Rig plan change ?

[Javelin]

Following on from the New sails thread it got me thinking.

I'm just about to order a new main and genoa BUT,
The current rig plan is a masthead typical 1980's with high aspect main and a big 140% ish genoa.
Main luff is 11m with a 3.2m foot
Genoa luff is 12.8m with a 5.6m foot
In practice, upwind, I get 90% boat speed through the genoa and around 10% once the main is up.

I'm not actively racing due to the fact there's no-one local to race.
However I still would like to maintain the option of racing as I could go down to Ramsgate week or similar.

I was wondering if changing the plan to a 105% jib and changing the main to fully battened with a large roach would be of benefit.
I guess my main worry is balance as currently the helm is almost neutral and she tracks upwind like a dream.
An increase in main area would possible encourage more weather helm which is self defeating.

Also off the wind on a fetch or reach I guess I'd then miss the extra genoa area.
Downwind the kite is up and the jib is furled anyway though a bit more main area might help.

or do I stick with the current rig plan.

 

[dunedin]

What problem are you trying to solve?

 

[Javelin]

Problem ?

I might not have one, that's the issue.

The original plan was conceived during the old IOR days where the extra overlapping area was not measured which led to huge overlaps and little mains.
Without that rule anymore I was wondering if there was a better way.

 

[Ingwe]

If I were you I would search for the 2 most competitively raced boats of your design and pay for copies of their IRC certificates to see what is working for them - I know it costs a few pounds for the certs but if it saves you having a sail made up that isn't suitable it will save you a few thousand. It's also worth comparing the other boats weights as often the cheapest way to improve rating is to have your boat weighed and measured.

 

[Kerenza]

The only two pennarth I can add here is when I tried the laminate blade jib with the cruising main it was not as effective as with the laminate main. Equally the genoa was better, even when reefed, I guess because the cruising set up produced more power (torque?) then the laminates (hp?). That could be twaddle though....
What I am sure of though is Sailmakers can be quite clever people and a balanced rig, with sails designed to work together, is a combination to be treasured.

 

[doug748]

My boat has a similar rig and I had a suit of sails made recently. It is a conventional set in good quality Dacron

I went for a slightly smaller headsail, with a raised clew, and I fly it a little clear of the deck. This makes tacking a bit easier singlehanded, aids forward vision and means I no longer have to skirt the main hard on the wind. The overlap is probably still larger than 105% though.
There is also some added roach in the fully battened main, but the increase in area is small and it is mainly there for cosmetic reasons.
FWIW the changes have not altered my enjoyment of the boat except to make it more convenient. My club style racing is such a bran tub, I don't think it has more than a tiny impact on results.

With the particular boat class there is also a significant reduction in the area of the genoa in order to use a furling gear, a furling genoa will probably be getting on for no 2 size. In ordinary sailing the difference seems negligible but you would obviously see it in light weather racing. The question is: can you put up with this for your occasional forays to a racing week. I would suggest you can if it makes your boat more handy to sail for the rest of the year, or if you are not devastated by middling results or (particularly) if you can get recompense for the lost area in terms of your handicap.

 

[Javelin]

Yes the Contessa 32 rig plan is very similar to my own.
Skinny main and huge Genoa, not great for short tacking when single handed.
I have a racing laminate 105% but the luff is too long for the harken furler and it has a couple of battens.
I could get this shortened by a foot and have vertical battens fitted and see how that works and go for the full size Genoa for my light wind cruising.

Thanks all for the comments.

 

[lpdsn]

I was wondering if changing the plan to a 105% jib and changing the main to fully battened with a large roach would be of benefit.

I think it is pretty universally accepted these days that the 105% jib will give you a benefit under IRC, but IRC is also believed to heavily penalise excessive mainsail roach.

Try putting in a trial certificate. Cheaper than buying the sails then finding out what the handicap is.

There are other factors to take into consideration. The obvious one is weather helm. The second is that a blade jib works best where you can sheet it in an point higher, but that means having an underbody that has been designed for higher pointing. As you're making no changes there, changing the sail plan to one that will point higher won't give you a benefit - this is much better described by Mr Marchaj - if you can get one of his books out of the library it'll explain how the balance between lift and drag in the sail plan and the keel/hull/rudder have to match.

In general, I'd vote for sailing the boat you've got as well as you can, and if you're sailing very well and still can't win, then think about changes.

 

[Birdseye]

I'd be a bit nervous Javelin. Your boat is designed with a certain relationship between the location of centre of effort of the sail plan and the keel. You would be moving that C of E backwards which will definitely alter the balance of the boat. But I see that you are a boat builder. Can you not use one of your designer contacts to advise? Likely to get a better answer than on here.

 

[Boo2]

I think it is pretty universally accepted these days that the 105% jib will give you a benefit under IRC, but IRC is also believed to heavily penalise excessive mainsail roach.

Try putting in a trial certificate. Cheaper than buying the sails then finding out what the handicap is.

Is the IRC not determined by a public formula then ? Can't the OP just plug his own figures into that ?

Boo2

 

[lpdsn]

Is the IRC not determined by a public formula then ? Can't the OP just plug his own figures into that ?

Boo2

IRC is very definitely a secret formula. It is such by design in order to overcome some of the issues with IOR. However, some info on IRC does get out and sometimes it is not too badly mangled by the rumour mill.

You can ask for a trial certificate for changes you are considering. Plug in the proposed measurements and get out an IRC TCF. I presume there are limits on what you can ask for to prevent a systematic approach to reverse engineering the formulae but I don't know them.

 

[Javelin]

I would think reducing from 140% to 105% fore triangle will make little difference to balance but chucking extra roach would give her more weather helm but given I have next to zero weather helm currently I think I could live with some.
I guess the trick is knowing how much more and whether its worth it.
I'd also expect the coe would be raised higher producing more heal possibly
Also fully battened will be harder to set with a big overlap increasing the chance o stalling the slot.
So answering my own question its probably not worth touching the main.
Thanks for the comments making me think about it properly.

The smaller jib I think may well pay if wanting to reduce rating but i'm no longer serious enough to play the rating game.

 

[mrming]

I went through this process over the last few seasons with a fractionally rigged boat which originally had an overlapping genoa. Our feeling was the boat was too tender, so we dropped the genny in favour of a 100% blade and a lower rating.

Now we've got to know the boat a bit better we've worked out she can carry a lot more canvas than we thought (with the right techniques), so this year we've gone back to the 145% headsail and the higher rating which I now feel is worth the hit for the extra power.


One thing I learned when messing about with IRC is that extra pole length is pretty heavily penalised. We had an asymmetric with a 1m bowsprit which was having a big impact on our rating. I initially reduced the sprit to 6 inches over J thinking this would be okay, but I finally found it was best to get rid of it completely and just stick with a conventional kite / pole the length of J.