AC 36 Foiling Monohulls

When the flap is up the force from the foil is down depending on the angle of incidence of the foil set-up. Many main foil set-ups are+2.5 degrees with the flap in neutral and the rudder t-foil at zero degrees.
"Although not intuitive, from a sailing perspective flap up
(shedding lift) is more important than flap down (adding
lift) because of the dire nature of the crash that comes from
the inability to shed lift adequately."
From Bill Beaver at The 19th Chesapeake Sailing Yacht Symposium, March 2009
------
The AC 50's used windward rudder downforce......

 

Apparently. The rules include an introduction where the second paragraph states (in part):

“The AC75 Class Yacht is a 75 foot high-performance monohull intended to … permit technological development to spearhead the development of sailing and maintain the America’s Cup as the world’s premier sailing event”​

So it would seem that your suggestions are considered inconsistent with that goal, at least by the people writing the rules.

 

Nonsense. These same "Rulemakers" or people like them changed the WHOLE BOAT in 35 to the chagrin of many people. "Rulemakers" will change if they're pushed into it by facts.

 

You seem to be confusing the issue.

There is no restriction in the rules on flap angle. Just beacause the flap is above neutral (i.e. “up” with respect to some datum) doesn’t mean that the foil* is producing downforce, as you point out. But the rules expressly forbid the foil overall from generating down force with no reference to how that is achieved, be it by flaps, AoA or anything else (including distortion of the foil or just the flap).

That is, forbidding downforce doesn’t mean the flap can’t go”up”, it just means the foil can’t generate a force downward.

The AC75 rudder will certainly produce downforce, there is nothing in the rules against that and it is almost certainly required to control pitch and hence will have an effect on ride height. There’s nothing novel in that. The rudder may also be used to generate righting moment through downforce (given it’s offset from the lift of the leeward main foil so up/down force will affect RM), but that supposes there is some other force to counter its bow-up effect on pitch.

In the AC50s, that additional downforce could be offset by the other rudder, but these boats only have one rudder so much more complex to control excess rudder down force (i.e. that induced beyond what is needed for pitch control to make some available for RM) through, say, sail trim.

But I don’t discount that they will try it.

* where “foil” is the whole assembly of the foil, including the flap and all its parts.

 

Rule 24 on the instrumentation and logging system (ILS) includes:

24.2 The ILS must provide a single data stream to the Media System, which:
(a) must use a specified protocol;
(b) must include specified data channels for broadcast and/or verification of AC75 Class Rule compliance​

There are other rules stating that certain sensors must be fitted. So yes, Big Brother will be watching. ;-)

E.g. rule 26.5:

“If an FCS is frequently being commanded to drive the foil to a more raised position, and that foil is generating net downforce, the FCS may … provide information to the Media System for the provision of racing penalties.”​

Noting that the foil control system (FCS) is a supplied component, so it will do whatever the designers want it to do.

 

When the Madness began:
America's Cup: When the madness began >> Scuttlebutt Sailing News https://www.sailingscuttlebutt.com/2018/06/28/americas-cup-madness-began/?utm_medium=email&utm_campaign=Scuttlebutt%205113%20-%20June%2029%202018&utm_content=Scuttlebutt%205113%20-%20June%2029%202018+CID_2593f2d9104809626622e5b4b89d20c7&utm_source=Email%20Newsletter&utm_term=Americas%20Cup%20When%20the%20madness%20began

Excerpt:
Until Team New Zealand and the RNZYS first won the Cup in 1995, the Cup’s first three trustees – the New York, Royal Perth and San Diego yacht clubs – had consistently printed their Cup victories in a standard font on the original base beneath the Cup that was probably no larger than may be 12 point.

In fact, one whole side of the original base after AC28 in 1992 was vacant and, if the font had been maintained, it could have accommodated the race results for up to four more Cup matches (perhaps up to AC32 or AC33).

Instead, the RNZYS dedicated that side to their 1995 victory in AC29 – all 5 races between TNZ and Stars & Stripes were engraved on the final vacant side of the original base in something that resembled a 20 point font!

Therefore, it was RNZYS’s decision to unnecessarily cover one side of the trophy with a 5-0 victory that required it to commission the first of the two extra tiers that followed. Onto this were engraved the results of TNZ’s defense in AC30 (in 2000).

It’s actually the Kiwis themselves that set the tone for subsequent engravings to be abused. I saw the Cup in person at the RNZYS in 2000 and 2003 and I have the pictures to confirm it.

 

Apparently the final rules (I guess those mentioned in Rule 33) will be revealed "tomorrow", which I guess is 30 June 2018.

Team New Zealand ready to reveal final rules around boat design for 2021 America’s Cup

The AC75 foiling monohulls will be finalised tomorrow but Team NZ’s designer has already been busy looking for an edge.
Head designer Dan Bernasconi has barely left the team base for the past year as he tries to find that extra element to keep hold of the Auld Mug.
Bernasconi is the man few would recognise but one who will go a long way to determining whether Team NZ can defend the Cup.​

So it seems ETNZ has already started design work based on a specification that hasn't been revealed to the challengers yet. Perhaps they should have put in place a more independent design team, but I guess the challengers knew the situation when they signed up.

