NEW AC100 - Two boats in One !!

This is the last design of the AC100-D.

Why Two boats in One ?

The design allow to change, as fonction of wind strenght, the bulb weight from 1933g to 2156g if the construction stays within 1050g.
The ratio Bulb/Boat is rather confortable up to 67% for the lateral stability and even more, according to the construction weight, that include a draft from hull bottom of 450mm. Respectively IOM has 59% and 420mm.

The lowest displacement is of 2983cm3 or gramms and the highest displacement is of 3206cm3.

The sailor can make his own choice without perturbing the overall performances since the waterplan variation is limited to 2.5mm while the LWL will change from 835mm up to 850mm the maximum allowed by the Rules under static conditions. The forward overhang is also increased while limiting the hull draft at 43/45mm.

Therefore as the weather conditions requires, the boat can be equipped, before the Racing period, with the most appropriated bulb. No need to have a second boat !!

More feature descriptions in the next days ?


A simple 3D view also because I’m not capable to do more !!!

The Sails

The shadows file & Rules updating!

This is a short history about the AC100-D design. (see attachment)

My Dream would be that some Model Clubs around the world would adopt this model design as such to become a Class reconised by a National Body !
In principle to become a Class at least 20 models need to be registered !



This looks very interesting. I may have to make this my next project.

Just my two cent of part of the message posted by Claudio in one of his last PDF:
“The AC100-B was developed in 2010 at the request of a Roman
Group AC100 -, after establishing the first Class Rules.
This group, for reasons unrelated to the project, has ceased its
activities in April 2011.”
I would like to underline few informations.
First of all the AC100 group not ceased its activity (e.g.
second the original website ( is KO due to the fact that the web master change class, now he is playing with a different RC boats and he is waiting the end of the contract to close the inactive site.
thks for attention

Hi Claudio,

Very interesting concept :slight_smile: I have question of clarification purposes between this “two boat in one design” and the new AC 100 rules.

“The displacement of this AC 100 D is variable from a minimum of 2983 cm3 up to 3206cm3 . This is achieved by simply changing, before the race period the weight of the bulb to cope with the expected weather conditions”. I assumed this meant through daily racing, if weather conditions changed, the skipper could change to different weight keel fin & bulb.

Then reading the “new rules” Section 7 – Radio Control Equipment, I read under 7.1.3 During daily racing, the skipper will use only the declared RC equipment and frequency, one Fin and one Rudder.

This is my point for clafication, are you suggesting to change displacement the skipper should change the bulb only:confused: if only one fin and rudder is pessimble during daily racing ?

Cheers Alan

Endeed Alan,
the choice made at the beginning period of racing cannot be changed later in the day.
You can either select only the bulb to be attached to the choosen Fin valid for the “full racing period” according to the expected weather conditions or change the full combined Fin+Bulb set up as you prefer. The Original Rules, are still valid , for the AC100-B, C, U and D.
The possibility to change something at the set up is called up by others classes. i.e Class M when selecting the Rig or the Fin/bulb.
This is part of the game, if weather conditions changes , pitty for the wrong choice.
More and more modelers that " like to win" go to the races with 2 models differently equiped, generally one light displacement and one heavy displacement probably the difference is called for a pound or more.
My AC100-D model , as is standing by design, offers a variation of 1/2 pound. A cleaver modeler can reach larger difference since the minimum weight allowed is 2750g

Pratically, without searching for extremes, a day with very light winds from 0 to 3 knots, hardly will change in a stormy conditions and in this case personally I will choose the lighter bulb and very probably a shorter Fin also to reduce the wetted surface…

The above is achieved because I have choosen to share the variations of the dispacement, by playing between LWL lenght within 850mm max, as per Rules, the hull draft and taking care about the hull lines ! (see CF parameter)


The complete design file of the AC100-D can be downloaded from :