Sorry Jim,
capability of making a good set of sails has nothing to do with Rating !
When I said ‘unfair’ is because every body knows that the Rules are actually misleading the modelers when they want to make a choice from ac1992 and ac2007.
It is pretty sure that a good replica of BlackMagic or America True will have hard life with an Alinghi or Oracle of 2007.
So why let modelers beliewe that they can race all together ignoring that some models are fast and the others are not all having the same set of sails ?
Agreed, but your messing with the sail area, that is to do with the rating.
Have you sailed these yachts with reduced sail area? They are pretty boring.
I have tried it, and I’m not impressed at all.
I am sure, even with the rating, the slow boats will still be slow. Except with some of the fun taken out.
therefore passing from 78cm² to 77cm² is a big handicap for you !
Since 2cm beam is producing similar effects, one could then consider to increase proportionally the fin lenght as function of beam, without touching the sail area !
beam : max - min width as per 28 -16 = 12 cm beam variation
Taking the fin lenght variation from 42cm to 48cm = 6 cm we can have : 6 / 12 = 0.5cm per each cm of beam increase from 16 to 28 cm
So for 20cm beam the fin lenght could be 20-16 = 4 x 0.5cm = 2.0cm cm longer or 44.0cm fin lenght !
This parameter being under water is invisible !! hehehe !!
Wrong units! Wrong assumption on sail area too…
Passing from 80dm2 to 77dm2 because someone else is sailing a lemon is pretty rediculous.
You avoided the question, have you sailed these boats with reduced horsepower?
I feel that they could do with more and your only interested in less…
What about Democracy !
Rating are just there for that purpose ! to let boats, pertaining ALL to the same AC120 Class, but of differents beam dimensions, racing together !
If your principle would be followed , non one will build anymore Il MORo or the NZL20 or similar wide beam boats being sure to be, on paper, less performing then others !
I’m giving up, I spent already too much time for that class, better to go back to Class M !!!
All I am suggesting is to give the lesser more, not the other way around. When I chose this class, it was exactly what I had been looking for. Full on racing machines.
I have an IOM hull - It was sat in the mould for 3 years. I have the bulb, foils & sails, Why have I not finished it? Because I do not really like the IOM class as its tame, and very restrictive.
From my experience these yachts are quite happy with 80dm2… and in winds 8-10knts could easily run with more.
Upwards of 13knts the skill required to sail fast goes up, especially in the manoeuvres.
That’s when these boats come alive, they absolutly charge…
No worries Claudio, and I’m Sorry for your obvious frustration.
I’m not worried for my personal choices, and I do not knows how many ac120 you met on the water equipped with good sail set up !
But for sure I knows that if you go back to previous classifications resulting from the Rating calculations, you will notice that the Victory is classified 12 out of 16 models. That’s means that models like Mascalzone Latino, Luna Rossa B, ChinaTeam, Luna Rossa C, ETNZ, Alinghi, are all, on paper, faster then Victory. If I recall well the Victory has a beam of 3.70mt = to 18.5cm at model level that is far away from the 16.5cm of Mascalzone Latino or others similar models of 2007.
The day you will meet them, you will see who is the best model boat, for sure will not be the Victory. All that inside the 2007 AC.
This situation would not occurs with the rating application at the time of the final classification of a race !!!
Look at the Maxi yachts , Alfa Romeo is arriving first at most of the races, but not always is the winner, because of the Rating, otherwise the other yachts will be frustrated all the times, since Alfa Romeo is winning almost all.
Hope you will take few minutes to think about more closely to the real subject !
Jim’s points are 100% valid & so are yours Claudio, you can see in AC-120 events the same boats are always winning and results show they are all V5 hulls designs, it is also impossible to separate the skill factor unless all boats were the same & there is no doubt that the winners are very good sailors.
The whole objective of this proposal was to give those starting their own AC-120 events a perspective how to better handle different designs in the class to have more level playing field (read fun) on paper.
One option suggested by Claudio is to have one design hull & have people use their preferred team graphics, then there is always going to be some-one who thinks another design is better than what is being used.
Another option is to limit class beam width to 160-180 mm then all designs would be relatively close, on paper and no need for a rating ?
what about reducing to scale 1/20 a boat like Il Moro or America3 or Young America, that have beam width going up to 5.5mt ?
The resulting AC120 should have a beam of 275mm, almost 10cm wider for the same lenght !!
Are these boats exluded from racing ?
If this is the case, then the Rules are totally wrong !!!
Hope some interested readers will take deeper look to this aspect !
Another way to look at the problem if a problem is !!!
The hull contribution to the final result is about 15%.
One may ask, why to bother about it is only 15% !! but being 14% or 16% is another story !
Observing the presented tables with rating figures, it can be seen that from the highest rating to the lowest there is about 1.03% difference.
Assuming a direct contribution to the speed, all other parameters and skipper being the same, the fastest boat may have an advantage speed of 1%, that in my opinion is enormous.
i.e. from a racing lasting 20 minutes, the fastest of the two boats will cross the line several seconds before or various boat lenghts.
Vb = Vr x LWL sq.root = 0.9 x 10 = 0.9m/s . i.e. 5sec = 4.5mt or 3.7 boat lenghts.
Vb = boat speed
LWL = 100cm
Vr = 0.9
(can vary from 0.5 to 1.25) Vr = 1 equal max boat speed where the wave generated is long as the LWL.
was not my intention to be agressive with my explanations.
Was just pointing out that you suggested to keep hands off from the models derived from AC 2007 and shall not be involved with the Rating, rather to apply the Rating to previous issues V1-V4.
Has been proved so far, at various race meetings, that the better performing ac120 models are the one that have the narrover beam and lesser wet area.
The rating formula is the supporting evidence.
Inside the AC120 from 2007 there are various beam width when compared with Mascalzone Latino and some others and therefore different performances are expected.
The situation would exist with or without V1 to V4
Rating would cancel the differences imposed by the Rules !
If my explanation of facts is considered a cheap shot, I’m sorry !
The problem of scaled weight that is insufficient for a 1:20 IACC (about 3,3 kg max) is the last problem: every formula doesn’t change in the substance if you put a coefficient.
In this case (IACC true formula) it is sufficient put a coefficient for the weight (and/or everywhere is needed) and change the “malus limits” for max draft in way of utilizing the preferred range of weight, length, surface and maintaining quite the true IACC shapes.
In France someone made in the past AC/20 with weight of about 4-4,5 kg with genoa (I have seen it on 2007 near Bordeaux)and the same rule scaled down of the AC/10 that is the same of true IACC rule issue 4: the only problem is that a boat like this is very difficult to be projected and realized:it was/is a reality and also big challenge for a very good modeler… not BS
Bye
Hi ClaudioV, I really apperciate your comments, but your talking about designing new class boat …if I understand you correctly ?
The discussions was intended to look at what we all ready have with over 30 AC-120 designs and how to possibly have them compete more equally, given the wide range of designs & plans already available today.
I don’t think anyone really wants to start a new class.