The Offshore Voyaging Reference Site

Q&A—Sailboat Performance, When The Numbers Fail


I’ve compared a Valiant 40 to an Island Packet 40 using Tom Dove’s Sail Calculator and it appears to me that the IP 40 beats the Valiant in almost all categories. And yet the IP is slower based on its PHRF rating. And of course the IPs also have a reputation for being slow. Wonder what’s going on here? Does the additional wetted area of the IP’s keel make the difference?


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Ken Ferrari

We cruised alongside an IP40 for several months in the Caribbean. We were in our Morgan 382. We generally outperformed the IP everyday, but… going to weather? They might as well have not even tried – we skunked ’em every time. I understand that this doesn’t really have a whole lot to do with this article, but it’s a fun memory nonetheless. 🙂

Dick Stevenson

Hi John and all,
A very interesting comparison. I have always thought Valliants sailed “above their numbers” and that Bob Perry had nailed some sweet spots. But I am clearly not an uninterested party.
Since there is a frequent confusion that often comes my way, I will clarify that a Valiant 42 (which I have sailed for 20+ years), while having the same (or very similar hull) as the Valiant 40, has a taller rig with more sail area, an upgraded underbody with a newly designed keel, and a 2-foot anchor handling platform (hence the “42”) allowing the jib to be farther forward. These were among numerous cosmetic changes.
Both are great boats that have many miles under their keel. (And may hold the record for circum-navigations among production [semi-custom] boats).
My best, Dick Stevenson, s/v Alchemy

Gregory Beron

I’d like to make a couple of points that will clear up this “mystery“.

1. Carl’s Sail Calculator, hosted at the Tom Dove website is a wonderful tool, BUT It’s subject to the same problem any calculation tool is vulnerable to: Garbage In = Garbage Out. In this case the source of garbage is that users supply the data on various boats. I have submitted quite a few myself, mainly because I was unable to find an existing entry with anything like correct numbers. I can remember looking at three different entries for the same production sailboat, with numbers that were all over the place. Some are so far off that you couldn’t even blame fat finger data entry, somebody just had to make some numbers up! You simply cannot rely on the data for any given boat without vetting it thoroughly yourself. There are lots of sources for doing that: Sailboat Data, scans of owners manuals and, sometimes, a factory website… Which brings us to my second point: the curious case of Island Packet.

2. Both the Valiant 40 and the IP 40 are cutters, and have similar sail areas. Wait, what did he say??? The graphs above show the IP 40 with a much greater sail area and a much better SA/D ratio! Yes, they do. And the numbers for the IP 40, seem to be drawn directly from information provided by Island Packet. But there’s one very big problem. The conventional, accepted way to measure sail area is to measure 100% of the fore trangle,. Stay sails on cutters are NOT counted. This makes a huge difference when comparing a boat designed by Bob Perry, who is very scrupulous about using accepted values, and a company that, let’s say, likes to provide numbers that present their products in the most favorable light. Plug in the accepted measurements for the IP 40 and you get a SA of 774 sq. ft., just about the same as the numbers given for the Valiant 40. This results in a ripple effect of other values and, when coupled with the reasons given above as to why the Valiant 40 should be faster, you quickly see why the V40 will be faster on almost every point of sail.

Dave Warnock

I guess this comes from Sailing Atticus given their recent videos.
I’ve had a quick look for our Rival 38 to see how it might compare (with a reputation for being slow in light airs).
PHRF 141 which is right in the range of values for a Valient 40.

Sadly the RYA system called NHC which replaced the Portsmouth Yardstick for cruisers doesn’t have the IP or Valient in its base list (which is now 6 years old so not sure if it is being maintained)

I guess there might be some with an IRC rating but from here it looks like we can’t get a comparison without knowing the name of an IP40 or Rival with a rating.

Plus ours is the ketch version of the R38 (possibly the only one still rigged as a ketch) so everything is going to be different.

John Cobb

Thanks for the explanation.

Dave Warnock

Another thing I was thinking about for the older boats is that there will be a very variable take up of different technologies, particularly in terms of sails.
So how many boats have retrofitted in-mast furling without battens? How many have invested in asymmetric downwind sails, in code zero upwind?
I would imagine that there will be a much wider spread among these older classes now then there would have been when they were built.

Edward White

I used to race my Cal 35-2 (modified fin 5’) and in my fleet there were 3 J 30’s. They always, always ate my lunch. HOWEVER, the last time I raced with them the wind was blowing 15-20 minimum. We were going upwind against some current/tide and 2-2.5’ waves. I did not reef and they could not stay with me. If you could’ve seen the look of WTF? in their faces, it was, to me, a very satisfying afternoon. I built up a large enough lead that they couldn’t catch me downwind ( broad reach, where my boat excels) and I took 1st place….I stopped competitive racing on my boat that afternoon, on top. Yea haaaaa.

Marc Dacey

Sailing a stumpy-masted, cutter-rigged steel motorsailer, I can relate. I was able to get 3.3 knots SOG in 8 knots of apparent wind sailing through a race course off Toronto on the most favourable point of sail for me, and the gap in the fleet was enough to make it through without affecting the race. I got unusual pleasure from seeing the racers looking at the boat, and then looking at the stern for the telltale sign of prop wash, and then looking at the boat’s serene progress. The point is that any boat can sail up to, and occasionally beyond, its “numbers” if the situation and the skill set permit, which is why I don’t think they should ever be taken as gospel, merely a set of probabilities. There’s too many club fleets dominated by old boats driven by canny skippers and a generous rating to really argue otherwise.

Dennis Duke

My understanding of PHRF ratings is they are based on past racing performance rather than design…… if you do well racing, your handicap changes so you do less well.

How this applies to a series of production boats as compared to one-off’s maybe reflects what type of sailor as well as the racing ability of the sailors that buy them.

William Koppe

Hi John,
In 2002 I had the hull of my steel 45 ft motorsailor Delta Wing , faired, and I modified the rudder for slightly increased area.
My next race was the 400 mile Lord Howe Island race which I won on performance handicap. As a result my handicap was increased.
The next race 2 months later was the Sydney Hobart and we enjoyed a following wind for the entire race varying from 20 to 43 knots. Despite blowing out our only spinnaker and resorting to the much smaller MPS for the last 200 miles, we also won that race on performance handicap. Our handicap was really upped then.

Jesse Falsone

If I were doing this comparison where the usual suspect parameters and ratios s tell a counter-intuitive story, I’d be inclined to also look at the hull lines and other particulars like prismatic coef. and wetted surface. I would venture a guess that the IP is considerably higher on both accounts. I also think published displacement numbers are merely suggestions. With boats like these that have 1500lb per inch immersion (which suggests waterplane areas are about equal), you are looking at a very considerable increase in displacement sitting only a few inches down, which is usually not perceivable to the untrained eye. Lastly, those IPs tend to use in-mast furling which produces a terrible mainsail shape. Just as good sails are unrated speed, bad sails are unrated drag.