JPK 39 FAST CRUISER VERSUS JPK 11.80 CRUISER RACER

When this boat was being built I made a post about the JPK 39FC, the successor of a great performance cruiser, the JPK 38FC. There is also a complete post about the 38FC:

https://interestingsailboats.blogspot.com/2021/05/jpk-39fc-best-small-fast-voyage-cruiser.html

http://interestingsailboats.blogspot.com/2016/01/jpk-38fc.html

But now that it was launched, and has even been tested by a sailing magazine, a new post makes sense, even if not only to look at the real thing, and not just the drawings.

And the real thing looks much better than in the drawings, a beautiful boat, nicer than the previous one, with a not very different hull, in fact in what regards sailing performance it will be very close, but the 39FC is just a bit better in everything, from sail area, to interior space and cruising amenities.

Valer (the NA) and JPK resisted the temptation to increase volume increasing beam (as almost every brand is doing) and this boat has about the same beam as the previous model (3.98m to 3.99m).

We would be tempted to say that the 38 was even slightly beamier, taking into account this one is longer, but it would not be fair to look at beam and interior volume only in what regards maximum beam, especially in this case because the 39 has fuller bow sections and fuller stern sections, allowing for a larger front cabin but losing a bit in what regards bow finesse.

But if we compare JPK 39FC with the Bavaria C42, two cruising boats with a not very different hull length (11.72m to 11.99m) we will see that the difference in beam is huge (3.98m to 4.30m). If we compare the JPK 39FC beam with the one of a Pogo 12.50 (that contrary to what it looks has not a much bigger hull length – 11.72m to 12.18m) we can see that the difference in beam is even bigger (3.98m to 4.50m).

Of course, the Pogo and the Bavaria are completely different sailboats, the Bavaria displacing more than 10T, the Pogo 5.5T (the Pogo displacement similar to the one of the JPK) and having bow entries much finer than the ones in Bavaria. In fact the Pogo has the hull of an older Pogo Class40 racer and it is, like the JPK 39FC, a very fast performance cruiser.

So, what does that huge difference in beam between the JPK and the Pogo mean? It means that the Pogo is very much maximized (like all 40class racers) for downwind sailing, transats or trade wind sailing, that is what the 40class racers are all about, while the JPK 39 has a much more all around balanced performance, even if in the design of the transom does not diverge much from the one in the Pogo, a design that increases rapidly hull form stability (and drag) with heeling, making it a very stable platform for solo or short crew sailing and easier to be steered by an autopilot especially when sailing fast.

There is a common misconception, that has been serving to justify, performance-wise, the huge increase of beam in cruising sailboats, and even in performance cruisers, the brands stating that this huge increase in beam is favorable to sail performance and that the reason why racing boats are narrower is to make them competitive in IRC/ORC handicap racing, implying that beamier boats, not being designed specifically to be competitive under those rules, are faster.  That’s a publicity stunt (considering overall sailing performance).

That misconception, in what regards performance cruisers, is particularly strong in what regards Pogo cruisers, that on the wind conditions for which they are maximized to perform best (trade winds) are almost unbeatable (size by size), but that in mixed conditions, even when they are strong ones, are not as fast as those performance cruisers that supposedly where only fast on the paper (IRC /ORC), not on the water.

Journalists have been responsible for this misconception, even if I remember that on one of the first test sails of the boat that would be called Pogo 12,50, a comparative test with a Dufour 40p, they had made a simulated a race, upwind and downwind, to find with surprise that even if on the water the Pogo speed was higher, both boats ended showing a similar performance, due to the Dufour better pointing and ability to sail downwind at bigger angles….and the Dufour 40p it is not a particularly fast performance cruiser, being considerably slower than a J122.

JPK 39FC

I have posted many race results (in elapsed time) to show this, and the results in the last Middle Sea Race, that was raced in medium and strong but variable winds, show once more that the Pogo 12.50 is not as fast (in real time) as fast cruiser-racers , when the wind conditions are varied.

In the last Middle Sea Race there was a Pogo12.50 racing, and making it in 3days, 16 hours and 20 minutes, two JPK 11.80 made it in 3d 0h 22m and 3d 8h 21m, a First 40 (3d 9h 52m), 4 J122 (3d 10h 32m, 3d 10h 35m, 3d 10h 48m, 3d 12h 38m) and a JPK 45FC, that made it in 3d 9h 19m, a surprisingly good result, especially because it is an Australian boat, probably equipped for bluewater sailing.

JPK 11.80

A pity the Pogo 50 from Fast Sailing did not race on this edition, it would be interesting to compare the performance with the JPK 45FC, which I believe would not be very different, even if the Pogo is a bigger boat. The JPK 45FC, like the smaller sister, the 39FC, are not so maximized for downwind sailing, as the Pogo, and that would translate in better results, size for size, in a race with mixed winds.

Anyway, the point here is that the JPK 11.80 is much faster than the JPK 45FC and would be certainly be faster than the JPK39FC. So let’s have a look at those two designs to understand why the JPK 11.80 is much faster than the JPK39C.

The JPK 11.80 is the most successful 39ft cruiser-racer in a long time, having won this year the Fastnet and would have won the Middle Sea Race, if they had not changed the finish line. It had won already that race back in 2018, among many other races and regattas.

