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-   -   Will the real PHRF please stand up (https://www.sailnet.com/forums/boat-review-purchase-forum/329098-will-real-phrf-please-stand-up.html)

Jeff_H 04-09-2019 01:51 PM

Re: Will the real PHRF please stand up
 
Quote:

Originally Posted by Hudsonian (Post 2051594836)
I crewed aboard a sister ship and raced against her. Based upon those observations, it seemed that the boat could not sail to her ratings when equipped with a symetrical spinnaker but was very competitve when sailing with with an asym.

The owner races out of the Hudson but cruises for several weeks each season on LIS, Narraganset Bay and Block Island Sound. He reports very satisfactory performance when cruising with the asym

That is interesting. I would never have expected that. Normally, the C&C 34+ would seem like a poor candidate for an assym chute. Assyms usually work best on light weight fractional rigged that can have big speed gains by sailing hotter reaching angles. Those are usually boats with an L/D around 150 or less.

The C&C 34+ wk is up in the 180's range and masthead rigged. Normally masthead rigs have larger sym chutes than fracs and once a boat is much over L/D=180, it is less likely to achieve semi-displacement mode. The net result is that a boat like this can get its best VMG at a deeper angle than a lighter frac and so does not have achieve big gains (or any gains) from an assym since the speed increase is too small to offset having to sail the hotter angles.

Jeff

BarryL 04-09-2019 05:15 PM

Re: Will the real PHRF please stand up
 
Hi Jeff,

The main boat I race on is a 1988 C+C 35 mark 3. We raced for years with sym chutes, poles, guys, uphauls, downhauls, the works.

Two years ago the owner converted to asym chutes. He installed a removeable bowsprit (selden) and bought two new spinnakers - a VERY large one primarily for reaching and a smaller one for running.

For DISTANCE races the performance of the boat was really improved by the asym chutes. For windward / leewards races the performance is better, but less so. Setting, gybing and dousing are much easier. For distance races the reaching chute is super effective. The ease of sailing with asym has improved overall performance for windward leeward racing although I think that pure downwind speed probably was higher with the sym chute and spin pole. Our weekday races are fairly short and put more a premium on sail handling than on overall boat speed. IE when the downwind leg is only a mile or two you can't afford to make any mistakes in the set, gybe or douse. With the sym chutes we rarely got all those perfect. With the Asym we rarely make mistakes.

Barry


Quote:

Originally Posted by Jeff_H (Post 2051594860)
That is interesting. I would never have expected that. Normally, the C&C 34+ would seem like a poor candidate for an assym chute. Assyms usually work best on light weight fractional rigged that can have big speed gains by sailing hotter reaching angles. Those are usually boats with an L/D around 150 or less.

The C&C 34+ wk is up in the 180's range and masthead rigged. Normally masthead rigs have larger sym chutes than fracs and once a boat is much over L/D=180, it is less likely to achieve semi-displacement mode. The net result is that a boat like this can get its best VMG at a deeper angle than a lighter frac and so does not have achieve big gains (or any gains) from an assym since the speed increase is too small to offset having to sail the hotter angles.

Jeff


SchockT 04-10-2019 03:56 PM

Re: Will the real PHRF please stand up
 
I certainly looked at PHRF ratings when choosing my last 2 boats, but they are just one of many data points to consider.

Before we bought Azura, we looked at lots of other boats, and I did scratch a few off the list because I knew they would be too slow for my liking, and their phrf number confirmed what I already suspected from looking at their sail plan, displacement, hull form etc. Others, on the faster end of the phrf spectrum we found lacking in interior amenities and storage space. Also, I knew that for a relatively heavy boat to rate down in the phrf 60 range it would have to have a very powerful sail plan, which is great when you have a crew of apes on the rail, but not so great when it's just the wife and I out cruising.

One thing that must be kept in mind about PHRF ratings is that they are much more accurate on models that are popular for racing. On those boats the rating evolves over the years as the true performance of the boat becomes known. If a particular boat design dominates on the race course the rating gets appealed, and adjusted to more accurately reflect the design's performance. On the other hand, a base rating calculated on a boat that seldom gets raced, that rating IS purely a number generated by a formula. Of course many of those boats are on the slower end of the spectrum to begin with which is precisely why nobody races them, but rating inaccuracy can also afflict limited production or custom made boats. The more rare the boat is the less likely it will have an accurate rating.

Regarding Asymetric sails on displacement boats for racing, it is true that they don't give the same benefit they do on planing sport boats that can push their apparent wind forward with raw speed. On the other hand, the simplicity gained from an asym setup should not be under estimated. Certainly they will be at a disadvantage if you are trying to sail deep against symetric boats, but you just need to play the angles better. These days asymetric designs have improved so that you can sail much deeper than you used to. On my old Santana, which was a classic IOR "broach coach", running deep was not very enjoyable, and required a skilled hand on the helm and good crew in order to tame the dreaded "death roll". Reaching, on the other hand, was one of the boat's strong points, so the asym allowed me to take advantage of that strength.

Sent from my SM-G960W using Tapatalk


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