1976 O’Day 20 rig tuning

Sep 9, 2016
28
ODay 20 Manchester, NH
Does anyone know what the forestay length is supposed to be for a 1976 O’Day 20 fractional rig. I will be attending a rigging tuning class at our local yacht club and have been told that this length is often the “starting point”. Any ideas or suggestions would be greatly appreciated, thank you.
 
Feb 21, 2013
4,638
Hunter 46 Point Richmond, CA
Same question came up on this thread forestay length | Sailboat Owners Forums

Forestay length:
1. Attach a tape to your halyard, hoist it up to the forestay attachment on the mast and measure the distance from the mast to the attachment point on the deck or roller furler, or
2. Approximate it by calculating c from the Pythagoras Theorem below with a (I = 23.8 feet, measured along the front of mast from the jib halyard attachment to the main deck from SailboatData.com - O'DAY 20 Sailboat) and b (J = 7.8 feet base of the foretriangle measured along the deck from the headstay to the mast from SailboatData.com - O'DAY 20 Sailboat), or
3. Have a rigger measure it.

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Sep 9, 2016
28
ODay 20 Manchester, NH
Actually, I don't think I was clear in my original posting. I know how to calculate the current forestay length, I am trying to see if there is a recommended forestay length to assist me in setting up the rest of the rig, or is it just a matter of getting the mast straight (fore and aft, port and starboard), realizing that there should be a bit (how much?) rake.
 
Feb 21, 2013
4,638
Hunter 46 Point Richmond, CA
..........or is it just a matter of getting the mast straight (fore and aft, port and starboard), realizing that there should be a bit (how much?) rake.
You are on the right track but others in the forum will also have a view. Might do an internet search on "sailboat standing rig tuning" to find good articles like How to Tune Your Rig | North Sails
 
Nov 9, 2012
2,500
Oday 192 Lake Nockamixon
Seldén Mast's "Hints and Advice" PDF booklet here: Rigging instructions & sailmakers guide : Seldén Mast AB can help you with general rigging and tuning tips for a variety of rigs. Personally, I like to get my mast straight side to side using the main halyard pulled to the chainplates, then start to adjust the forestay tension so that the swept upper shrouds vs. the forestay give about 3/4" of mast pre-bend (as per my mainsail maker.) I use the main halyard pulled down along the sail channel to visual the pre-bend. Adjusting the lowers will make sure the mast is straight up both sides, without a bow to either port or starboard, and tight enough that they don't slack and move around much while close hauled in steady breeze. However, lowers can be tightened enough to pull the pre-bend out of the mast, so be aware of that. Then, while sailing close hauled in about 8 or 10 knots of breeze, I will adjust mast rake between forestay and uppers (tripod, yeah?) so that there's about 6º of weather helm on the tiller. That's enough to give a bit of lift to windward from the rudder, but not so much to cause drag and slow you down. Backstay on my boat I try to keep snug-ish, because too much backstay tension on my rig causes the top of the mast above the hounds to kink pretty noticeably aft, and I don't like the look of it.