Can anyone tell me how to properly rig the mast for racing (rig tension, rake, etc.)? We bought the boat used with a mix of sails and we don't have a sailmaker that is familiar with the J-30.

I would follow the Banks Tuning guid.
http://www.j30.org/html/technical/tuning_guide.html

Be prepared for a ton of pressure on the shrouds. They are like a piano but it works. If you sail in light air maybe back them off a bit.

I also have the UK tuning guid off the jboat site before it became unavailable.

I can email that to you.

David,
#397

Pay attention to all components of the tuning guide. I sailed with my mast butt 3/4" too far aft for a couple of years, and I could never get the rig to set up right (way too much prebend).

Mast butt max forward, headstay class max, THEN start setting tension according to the guides.

I have North sails, and generally err on the light side of tuning ranges. We go pretty floppy in light stuff-seems to be fast.

Steve, you'll be amused to know that too little pre-bend is just as fatal to decent tune.

- David

In my opinion unless it blows where you are 44-46 is too tight. We only go that high in 20+. Base tune on our boat is 40-42 for 8-10 knots. I always tighten lowers first uppers next and loosen upper first lowers next to minimize excess pre-bend. John White sailed his J/30 with much looser shrouds and a headstay tighter than max. Tune varies by mainsail shape which depends on make and age.

I'm confused about "headstay class max". When I installed roller furling with a new headstay, I carefully measured and pre-set the headstay to the max. spec. This resulted in a lot of mast bend, a very loose backstay, and a lot of headstay sag in a breeze. I've now shortened the headstay an inch or so and still have lots of mast bend. How much tension is assumed when doing the class measurement for headstay length?

A follow-up question about Loos gauges. CAN-106 came to me with two: Model "PT-2" and "Model B". When the tuning guides refer to "the new style Loos gauge"....which is it?

-Corey

You can convert Loos Gauge measurements from the various types using the chart on the Loos web site. See this link, then scroll down near the bottom: http://www.loosnaples.com/howto/ptgauges.htm

PT-2 is the best. It just hangs on the shroud while you adjust.

You can follow the pounds of pressure vs the number. That is how to convert.

David
#397

According to the Banks guide, the uppers are 44-45 and the lowers are 45-46. I'm prepared for a "ton" of pressure but did you really mean 2000lbs?

On the Loos model "PT-2", the gauge maxes-out at 40 (2000lbs) and the model "B" maxes-out at 43 (1800lbs) for 1/4" shrouds.

The Loos guide suggests that the breaking strength of 1/4" stainless is 8200 lbs and that a starting tension for the forestay on a fractional rig is 15% of breaking strength or 1230lbs. The starting tension of the shrouds on a fractional rig with swept-back spreaders is 20% or 1640lbs.

Can someone comment on shroud tension in lbs instead of loose Loos #'s?

Different guides say different tensions.

From the Shore Sails Tuning Guide
Light Heavy
Uppers 1700 2000
Lowers 1300 1800

From UK Tuning Guide:
6. Tension the uppers and lowers gradually and evenly (counting turns as you go), until there are approximately 1800 lbs. On each, as measured with a Loos tension gauge. Start with the uppers, adding just enough tension on the lowers to keep the mast in column as the uppers get tight. Put final tension on the uppers with backstay fully on. Release backstay, and put final tension on the lowers. As you tension the lowers the pre-bend will be reduced (they pull back on the center of the mast). Tighten until pre-bend is no more than 2-3".

7. Upper and lower tension should now be close to even. This should leave you with about 2" of pre-bend (it probably looks like more, but you can measure it by putting the mainsail halyard against the back side of the mast, and subtracting 2" from what you see). Tighten the lowers to reduce pre-bend (make mainsail fuller), let off to increase, (flatten mainsail). Conditions and mainsail shape will dictate the correct amount of pre-bend.

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.

From Banks Sails Tuning Guide
Uppers: 44 - 45 on the Loos Tension Gauge.
Lowers: 45 - 46
***Note: These are Loos Model B numbers. Using the chart at this link with conversion from Model B to PT-2 gauge (Numbers Extrapolated linearly at end of chart for PT-2 values on scale greater than 40): http://www.loosnaples.com/how-to-use-pt-series-tension-gauges
Uppers: 44 - 45 Model B
Uppers: 41 - 42 PT-2 (Off-Scale)
Lowers: 45 - 46 Model B
Lowers: 42 - 43 PT-2 (Off-Scale)

Echoing Bob Rutsch's comments - the Banks Sail tensions listed are too tight in my opinion, and if done this way tension the rig greater than 2000 psi. Bob's suggestion for 8-10 kts wind has readings of 40-42 on the Loos Model B that equate to 36-39 on Loos PT-2 which is 1100-1600 psi

[This message has been edited by whk (edited 05-09-2007).]

