Rule 13 Question

[David Sanderson]

I have been reading the rules, to start with because of my large headed jib, but I came across the list of general prohibitions in Rule 13.1:

13.1 Bowsprit, bumpkin, outriggers, sliding seats, bilge boards, double rudders and all
similar contrivances; inside ballast, hydraulic, pneumatic or electronic equipment;
electrical equipment other than lights save that the following electronic items are
permitted:
(a) One or more electronic time pieces.
(b) One or more electronic devices correlating only data relating to magnetic north
and the boat's heading.

What is the definition of Hydraulic or Pneumatic equipment?
I'm also interested in why this prohibition is here - what was the feature that is now banned?
I guess that 13.3 was to prevent very complex (expensive?) boats - I've seen a YouTube with a 12 that had hull shape shifting.

Dave

[NTOACertification]

A lot of the prohibitions are standard RYA prohibitions  from when the Class was started and are common across other Development Classes , they were designed to keep the boats Simple !!!.

Hydraulics and Pneumatic systems were banned for similar reasons. I recollect that a Hydraulic system to control rig tension and mast rake was used on a 505 many years ago but I think it was banned or didn't operate too well. 
I don't think or recollect of Hydraulic or  similar system being used  tried out om Twelve.

Sometimes  some of the Classic definitions have been used to prove or disprove the legality of a feature.  like the Daggerboard on Jo Richards Bouncer in the 70's

[David Sanderson]

A hydraulic mast ram I could see, but I can't see how it would be any advantage over a muscle box or normal sliding ram. I can't think of many other uses of hydraulics in a dinghy. Likewise pneumatics - I'm not sure I can think of a practical application on a dinghy.

Its interesting.

Dave

[StuW]

They were used quite successfully on a number of merlin rockets in the late 80s. Diamond Smiles was fitted with them for adjusting the shrouds, were fitted on tracks like a number of 12s have, and I think John Turners Passion did too. Theory was it took all the load out of the Hull as the master cylinder could be located wherever you wanted it to go.
Think cost was a major issue.  Most yachts use hydraulics as the norm.