North Sails: News Details


J70 Tuning and Trim from Charleston Race Week

Report by Tim Healy


I have just returned from beautiful Charleston, South Carolina after completing another fantastic Sperry Top-Sider Charleston Race Week! The entire event was so impressive and the organization on every level was impeccable, from the race committee work to the hospitality on shore, the event was well run, welcoming, and fun.  The food was fantastic, and even though the sheer number of boats and sailors must have been a huge logistical challenge, the Charleston event team pulled it off seamlessly which made for an incredibly enjoyable regatta.

A whopping fifty five J70’s were entered, making it the largest class of the nearly 300 boats that competed. As with the two other J70 regattas our team has sailed in 2013, our learning curve was steep. Here are our thoughts, lessons learned, and the adjustments we made to our boat in conditions that ranged from 8 to 25 knots and water that could be flat one minute and choppy the next.


Playing with the Rake Settings:

J70 Tuning Measurement
We rigged the boat on the Thursday morning before the regatta at James Island Yacht Club where we launched and hauled.  We are still playing with the rake a bit, trying to figure out the optimum settings for conditions, but we decided to use the same setting we used at Key West Race Week (see Key West Regatta Report here) so we set the rake at 4’ 6 1/4”, measured from the mark on the headstay to the pin at the bottom of the headstay on top of the furler system (corresponds to the mast band as described in the J/70 Tuning Guide). This had worked for us in moderate to heavy air and we anticipated similar conditions in Charleston. Earlier, at Miami Bacardi Race Week, we did experiment a bit with a longer headstay, with about 2” more rake, but it was not a very forgiving setting as we had trouble making the “bow down” mode work when we had to sail low and fast for waves or traffic.  I think we are finding that 4’ 6 ¼” is still a very good all - purpose setting, especially considering that you cannot adjust your headstay after you leave the dock for racing. 

North Quick Tip:

  • 4’ 6 ¼” is still a very good all - purpose rake setting

The Rig:
On Thursday afternoon, before we went practice sailing, we set the rig at 22 on the uppers and 12 on the lowers using the PT-2 Loos tension gauge, because the wind was about 8-10 knots from the southeast. This setting worked well for the conditions because it allowed a decent amount of headstay sag in the lulls for a powerful jib shape, and in the puffs, when the main sail is trimmed tighter, the tension from the main sheet is partially transferred to the headstay which then gets taut and flattens out the jib shape for better top end speed and pointing.  We found this also allows us to apply a little backstay tension in the puffs to further tension the head stay and also flatten the main. 

On Friday morning it was blowing about 15 knots and we set the rig at 28 on the uppers and 24 on the lowers using the PT-2 Loos tension gauge before we left the dock because the forecast was calling for the breeze to build to about 20 knots.  This was a little tighter on the lowers than our tuning guide called for, but I figured it was easier to do the adjustments at the dock, rather than to try to increase the tensions in the big breeze and lump out on the course. What we noticed when we got out to the race course was that this setting was about right even though the breeze still had not yet built to the predicted 20 knots.  We found that we needed to pull on a considerable amount of backstay to get the headstay to stop sagging or bouncing in the puffs and waves, and because we needed the backstay on hard, we liked the lowers where they were (fairly tight at 24 on the Loos gauge) to stiffen the rig and keep the main from getting too flat.  

A note about shroud tension and headstay:
One thing that we have learned is that a stiff rig (higher shroud tension) on the J70 also transfers the backstay tension to the headstay more efficiently because the mast is not bending or compressing. When the mast bends and compresses, the distance from the deck, where the shrouds are attached, to the points on the mast where the shrouds terminate, becomes shorter and shroud tension decreases. The result is a mast that is not only bending fore and aft, but also side to side, and the tension from the backstay is having little effect on the headstay tension. In short, when the mast bends too much, it is hard to keep headstay tension and shroud tension no matter how hard you pull on the back stay, so increasing the tension in the lowers is a real factor in controlling headstay sag.

On Saturday morning we set the rig tension a bit lighter based on the forecast of 10-15 from the northeast, slowly dying to below 10 in the late afternoon.  We left the dock set at 24 on the uppers and 15 on the lowers using the PT-2 Loos tension gauge on the shrouds, and left it there for the first two races while the breeze was 12-15 knots.  When the lulls started to drop below 10 knots, we eased the shrouds off to 22 on the uppers and 12 on the lowers.

On Sunday we left the dock early before the breeze really picked up, and we were set at 28 on the uppers and 24 on the lowers using the PT-2 Loos tension gauge again and prepared to go up to 30-27 if we were going to race in 22+knots. However, as expected, the breeze quickly picked up and started gusting close to 30 knots from the east while the RC was setting a course. By 10:30, with the prediction for the wind to increase even more, racing was canceled for the day. As with the rest of the week the committee was spot on, and this was a great call because soon the wind picked up to gusts of 40+ knots!

