[Public-List] america cup

[Michael Connolly via Public-List]

Jim, 
I haven't had enough coffee this morning to get into this.......................will speak up later. 
Michael 

----- Original Message -----

From: "Jim Mennucci via Public-List" <public-list at lists.alberg30.org> 
To: "Alberg 30 Public List -- open to all" <public-list at lists.alberg30.org> 
Sent: Wednesday, May 31, 2017 10:11:05 AM 
Subject: [Public-List] america cup 

Can anyone add to my understanding of how the hydraulically driven 
hydrofoils work on the Americas cup 42 footers now racing in Bemuda-- 
here's what I think i'm seeing: 

- In a way its kind a cool--going 30+ knots up and down wind doesn't 
require much sail trim...hydrofoil trim is another matter. Talk about 
changing sail boat racing as we all understand it. Trophy goes to team 
that is best at hydrofoil control, in fact hydrofoil control is the only 
area of boat design the is somewhat left to the syndicates to control on 
their own. . Optimizing hydrofoil control maximizes speed. 

- unlike the 72 footers, the 40 footers will use hand controls i.e., no 
closed-loop feed-back controls for the hydrofoils--this is what I wonder 
about? The hydraulic directional control valves used to pivot the foils 
use some sort of electrically controlled linear actuator to open and close 
flow to the hydraulic actuators, It would be easy to add some feed back 
control to the electrical part of the valve and if they don't that's good 
because of the additional skill needed to manually maintain stability 

- article I read says stored energy (accumulators) are not allowed and the 
hydraulics must be provided by hand pump--hence they're always pumping 
(like maniacs) to have fluid under pressure (must be a relief valve to 
regulate pressure) 

- the article talks about 3 hydrofoil controls: Cant, lift and pitch are 
the 3 names used.in the article. 
- It sounds like cant angle corresponds to roll which is used to 
add/control righting moment. Canting the wing off vertical tilts the 
horizontal part of the wing which should result in some loss in lift making 
an adjustment to the angle of attack to rebalance the lift--this is where 
feedback control would be nice but making the helmsmen do the adjustments 
in a manner that maintains foil stability adds old-fashioned skill to the 
mix. Thoughts? pivoting the hydrofoil outboard adds righting moment 
- lift control would pivot the hydrofoil in the pitch plane to 
change angle of attack 
- pitch control to me is the same as lift except its listed as a 
separate function. So I wonder if the dagger board and the rudder foils 
work in concert to change the pitch of the boat--much like bow and stern 
planes on a submarine 
- looks like linear hydraulic actuators are used to control 2 rotational 
degrees of freedom on the dagger board foils and a single actuator to pitch 
the rudder foils. 
- the foil controls are built into the helm wheel and its looks like they 
run the system open circuit i.e., no feedback control. They hit buttons 
built into the helm to open the directional control valves. So the 
helmsmen is also the foil trimmer. 

any insight, thoughts appreciated 

Jim Mennucci 
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