Alan,
You could always glue it back on…
I have seem a TP52 bulb have 200kgs added by ‘sheathing’ it in lead… If the max draft was increased also, you could just bond it on the bottom of the bulb…
Cross checked my ac120 designs with rating formula.
Some simulations added by changing the SA, Beam and Dspl since the Ac120 concept has large room for manouvers.
Certainly, narrow beams and lower Dspl will increase the Rating suggesting faster boats.
I should chek with water beams !
This table shall explain why the Rating is necessary to let various models racing together in spite of the differences , maily the beam, that influence the performances according to the Rating formula, all other parameters being identical !
ClaudioD
PS: check with deck beam and water beam
answers, reply, comments about the question in red??
…
From above table it is evident that using the rating formula, the “Young America” model is the one that have the lowest rating, whether the LOA or the LWL are considered, therefore being the less speedy of all.
WITHOUT the RATING , all other parameters being the same, a modeler will probably esitate to choose the Young America or Desafio or ETNZ boats, among the various choices offered by the Rules that include all boats from 1992 to 2007.
According to the above “table”, without rating, the best choice would be the “Mascalzone Latino” or “Luna Rossa B” that have the longhest and allowed LWL and the narrower and allowed Water Beam.
It can be therefore observed that there will be more interest to shorten the LWL lenght, instead of lenghtening, and adopting a wide beam in order to get “lower figure” by the rating, like “Il Moro” or similar boats of 1992 Amecica Cup.
Another solution could be the esclusion of boats designs not pertaining to the America Cup 2007 !
Practically and according to the existing rating formula, a boat with LWL of 96cm and a Beam of 29cm will be very probably less competitive then a boat with LOA 100cm and 16cm² of Beam. This is exactly the actual situation imposed by the AC120 Rules.
Rating is the most democratic issue where all models do receive a “weighting factor” in order to compensate the results allowing all differents boats “of the same Class” racing together.
The need of rating will be useless if all models would be coming out from the same mould, unless changes are forbidden and discouraged by the Rules.
ClaudioD
Hi ClaudioV, The spirit of RC model class is to be similar to true IACC with added challenge of covering different generations of hull design which is not easy thing to do & it’s not desired to give advantages to one design over another, but to give them all similar performance…this is the only reason for proposing rating.
If people just want to compete with latest Ver 5.0 hull designs to max spec fine !, no need for rating system then & agree with you 100%…but it wipes out opportunity of pre Ver 5.0 hull designs from being competitive.
The idea is to give others countries opportunity to learn from early AC-120 class development and decide for themselves which direction they wish to take, if they want multi-generation hull design fleets, then rating system will help have all boats have similar performance.
If they want only latest Ver 5.0 design boats, well no need for rating system.
Only wanting to help those interested in developing class by sharing opinions.
Cheers Alan
Perhaps that is the answer… Give the pre V5 yachts the additional horsepower, and close the gap that way. In fairness, the pre V5 yachts had another 1000kg in the bulb. Max V4 weight was 25,000kg and reduced for V5 to 24,000kg with an increase in draft to 4100mm to retain the righting moment…
Hi Jim,
I think is not possible, since the parameter that create the variances, according to the Rating Formula, is the Beam only and only the Rating can equilibrate the situation.
I exclude that pre-V5 should be treated differently or with different Rules.
The problem will not esist if only 2007 designs would be considered.
Unfortunately at the time of writing the rules, nobody considered that the 1992 parameters would impair the theoretical model performances when compared with the ones issued from 2007 design.
Do you have a specific suggestion in mind to increase power to pre-V5 models only, other then the proposed Rating ?
Thanks a lot
ClaudioD
If I follow Jim correctly (?) I think he’ possibly suggesting:
All boats can use same max/min SA
V1-V4 rules to be defined by beam width has 3,200 gram Fin/bulb with fixed 420 mm total draft
V5 rules to be defined by beam width has 3,000 gram Fin/bulb with fixed 450 mm total draft
And no rating needs to apply !?
