tuning the fractional rig

[Megunticook]

This was the 3rd year I tuned my Ty Senior's fractional rig, and today it actually went very well. I used a Loos gauge and followed the procedure outlined on the North Sail site (https://northsails.com/sailing/en/2016/ ... e-your-rig) although I also read the Loos instructions and the Cape Dory manual.

I'd be curious to compare notes with others who have this type of rig though, with the swept back spreaders. My final tension numbers were 20% breaking strength on the forestay, 24% on the lower shrouds, 17% on the upper shrouds, and about 8% on the backstay.

Rake looks perfect with a slight bend in the upper half of the mast, and the mast is centered side-to-side.

I find avoiding too much mast bend to be tricky. But things looked spot on and felt solid today.

[Steve Laume]

I am not an expert on tuning but 24% seems pretty snug for the lowers. If you eased them up a bit, I would think it would tend to reduce the mast bend.

Don't forget to pin the turnbuckles and recheck the tension after sailing for a while, Steve.

[Megunticook]

24% seems pretty snug for the lowers

Agreed, sounds like 25% is the max. and 15% the lower limit.

If you eased them up a bit, I would think it would tend to reduce the mast bend

Actually with a fractional rig it's just the opposite. The chainplates are aft of the mast, and the lowers pull the middle of the mast back and reduce the bend created by the backstay and uppers.

I'm aiming to get a moderate bend, but maybe I need to relax and allow for more bend.

If I loosen the lowers and tighten the backstay, the bend quickly increases.

[tjr818]

Really...this is what the manual says:
3.29 TUNING THE STANDING RIGGING
The purpose of tuning the rig is to adjust the center of effort of the sail plan fore or aft to obtain a slight weather helm in moderate winds, and to keep it straight without hooks to port, starboard, fore or aft. Properly tuning the rig is an important process which should be attempted only by qualified personnel; consult your Cape Dory dealer.
The fore and aft alignment of your mast can be checked by comparing it to a vertical structure such as a radio tower, chimney, etc. Before checking the mast alignment in this manner, be certain that the boat is resting on her design waterline. If the mast is leaning fore or aft, ease the turnbuckle toward which the mast is leaning a few turns, and take up a corresponding number of turns of the opposite turnbuckle. (Note: when adjusting turnbuckles never use excessive force or the turnbuckle may be contorted.) Always prevent the upper threaded turnbuckle stud from turning. The Cape Dory 30 ketch has a split backstay with two turnbuckles. Headstays and backstays should never be taken up so tightly that they will not “give” an inch or so if you pull on them with moderate force.
Upper shrouds should also be tightened equally and have about an inch of “give” to them. Forward lower shrouds should have one to two inches of “give”, and the aft lowers slightly more.
UNDER NO CIRCUMSTANCES TAKE UP THE RIGGING TO BAR TIGHT TENSION. Both the mast and the boat can be severely damaged by excessive tension.
Fine tuning of the rig can be completed after the boat has been sailed, and may have to be done again after the boat has been out in strong winds. When sailing, it is important that the mast remain straight and as nearly in column as possible at all times. While sailing close hauled, sight up the mast track and note any mast curve. Does the mast appear to be falling off to leeward at the top, or does it hook upwind? Repeat this procedure on the opposite tack.
If the masthead is falling off on both tacks, the forward lower shrouds are too tight and the upper shrouds are too loose. If the masthead hooks to windward, the upper shroud is too tight in relation to the lower on the same side. When sailing to windward, the forward lower shrouds bear a greater load than the after lower shrouds; however, the after lower shrouds on the windward side should never be
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loose. All shroud tuning should be done from the leeward side. If the rig seems to be equally balanced when you begin, duplicate every half turn from side to side.
On Cape Dory boats with bowsprits, try to keep the bowsprit straight and not bowed up or down. This should be checked while sailing upwind in moderate conditions.

[Megunticook]

Thanks, I have read the manual backwards, forwards, and sideways several times. The section on rigging is helpful but a little vague on tension. And pretty general, nothing specific about the fractional rig, which from what I'm reading online is generally rigged a little tighter than a masthead rig.

I'm thinking I should tighten that backstay up to at least 10% and let the mast bend increase. But would love to hear from others who have fractional rigs.