North Quick Tip:

  • Backstay alone cannot control headstay sag in big breeze
  • Using a Loos PT-2 tension gauge:
  •  8-11 knots: 22 uppers/12 lowers
  • 10-15 knots: 24 uppers/15/lowers
  • 15-20 knots: 28 uppers/24 lowers

Jib Trim

We sailed with the jib leads at either 4 or 5 holes showing in front of the jib car for the entire regatta.  In the lighter wind (8-11 knots) we had the leads forward with 4 holes showing and when the breeze was up (12 + knots) we had the leads back a bit at 5 holes showing.  On Friday it became extremely gusty from the south west with wind speeds ranging from 15-25 knots and huge puffs. It was very important to be ready to ease the jib sheet if the backstay, traveler and main sheet were no longer working to keep the boat flat. We had the jib sheet cross sheeted to the weather winch, and if I could not keep the boat under control with the main sheet, backstay, and traveler, then I would ask for jib ease.  One thing that worked very well for us was our team communication. For example, in a strong puff I would say, “Ease, ease , ease” and with each “ease” , Will Welles (our jib trimmer), who was hiking legs out with the jib sheet in his hands, would ease about an inch.  When the puff passed and breeze dropped down I could then winch the jib sheet back in and work on speed and pointing. One important thing we found out while sailing in heavy air and working the jib sheet on every big puff, was that if the jib is eased before the main, the boat will quickly become unbalanced and want to round up.  The main should be eased first and when that is not enough, than we start easing the jib in those one inch increments.

During the entire regatta, in all conditions, we used a considerable amount of weather sheet on the jib.  We used less when the puffs got over 20 knots because we had to start easing the leeward sheet to keep the boat under control.  In 15-20 knots we would pull the weather sheet until the clew was 1-2” from the cabin top. And for the rest of the event (8-14 knots) we would pull the weather sheet so the clew was about 1” off the cabin top.

The jib halyard was set so that wrinkles in the cloth at the luff were just noticeable up until we were overpowered (18+ knots,) at which point we would eliminate all wrinkles to flatten the sail as much as possible and to move the draft forward for a good heavy-air shape.  In lighter wind (0-6 knots) it is good to have slightly more wrinkles, but I don’t think it is good to have the wrinkles extend beyond the first panel in the luff (or more than 8” back) from the luff.

We marked the spreaders with white tape so that I could look through the spreader window on the main and repeat a trim setting for any given condition.  The marks are placed at 18, 20 and 22 inches from the mast.  In flat water and 10+ knots we can trim the leech of the jib in to the 18 inch setting once the boat is up to speed.  In choppy conditions or light air, the leech is closer to the 20 inch mark and in 20+ knot puffs, the jib is eased to the 22 inch mark (or even beyond).

North Quick Tip:

  • Jib leads were at 4 or 5 holes showing in front
  • Weather sheet 1” off cabin top up to 15 knots; at 15+, 1-2” off cabin top
  • Helmsman calls for jib ease in large puffs
  • Jib leech trimmed in to 18” mark on spreader was max trim
  • Under 14 knots: halyard tension should be set so scallops appear
  • At 15+: remove all scallops


Main Trim

Control in Puffs
It is important to keep a constant angle of heel to balance the helm because when the boat heels over too much it slides sideways and you will have difficulty pointing and holding a lane. You should be able to control this with small main sheet adjustments (See video clip). If your mainsheet adjustments are too big or unmanageable (for example in big breeze) this means that your backstay and/or traveler are not set correctly. Typically this means your backstay is not tight enough.  In heavy air (18+ knots) your gross adjustment on your backstay legs should be pulled tight enough so that the backstay “whip” at the head of the mast, is all the way down and there is almost no deflection left in the backstay. The overall purchase in the backstay system will be increased because while the blocks are high up on the legs with the best purchase, the backstay is pulling directly on the mast and not just pulling down the whip.

In general, when it is above 15 knots and puffy, our adjustments in the puffs will be as follows: backstay on tighter, ease main, ease jib, in that order. The necessity of each step depends on the strength of the puff. It is nice to go to the backstay first because it affects both sails at once, in that it pulls the headstay tight and flattens the jib and it bends the mast and flattens the main. The traveler is set in this situation for a median wind speed and should not be adjusted for every puff and lull.

North Quick Tip: 

  • Backstay on tighter, ease main, ease jib – in that order




Setting the Main and Jib Together
The main shape works in concert with the jib shape, and more specifically, the headstay sag.  We look at the headstay sag and ask ourselves if we have enough (light air, chop) or is there too much headstay sag (heavy air).  If we are overpowered and there are few lulls that we need to power up in, than we go with tight uppers and lowers and pull the backstay on to remove the headstay sag and to flatten the main.  If the lowers are too tight, then while you can get the headstay tight enough by pulling the backstay, it tends to make it hard to get the main flat enough.  If the lowers are too loose then the mast bends too much when the backstay is pulled, resulting in a very flat main but not enough headstay tension. One thing we have learned along the way is the importance of understanding the relationship that the uppers, lowers and backstay have on both mast bend and headstay sag and creating repeatable settings.

