to switch.

anyway, I still need an idea of what to use this weekend.

jopo

SCHRS publishes a conversion to RYA Portsmouth: https://www.schrs.com/pylookalike.php

Basically their published value for a Nacra 17 C-board is 67.2. For an F18, its 67.8.

Hence the delta is 0.6. Going over to US DPN, (table here: https://www.ussailing.org/wp-content/uploads/2018/01/2017-Portsmouth-Precalculated-Classes.pdf), the F18 is 62.4. Subtracting 0.6 from this gets your Nacra 17 C-board boat a number of 61.8. That seems reasonable. The other approach is to use the SCHRS number more directly, i.e the Nacra 17 C-board is rated at 0.991; the F18 is 1. So 0.991*62.4 = 61.8.

That is probably the most reasonably accurate number you are going to get, and it does make a bit of logical sense. The Nacra 17 C-board boat is effectively a Nacra F18 Infusion with C-boards, carbon rig and ~70 lbs less weight (146.6 kg vs. the 180kg F18). That would mean more if they didn't cut the sail area down some. All in all a good boat with t-foil winglets but not a ton faster than a stock F18.

I can get behind that logic. 61.8 sounds like a good place to start. I appreciate the input. cheers

you guys should try using SCHRS - portsmouth isn't really maintained anymore, and without the volunteers that used to collect data and refine ratings, i think they've gotten pretty out-of-whack. look to Mission Bay YC as a good example of the less-trouble-than-expected transition; the Nacra 20 guys felt like they just couldn't get a fair shake when racing F18s, so they moved to SCHRS. happy faces at the bar again.

had dinner with terry here in CA last week - she made me awfully nostalgic for those OSYC people. hope it goes smoothly.

If not now... when?

One of the major values of a rating SYSTEM is to generate a full table of ratings. Within the system, the ratings to all classes in the fleet is fair. You can fool around with temporary patches... N17s into PN... but... the fairness factor is just a maybe...The integrity of the PN process is out the window.

So, what is your fleets expectations for the future?

I'm totally on board with the transition. I'll try to get that oyster through the keyhole this weekend. wish me luck

CRAM moved to SCHRS this year. One regatta under our belt. So far no complaints, although our open fleets are fairly small these days.