There has been some discussion on the Replacing Spin Halyard thread about the replacement aluminum Jib box assembly offered by Rig Rite to replace the stainless one that is no longer offered. This is the link to the Rig-Rite page with the information on the sheave box.

I am pasting the text below from the Rig-Rite web page and adding emphasis (red text) for the class measurer to investigate the impact on J/30 Class Rules under paragraph 5.8.2 Prohibited Alternatives or Additions, specifically paragraph 5.8.2.1 which states A headstay length which exceeds 10935 mm when measured from pin to centerline as shown in the following diagram. (See figure 1.)

Text from the Rig-Right page is as follows:
(This is new Assembly)
Aluminum Jib Box Assembly w/ 3/8" Pin: K-11597-1:
Cast aluminum four (4) halyard internal Jib Box Assembly with 3/8" pin and 3/8" Forestay Toggle. Accommodates two spinnaker halyards over two jib halyards, in a trim, narrow and lightweight unit. Features heavy-duty Nylatron Sheaves: (2) 2" Sheaves for Spinnaker Halyards, K-11594; (1) 2" Sheave for Upper Jib Halyard, K-11640; (1) 1 3/4" Sheave for Lower Jib Halyard, K-11639; and (2) 5/8" secondary Sheaves (forward) for the 2 Upper Halyards, K-11585. Jib Halyard Sheaves are suitable for use with wire or rope halyards. All Sheaves are 1/2" wide for snag free handling of halyards up to 3/8" diameter. Assembly fits in mast cutout 9 3/4" high x 1" wide, and fastens with (4) 1/4"-20 machine screws (included). Internal mounting flange is slightly curved to fit a variety of masts. Assembly is designed to fit through the mounting slot and is then fastened from the outside. Forged Chrome Bronze Toggle, Mer 5770-412, is included. Unit measures 12 7/8" long x 1" wide and projects 2" (maximum) inside of mast. Suitable for use with a variety of mast sections on boats with forestays up to 1/4" dia. As used on J/30, J/29F, and others. A2-4, 4-5



(This is old Assembly)
SS Jib Box Assembly w/ 3/8" or 1/2" Pin: K-10658**D:
Welded SS four (4) halyard internal Jib Box Assembly with 3/8", or 1/2" pin for Forestay Toggle. Accommodates two spinnaker halyards over two jib halyards. This heavy Jib Box was used on a variety of MORC boats including many of the J/30's and J/29F's. Assembly fits in mast cutout 9 3/8" high x 13/16" wide, and projects 2" inside of mast. Mounting flange is fastened to the Mast with (12) 1/4" fasteners. This part is discontinued, having been replaced by the much lighter K-11597-1, above. A sheave and bushing replacement kit, K-10658SK, is available, see below. Please note: When replacing this item with the new K-11597-1 (the mast cutout needs to be widened and extended downward), the Forestay pin will be 1" higher on the mast; the forestay length will change accordingly. A7-4

I believe that there may be a change to the class rules for allowable headstay length so the mast is in a consistent position intended by the class rules, dependent on the type of jib box installed. Class measurer, please take for action and report your findings. Class feel free to discuss your comments on this topic in this thread.

I suppose we're closing the barn door after the cows are gone. I don't like the idea of the lighter weight or different location but I do live in the real world. Measurer might check if Hall uses this box or some other and where their forestay pin is located.

Lighter weight that high up is a pretty serious change if the weight saving is significant.

The headstay length could be corrected by installing the box 1" lower on the mast, couldn't it?

As Class measurer I will be reviewing this issue to see if this box will meet structural requirements, issues on location, impact on the weight, and how it effects the rig tune.
At this time use of the rig rite box is not legal at this time for one design events

After reviewing the avialablity of the orginal sheeve box and alternates As class measurer I recommend that the Rig rite sheeve box be approved for use only in replacement masts. Due to location differences and hole size it can not be retro fitted to old masts.

Once the availability of the original sheeve box declines and someone has problems with the sheeve box, they will need to replace the whole mast? Ouch.

Keep in mind that the orginal box is almost unbreakable you may have to replace sheeves and roll pins The only time you would need a new one is if the rig was lost over the side

Charlie is correct. The old one is a beast and there is no reason for it to wear out. All my sheaves were frozen so I pulled the box out and replaced the sheaves. The box was perfect. It also weighs a ton unfortunately.

So OK ... now you guys may have a problem ... At some point it appears that kenyon changed the boxes it installed in the mast ... from a 12 screw version to the 4 screw version.

I am thinking it may have been on the last 100 or so j30s often referred to as the 500 series.

The question then seems to be ... if both are "original equipment" they should then be legally interchangeable?

526 was measured for forestay at 2010 NA and it was not a problem .


From memory I think that 505 also has the 4 screw box.

photo of box on 348/349 vintage

The picture from 349 is the original - same as I have on Rhapsody. The one on 526 appears to be the new one shown at the top of this post. Charlie has contacted Rod Johnstone and the new version is discussed in the 5 May BOG meeting minutes.