North Sails: News Details


J/70 Sail Testing

Report by Ched Proctor


One of the great things about the new J70 was the opportunity we, here at North Sails, had to be in on the “ground floor” of the project with J/Boats and Southern Spars on rigging and setups which would optimize the performance and fun factor for new J70 owners. Using the North Design Suite our team was able to develop the rig and sail plan for the boat as well as provide us, from the Flow program, tuning numbers, including rake, rig tensions and mast placement. With only these computer generated “virtual” numbers we hit the water and, from the get go, our clients are having great success. That said nothing is better for learning what makes boats go faster than to get out and sail them! In mid December we were able to get 3 boats and teams of J70 owners to hit the water in Biscayne Bay to do a few days of sail and speed testing as well as try some new ideas to help our clients go even faster in 2013.

We were lucky to have a great group of folks come help us with our testing. Henry Brauer, Will Welles, Max Skelley, Ched Proctor, Jim Cunningham, Karl Anderson, Greg Tawastjerna, Heather Gregg Earl, Stu Johnstone, Joe Bardenheier  and Bill Shore, who served as coach and observer in motor boat, all dedicated a few days to help us learn more about making J70’s go fast!

Our goals for this session were fairly simple. We wanted to learn a little more on how to sail the boats and what setups worked with crew placement and trimming techniques while also test our tuning numbers, particularly the rake settings we developed. All 3 boats were set up with the basic North Tuning guide at the base settings and all 3 had the standard Radian North Main and Jibs. All were new or nearly new for the testing days.  We kept all boats set up the same on the first day while tried different sail trim techniques and adjustments that w felt were fast and consistent. On the second day we tested four different headstay lengths.


North Sails J/70 jib
In the early part of the first day USA 48 seemed consistently faster and we began to use their trim as the benchmark. USA 94 tended towards a tighter mainsail trim with the traveler well to weather and the boom above center line. USA 95 started out playing the mainsheet with the vang on, always easing sheet in the puffs. After a series a 5 minute “tests” the most consistent trimming technique was trimming the main so the back of the long batten was parallel or slightly closed from the boom and the traveler set so the boom was as near midships as possible and playing the traveler to keep the boat flat in the puffs. For jib trim the tests showed that the jib liked to be weather sheeted about 4” for best all around upwind performance. On USA 48, the benchmark boat, they set up with a bit more twist when sailing into the waves (starboard) and tighter trim on port where the waves were not as severe. Tips we learned from Day 1-

  • Trim main with top batten just a bit closed from parallel.
  • 4” of weather sheeting for the jib.
  • More twist going into “lump” gives less point but much better VMG.
  • Playing the mainsheet in the puffs hurts point without VMG gain. Use traveler to “dump” main in puffs.


Day 2 was rake day. Max sorted out a quick way to change headstay lengths without affecting shroud tensions and we kept two boats at the “mean” setting while only changing  the rake on the “guinea pig” boat (USA 48). He determined that for 1” change in headstay length, the required change on the uppers is 3 full turns and on the lowers 1-¾ turns in order to maintain equal tensions.
We tried 4 different headstay lengths.

Our tests were:

  • Headstay 1” longer than the 4’6” standard measurement
  • Headstay 2” longer than the 4’6” standard measurement
  • Headstay 1” shorter than the 4’6” standard measurement

Conclusions on this day were mixed as the wind velocities and direction made the results of many of our test runs inconclusive but we did have some data which we feel we can work with moving forward.

  • Generally we were able to get all 3 J70’s to match up fairly well when trimmed and setup with the same tuning. This is important so we know we can easily get people up to speed quickly with our base settings.
  • The longer headstay (2” beyond standard) showed some decent results in the 10-12mph wind range with the caveat that conditions and shifts had some bearing on the results. The longer headstay did have some limitations which we weren’t yet comfortable with which led us back towards our base setting as the standard for now.
  • The shortest headstay test did not yield any quantifiable data even though the breeze began to cooperate and settle in the clock did not and we ran out of usable daylight to continue safely testing.

Overall conclusions

The session yielded some great results to share with new J70 owners including trimming techniques we used (traveler, twist, weather sheeting) and tuning data we will continue to experiment with. The most encouraging development was how quickly we were able to get all 3 J70’s up to speed with our standard tuning numbers and how small variations in trimming, steering and technique made a difference in performance. In regards to rake, well the jury is still out and we will continue to work with JBoats and our clients to make sure everyone is up to speed on any new developments but, perhaps, the best conclusion we were able to draw was that the standard settings from the North tuning guide will get you up to speed quickly and keep you in the ballpark.

Many thanks to our J70 test session team. They were terrific to work with and our 3 boat session enabled us to learn that we have solidified the tuning numbers for making J70’s go fast and learned a few things to share with all of you the get you up to championship speed as well.


Donwload new tuning guide here.