Thank you - this is the type of info that I have been after.

Do you have the rest of the UK guide online? If so, would really appreciate a copy.

-C.

UK Tuning Guide - http://www.ukhalsey.com/sails/onedesign/j30/J30Tuning.pdf

[This message has been edited by whk (edited 12-01-2008).]

Let me try to work it out.
*Mast has excessive prebend so headstay sag is excessive. Thats checks out.
*Top of main won't behave because the backstay is too tight, creating excessive prebend. The backstay is a fixed length, and it's tight because the maststep is too far aft, which places the masthead more forward than the backstay wants to allow. The mast never becomes straight. It's like you always have some backstay trim on, even when the purchase is fully eased. Consequently your top batten and the top of the main refuse to trim up. They spill. The top batten won't align.
*When you move the step aft to class position, you'll tighten headstay sag and you'll actually have a straighter mast at the mast head. Your main will look better upwind and your boat should perform better in light air upwind and downwind.

1. eliminate concept of backstay tension causing problem. that was really loose.
2. Mast at fractional is too far forward when set further back than 25mm at step ... I am thinking it is impossible to get Max headstay tension and length unless at min step set back.
3. continue to wonder why most of the comments in these two threads talk about the need to change factory positioning of the step {Production line error? or just not enough feedback in the manufacturing run}
4. remember that the original j24s were based on launching spin from bag ... what we are seeing, I'm thinking, is that engineering 30 years ago ... was winging it by today's sophistication. dito need to template keels.
5. is there any advantage to being set at 40 mm which seems to be the max set back over 25 mm which seems to be the min set back?
6. the races that killed me this week were talking VMG speeds of ~3 kts. real light wind races.

#2 - correct. All the moving parts work together for optimal setup.
#3 - I think you answered your own question. You'll need to go through and check all the rig measurements. Note Dave Erwin's comment about his mast plate being off center when they rebuilt hull #87.
#5 - I guess if you had a main cut for that setup, it could work, but that is not what the sailmakers build the OD sails to.
#6 - every little bit helps to tune for light air. Your smaller jib doesn't help you either in those conditions.

I'm going to take a stab at answering Vic's question:
5. is there any advantage to being set at 40 mm which seems to be the max set back over 25 mm which seems to be the min set back?

First, while the position of the mast step, rake, and pre-bend are all tied together, they are also separate
Position of the mast step, by itself, should not affect the mast rake. In other words and for a moment think that you are starting with a mast that is straight and verticle (perpendicular to the waterline), then, moving the mast step aft, will not necessarily move the mast tip forward. Moving the mast step aft with the mast fixed at the deck will cause the mast tip to move forward but if the mast is free to move at the deck, then moving the step aft will move the whole rig aft thus moving center of effort aft which, in theory will induce wheather helm, which should help light air performance.
However, moving the step back will, in effect, reduce the amount of rake that can be induced (with the mast step further aft, the entire mast is moved back closer to the back of the hole at the deck level) therefore the mast will not angle aft as far as it would if the step were further forward.
Although I have not trigged this out, my guess is that moving the step back from 25mm to 40 mm will not induce as much affect on moving center of effort as setting the step at 25mm and raking the mast.
After mast step position is set, shroud tension, forestay length and backstay tension, as adjsuted, will then determine rake and mast pre-bend. Depending on where you want to induce mast prebend will affect when you block the mast at the partners.

The One Design Class Rules topic Mast Step Position turned into a discussion on mast rake, headstay tension, etc. Searching using the word ‘headstay’ right here in Racing Tools and Techniques turns up a number of good discussions including weather helm, headstay sag, and prebend. There are also five sailmaker tuning guides accessible under Rig Tuning from the front page.

My experiences on these subjects:

Balanced rudder/weather helm- I replaced Madcap's rudder with a "balanced" rudder 2 years ago. It adds some power steering for my autopilot. I race solo and double handed races and use an autopilot often. I agree with other posts that a well set up boat in a windward/leeward race should not have much wether helm with the original rudder. Reaching is anouther story. My balanced rudder only helps a bit. The planform is shifted forward about 1.5''

Mast step- When I got the boat it was all the way forward and the RF headstay was 1'' longer the class max. This setup worked ok. I tried moving the mast step all the way back, and shortend the headstay. Much slower in light air and upwind.
Currently I have the mast step 1'' back from the molded step and the headstay length about class max. This seems to be the best set up to me.