Interesting that the final rules will be released on the same date as the last day to submit a challenge. ;-)

 

Latest rules: AC75 Class Rule v1.1 29 June 2018

There are a number of changes, it will take time to go through them all. There is a lot more detail on how the foil cant system (FCS) can and can't be used. There is still speculation that it might be used for downforce, but I don't think that it will be allowed unless all the teams agree to allow it (it might well happen if it makes the boats easier to manage, they might be diabolical through transitions without it).

 

AC 75 Rule- Thanks for posting!

27.4 The AC75 Class Yacht is not designed to resist righting-moment created by hydrodynamic downforce on
the windward foil. Following sailing trials and experience gained by Competitors, the Rules Committee,
with the agreement of COR/D and the Regatta Director, and in consultation with Competitors, may amend
this Rule to place restrictions on the use of the FCS including, but not limited to:
(a) a restriction of:
(i) the amount of negative cant moment (moment in the sense of reducing cant angle) that may
be sustained by the FCS; and
(ii) the cant angle that may be set for the windward foil;
(b) which may be applied at all times, or only in certain conditions, such as:
(i) when in a normal sailing mode, and not through a manoeuvre;
(ii) when within certain yacht speed or wind speed ranges; and
(iii) during certain stages of a race.
Such restrictions may be developed through sailing periods, but shall be frozen according to Rule 34.

 

TNZ may offer potential teams help:
America's Cup: Grant Dalton offers smaller teams the help of Team New Zealand https://www.nzherald.co.nz/sport/news/article.cfm?c_id=4&objectid=12081197

 

Regarding Dalton's comment:

"We've shown that David can beat Goliath, and can beat him well if you make smart decisions"​

Of course the winner can say that. The smartness of a decision can only be determined in hindsight, in the last AC the NZ team made a series of major decisions to develop the boat the way they did, fortunately history proved them to be the right ones. If any one had been wrong, or perhaps even marginally less than optimal, they could be saying:

"we should have <insert alternative option> instead of <insert failed option>"​

Wasn't that the story from the AC before that that they lost? When Goliath beat David?

Winners are grinners. It will be interesting to see if Ainslie's $200+ million challenge can overcome the Kiwi's defence at one third or one quarter of the cost. In many ways it might be better for the AC if it doesn't.

 

Team American Magic Roster:
America's Cup: Sailing roster for USA Challenge >> Scuttlebutt Sailing News https://www.sailingscuttlebutt.com/2018/07/02/americas-cup-sailing-roster-usa-challenge/?utm_medium=email&utm_campaign=Scuttlebutt%205115%20-%20July%203%202018&utm_content=Scuttlebutt%205115%20-%20July%203%202018+CID_82699839919d0d3aa6cbbc9f8675a661&utm_source=Email%20Newsletter&utm_term=Read%20on#more
================
Sailing Team: New York Yacht Club American Magic
----
Skipper & Executive Director:
• Terry Hutchinson (Annapolis, Maryland, United States)
Helms/Tacticians:
• Dean Barker (Auckland, New Zealand)
• Andrew Campbell (San Diego, California, United States)
• Bora Gulari (Detroit, Michigan, United States)
• Ian Moore (Cowes, Great Britain)
Sail Trimmers:
• Trevor Burd (Marblehead, Massachusetts, United States)
• Maciel Cicchetti (Mar del Plata, Argentina)
• Paul Goodison (Sheffield, Great Britain)
• David Hughes (Miami, Florida, United States)
Specialists:
• Matt Cassidy (San Diego, California, United States)
• Sean Clarkson (Mill Valley, California - Nationality: New Zealand)
• Jim Turner (Auckland, New Zealand)
Grinders:
• Cooper Dressler (Coronado, California, United States)
• Luke Muller (Ft. Pierce, Florida, United States)
• Caleb Paine (San Diego, California, United States)
• Luke Payne (Fremantle, Australia)
• Joe Spooner (Auckland, New Zealand)
Head Coach:
• James Lyne (Granville, Vermont, United States)

 

Gladwell on the new Rule:
America's Cup: Amended AC75 class rule released https://www.sail-world.com/news/207123/A-new-version-of-the-AC75-class-rule-is-out

 

=====================
Follow-up on this story: https://www.sail-world.com/news/207305/Am-Cup-Emirates-Team-NZ-extend-design-leg-up

"Emirates Team New Zealand have confirmed that they have offered new Challengers a basic AC75 design package, repeating the design deal they had with the now Challenger of Record in the 2013 America's Cup."

 

Brad Butterworth on the AC: America's Cup: Brad Butterworth on Dalts, the AC75 and Team NZ https://www.sail-world.com/news/207431/Four-time-Am-Cup-winner-on-low-entries