Yes, it is me again. (joke)
for some reason I've been very interested in the jib sail for some time now as its behavious determined its future in a specific class in which I'm involved. Some will call the following remarks spin others propaganda, some will read them and take the info that they are interested in. I hope you are the last kind.
But first a jab under the belt to Goran.
>>Some impressive boats like theM20 (Goran says you don't need a jib, but he doesn't sail here)
Well that M20 still has a whole lot of problems finishing ahead of Gorans own tornado designs which, as we all know, is a sloop rigged catamaran of 50 kg more weight. And I'm talking elapsed time results. And don't get me started on that other design now that the Tybee 500 has proven to be so insightful.
>>Ok, I'm talking about mainly light to very light air in North American summer sailing.
Roger that. Ehh, lets not forget that in these condition waterline length is NOT important anymore (better measure would be prismatic ratio but we'll just forget about that). Only thing that is important here from A-cat to nacra 6.0 is wetted surface area and its related friction drag. It is absolutely possible that a heavier shorter hulled boat has less wetted area than a lighter longer one like the M20 for example. So when the rigs are comparable than a shorter heavier boat can been seen to be in front against "common sense".
>>Logic seems to indicate that with a high aspect main and spin you really don't need a jib.
Well that is true to some extend. Is is always more difficult to trim a boat well without a jib as some are finding out now. Also the spinnaker can not be flown always as another poster has indicated. If it doesn't fill than the spi is only an item that introduces extra drag. But in most conditions the spi will make it easier to sail well downwind as she will replace the jib trimming function. Even the A-catters will tell you that downwind sailing with only a FULLY battened main is the most difficult part. In light air the battens make the sail riggid and it hardly reacts to chanhes in trim. On say laser 1 you can tell sail by looking at the luff of the mainsail curving in but the battens on teh cat sails prevent this.
>>Of course the jib helps turn the boat quickly, but that can be overcome with improved technique.
Indeed, besides using the jib to turn is like putting the breaks on to make the corner, it slows you down. With proper technic the jib is not needed and the speed of your tacks improof to such an extend that you just the jib over and nothing more. Rolltacking is an important technic to learn here; especially in light winds. ALSO you must move gently and only when you have to.Sitting still on the boat and wait makes each boat go faster and faster with each passing second.
>>And it has been proven repeatedly by A-cats and others that the jib doesn't get you upwind any faster in most conditions.
Not this is simply not true. The people who say these thigns are comparing A-cats to some other completely uncomparable design and concluding that it must the absense of the jib that causes the difference. This is just BS.
What any zealot of the "Jibs don;t make you faster" theme should do is pick a sloop rigged boat; arrange for two of them on the water and race them against one-another where one boat has no jib. WITH FULL COMPLEMENT OF CREW of course.
Example : get two I-20's or two H20's and get two equal crews, remove the jib on one of the boats and correct the mast rake accordingly. I can tell you that that boat with the jib beats the jibless one EVEN on upwind legs.
Of course now starts the screaming. "But you've got more sail area !" Yes of course, that is the charactertic of sloop rigs; they allow more area to be carried than when without a jib. And I think that you ,Steve, don't two mains of different size (You are sailing the FX right?). One for its sloop rig and one for its uni-rig setup. So in Steves case, the A-cat setup does not entlighten us to HIS choice between "just the main" or "the same main with a jib". I figure that you are not cutting down on you main when you fit the jib, are you ?
So in this case (and that of other sloop rigged boats that can be sailed singlehandedly in both the sloop and cat rigged setup) the fact that the jib increases the overall area of the rig significantly can make the sloop rig faster upwind than the same rig but without the jib.
>>>I say MOST conditions. My observation is that in light to very light wind the jib not only helps read the wind (see other post) but makes a big difference in speed.
Bigger overall area and that fact that you can get the sloop rig to be dailed in for much longer periods than the cat rig make the sloop rig feel more powerful and more forgiving. This is my experience in this design too as well as on other designs. Maybe the catrigged setup that is achieved by leaving of he jib of an otherwise sloop rigged design may be slower and feel slower as a result of these points rather than you sailing skill.
>>Much more than its area would suggest.
Well, Bethwaite had indeed some insightfull things to say about how the jib acts together with the main. One the more striking things was that he and others liek Arvil Gentry found that it is not the jib which makes the main more powerful but rather that it is the main that make the jib more powerfull. The ventury effect has been put to rest and a new theory with much the same overall result (more power in the rig than you would expect) is coined. But Personally I think that its usefulness in setting and maintaining the optimal trim plays a very large part in the light winds we are talking about here.
>>>I read that the I-20 substantially outperformed the f 18ht in light air (less than 5kt?) and I don't think it is just because of more sail area. They have a LOT more weight, which usually kills light air performance. I hate to pose such a subjective question, but I would like some indication that either my sailing technique needs a quantum leap in improvement, or that a jib is more than a crutch, at least in light air.
Again, MY PERSONAL OPINION is that the jib makes the basically sloop rigged design feel more powerful and feel faster. It is also my opinion that they are faster too in light airs unless the catrigged sailors is really skilled in achieving and maintaining optimal sailtrim of this rig. The last thing takes alot of experience and is mostly done by the feel of the boat. It is my opinion that it is very easy to sail out of the optimal trim on a catrigged boat in light winds. On sloop rigged you see little warning signs when this happens like the luffing of the jib and thus can react much sooner and more adequately to the changing conditions/trim.
I have however no doubt that a uni or cat rigged boat is more efficient in light airs for a GIVEN TOTAL AREA and that it should be faster upwind as a result. However this efficiency only "works" in the period when the rig is optimally trimmed and this trim is maintained. See it like this a 25 % more efficient rig (say 100 %) that is only efficient in 50 % of the time WILL loose from a reference efficient rig (say 80 %) that is kept working for (only) 63 % of the time or more.
Notice how small the difference in "dailed in" time is ? And more strikingly this difference DECREASE when the cat with the efficient rig is less capable in keeping it efficient.
For novices to medium skilled sailors the time that the rig is set optimally in light airs is so small that sloop rigs easily can outperform cat rig setups by having better "engaged time ratios). Ratios of "50 % of the time properly dialed in" are pretty high in light air for normal sailors. OF course the top sailors achieve higher ratios and here the more efficient rigs will start to excel. When the total areas are the same of course. When the sloop rig has more sailarea as well than it dependents on the sailarea's wether the catrig will be faster or not.
Once again "there is no free lunch"
I personally liked the FX with a jib better in all conditions. I thought is was a better balanced boat like that and it felt more powerfull. Some of us in the class where I'm involved in are looking into "super-slooping" as their singlehanded setup. I think I will go along with that and fit a selftacker to make it easy on me. The past year I have competed in the clubchampionship with my "superslooped" Prindle 16 and the experiences there comformed all my believes.
Wouter
