Some time ago I wrote about the ORC Speed Guide (here my previous article ORC Speed Guide), one of the ORC services available to its members. I promised that, as soon as the new sail inventory landed, I would request a speed guide for Veloce and describe what we got out of it.
Veloce’s new sails have now landed and with them, their final and verified measurements. Time to run the ORC’s velocity prediction program (VPP) and see what we can learn.
After looking through all the Sun Fast 32i hulls available on the ORC registry, I found one with a displacement pretty much identical to Veloce, saved it and used it as a baseline for my own analysis. Not having an ORC certificate, nor the many required measurements, this approach is a great way to get an almost identical hull to work with.
Since we sail only shorthanded, I edited the crew to a double-handed configuration amounting to 165Kg. This is what I expect myself and my co-skipper to weight in full gear.
Rig dimensions matched almost exactly Veloce’s and I updated only few dimensions with minimal changes.
Finally, I configured Veloce’s sail inventory with each new sail and their dimensions.
With a nearly exact configuration for Veloce, I requested a test certificate. A needed step if you want speed guides or target speeds.
Both the test certificate and speed guide arrived via email within minutes. Just the time for the VPP to run.
A very comprehensive explanation on how to reed the ORC speed guide can be found here. However, some important points worth mentioning to set expectations right:
- Polar curves reflect the largest sail of their type (larges headsail, largest spinnaker, largest headsail set flying, and so on). A bit disappointing as I expected polars curves for each sail configuration and their optimum.
- Flattening reflects not only trim, but sail shape and aspect ratio, even if it means changing jib.
- Reefing refers to total reduction of sail area, where reefing mainsail is associated with jib reduction as well. Note that the reefing factor must be squared to obtain the total area in %.
Worth the money?
The cost for a test certificate and a speed guide is 60€ at the time of writing. Sure, yet another cost on top of many other small and large expenditures. But is the information it provides worth the money? As usual, there is no right answer, but a bunch of new questions, which is often a good thing. We were able to take home some interesting lessons:
- Previous seasons polars and target speed were taken from a similar yacht in full crew mode. Polars from Jeanneau are provided in full crew mode as well. While I was aware that they must differ from our double-handed performance, I didn’t realise the magnitude of the error and its distribution. We expected better performance downwind and in the very light stuff, but not over 5% performance reduction in VMG upwind in a breeze! Inability to hike hard causes a considerably lower boat speed and 2 degrees wider beat angle.
- Heeling angles have kept me awake at night. Beamy flat-bottom yachts should be sailed straight on their feet, they say. How straight, I say. We often struggle with heeling and sail her on her ears. And wonder why VMG suffers. So what is the right level of heel throughout the wind span? We feel that the groove is at heeling angles between 20 and 28 degrees in most conditions. And now, our speed guide confirms our feeling.
To summarize: the ORC guide provides us with a accurate theoretical baseline. It is a great tool and input in our own growth and development process. Data collection on the water and fine tuning are important step from the baseline. Don’t forget to calibrate your instruments!