Rig tune- I like the UK quide, and I do a light/medium/heavy tune. I have learned to tune to tighter settings, so to not get caught with headstay sag when the breeze comes up.

Let the record show my error. Suffice to say "when you move the step to the correct class position..."

I don't understand the point about better performance downwind ... assuming that we always use spinnaker downwind?

the difference is at the most 3 in. at the fractional ... or are we referring to a straighter mast with minimum bend?

I am estimating that the angle range of the mast -- controlled by the movement of the mast step set -- is ~2 degrees.

Vic - I believe the downwind comment is related to where the effective center of effort is based on the position of the mast and forces on the boat.

WOW. I have been reading the comments on rig tension and I am absolutely amazed. I am sailing with 1300 on the uppers and 1100 on the lowers as my base setting, and the boat is FAST. The J-30 has the identical problems that the J-24 has. It is underpowered, with an undersized keel. The goal for upwind performance has is to power up the rig for light to moderate air by inducing a large amount of head stay sag. You know that the shroud settings are correct when the leeward shrouds are just kissing slackness. At my settings, my leewards rarely slacken, even in 20+ knots. So what to do if the main looks funny? That is controlled by the ratio between the lower and upper shrouds. If you have a large amount of curve in the main luff, you will want a more prebend in the mast, therefore the difference between the upper tensions and the lowers will be greater. If the main has less luff curve, the ratio will be closer, pulling the spar straight. The position of the mast butt is set to provide the static mast bend that the sailmaker recommends, such that application of backstay and main sheet tension do not invert the mainsail.

If you have sailed a fractional rigged boat with running back stays such as a Star boat, you can see the relationship between our shrouds on the J-30 to runners on a Star. The lowers do the same function as the check stays, ie. straighten up the mast and add headstay tension by countering the tension applied by the upper shrouds. This enables the balance between draft depth in the head sail established by headstay sag, vs. flattness of the mainsail. Sailing side by side with a tuning partner and changing rig settings is a good way to establish base shroud settings.

As indicated in the previous post, shroud tension influences rake, mast prebend and headstay sag. Likewise for fixed backstay tension, but in light to moderate conditions it’s best to adjust the turnbuckles so the block rises to the top of the split backstay allowing you to depower using the adjustable backstay.

Maximum rake with the mast step forward gives you just a touch of weather helm in light to moderate conditions, providing some lift from the rudder. It does depend on having enough weight on the rail to maintain a reasonable angle of heel. If your crew is underweight and the boat is heeling over too much you don’t need more weather helm.

You don’t want so much weather helm that you are dragging your rudder through the water upwind. It may be the modified rudder, but I also wouldn’t want to have ‘no hands’ like the picture in the rules thread.

Regardless of where the mast step is set, I think an excessively saggy headstay also hurts pointing. Since shroud tension is so much higher than headstay tension I’d theorize that adding a few turns isn’t going to reduce mast rake. As wind speed increases and you begin to heel more, you can depower by adding turns to the shrouds. Since you don’t need more weather helm why not maintain the same mast rake by adding turns to the headstay?

Not quite. Headstay sag will result in increased draft in the sail. This helps provide the power that the boat needs. A saggy headstay actually pulls the mast forward. Think about the geometry. If I add sag to a line, the points at the end must come closer together, resulting in the top of the mast coming forward. Pointing ability results from the angle that the leading edge of the sail makes to the apparent wind. If the halyard tension is loose, the draft is further back, resulting in a higher pointing angle in light air. This is why many of the top J-24's have ugly scallops along the leading edge. As the breeze comes up and the sail stretches a bit, we tighten the luff of the sail via halyard tension. We also tighten the shrouds, tightening the headstay, and flattening the sail since the headstay sag is less. BTW, the large amount of sag I was referring to in my earlier post is approximately 6 inches in the 24, and I am approximating between 8 to 10 is about right in the 30.

Light air - Deep Draft in Genoa, max headstay sag, loose genoa halyard tension
Medium air - Less draft in Genoa via tighter headstay and less headstay sag, start to tighten halyard. Don't forget that headstay tension also is a result of main sheet tension. As the breeze comes up and you tighten the main leech, you are also tightening the headstay.
Heavy air, tighten shrouds if not done already, tighter headstay, tighter halyard tension.

I understand the geometry but disagree with the conclusion. Are you assuming the headstay is a straight line and pressure from the Genoa causes the headstay to sag and pull the mast forward?

At max headstay length the sag is built in. Grab the upper shroud at 1300 lbs and pull. Pretty tight. Now try the same thing with the loose and wobbly headstay. You can add quite a few turns before it will be tight.