Low "reefing" holes in main sail

Dec 1, 2020
129
CAL 27 Illahee / Brownsville WA
Hello experts,

Can someone explain to me what the "reefing" holes in my main sail about 6" up from the foot at the tack and clew are for?

1617810450214.png
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
That is for a Cunningham. The Cunningham applies tension to the mainsail luff drawing the belly of the sail forward. It is typically a block and tackle secured at the base of the mast and with a hook that goes into the Cunningham hole.

The main halyard also tensions the mainsail luff, however, it also tensions the leach. The Cunningham counters some of the leech tension because the pull is only vertical. The halyard tensions in 2 directions, along the luff and leech
 
Dec 1, 2020
129
CAL 27 Illahee / Brownsville WA
I realize I messed up the photo. Here is an update.

I think I understand the hole now at the tack, but the clew hole - how is it used?

1617811429873.png
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
It is a flattening reef. Sometimes you only want to take out some of the sail's fullness, the flattening reef does that, it pulls the shelf into the boom and reduces draft along the lower part of the sail.

 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
I think typically found only with mainsails with the shelf (bolt rope in the boom track), no?
 
Jan 1, 2006
7,040
Slickcraft 26 Sailfish
The last time I saw one of those was on an Olson 40 - thirty years ago. It was very effective. It could make that main flat as a piece of plywood. I don't think the flattening reef lived past Dacron sails but that is conjecture. You could contort Dacron sails into various shapes. Laminate sails are largely the shape they are.
As for the question on how to use them: I think you'd want tension on both the luff and tack. One loose and one tight would seem to me to stress the sail.
 
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Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
I had a C25 with a flattening reef and used them independant of each other. The tack was used for the Cunningham to tension the luff and the clew was used to pull the belly and draft out of the foot just above the foot shelf.
 
Dec 1, 2020
129
CAL 27 Illahee / Brownsville WA
Thanks for the input. I will try to come up with some type of rigging to make playing with these easy from the cockpit.
 
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cas206

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May 15, 2012
24
Cal 27-3 Solomons
Thanks for asking this and for all the responses. I have a "new to me" Cal 27-3 and was just web searching for the same question. This also explains why there is a assembly of blocks and line I found stored inside. Must be the Cunningham.

The manual says there is an internal outhaul and reefing line within the boom. So I'm guessing that this reefing line is used to flatten the sail as mentioned above and not to reduce sail area in the "usual" method of reefing the sail.