The America's Cup Measurement Committee was asked to issue a Public Interpretation, in response to the questions to clarify the restrictions under ACC Rule (Version 5.0) on altering the support of a fixed appendage to vary the heeled righting moment while racing. These are the questions and answers:

1. Does the term‘components’ include reference to:
a) hydraulic cylinders,
b) locking systems, or
c) structural response damping systems
any of them, with moving parts or variable geometries?

1. Yes. However, any component as described with moving parts or variable geometry shall be fixed, and if deemed necessary by the Measurement Committee, disabled to prevent movement, alteration or adjustment whilst racing.

2. Would a fixed appendage supporting structure that deforms gradually over time, either due to:
a) creep,
b) passive locking system, or
c) the presence of a damping system,
contravene the requirements for a fixed appendage within Rule 17 or any other Rule?

2. Yes, an appendage that is supported by structure that alters the deflection of the appendage due to gradual deformation either due to creep, a passive locking system or a damping system would be considered to be a moveable appendage. If the axis of rotation of the appendage is not at an angle to the MWL plane exceeding 45 degrees then it will not comply with Rule 17.10 (b).

3. Would the requirements for a fixed appendage of Rule 17 also be contravened by the constraint of a fixed appendage in a deflected position arising from the hydrodynamic and gravitational forces as described in answer 4 of the same PI 22? (i.e., Is it permissible to constrain a fixed appendage, by a mechanism which would maintain the deflection either to one side or the other, while deflected to leeward before tacking resulting in some deflection to windward, or less deflection to leeward, on the new tack?) (See as examples Figures 1 & 2).

3. Possibly. The definition of “fixed” as used in Rule 17 would be contravened if a fixed appendage was constrained by a mechanism which would maintain the deflection to leeward before tacking resulting in some deflection to windward, or less deflection to leeward, on the new tack.

4. Would the answer to the previous questions be similar if the fixed appendage, or its supporting structure, was not fully constrained but instead restrained thus producing a similar but time dependent behavior when changing tacks (ie, the fixed appendage would gradually return to have similar deflection to leeward on both tacks over some finite period of time)? (See as an example Figure 3.

4. Yes. See answer 3 above.

5. Would the control or adjustment of the constraint or restraint of a fixed appendage while racing contravene rule 17? (See as an example Figure 4).

5. Yes. See answer 3 above.

So, we now have some idea of the device that one of the America's Cup teams has in mind. What we do not know is which team it is.
Nor do we know whether, after that interpretation, they felt - or will feel - able to use such a device, without contravening the rules!