Hi Alan,
according to your figures, the V5 will have further better torque :
VI- V4 : 42cm x 3.2kg = 134.4 kgcm
V5 : 45cm x 3.0kg = 135.0 kgcm
Imo, the full group of models cannot be separated in 2 differents categories, because as said above, the Beam variability is also present within the V5 and this produce also different Rating.
In V5, the Beam may vary from 160mm to 170mm.
That’s means that modelers will choose, only one model, the one that on the paper, has the better Rating and performances, like Mascalzone Latino or my last revised Fast2000 that is close to 34.00 or even higher, if the Rating is not considered anymore.
As I see it, the are only two options : or the rating or the best design being unique “one design” for everybody, where only the decorations will changes.
I still of the opinion that the bulb shall be allowed to be up to 3200g and the Draft allowed up to 450mm.
Within these ranges a modeler has plenty of choices.
The other option is to allow the Weight go down to 4000g and Draft to go up to 450mm and no rating at all, while the cleaver modeler will be free to choose.
Cheers
ClaudioD
PS : In the AMYA boat list there are 34 different models : 23 “one design” and 11 “developmental design”
Probably the ac120 could be really a “one design” and instead of discussing around Rating, would be better to call for “one design” proposal and the selected one, by vote, will be the New International AC120.
I Alan, I love numbers and so I think that the formula is the real “spirit” of IACC .
http://en.wikipedia.org/wiki/International_America’s_Cup_Class
Words could leave free to be understood, but numers are always true
In the IACC formula isn’t written if you have to make a large or a short beam boat… there are no differences about it if you don’t exceed the chains standard maximum values (expecially in the aft side of LBJ)
In the formula there are only 3 kind of numbers: length of the boat, surface of the sails and overall weight + a lot of coefficients and precise indication to do measurements and to apply the corrections required by the rule (chains and so on).
Your rating formula, is the same of old IACC Italian Safalero Cup that was copied from the “more” old rule to make rating competition in Turin in ’90, but it is completely different from the spirit of the true IACC formula.
Could be interesting, but it is another thing.
Anyway I think that you have to work a lot in different coefficients to obtain a good all-weather “large” boat (30 cm ) to arrive beating a also with your formula a normal large (20 cm) boat.
It could happen and the TS2 IOM is a demonstration… but I think that in the recent IOM history there was only 1 TS2.
You now really looking for good fantasies ? The real America Cup boat formulas scaled down 1:20 would sail like this …
The only true numbers “if scaled to 1:20” is the LOA…AC-120 cm …the rest is BS
Cheers Alan :zbeer:
I like it Alan !!
sorry, you forgot the Mast of 1750mm !! eheheh
ClaudioD
Is this to 1:20 scale ? 
35mt/20 = 1.75mt +/- 3mm heheheh!!!
CD
Not quite, I was hinting that there is not much demand to change the V5 specific generation, which means no applicable change in draft/sail area or bulb in that circuit. Then, no alterations mean no more issues… Everyone can sail under the current rules and so on…
Only previous generation yachts could have more draft and/ or sail area to even out the performance… Why not make those boats even faster than the V5’s on paper?!
Cheers, Jim
Hi Jim,
This is exactly what the rating does, gives V1 more power with larger SA than V5’s.
Agree, should not change current class spec’s, just means finding the “right rating window” so those with V5’s don’t need to make/buy new smaller sails.
Maybe could be class rules increase SA specs for V1 etc. too allow increase SA in this example V1 boat could use max 82 dm2 and V1 limited to 77.5 dm2.
Cheers Alan :zbeer:
P.S Is Camper going to win a leg ? …not looking good on this one :grumpy:
Jim,
I bring two examples of boat models derived from V5.
Boat A beam 16cm - Sa 78dm² - Bulb-Fin 3.0kg - DSPL 4.5kg
Boat B beam 17cm - SA 78dm² - Bulb-Fin 3.0kg - DSPL 4.5kg
Apparently the two boats can race together considering them rather similar, same Sail Area and same Bulb-Fin weight, same DSPL.
