Furler Forestay SS Wire Rope Type

[GwalarnYacht]

We need to replace our furler forestay on a project boat. The noticed that the current wire rope is 10mm 1x19, even though the rest of the standing rigging is all 8mm 1x19.

Unfortunately, due to limited availablity at our location, we are now faced with the choice of replacing it with a 10mm 7x19 or an 8mm 1x19 wire rope.

Should we "downgrade" to 8mm or is a 10mm 7x19 acceptable as forestay?

[psk125]

Rigging sizing is most often determined by the load the naval architect anticipates. The forestay on your boat may have higher loads than the rest of the standing rigging. Downsizing would probably not be a good idea.

[GwalarnYacht]

Originally Posted by psk125

Rigging sizing is most often determined by the load the naval architect anticipates. The forestay on your boat may have higher loads than the rest of the standing rigging. Downsizing would probably not be a good idea.

Thanks for your feedback. So is a 7x19 wire rope acceptable as forestay? I understand its less stretchy and more flexible, which make it less ideal, but can it be used given the lack of other options?

[GordMay]

1x19 wire rope is rated about 20% stronger than the 7x19, and has a lower modulus of elasticity. For a 50 foot wire, the 1x19 will stretch about 1½" at 25% of it's breaking strength, whereas the 7x19 will stretch about 2". Since the 7x19 stretches more, the stay can go slack & “whip”, causing greater shock loading on the rig. The 7x19 will fatigue faster and fail sooner than 1x19.
The 1x19 is more expensive than 7x19, of the same diameter.
Personally, given the trade-offs, I'd use the 8mm in 1x19.

Originally Posted by GwalarnYacht

Thanks for your feedback. So is a 7x19 wire rope acceptable as forestay? I understand its less MORE stretchy and more flexible, which make it less ideal, but can it be used given the lack of other options?

[psk125]

Not sure the 8mm is strong enough. 8mm 1x19 ss shows a breaking load of 4640 kg. 10mm 1x19 ss shows a breaking load of 7250kg. 10mm 7x19 galv (couldn't find ss) shows a breaking load of 6531kg. You may need to explore other options. This chart might be helpful:
https://www.ronstan.us/marine5/wirel...risontable.asp

[roverhi]

Every boat I've ever owned has had 1 x 19 SS wire. The headstay has been the same diameter as the cap shrouds and backstay. From observation it would seem the cap shroud has the potential of carrying the highest load. Never considered anything other 1 x 19 because of the stretch and lower strength of the other types of wire.

You didn't state the size of the boat but assume from 8mm rigging it's at least 20,000# and over 40'. Knowing boat length, displacement, and height of stick would help getting specific responses to your query.

[psk125]

To further muddy the waters, this link shows differing breaking loads for wire ropes made of different types of stainless. It also suggests that European and American wire of the same size might have different breaking loads as well. Who made it, what it's made of, and where it's from may all make a difference in what you need to get.
https://www.harken.com/uploadedFiles...oads_HORIZ.pdf It may be best to simply determine what you need and get it shipped to you.

[Alan Mighty]

Originally Posted by GwalarnYacht

Unfortunately, due to limited availablity at our location, we are now faced with the choice of replacing it with a 10mm 7x19 or an 8mm 1x19 wire rope.

You're in Malaysia? And no one in MY has or is prepared to order 10 mm 1x19 ss wire rope?

Are in you in one of the duty-free ports in MY, such as Labuan, Langkawi, etc?

Have you contacted ss wire rope suppliers in Singapore, or Precision Shipwright Services/East Marine Rigging in Phuket?

[GordMay]

I just noticed that the OP has a furler on his headstay. I expect that the foil size may determine the required diameter of rope. They have to fit together.