Measurers Corner

Measurer’s Interpretations and Recommendations

Topic:Backstay/Boomvang/Outhaul Adjustments
Question:Is wire the only permitted material for the connection of the backstay through the backstay gland?
ID Number:000015
Short Answer:No 
Answer:The backstay is specified as wire but the backstay pennant may be wire (5/32" SS 7X19) or equivalent strength non-wire. 
Action Date:2008-10-15
Thu Nov 30 23:00:15 2023
2008-07-14Bam MillerI was sailing a shields this weekend that had significant fraying of the backstay pennant that was made from Vectran fiber. I was under the impression that the pennant (the length of line below deck and through the gland) was supposed to be wire. I have reviewed the class rules and there is no mention of it, except to say the backstay is supposed to be 1/8" s.s 1x19 wire. The plan doesn't even show the disconnect for easy removal.
2008-07-15Cape Cod ShipbuildingThe old style wire backstay pennant was 6' long. The new pennant is the same diameter but the length is 43" and most Shields have upgraded to the new backstay system in order to run the purchase system under the aft deck. The backstay pennant has always been 5/32" 7x19 wire.

It's easy to replace the pennant. You need wire cutters, a nicropress tool, 1 nicropress sleeve and thimble, the new wire pennant with swaged jaw fitting. Remove the backstay deck casting, remove the old wire by cutting one end. Feed the new pennant into the backstay casting top to bottom. Make sure the wire is fed the correct way through the keeper pin so the wire is resting on the sheave or casting. Nicropress a loop in the lower end of the wire using the sleeve & thimble. Re-install the backstay deck casting. This can be done on the water as long as you shackle the main halyard to the aft mooring cleat to support the mast while the backstay is disconnected. Replacement can also be done without removing the deck casting, but you have to climb into the aft tank to do the nicropress.
2008-07-15Richard RobbinsProposed change to Official Plan 2 - Fittings and Rigging Plan:

(34) BACKSTAY 1/8" SS 1x19
(34a) BACKSTAY PENNANT 5/32" SS 7x19
2008-07-22Greg DavisI would actually make the argument that a rope pennant is easier to service and inspect than wire since it is obvious when and where it is chafing. I have yet to see a rope pennant fail, but have seen two wire pennants fail in the last year or two. I suspect that since the wire does not show fatigue in the same way rope does it is often overlooked. With 3/16 inch spectra having well over double the breaking (5400lbs) strength of 5/32 7x19 wire (2000lbs) an owner could replace the pennant by simply tying knots thereby cutting the breaking strength of the spectra rope in half and still retain the same margin of safety as wire. If there is any doubt regarding the integrity of the line it takes minutes and no special tools to replace spectra.
2008-07-28Richard RobbinsAnother reason for requiring wire is that the backstay is part of the grounding system and should be wire for safety of the mast grounding.
2008-07-30Andrew BurtonThis question has already been addressed in a measurer's ruling in the past 10- 12 years. Materials other than wire are permitted. No idea where to find it but this ruling is more than 5 years old. Re the point from CC Ship: their method is opposed to tying two knots in a piece of line. Greg's points were a part of the reasoning behind the ruling. I find that Spectra is way better than wire because when it shows signs of wear I can crawl back and replace it, rather than having to go buy wire, borrow a swaging tool and take the whole assembly out to the boat to make the repair. Because of the sharpness of the turn, wire doesn't last much longer that Spectra either. Let's remember that the rules are in place to keep the sailing cheap, simple, and even. There's no good reason to specify wire and no advantage to another boat either way.
2008-08-04Greg DavisRegarding the comment on grounding, the forestay also has a grounding wire connected to the keel bolts. I would hope that is sufficient to protect the boat/crew.
2008-09-12Richard RobbinsBased on discussion of the Technical Committee on 9/11/2008 the following interpretation is added to allow non-wire rope for the pennant: The backstay is 1/8" stainless wire 1x19 and the backstay pennant is 5/32" stainless wire 7X19 or equivalent strength non-wire rope. (See Section VII - Official Plan 2)