I'd recommend Selden Mast's booklet Hints and Advice on Rig Tuning - you can download the pdf. They give a neat "folding rule" method (pg 32) of determining tension based on the fact that 2 meters of any diameter of 1X19 wire stretches 1mm for each 5% of breaking strength applied.
So, for example, if you want to tension your 12mm cap stays to 20% (Amel tight, maybe!) just tighten them until 2 meters stretches by 4 mm. That stretch will give you about 5600 pounds of tension, as the breaking strength is about 28000.
The Loos gauge doesn't handle wire over 10mm (actually 9.5 mm as it's rated for 3/8) and only goes up to 4500 pounds. That's why the results Nance and Underwood gave Steve Morrison in his post just show "very tight" for his 12mm stays.
After you get a sense for "very tight" you'll get to trust just feeling the stays and being able to judge if they're right. And use Joel's suggestion to go out, sail upwind in a good breeze and see if your lee shrouds are at all slack. If yes, they're way too loose. Oh yeah, and recheck after a while as the wire will stretch over time.
On the headstay there is a turnbuckle screw under the furler. ACMO just calls it "special" , as it's shorter than standard ones so the furler can be closer to the deck.
Have fun tuning!
Craig Briggs SN68 Sangaris
, wrote :
I'm about to embark upon tuning up my rig, which I feel is a little loose, but I'd love some guidance on how to do that. I've scoured the archives of this list and found many mentions of guides from both Joel Potter and Olivier Beaute, but I haven't been able to find them. The best guide I've found thus far is this one
. Can anyone link me to the gold standard(s)?
Also, has anyone done the tuning in a more scientific way, with a Loos Gauge? I'm struggling to understand via qualitative descriptions just how tight is tight. I think a quantitative measurement would be very helpful.
And finally, how does one adjust the forestay tension? I admittedly have not studied it in depth, but I didn't see a turnbuckle or any other obvious mechanism.
SM 233 Iteration
Boston, MA, USA