I am a little cautious about numbers for Xp-38 (and some others). Comparing the Polar Diagrams for one boat against real-world testing of another can give drastic misinterpretation. Polar diagrams are theoretical calculations from sail, hull and keel data; real-world tests are how people actually sail.
Polar speeds, made by the boat designer are quite accurate. They normally prove true with the real performance of the boat, if the sailing conditions are the same.
The Xp-38 has not been tested as far as I know; it is not to be launched until summer 2011, so instead of finished boat we have the polar charts. The manufacturer publishes a chart for Xp-38, and they do not show data down to 30º; it stops short by a few degrees and seems to show stalling from there onwards. They also specify flat water. It would be optimistic to state anything about its 30º performance when X--Yachts doesn’t.
On polar speeds, boat manufacturers only show speeds at angles that are normally used. The XP 38 starts at 32º and at 5K wind.
You can obtain a quite accurate reading if you prolong the curve, with the same shape till you reach 30º (it is really a very small gap). The Xp 38 with weak winds would not be efficient sailing at 30º (meaning you can have more way if you sail with a slightly bigger open and more speed), but with stronger winds it can sail efficiently with 30º of wind, specially if you need to (to pass a cape or an obstacle, for example).
The X-34 performance cruiser is in the same league as Xp-38; beyond that I found tests of Xc-42 and Xc-45, both in the cruiser range.
X-Yachts quote this test of the X-34, so they must be pleased with it: It says that: in “wind .. force 3 to 4 (i.e. 7-17 knots)” … “she moved with 6,5 knots and 40 degrees true wind angle up the beat.”
The test of the Xc-42 says “in strong winds” … “close-hauled it maintained an angle of almost 40 degrees to the true wind and maintained speeds that were consistently above 7 knots.”
The test (Yachting World) of Xc-45 says, “Powering back up onto the wind, she consistently stayed above 8 knots, between 40º-50º off the wind, tacking through 80º at over five knots.”
We have three real-world tests of X-Yachts all speaking of beating angles at 40º plus. Allowing for some improvements in the Xp-38 we can hope it is better, but it takes a leap of faith to believe that X-Yachts, experts at designing upwind performance, should suddenly invent a yacht going a full 10º higher.
I really don't understand your point. I never have said that the Xc 38 or the Xc 42 could point in the area of the 30º. They are completely different boats from the Xp 38. The Xp 38 is much faster and can point a lot higher. When I said that you should compare your boat with the Xc 38 (and not with the Xp 38) was because it would make some sense comparing it with the Xc-38 and none with the Xp 38.
Regarding the Xp 34 speed, the value that was measured by the boat testers is accordingly with its Polar speed. It was not said (on the boat test) that the boat could not do less than 40º but that at 40º was making 6.5K an excellent performance for a 34ft boat. If the boat could make (in 3 to 4 B) 6.5K, it could still made good speed with a lesser wind angle (certainly you now about that).
... Why not put some vital stats of Xp-38 alongside Ovni 395? The similarities are striking
, although nuances are obvious. Luckily, the two have identical LWL, making for sensible comparison
There is a set of formulae often used for estimating performance and so forth; you can find them at US Sailing:
Sailboat Design and Stability
Real differences, not revealed in formulae, lie in sail handling gear, details in hull shape and more. I noted the claim that X-38 can “plane” – just for reference: so does Ovni, and it can do it with the keel up. Good fun!
Overall, the numbers resonate with gut feelings, that both are good boats and in real-life usage not as dramatically different as one might assume
You are wrong about this and continue to insist on it. The Xp 38, in what regards sailing performance is a completely different boat from the OVNI 395 and not a comparable boat. We are comparing a boat that by modern standards is very fast with a boat that has an average sailing performance (a good one if we take in consideration that is a central boarder with all ballast inside the hull).
Even if we compare it with the X-38 the OVNI 395, that is a bigger boat, will be a slower boat, pointing considerably less to the wind ( at least 5º, possibly more). The only sailing position were the OVNI, if not very loaded, will not be significantly slower is downwind and even so I would have to look at both polars to be sure.
When the OVNI 395 was tested by the French magazine "Bateau" they have said very nice things about the boat and its improved sailing performance (in regard to older OVNI). On the conclusion they have rated its sailing performance upwind as 3 (average) and downwind as 4 (good).
That's in their opinion an excellent performance for a center board boat. They are, by design, not properly good going upwind. A good and fast cruiser like the Jeanneau 409 would have deserved at least
4 (good) on both counts and a top performance boat like the Xp-38 would be rated 5 (very good) also on both counts.
OsmundL, this is not personal but this thread is also about boat design and I want to provide here a fair perspective about each type of boat and that includes centerboarders.
If I can find an OVNI 395 boat polar we could join to the numbers that were posted by Myocean, the numbers from the OVNI and from some 40ft cruising racers, like the First 40 or Elan 410 and that will give us a fair perspective of the sailing performances of the three types of boats (same size).
That will contribute for a better comprehension of how boat design relates with performance.