AC75 crew zone

Hi everyone,

Could you please help me with the interpretation/understanding of the rule 7.9 (c) & (d)

7.9 Any volume that is designed for a crew member to operate within for a sustained period shall be declared as a crew zone, where each crew zone shall:
(c) be a volume formed by extruding a crew zone planform along an axis orthogonal to MWP;
(d) extend in height from MWP to 2500 mm above MWP;​

With the following defintions :
3.1 The Measurement Waterline Plane, MWP, is defined as the horizontal reference plane of the yacht.
3.2 The Longitudinal Centre Plane, LCP, is defined as a vertical reference plane, orthogonal to MWP.
3.3 The Transom Reference Plane, TRP, is defined as the vertical reference plane orthogonal to MWP and LCP.
3.5 Except where otherwise specified, terms such as “above”, “below”, “up”, “down”, “forward” and “aft” refer to directions or relative positions aligned to the xyz‐axes in the yacht‐fixed reference frame, where:
(a) the origin is at the intersection of TRP, LCP and MWP;

As I understand, the crew zone shall be a prismatic volume of height 2500, starting @ MWP. Quite an impressive height for crew to fit in. I just can't figure how to place the crew inside. Got any advice ? How would you do ?

 

Hi Alan
I may not be understanding your question - the volume of the crew zone defined in 7.9 (c) and (d) taken at face value seems straight forward; the detail and complexity of the design of the cockpits comes from the entirety of sections 7.8 through 7.15.

The definitions towards the end of the Technical Regulations are very helpful.

 

Where can I find the AC75 rules?

 

Thank you very much, Tiny Turnip. I made a confusion between freeboard and the height of the crew zone. I'm sketching something, to share my understanding of these requirements.

Cheers,

 

Here they are. I did not attached the part, specific to the race organisation itself.

 

Looking at the totality of the rules where "crew zone" is mentioned it becomes very obvious that they are trying to prevent another entrapment drowning.

 

Thank you very much @Alan Cattelliot
Basically I already had it but an outdated version.

 

Here's the link for the latest updates:
AC37 Noticeboard https://ac37noticeboard.acofficials.org/

 

I've drawn this, for a side view of the crew zone. Have you got any remark, comment ?
Aside from the general arrangement, my goal is to work on the parasitic drag of the boat, assuming that there could be some significative progress to be made. For this purpose, it is important for me to have a perfect understanding of the crew zone, as the whole aerodynamic model should integrate its contribution to this parasitic drag. When consolidated, I will be able to draw a shape that will be tested in CFD, in concurrent engineering with a 'classical shape', already seen in previous design. Lot of fun.

 

Your hull is waayyyy to deep for good aerodynamics. Read the rules, they expect the grinders to be recumbent; and they get more power that way.

 

I would interpret the rules as there is no requirement wether primary force input devices are recumbent or not. But if they are recumbent there are special rules as for example the length of the crewzone.

 

Thanks you Jehardiman and Mc_rash.

I understand that recumbent primary input devices are not mandatory, only particular rules apply when used.

As a matter of fact, I have the idea of using recumbent primary force input devices to minimize the frontal area, but I didn't show it in the very simple drawing I've posted. First thing first, I had first to be sure of my understanding of the crew zone heights. One point is to seek for less frontal area. Another is to guarantee also a good field of vision for the helmsman and the trimmer, keeping also enough proximity for direct and indirect communications.

Finding the balance between aerodynamics and ergonomics is always a matter of compromises. It's the subject of this little exercice. There is quit an impressive sum of experience on this forum, and I will be very interested to see where we can go. Let's keep on, and cheers to all.

 

True...I'm allowing my bias to show.

 

First photo I've seen of a new-gen AC75: Pro-Set named official materials supplier for New York Yacht Club American Magic https://www.compositesworld.com/news/pro-set-named-official-materials-supplier-for-new-york-yacht-club-american-magic.