The JPK 11.80 is a cruiser-racer designed for racing and winning, and the hull is designed for maximizing performance, the JPK 39FC is a performance cruiser, designed to be fast but also to have a maximized interior space (and storage) and to be easy to sail, especially with a short crew.

Transom design: JPK 39FC and JPK 11.80

This comparison is very interesting because both boats have not only a close hull length and LWL (first the 39FC, then the 11.80): 11.72m-11.00/11.80-10.39m, but also a similar max beam, 3.98/3.95m. 

What differs is the hull design, having the 11.80 finer entries, the beam not quite all pulled back, and a very different transom design, a less voluminous one that allows more heel, without increasing drag so much.

Surprisingly, even if the hull length of the 11.80 is bigger, the 39FC LWL is considerably bigger that the 11.80 one. This has probably to do with the 11.80 being designed for sailing with more heel, and while heeling the LWL will be considerably increased asymmetrically, between one of the rudders and the bow.

While the JPK39FC hull has more hull form stability, the 11.80 hull assures a better power/drag relation, and it is that what makes it a faster sailboat. The 11.80 has less hull form stability but more coming from the bigger ballast, when the boat heels.

Curiously the 39FC is the lightest of the two (5500kg/5900kg) probably due to the two boats being built in a similar way and with similar materials and the 39FC, having considerably less ballast (1900kg/2650kg).

This difference in ballast, that is translated in a 34.6% B/D versus a 44.9% one, more than compensates the difference in hull form stability and that, and a slimmer hull, are responsible for the considerable bigger Power/Drag ratio on the 11.80.

Note that the draft is also smaller on the 39FC, 2.15m/2.34m but the ballast on the 11.80 probably refers to the IRC keel, without torpedo (can have a torpedo as an option) and the difference in draft probably roughly corresponds in RM to the difference in efficiency of the two keels (with a torpedo and an IRC keel), in lowering the CG.

First, JPK 39FC, then JPK 11.80

It is not about the power, but about power/drag that fast sailboats are about. Beamy hulls increase much drag, especially wave drag, and reduce light air performance, while if the hull is too narrow, it will go more deeply in the water and will make the boat more difficult to attain planning speeds.

To the hull design you have to add the right ballast, knowing that, with too much ballast, the boat will be slower with light winds and that with less than desirable ballast, it will have less power upwind and on a beam reach.

To complicate things, depending on points of sail and wind intensity the requirements for maximizing performance are often contradictory, and when you improve on a given performance, you lose on another.

JPK39FC

The different compromises are today evaluated through computer programs (CFD) and many hull variations are tested to try to get the better option for overall performance, but the truth is that only through racing will we know for sure, if the computer got it right or not, and the funny thing is that Jacques Valer, the magician that designs the JPK, the most successful IRC racers of the last years, is known to have come late to assisted computer design, and can be considered an old-timer, in what concerns using a computer for sailboat design. Of course, what counts are results and nobody designs boats that win more races than Valer.

JPK 11.80

I use to post SA/D and  D/L as a measure of boat performance, but the comparison of those ratios, between these two boats, serves mostly to show that those ratios have to be seen with caution, because they exclude a very important piece of information, the  power/drag relation.

The SA/D gives you an approximate measure of sail power, but displacement, even if important as a measure of drag, excludes the shape of the hull, and hulls with the same displacement, but with less beam, finer entries, and less full transoms, has, for the same displacement, a lot less drag than beamier hulls, especially if wave drag is considered. They need a lot more sail for the same performance.

JPK 11.80

D/L gives you a measure of the boat lightness but does not give you a measure of how much of the weight is used on ballast to increase boat power.

If we consider these two ratios as an absolute measure of boat performance we will be surprised to find out that according to them the JPK39FC is faster than the JPK 11.80, when we know that it is not the case, quite the contrary and by a large margin. The 39FC has an upwind 26.8 SA/D, a downwind 45.1 SA/D for a 115D/L and the 11.80 has an upwind 24.9 SA/D, a downwind 43.0  SA/D for a 146.5 D/L.

What makes the design of the 11.80 truly amazing is the success in combining these different requirements and different compromises in a way that makes the boat really fast in a very variable set of conditions, from the low middle to high winds, downwind, and upwind. 

The weakest sailing condition regards very light winds, but the performance is not so weak as it would be expected, due to the very good performance with medium and stronger winds, obtained through the maximization for those conditions. That’s the overall balance that makes it a winner.                     JPK 11.80

JPK 39FC

What makes the 39FC an amazing design is the ability to offer an excellent spacious cruising interior without compromising too much sail performance, a balanced performance, having in weak winds the weakest spot (worse than the 11.80). As strong points, the easiness in sailing fast with medium to strong winds (due mostly to hull transom design that limits heeling, making it a steady sailing platform), and the easiness in sailing fast on autopilot.

Both boats are very well built, using vacuum infusion, cored hulls with and airex core, vinylester resin on the 11.80, vinylester and polyester on the 39FC, both have a hull structure integrated on the infusion process (and becoming part of the hull), both have cored composite bulkheads stratified and bonded to the hull and deck.

I bet the JPK 39C, that allies cruising sailing performance to a very nice spacious interior with all-around views (and manages that without becoming ugly), is going to be elected by the European sail press as European Yacht of the year, probably on the performance cruiser category.

The price is fair for the quality and without VAT, standard, at the shipyard the 11.80 costs 209958€ and the 39FC costs with the standard keel 196887€ and 216748€ with the swing keel, with all ballast on the keel.