Now if we apply the Rating formula = 32 to 34, described above, we have for :
Boat A…: (120 + 78 - 16) x 0.2 = 36.4
weight ratio…: (3.0 +1.5) / (3.0/1.5 = 4.5kg / 2 = 2.25
thus…: 36.4 - 2.25 = 34.15…boat A is out of Rating
Boat B…: (120 + 78 - 17) x 0.2 = 36.2
weight Ratio : (3.0 +1.5) / (3.0/1.5 = 4.5kg / 2 = 2.25
thus …: 36.2 - 2.25 = 33.95 …Boat B is OK in regard to the Rating
The Boat A can be recovered if the Sail area is reduced to 77dm² as :
…: (120 + 77 -16 ) x 0.2 = 36.2 - 2.25 = 3.95…Boat A is OK in regard to the Rating at the condition to reduce the SA at 77dm².
This is just a simple example that explain how the Rating works also inside the same iacc Rules version.
You can also use different parameters combinations that will shows that each boat has is hown identity in terms of rating not only because of V1 to V5.
Other formula applications adopted for real scale boat cannot be re adapted to 1/20 models because all the parameters are not scaled to the same criteria. Some examples :
Real AC = 24000kg DSPL scaled to 1/20 would be 3.0kg, but in reality the models are = 4.5kg
Real AC = 20000kg Bulb scaled to 1/20 would be 2.5kg, but in reality the models are = 3.0kg
Ratio Bulb /DSPL on real boat is 0.833 but on reality the models are 3.0/4.5kg = 0.66
Real AC = 18.0mt LwL scaled to 1/20 would be 90cm but in reality the models are = 100cm
Real AC = 350m² SA scaled to 1/20 would be 0.87m² but in reality the models use 80dm² max, but most of the time 78dm²
Hope it is more clear now, why deciding to make ac120 models issued by V1 to V5 are not the same, without a rating, once in the water .
Cheers
ClaudioD
Hi Claudio,
Thank you for the in depth analysis, I appreciate the explanation.
I am very aware that there is an evolutionary aspect and that the V1 - V4 boats are at a disadvantage… It’s a reality. They are and always will be, that’s the nature of the beast.
My point is that the V5 yachts were the last generation and pretty much represent the majority on the water, and have the benefit of being the closest matched so I think that they should be left out of the rating, but the minority pre V5 boats can have their performance enhanced to stay in the game…
Cheers, Jim
Hi Jim,
will be right with you if the Rules will exclude all Versions, but 2007.
Would be unfair letting racing together formula 1 against formula 3 just because all have 4 wheels !
imo the AC spirit shall be keept with “All In” with similar performances and competitiveness !
The skipper only should make the difference.
Ciao
ClaudioD
PS : between us : I regret anyhow that this class has not adopted up to now, the “one design” concept
Hi Claudio,
Unfair you say?
On the other side of the coin, I consider it unfair to reduce the yachts performance to the slowest by reducing sail area from max 80dm2 should you want to use it.
“skipper should only make the difference” does not apply as that would mean a whole new angle on the rules and swaying to a true one design concept, with everything identical on the yachts. Hulls, foils, bulbs, rudder, mast, sails and radio.
Which is not very practical.
Just to touch on the sails a little more… These items make or break your yacht. You can have a quick design on paper but, on the water, if your mainsail cut is not quite right your boat is instantly slower upwind. Maybe not by much, but still slower. You need the extra sail area down wind to help recover the lost speed from the upwind leg. This is not available to you under the rating as your ideal speed has been calculated on a perfect setup on a perfect day, which today is not!
Sails are easy to build, but its not easy to build a perfect set. I think that the rating is not allowing enough room for characteristic differences these yachts have, their diverse sail plan arrangements and their sensitivity to an imperfect setup.
For example: I.M.O.one of the reasons Matthias is consistantly fast because his yacht has some of the nicest set sails out there.
With the rating, it would still end up with a class that just needs “X” hull with “X” foils, “X” mast “X” sails tuned to “X” setup to go out and be mixing it up at the front. There will always be a setup that is faster than the rest, rating or none. That’s why you test and test again searching for that perfect mode.
Does that make it clearer?
Cheers, Jim