Tune the Rig

Notes:
1. 11/02/2013: Mast re-stepped, full tuning completed. Loos numbers: Fore ?/Back ?/SB Top 38/P Top 38/SB Aft Mid 22.5/P Aft Mid 22.5/SB Fore Mid 29/P Fore Mid 29.
2. 02/27/2014: Spreaders drooped. Loosened top shrouds only, fixed spreaders, re-tuned. The tip of my mast has a centimeter of fore and aft movement when the bow tries to bury itself into the face of a wave while sailing upwind in Force 4/5 wind. May need more tightening of the fore/backstay. Loos numbers: Fore ?/Back ?/SB Top 42/P Top 42/SB Aft Mid 24/P Aft Mid 23/SB Fore Mid 30/P Fore Mid 29.
To make minor adjustments to a previously tuned rig:
After the 2013 rigging replacement.
1. Keep an eye on the amount of mast movement under sail, standing rigging slop on the leeward side, and every few months measure the tensions to ensure the rig is not loosening too badly.
2. If the tensions are off, the rig will need to be re-tuned.
3. When turning the turn-buckles, first lube the threads liberally with Lanocote to prevent galling of the stainless steel. Lanocote lasts for a couple years and will prevent galling. (I used 3-1 oil because it was handy, but it won’t last long. Next time I get a chance I will lube all the threads with Lanocote.)
4. We’ll assume the rigging has previously been tuned and we just need to make adjustments.
5. At the dock, note the standing rigging’s characteristics before tuning.
  1. It should be straight athwartships.
  2. It should have a very slight curve fore and aft with the mid-point of the mast forward. Less than a mast’s width of bend is normal.
  3. The fore mid shrouds should feel slightly tighter than the aft mid shrouds.
6. Adjusting the shrouds should be done while under sail. Try to do initial tuning under lighter Force 3 conditions, then make final adjustments under Force 4-5 conditions.
7. While sailing, sight up the mast and note any bending or movement of the mast.
  1. If the mast head is moving side to side, the top shrouds need to be tightened.
  2. If the mast head is moving fore and aft, the stays should be tightened.
  3. If the midpoint of the mast is moving, the mid shrouds should be tightened.
  4. The mast should always curve slightly backward so the midpoint of the mast is forward of the mast head.
    1. If the reverse is true, this is very bad and the mast could break (especially downwind with a spinnaker pole putting backward force on the midpoint of the mast.) Tighten the fore mids while loosening the rear mids to introduce the curve. If the midpoint continues to move fore and aft under sail, tighten the mid shrouds.
    2. If the main sail is new, a straighter mast can be more efficient.
    3. As the main sail ages and bags out, more fore and aft bend to the mast can pull some of the bagginess out of the sail for better performance.
  5. If the mast curves athwartships, adjust the leeward top shroud only, tack about and adjust the other top shroud sighting up the mast to see the results of your adjustments. Repeat until satisfied.
8. The tuning is complete when the mast is perfectly straight athwartships on both tacks, the leeward shrouds have a looseness to them which is not great enough to cause them to want to jump off the end of the spreaders. They shouldn’t be too tight or it can cause unnecessary strain on the chainplates and bulkheads. But they shouldn’t be loose enough to look like a jump-rope, either. The mast should have a slight curve to the rear and should not buck at all while upwind sailing against choppy seas.
9. Finally, insert cotter pins to prevent the turnbuckles from unintentionally loosening.
Full tune from a slack rig:
1. After stepping the mast and all stays have been connected but not yet tightened, you must get the mast straight at the dock before adjusting under sail.
2. I was away when this was done on Siren, but here’s a great website: http://www.thecoastalpassage.com/petrearigging.html

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