Estimating Boat Performance

Barry,

I like the way you're going about your search -- gathering data, comparing values etc. I also agree that the PHRF numbers are useful for getting an idea of the speed potential of various boat designs.

But I also feel it's possible to put too much emphasis on those PHRF figures. You already know that they assume certain factors that may or may not be present on any given boat -- folding/feathering prop, max allowable-sized genoa (plus a full complement of other headsails), very rarely equipped with roller furling, max allowable spin pole, etc. Other factors that affect ratings are how competitive the fleet is. In competitive fleets racers are more likely to renew sails annually, purchasing racing cut sails from more expensive materials, fair the boat's bottom with racing paint, keep it scrubbed, race with seasoned crew, etc.

Another factor is that the boats that are being used for racing are generally never loaded like a boat used for family cruising. In fact, they are frequently stripped of every non-essential piece of gear that adds weight.

So while some of the figures you see for certain boats may appear attractive, those figures in no way reflect the real world effect on performance of sailing those boats with a short-handed crew, using a single roller-reefing headsail, an asymmetric cruising chute, a ten year old full batten dacron mainsail, loaded up with provisions and family cruising gear, sitting two inches lower on the waterline, towing a dinghy, etc.

How will you be using your new boat?

Barry, you are on the right track. Really work those numbers. Out here in SF/NorCal, the base (without any adjustments) PHRF calculations pretty closely follows the regression analysis that was discussed in another thread. So these numbers might level the playing field when comparing boats. Base PHRF for the 361 is 138 and Base for the 36.7 is 120/123 depending on regular or shoal keel. The 36.7 hands down is a better performing boat. If I was looking for a number or ratio that would indicate how closely a boat sails to their rating, I'd look at total displacement and the ballast to displacement ratio for a given LOA. Beautiful, wooden interiors are not conducive to sailing fast.

I have a fair amount of experience in sailing the 361 and was able to closely observe the 36.7's as they started immediately after us in the Rolex Big Boat Series this year. The 361 is a pretty boat and a comfortable cruiser. The forward stateroom is a little cramped for my 6'1" frame but is very doable for two couples on long weekends. The main salon is very comfortable and nice. Sailing characteristics are a bit pedestrian for my tastes. I don't like the Lewmar traveler and the boat's freeboard is a little high (but man, what an interior!). My lowly C34 is faster on all points of sail (yes, I've raced both), but you could improve the 361 by getting decent sails, upgrading lines and junking the Lewmar blocks. The 36.7 impressed me in the BBS. They were pretty fast and lively and looked like a lot of fun to sail. When the wind piped up to 20+ kts, they did get blown around a bit and I saw them get over powered and even a round up or two. This might be a function of the fractional rig and as these guys were racing, they were loathe to reef. If your average winds are in the mid teen, I'd say this would be a fun boat to have either single, double handed or with a full crew.

Sorry, I could not find any NorCal PHRF data on your Oday 35. Our local PHRF gives only 6 seconds for a 3 blade fixed prop. When I was Chief Measurer for the C34 Class Association, I did a lot of analysis on props and prop drag and our big 3 bladed props were more like 20 seconds a mile slower. The biggest performance improvement you can make is going to a 2 blade folder, followed by new sails, new (high tech) lines followed by a faired bottom. Remember, speed costs money. How fast can you afford to go?

Outside of securing the polars for every boat you'd like to consider, PHRF numbers are about the simplest way to go to compare the performance (speedwise) of various boats. They don't tell you how easy the boat is to sail to its rating. People above suggest you need full sail inventory, full crew, to sail to a rating, and that may be more or less the case, depending upon the boat. Frequently a wide racer is designed that way to put the full crew outboard to hold the boat flat in a breeze. If you're sailing short-handed on some boats you may therefore never be able to sail to your rating because you can't hold the boat flat. A narrow boat will be less likely to be affected the same way. The PHRF number doesn't tell you that. It also doesn't tell you how big the cockpit is, or how comfortably she sails in different conditions - all it does is tell you how fast she is compared to others. So, while it's a good number to bear in mind, it's not the only criterion. If you're looking for something quick, perhaps something like a J/35 or J/36 would fit the bill.