The new SUN FAST 3300 with a double concave line

I agree with what the others have said. What you see is a hull that is optimized for a fairly high heel angle and designed to generate maximum RM per wetted surface area when heeled at 15 or more degrees. It may not like light airs much if it can't be persuaded to heel, but the crew of a 33 footer can have a pretty big effect on trim, maybe enough to keep it from getting glued in light air.

"Guppy bellies" have been around for at least 200 years, and have shown up on high end racing boats like 12 meter and J boats, as well as on the most prosaic of sailboats, the New Haven sharpies. The two boats Ralph Monroe built after Presto, at 41 and 42 feet, both had pronounced guppy bellies, both in order to hold more internal ballast and to improve the form stability when heeled (the original Presto was kind of a dog, but the latter two worked quite well). Unlike the Skerries mentioned earlier, these boats use a very full midsection shape to generate RM through high form stability. The Skerries were renowned ghosters, and went with low form stability shapes that led to vee-shaped midsections and narrow sterns. They are at the very opposite of the spectrum in terms of optimization goals.

 

Here is the recent promotion video released by Jeanneau, with subtitles in English, which shows the boat in various sailing conditions, inc. some zoom views on the very rounded bow (the current trend !) . To note also the hull local shape at rudders interface (at 1:05) :

 

It does look great on the water, and the one in the video has all the go-fast goodies. I hope they offer a B-class version that is attractive to recreational customers who mostly just want a boat that will be trouble free for 50 years. The engineering and hull interior integration looks terrific.

The rudder pads are probably more about structural reinforcement and manufacturing convenience than anything else. You want a nice flat place to install the rudder's lower bearing pad. And that's kind of an awkward part of the mold to lay up. You don't want laminate problems there. The mold design helps to accurately locate and fix the reinforcements during the bagging process. It's not really a hydro trick as far as I can see.

 

Here is another video showing the boat behaviour in various conditions, and with comments in German :

 

Which of the J's did you have in mind? (Not challenging, just curious).

Cheers,

Earl

 

This kind - (Ranger shown here)



not this kind - (J/99)



(I should have said J Class)

 

Thanks for your reponse and sorry, I was unclear. I had the impression that you thought some of the Universal Rule J's had "guppy bellies" and some did not. Now I think you were referring to the class as a whole. Is that correct?

Isn't that hull form pretty inevitable for rules that limit draft but permit "large" amounts of sail area? I mean, the displacement and RM to carry "big" sails has to come from somewhere. I'm thinking of Universal and International Rules in particular.

Cheers,

Earl

 

Yes, I didn't have any particular one in mind, but Ranger had the greatest displacement of any J Class.

 

Of course such double concave keel line is not a novelty at such, but what seems new to me and deserve a thread was such line for a modern beamy design aiming performance in the Froude 0,45 to 0,7 semi-planning range, which is very different from same line adopted for a class J .

The US prototype participated to a first double handed race, result not very remarkable, neither for the Figaro 3 also participating , J33 and J35 did better :
Results :2019 Annapolis Y.C. Double Handed Distance Race on Yacht Scoring - A complete web based regatta administration and yacht scoring program https://yachtscoring.com/event_results_detail.cfm?Race_Number=1&eID=9531
Vidéo :

 

The tracker for that race is worth a look, both for the 3300 and the Figaro 3. At the mark rounding on the end of the course, four boats just snuck around before the tide held the rest of the field in place for about 4 hours. Nobody was going much of anywhere, but the four that got around were at least pointed in the right direction. Outbound, the 3300 made a tactical error that cost them about 20 minutes, and probably the mark rounding. Looks like it moves with the pack. It was sailed about a degree higher on average going downwind. It was only passed by one boat, and that was entirely a matter of tactics just at the end.

Tracker - Annapolis YC Double Handed Distance Race 2019 - YB Tracking Race Viewer http://yb.tl/dhdr2019 The 3300 is Alchemist

 

so, almost a year has passed, any new insight guys?
also who's the closest sf3300 opponent? dehler 0d 30? j/9?

 

It always amazes me how the old becomes new again and is called innovative, or a first. This abomination now called a double concave keel line has always worked as a way to cheat racing rules based on length and sail area. It crops up in increasingly freakish boats until the rule makers make changes to rule out such horrid designs. Here is an example from over a century ago, from the drawing table of no less than Starling Burgess. If you think this boat is ugly and disfunctional you would be half right. Due to a high sail area to waterline length ration this boat screams along. It is still garbage though.

 

It is kinda ironic.

In the past, the 'guppy belly' was used to shorten the LWL. Now it's being used to lengthen it (while deepening the hull without increasing the displacement too much).

A scow I designed also has a guppy belly in that the 'rocker' (fore and aft curve of the bottom) is double the hull draft.
This puts the bow and stern transoms well above the DWL.

Floating level, the DWL is about 0.70 times the length of the boat. But once the boat heels, it becomes closer to 0.90 times the boat length.

This was done to allow the boat to heel some without the transom corners digging in. But I can imagine this might make for easier turning when changing tacks.

Now I have to build the blasted thing.

 

Here are the boat specifications and pictures, including at the end a list of similar boats :
Sun Fast 3300 (Jeanneau) - Sailboat specifications - Boat-Specs.com (boat-specs.com)

 

Nope, it's quite interesting actually
And it's functional enough; it was built with only one purpose I assume-to race, and it does; what more do you need from a purpose built racing sailboat?