New sails arrived. Splash 4 weeks away. Time to get nerdy and look at some numbers.
Some time ago I wrote our reasoning behind the new sail inventory for Veloce, here the article. Not interested in following the J/80 one design class rules, nor wanting to optimise for round-the-buoy racing, we set up the boat to be
- manageable, simplicity and depowering being keys to doublehanded handling, especially on a boat with so little righting moment on races from half to 3 days
- all-round performance, mitigating lack of meat on the rail, exploiting low wetted area, compromising with lack of beam
So how does Veloce, adapted for doublehanded inshore racing, compare to other J/80s in one design configuration?
I based this analysis on the figures and certificates available on ORC Sailor Services.
The first step was to configure Veloce on the ORC database, based on one design hull, rig, stability parameters, crew (doublehanded, set at 175Kg) and the new sails’ dimensions.
The second step was generating a test certificate, and then a speed guide through ORC Sailor Services. I previously wrote how it works and how to go about – here the article. Lots of interesting reads on how the ORC VPP work and how their speed guide is generated on the ORC website, if you really want to get nerdy..
The Speed Guide provides plenty of useful information, that can be used for drawing your conclusion. How flat should the boat be sailed? How soon should we reef or twist off to depower?
The polar diagram and table are amongst the most valuable pieces of information for us. They provide us with a baseline to start.
These are theoretical predictions based on mathematical models. Refining, reworking and twisting as data on the water are collected is fundamental. For the sake of comparison, however, the VPP generated polars are a great tool.
The table above compares Veloce’s ORC polar in DH configuration against a J/80 DH International in One Design configuration. Both crews are set at the same weight (175Kg).
The first obvious observation is that we are “theoretically” and “potentially” faster on points of sail, in all winds. Sweet! Now we only need to live up to the expectations…
The only small exception, with a 0,18% disadvantage broad reaching in the lightest air, probably because of the flatter and smaller asymmetric. However, I’d guess that below the 6kts wind, our 0.5oz asym is going to be faster as it should hold a better shape with the slightest of breaths.
Quite a difference upwind in the light stuff, where the larger jib works its magic. The more it blows, the smaller the difference. Sails must be reduced or twisted off to depower a little earlier to keep the boat on its feet.
Broad reaching in a blow we should be a blast. Up to 8% faster!!! The smaller leech and flatter shape don’t overwhelm our “light crew” and we can exploit more of the generated power.
In medium air, especially reaching we should be a bit faster, but it is a dangerous zone. Here an OD configured boat with what J/80 call jib-top, can really leave us panting behind. We have a spare jib-top and we will try it out…we would like to keep it simple and avoid it, but never say never.
I also compared Veloce in DH configuration with the same One Design J/80 in full crew mode (350Kg).
As expected, the effect of those 2 extra people is evident. We are stronger when we don’t have to drag with us the extra weight, and weaker when lack of meet on the rail keeps us on our ear. What I didn’t expect was such a difference. Upwind, in 20kts, our beat angle is 4 degrees wider, costing us almost 10% VMG compared to our full crewed friends!!!
Once again, not much difference in the middle area, where weight plays a secondarily role. We hope to exploit better our larger jib with a sheeting point at the toe-rail and squeeze out some extra speed.
Finally, as a by-product of the comparison above we got a baseline for our target speed, angles and heel. Like for the polar figures, this table needs refinement and updates with insight from data collected on the water. But something is better than nothing!
Hi Federico,
the polars you show here are ORC doublehanded? Did you update them during the past time? I guess you are going quite a bit faster upwind? Do you want to share any updated polars? According to SRS I should be around 5% faster….
These are my upwind targets, which I meet from time to time ;)… (Hope the formatting works)
TWS (kn) BSP (kn)
4 3.7
6 4.9
8 5.6
10 6
12 6.2
14 6.2
16 6.2
20 6.3
//Fabian
Hi Fabian,
here are our ORC Speed Guide which is for a J/80 hull with our sails and sail configuration and a crew of 2 at 87Kg each.
https://drive.google.com/file/d/11Twkyef3ALkaI3yYKELyG0Ez4tc9kiDB/view?usp=sharing
Upwind, they reflect quite well or speed, although, I daresay in the lower wind speed, it is difficult to keep that target at such tight AWA.
Downwind, they should be updated, but we find speed changing constantly and very quickly to the point that having absolutely correct values is irrelevant.
Generally, we observed that we can soak way more, down to 165deg TWA in light air and even 170deg just before planing. IN the midrange however, these angles seem quite correct.
Thanks. Very interesting. I didn’t take out any speed guide yet, only target speeds for full crew and shorthanded.
I usually do not trust the angles from orc but try to match the targets pointing as high as possible (upwind). Downwind is of course tricky with sportboats. I guess you have way more data on the performance there. But even there I tend to look at the target speeds instead of angles. However, since the measured TWS is off going downwind, it is not easy to know which target to hit.
Would be nice to match with some rather similar boats. Maybe we should organize some sportboats workshop? On the monday night races we race against an XP33, First 36.7, Arcona 370, A31, Dominant 150 and Corby 33 (our class). So no boat that is somewhere close to how we perform. All much bigger and faster upwind, of course. Looks like a similar thing in bohusracet… We will see. I know that we can leave some bigger boats behind, even upwind, if the wind stays below 12 kn.
//Fabian