I can say we really liked the settings we used on Friday (23 knots) and Saturday (14knots) where we found we were able to pull on enough backstay to get the headstay tight but not over-flatten the main. This meant that we could get the headstay tight, to give us the flatter jib shape we desired while still being able to ease the backstay in the lulls for a fuller main and let the headstay sag a bit for a fuller, more powerful jib. An easy way to recognize over bend is when large wrinkles appear in the main that start at the luff just under the spreaders and run diagonally towards the clew.  It is okay to sail with a small amount of these “overbend” wrinkles temporarily in large puffs, but if you notice these more than 25% of the time, you may want to go up a setting or at least tighten your lowers a bit.

North Quick Tip:

  • To control headstay sag, adjust the lower shrouds and backstay


Vang Sheeting and Leech Telltales
On our boat we found that the main was almost never trimmed so tight that the upper leech telltales were stalling. The only time we would let this happen would be temporarily to hold a tight lane for a few seconds at a time.  The traveler was set anywhere from 10” above center in the 7 knot lulls, to centerline in the puffy 18-22 knots.  The last two races on Friday (18-25 knots) I actually just cleated off the traveler at centerline and vang sheeted the main.  The puffs hit so fast that vang sheeting was the only way to keep the boat under control.  The vang was pulled hard once the main was sheeted in and left there because the lulls were still 15+knots.  Vang sheeting accomplished a couple of things: for one, it kept the boom down which kept leech tension in the main, and it also bent the lower part of the mast, thus flattening the main and opening the slot between the main and the jib for better flow and less stall. 

When the traveler was up in the lighter breeze it was important to let the leech twist open and not over-sheet.  We found that when the main is over-sheeted, and the traveler is up, the boat will only want to point up into the wind and it will not accelerate forward for speed.

North Quick Tip:

  • Keep the upper telltales flowing 99% of the time
  • Vang sheet in big breeze


Crew Weight

We sailed Charleston Race Week with about 710 lbs of crew weight.  I trimmed the main, which allowed us to get the two largest crew members hiking legs out, and the bow man, who was the lightest, sat up front on deck next to the cabin house with his legs forward.  We were all stacked forward and I was sitting up next to the winch. It is important to keep the crew weight forward both upwind and downwind in displacement mode (not planing) to keep the bow knuckle in the water.  When the knuckle is in the water you know that you are sailing with the maximum waterline. When it got choppy at the leeward mark due to all the boat traffic we would all move back in the boat about 8” to keep the bow from plowing into the waves. When planing downwind, in 14-17 knots, the entire crew moves back at least 2 feet, and when it gets to 18+ knots downwind, the bow man should move aft of the helmsman to make sure the bow does not plow into the next wave. The main sheet trimmer should be pumping the main which should be done 1:1 from the boom and through the traveler car to the trimmer, and the traveler car should be all the way to leeward.  This allows the trimmer to pump the boom in and also down to close the leech and get maximum pull from the pump.  If you pull directly from the boom the upper leech does not move in the pump and only the boom and lower leech move horizontally and the upper sail moves very little.  

When sailing in displacement mode we found that windward heel was not very effective.  It worked to help steer the boat down a wave or carve down in a puff, but in a straight line we found it was best to sail flat for the best VMG.  The forward two crew members would constantly work on the heel angle to stabilize the boat to keep the spinnaker stable.

North Quick Tip:

  • In displacement mode, keep crew weight forward to keep bow knuckle in the water.
  • In planing mode (18+ knots), move weight back
  • When planing downwind, pump main from traveler car


Spinnaker Trim
Downwind, in displacement mode when we needed to soak low, we found that letting the spin tack up about 8" worked well and as soon as we went bow up again for more speed we would pull the tack back down. When the wind was forecasted to be above 15 knots we would move the spin ratchet blocks to the aft position on the stanchion so that more surface of the spin sheet was exposed to the ratchet, making the sheet more manageable. In the aft position the line travels through the block and makes about a 270 degree turn and when it the forward position it makes less than a 90 degree turn. The forward position is better for light air so the lazy sheet can get pulled around with less friction.

One last thing we did downwind from a boat handling perspective was before jibes, we would make sure the cockpit was cleared of the spinnaker sheet the best we could, and we all made sure we were conscious of not stepping on the sheet. We did inside jibes the entire regatta and found that waiting a bit on pulling the boom over helped our jibes tremendously.

North Quick Tip:

  • Ease tack line when you need to soak low
  • Above 15 knots move spin ratchet blocks to aft position
  • Wait a bit to jibe the main
  • Keep cockpit lines cleaned up


As I said, our learning curve in the J70 is still pretty steep. It seems there are many ways to get the same outcome in these boats, and we are enjoying the discussions that arise from different people’s experiences. I encourage you to contact me or any of the North Sails J70 experts to discuss what works for you or to answer any questions you might have.  We love to hear from you and always enjoy hearing different points of view.

North powered boats finished 1,3,4,6,7,8,10 at the 2013 Sperry Top-Sider Charleston Race Week. To learn more about North's ultimate performance designs for the J/70, click here.