8mm 7x7 galivanized standing rigging for 32ft ketch?

[rhumbunctious]

I'm planning to replace all the standing rigging on my Westerly Berwick (32ft ketch) in the coming months, and with the eventual not-too-distant plan to do some very extensive cruising (trans-Atlantic, and maybe alot further, perhaps all the way around).

C.f. http://www.westerly-owners.co.uk/boat_berwick_31.php



I'm planning on replacing the old SS rigging with 7x7 galvanized with liverpool splices (so I can avoid surprise failure and easily see the condition of the rigging, albeit with the additional regular maintenance that comes with galvanized).

I've been talking with a well respected rigger in the UK about some hands-on training doing the splicing at their workshop (I have your book, though there's nothing like an expert checking one's work, especially given where I plan to take the boat), and they noted that 8mm is the smallest that good quality 7x7 galvanized is available in. So to go that route, I'd need to go with 8mm all around.

Not clear why 8mm is the smallest good quality available. The rigger says that what's available in smaller sizes does not have as good galvanization and will rust within two years. Any opinion there?

Taking what I've been told at face value, for the main stays, I'm (ignorantly) assuming that 8mm would be fine, as they are 6.5mm now, and I'm happy to go up a size, especially since I'm changing from SS to galvanized. But the mizzen shrouds are notably smaller (I think around 4-5mm, though I haven't measured them).

What would the implications be if I went with 8mm for all of the standing rigging, both main and mizzen?

Thanks.

[Stumble]

Rhum,

You sneak in a few questions so here goes... hopefully I won't miss any:

1) I would suggest looking at Dynex Dux for shrouds and getting rid of the wire completely. It saves weight, can be replaced underway if need be, is lighter, easier to work with, and I personally hate the way galvanized stuff looks/feels. On the other hand I am highly prejudiced in favor of this stuff so YMMV. However I feel it is a much more cost effective rigging solution than other options, and havs the added benefit that you can cary a spool of the line down below in the event a repai is needed. Plus the weight savings up high help keep the boat on its feet.

2) I would agree that galvanized wire under some size gets pretty crappy. The problem is the lack of area for the finish to apply, and the amount of material scratches remove. It is just harder to do a good job on small detail parts. I don't know that I would put this point at 8mm, but I do think of it as a sliding scale thing, the smaller it is the worse the galvinazation.

3) Going up a size adds a lot of weight up high on the rig which is always detrimental. It also will add a good amount of drag to the boat. It may also be problematic finding fittings that match your chain plates in the larger size of the wire.

[Brion Toss]

Hello,
The ratio of surface area to volume is a big factor in the strength of galvanized wire. The surface varies with the square of the diameter, as I recall, and the volume with the cube. So the weakening caused by galvanizing hits the smaller diameters harder.
Having said that, I believe we've skipped past your motivation, which is to, "... avoid surprise failure and easily see the condition of the rigging..." I don't see how that connects to the use of stainless vs. galvanized. The boat's needs trump yours, in this case. Run the numbers to determine the right size, for both masts. Do what the boat needs you to do.
Fair leads,
Brion Toss