J/121 Tuning

[mkr]

Hoping to get advice on how to setup/tune J/121 for offshore racing. My questions are in the following areas:

Sail Combos and Crossovers
Is the North Sails tuning guide is pretty close on sail reduction recommendations?
DW: A2 / J2 vs recommended A2 / J4?
Reach: C0 / J2 / Storm Jib vs C0 / J2

Water ballast tanks seem to be fairly aft. Do you use them UW or mainly when reaching?

Any advice on how to rig the furling C0 to the bowsprit? It seems that 4:1 leverage is needed on the tack line in order to tighten the luff, but this creates a lot of friction and makes it difficult to tighten the luff.

Any advice on the approximate range between the minimum tension and maximum tension on the backstay?

Are published polars generally close to actual performance?

Thanks guys!

 

[221J]

From J122 experience tightening the C0 luff is both important and not so easy. First thing is to make certain that the pole is fully extended and the bobstay is taught. A bobstay is mandatory and must be short enough to attain tension by pole extension alone. Use the backstay to increase luff tension. I use a 2:1 for C0 tackline and 1:1 for spinnakers.

I wouldn't read too much into the sail reduction recommendations. You will need to figure out what is best given your crew, wind and wave conditions. There are more possibilities than a tuning guide could capture.

To determine max backstay tension use a LOOS gauge to calibrate and mark. Do this before going sailing.

Good luck.

 

[mkr]

Thank you for feedback.

J121’s have a DSK-90 Dyneema backstay connected to a -12 Harken backstay cylinder. I can measure the backstay tension with a Loos Gauge, but how do I translate Dyneema to rod rigging diameter listed on the Loos Gauge (is it equivalent of .281 or .330 rod rigging or probably something even stronger)?

Shrouds and forestay are -12 Nitronic 50 discontinuous rod with Uppers set to 52 (Loos Gauge) for 20+ TWS.

*** I am a newbie in rigging, hoping to get a sense of the operating range of this sailing machine. I am sure the rig was designed to handle a LOT more tension than we have been putting on, but it would be nice to get confirmation. ***

 

[JCoggs]

I use a 2:1 purchase for the code zero and it works fine. I make sure to tension the tack to the max with the backstay off quite a bit and then add tension. Keep the tack line on a winch and don't trust the clutch to keep the line from creeping.
When racing PHRF most J-121 owners in the Northeast US declare they won't use the water ballast. The tank placement so far aft is far from optimal but a trade off for space in the main cabin. The speed advantage vs the 6 or 9 seconds rating penalty just isn't worth it. You take that penalty 100% of the time and likely would only use it upwind in winds over 18 knots. And it's too slow to fill to be of much use racing around the cans. I do declare intended use when racing double handed which is usually distance racing. I just applied for an ORR rating (for the Halifax race) and declared we won't use it as well. Not sure how that would affect the ORR rating. The ballast sure comes in handy when doing short handed deliveries so I have not ripped the system out of the boat as some have to save weight.
Which J-121 do you own (or sail on)? New to you? I've seen a few come on the market since the end of the 2022 season. I own have owned Ceilidh (ex-Hot Pursuit) for 18 months and race in New England.

 

[221J]

Colligo has a LOOS dyneema conversion chart on their webpage. I would include the link if I only could.

 

[Jambalaya]

@mkr congrats on the purchase. Following with interest.

As for tuning and cross overs you are better off experimenting yourself using the tuning guide as just that, a guide. It's worth asking if the crossover chart assumes full crew on rail or just 2H. I don't know the 121 at all as pretty rare here in UK but I would look at outboard jib sheeting options if offshore is a focus for you. In IRC we can fly jibs (inc storm sails) inside the kite or standard jib so if that's allowed you might consider how you would do that with an inner forestay

 

[Roleur]

For headsails there are lots of options, but the proposed options seem like compromises.

Ideally, you would fly and A2 and a spinnaker staysail. A staysail is a better shape and weight for reaching/running. Otherwise you would be able to use the J4 down to lower wind speeds than the J2 because it is smaller, but also heavier, so not ideal.

For reaching, sure the storm jib inside the J2 could work, sometimes. In that case the storm jib is really acting as a genoa staysail. Some boats have both sails as a storm jib may be a bit small for ideal staysail work. You'll have to go out and sail to figure out when the GS makes sense. There are probably times with C0 + J2 makes sense, when the C0 + GS makes sense, and when all 3 make sense. On a smaller boat we fly the C0 + GS much more than C0 + jib

 

[mkr]

Getting information about specifications for rig tension has been a challenge. Any rig specialists out there who could clarify the difference in D1 tension between Owner Manual and RigPro guidance?

 

[221J]

Comparing tuning guides only works if the forestay is the same length and the mast butt is in the same place. Even then the tuning sets the mast prebend for a particular luff curve of sail. If you have North sails then the North guide applies. Tuning guides are a just a starting point. Crew weight, use of water ballast, wind sheer and waves are some of the parameters that affect tuning.

I'm assuming your boat is new to you. Have you checked out your turnbuckles? If not you should. If they are similar to mine they are slick but work a bit differently than a generic turnbuckle.