J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Rig Tune

Rob - If it works for your boat speed use it. The chart on the Loos site suggests that for 1/4" wire breaking strength is 8200 lbs, and there is a warning not to exceed 25% breaking strength (2050 lbs) in the paragraphs below. As long as the pole stays in the hole, you are safe.

As others have pointed out, there is no single "correct" tune. The tension will change as the prevailing wind conditions do. You need to play with it. Go out and try some settings and compare boat speed and pointing angle for conditions of wind speed and chop. Record what you get then make the adjustments based on that knowledge. I would say that for base settings you mention, you are way too tight for light air. You actually want some mast sag at the lowers in light air.

This from the UK tuning guide : Simply stated, the tighter the overall rig tension, the greater the headstay tension; as long as the tension is nearly equal on uppers and lowers. In lighter air, when more sag is desirable, ease both shrouds slightly, and ease the lower shrouds more than the uppers to allow for more pre-bend. In heavier air, use more tension (2000 lbs) on both; the lowers should be as tight or tighter than the uppers to reduce pre-bend.

Another tuning guide for reference:
Banks Sails tuning guide

Just a quick note to let everyone know that the conversion charts to interpret the Loos Gauge readings between the 90 Model B and the PT-2 with equivalent tension in pounds are now posted on the web site with the tuning guides. The chart is readable online, or can be downloaded as an Excel spreadsheet for printing. The numbers come from the Loos website.

The table is organized to show readings being approximately equal listed on the same row. You'll need to interpolate for exact conversion, but it's close enough for dialing in the settings you want.

Go to the J/30 website main menu at the top and mouse over Info, Articles of Interest, then click on J/30 Rig Tuning. It is listed at the bottom of the table labeled "Jump to Sections to read online or download:"

Here is the direct link, but we put the menu structure in place so you can find stuff in the future.

One question I always asked myself,....the wind reference in the tuning guide / is it true wind or apparent wind

Taras

Pretty sure everyone uses true wind speed. Even if you don't have instruments you can probably estimate. I remember reading an article on polars in Sailing World (June 10, 2008) by Stan Honey and Jim Teeters that says, "Most sailors can guess TWS within a knot."

Somewhere (maybe this) I read the Loos PT-2 calibration is 38/1300 lbs (Loos Table 1 seems to support this). Setting the shrouds to that tension initially may help you get more consistent 'turns to tune'.

YIKES. I am reading these tension numbers, wondering if this is part of the reason that my chainplates were broken when I bought my boat! I am using 1300 on the uppers, 1100 on the lowers, and up to twenty knots, the lowers do not slacken, so this base setting may even be too tight. I do not carry my 163 above 15, I found that my 140 is faster, flatter and higher in winds over 15 kts, so that may explain my ability to carry a looser rig. No problem with the bubble in the main either. Maybe this is a carry over from my J-24 days, as the number one in that boat is a 145%. Have not tried the light air settings yet, as central FL does not have much light air in the evenings when we are usually out, but if we have a drifter, will probably try 1000 lbs on the uppers, 800 on lowers. Recommend if you use settings over 1500 to check the rig on cold days, as the tension will increase!

I'm curious. How many of you have shortened the backstay the 3-5 in as recommended in the UK tuning guide. I have the headstay at 35-9.5. and the mast pretty straight. My backstay when released is quite loose. The idea of shortening seems ok.

Yes, I've shortened my backstay. I had the top section cut... only one cut needed there, so it's less expensive than having the legs of the Y cut.

Luke, I replaced my original chainplates with oversize ones. I also replaced the nylon backing plates with SS. I have plans for both if anyone is interested. I will take pictures of the new chainplates and attempt to figure out how to post the pictures on the web site.

I'd love to see the plans - I've thought about redoing mine - I've got a metal fabricator who can turn them out easily if I can give them a drawing, but that means taking them off the boat first which I have not wanted to do.

Be sure to use 316 stainless instead of the cheap 302 that TSP used for the new chain plates. Oversized is GOOD