tuning your rig

[GKuffner]

I just launched my boat on the weekend and stepped the mast the next day. I have a question regarding tuning the rig. I followed the instructions in the Selden manual for tuning the rig (ie I used a 200cm rule and stretched the cap shrouds and back stay to the recommended 30% of their breaking strength = 3mm of cable stretch as measured by a digital micrometer). While the rig is nicely in column, the mast has a small amount of rake and is bowed about 20mm, I am concerned about the tension. My rig is now much more taught than when it was set-up by the dealer that sold me the boat. I was wondering if anyone has the tension settings as measured by a loos gauge for the cap shrouds and the back stay?

Gary Kuffner
Glory Days
C309 #136

 

[jsalley]

Gary - I used a Loos gauge last year to (re)set my rigging, but didn't write down the settings - major oversight! I used a book called Illustrated Sail & Rig Tuning by Ivar Dedekam, which was really helpful (I think I got it from WM, but am sure you could find it at Amazon). As I recall, they gave tensions as a percentage of max breaking strength of each wire, which is also given in the instructions that accompany the Loos gauge and on the Loos website if you know the wire diameters.

The mast is supposed to have some forward bow - should be about half the mast width fore-to-aft, or about 3". It also should have some aft rake, though I reduced mine to about 3 degrees and it drastically improved my previously severe weather helm. I found the dealer's setup to be pretty far off the ideal, though in fairness I'm sure the rig stretched after its initial setup.

Next time I'm at the boat (and not in a hurry to sail!) I'll take the Loos and check my tensions. It sailed like a different boat after I changed the tensions last year.

 

[GKuffner]

John,

I bought the same book as you for probably the same reasons. I would appreciate knowing what the readings on your loos gauge are for the cap shrouds and back stay. No hurry though as the mast is up and hopefully not going anywhere.

I would be interested in knowing how you reduced the rake on your mast.

Gary Kuffner
Glory Days
C309 #136

 

[jsalley]

John,

I bought the same book as you for probably the same reasons. I would appreciate knowing what the readings on your loos gauge are for the cap shrouds and back stay. No hurry though as the mast is up and hopefully not going anywhere.

I would be interested in knowing how you reduced the rake on your mast.

Gary Kuffner
Glory Days
C309 #136

I'll check the tensions next time I'm at the boat - hopefully next week.

To decrease rake, you need to start with all of the rigging slack. Tighten the forestay turnbuckle a turn or so at a time, while loosening the backstay the same amount. This requires partially dismantling the jib furler (removing the drum and sliding the foils up the stay enough to access the turnbuckle). Obviously, the jib has to be unbent to do this. Once you have the rake where you want it, get the mast back in column and then tension the rig. Final shroud tensioning has to be done under sail.

Although I didn't measure the rake before I started, I took up most of the adjustment in the forestay turnbuckle, and it seems to be about right based on the improved helm balance.

 

[jsalley]

I just launched my boat on the weekend and stepped the mast the next day. I have a question regarding tuning the rig. I followed the instructions in the Selden manual for tuning the rig (ie I used a 200cm rule and stretched the cap shrouds and back stay to the recommended 30% of their breaking strength = 3mm of cable stretch as measured by a digital micrometer). While the rig is nicely in column, the mast has a small amount of rake and is bowed about 20mm, I am concerned about the tension. My rig is now much more taught than when it was set-up by the dealer that sold me the boat. I was wondering if anyone has the tension settings as measured by a loos gauge for the cap shrouds and the back stay?

Gary Kuffner
Glory Days
C309 #136

Checked my rig tensions with the Loos gauge today - then went sailing . Lots o'wind on the Bay today, but gorgeous weather.

Backstay (7/32" 1X19 wire, breaking strength 6300#) - 850#
Cap Shrouds (9/32" 1X19, breaking strength 9900#) - 850#
Intermediate Shrouds (7/32" 1X19, breaking strength 6300#) - 660#

My Loos gauge won't fit the larger fore and aft lower shrouds, but you don't need to tension those to a measurement anyway. I think these tensions might actually be a little less than optimal, especially on the backstay, since I set them up last year and haven't changed them, but they are in the ballpark (and the boat still sails as well as when I first set them up). Hope this helps.

 

[GKuffner]

John,

Thanks for those settings. I'm going down to my boat today and I think that I'll readjust my rig tensions accordingly.

Gary

 

[MED]

It seems amazing that we are talking about a production yacht that has produced over 152 hulls and the manufacturer does not give clear directions on mast rake and rig tensioning in the owner’s manual. Shall we ask them to provide guidance?

 

[jkittka]

Selden site for mast hints and tips
http://www.seldenmast.com/frameset.cfm?id=6608&randnum=611910497

 

[GKuffner]

We'll now that its been raining for 3 days I'll take the time to make a post on the tension settings for my rig. Using a borrowed Loos Gauge, which is essential to have in my opinion, I tuned up my rig as follows.

Back stay - Loos reading = 37 = 1210#
Cap Shrouds - Loos reading = 47 = 1330#
Intermediate Shrouds - Loos reading = 37 = 1210#
(note: that becuse the backstay has a greater angle of attachment to the mast than the intermediate shrouds, it exerts more tension than do the intermediate shrouds at the same tension setting on the Loos Gauge)

Forward lower shrouds are tensioned until I had 3" of bow in the mast.
Aft lower shrouds hand tight plus a little (so as not to lessen the bow in the mast.

I had the boat out last week in a +25K breeze with gusts to 33K and it performed quite well. The intermediate shrouds on the leeward side were slightly loose so I tightened them back at the dock to the setting described above. The cap shrouds were fine and held the top of the mast to only a slight bend to leeward under those conditions. Forestay sag was approx 8". Moving around the fordeck in 30K is not my idea of fun but I had a good friend on the wheel so there were no surprises.

I know that these settings are tight but they are with in the tolerances allowed by Selden. I want to monitor the weather helm over the next few weeks and if I find that its too much i'll back off on the back stay tension a little. The good news is that all the cabin doors still open and close.

Gary
C309 #136
Glory Days