proposed class rule amendment, jib car adjusters

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Bengt J
Posts: 54
Joined: Tue Oct 25, 2016 2:36 pm

proposed class rule amendment, jib car adjusters

Post by Bengt J »

The Technical Committee is proposing the following amendment to the class rule:

4.3.17 The maximum power ratio of the jib lead adjusters will be increased to 8:1


Background: to get the full advantage of the recently approved in hauling rule, it would be beneficial to increase the power ratio of the jib car adjusters to allow adjustments in medium/heavy air.
JBoats have indicated that if the J109 were designed recently it would be specified with a 6:1 adjustment and in haulers
A very simple change to the existing class legal 4:1 adjusters is to add a 2:1 cascade between the forward turning block mounted on the track and the existing cleat, creating a 8:1 adjustment (not suitable for overlapping jibs).
The TC suggests this amendment is fast tracked for a vote before next season starts, implementation by April 1 if approved.

The following drawing added to show existing class legal system
jib leads.jpeg
jib leads.jpeg (124.02 KiB) Viewed 14069 times
Bengt J
Posts: 54
Joined: Tue Oct 25, 2016 2:36 pm

Re: proposed class rule amendment, jib car adjusters

Post by Bengt J »

I have gotten a few requests to explain/show how the standard 4:1 plus a 2:1 cascade could work. I rigged a temporary system on Zig Zag today. The distance from the forward turning block on the track back to the termination point at the back end of the track is 122" giving us a maximum travel of the jib car of 30 1/2". in our case that is +/- 15" around the base position for the class jib. These dimensions will vary somewhat boat to boat.
Attachments
Termination of back end of cascade
Termination of back end of cascade
IMG_0701.JPG (431.66 KiB) Viewed 14017 times
Jib car at base position, showing the turning ring for the cascade
Jib car at base position, showing the turning ring for the cascade
IMG_0705.JPG (346.9 KiB) Viewed 14017 times
Jib car max aft, ~ 15" behind base position, showing the low friction ring of the cascade preventing the car go further aft
Jib car max aft, ~ 15" behind base position, showing the low friction ring of the cascade preventing the car go further aft
IMG_0704.JPG (357.36 KiB) Viewed 14017 times
Jib car max forward, ~15" forward of base position
Jib car max forward, ~15" forward of base position
IMG_0703.JPG (450.01 KiB) Viewed 14017 times
drosowj
Posts: 11
Joined: Wed Dec 31, 1969 8:00 pm

Re: proposed class rule amendment, jib car adjusters

Post by drosowj »

From the Class Secretary:

Preamble:
The proposed rule change was brought by the Technical Committee to the Executive Board for review and comment. The Executive Board approved proceeding to vote the following, with Executive Board comments incorporated.

Background:
To get the full advantage of the recently approved in hauling rule, it would be beneficial to increase the power ratio of the jib car adjusters to allow adjustments in medium/heavy air. JBoats have indicated that if the J109 were designed recently it would be specified with a 6:1 adjustment and with in haulers. As an example, a very simple change to the existing class legal 4:1 adjusters is to add a 2:1 cascade between the forward turning block mounted on the track and the existing cleat, creating a 8:1 adjustment (not suitable for overlapping jibs). The system is not permitted to be operated or rigged to the windward side. More information and pictures are available on the Class Forum.

New Proposed Rule:
4.3.17 The maximum power ratio of the jib lead adjusters permitted is 8:1. This can be done by adding sheaves to existing tackle or, adding a 2:1 cascade to the existing 4:1 tackle. The jib lead adjustment line must use the existing cheek block and jib lead cleat on the same side as the jib car it adjusts.

A ballot will be prepared shortly and sent to all members.

Respectfully,
David Rosow
Secretary
drosowj
Posts: 11
Joined: Wed Dec 31, 1969 8:00 pm

Re: proposed class rule amendment, jib car adjusters

Post by drosowj »

From the Class Secretary:

The proposed rule 4.3.17 regarding the jib lead adjusters received more than the two-thirds votes necessary to be adopted. The new rule becomes effective on March 1, 2017. The updated class rules will be posted on the website shortly.

Respectfully,
David Rosow
Secretary
Dan Corcoran
Posts: 278
Joined: Sun Jan 29, 2017 4:32 pm

Re: proposed class rule amendment, jib car adjusters

Post by Dan Corcoran »

Is it possible to upgrade the car and sheeves on the track to get the additional purchase? Has anyone shared the part number in another post?

Thank you
Dan
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