Main sheet lower block upgrade

Topics about Class Rules and the RRS.

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bmastror
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Main sheet lower block upgrade

Post by bmastror » Fri Oct 13, 2017 8:54 am

Harken has upgraded the lower block and the traveler swivel (you have to buy the entire assembly)
Item Number: HSB456, Description: #14CAM BASE-LG SWV J109 UPGRADE

The replacement U adapter info:
Item number H-29180A, Description: U-ADPT FOR 1/4in PINS J109
I attached a picture with the old U adapter next to the new one. As you can see, the new one is much larger. Hopefully this will prevent the U adapters from breaking in the future.
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Bengt J
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Re: Main sheet lower block upgrade

Post by Bengt J » Thu Oct 19, 2017 9:08 am

Brooke, Thanks for posting this info!
The upgrade is a safety issue and absolutely Class Legal. Other custom solutions for heavy duty versions of this connecting piece are also Class Legal as long as the function of the Block/Swivel assembly is not changed.

Bengt Johansson

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Vento Solare
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Location: Newport, RI

Re: Main sheet lower block upgrade

Post by Vento Solare » Tue Oct 16, 2018 10:40 am

This past week with big wind at the NAs three boats blew up the plastic swivel plate that holds the upright clevis pin attached to the lower block. Additionally many boats deformed the stronger Harken model H-29180A, U-Adapter with 1/4in pins made for the J/109.

This winter I will look at the possibility of fabricating a small stainless disk that fits over the plastic swivel and is bolted using the existing 4 screws. Something like this should take the load off the plastic piece. If successful, I'll suggest that Harken may want to incorporate the upgrade.

category 2
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Re: Main sheet lower block upgrade

Post by category 2 » Tue Nov 06, 2018 11:38 am

The Harken midrange swivel, 1574, fits the existing platform, sports a 280 offshore cam cleat and should be much stronger. It utilizes 1/4" fasteners and 5/16" pins which accept the 1550 midrange ratchet block. This is a readily available stock piece of hardware.

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Vento Solare
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Re: Main sheet lower block upgrade

Post by Vento Solare » Thu Nov 29, 2018 2:57 pm

from the previous post:
"The Harken midrange swivel, 1574, fits the existing platform, sports a 280 offshore cam cleat and should be much stronger. It utilizes 1/4" fasteners and 5/16" pins which accept the 1550 midrange ratchet block. This is a readily available stock piece of hardware."
Today I met with Harken folks and learned that the 1574 Midrange swivel is NOT bolt in compatible with the existing swivel on the J/109. The 4 screws on the midrange block are 1-1/16" spacing while the existing swivel screw spacing is 3/4".

The Technical Committee is meeting on 3 December to discuss the topic and will work on a path forward for a class legal solution. In the mean time, it is suggested that anyone planning to install the midrange swivel hold off, as that probably will not be the approved solution.

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Vento Solare
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Re: Main sheet lower block upgrade

Post by Vento Solare » Thu Dec 06, 2018 11:42 am

The technical committee has reviewed the mainsheet swivel assembly issue and posted a Measurer's interpretation in the post labeled Mainsheet Swivel Strengthening Modifications Allowed

I also received an email from Kurt Larsen on 3 December with the following information and picture. Subsequent to this email, the modified approach was approved by the Technical Committee.

I installed the mid-range block on “Rush” as an emergency repair during the recent championship regatta. During that regatta at least 3 boats broke their mainsheet swivels. The swivel base itself is what broke. Not the cam arm or the “U” adapter. The midrange block has a wider footprint but still fits on the existing aluminum platform. The larger base uses 1/4-20” fasteners and I positioned the aft one so as to replace the existing tie rod fastener which is also a 1/4-20”.

I just upgraded the swivel on “Freedom” with the midrange and made a new aluminum baseplate to eliminate the extra holes from the old swivel. Picture enclosed.

The day after I completed this I heard that the class has not yet ruled on this. This upgrade does not change the sheeting locations or the amount of purchase and is identical from a competition standpoint. As a larger and more robust fitting it should be far less prone to failure.
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