Reefed sail proportions

[Robih]

Does anyone know of what might be considered as standard proportions of sail deployed for 1st, 2nd, 3rd reefs? If a sail is 40msq then might first reef be 32msq deployed, 2nd reef 26msq, 3rd reef 18msq. I’ve made those numbers up for illustration only, I’m guessing.

 

[Roberto]

As general reference reefs are placed at 12.5% - 25% - 37.5% of E measurement
If E = 10m then 1st reef 1.25m above the boom, 2nd at 2.5m, 3rd reef at 3.75m, distances, actual measurement are adapted depending on full batten positions etc.


Edit
Just checked the actual measurement of my full batten mainsail
Area 35.7 m^2= 100%
Area with 1st reef = 22m2 = 81%
Area with 2nd reef = 29m2 = 62%
Area with 3rd reef = 16m2 = 45%

 

[Robih]

As general reference reefs are placed at 12.5% - 25% - 37.5% of E measurement
If E = 10m then 1st reef 1.25m above the boom, 2nd at 2.5m, 3rd reef at 3.75m, distances, actual measurement are adapted depending on full batten positions etc.


Edit
Just checked the actual measurement of my full batten mainsail
Area 35.7 m^2= 100%
Area with 1st reef = 22m2 = 81%
Area with 2nd reef = 29m2 = 62%
Area with 3rd reef = 16m2 = 45%

Very helpful, thanks.

 

[johnalison]

As general reference reefs are placed at 12.5% - 25% - 37.5% of E measurement

If the sail were a triangle, then those numbers would just be doubled to give the area taken away, ie 25% at the first reef, but of course the curve of the roach changes things, unless someone is clever enough to give the formula assuming an elliptical curve.

 

[Robih]

If the sail were a triangle, then those numbers would just be doubled to give the area taken away, ie 25% at the first reef, but of course the curve of the roach changes things, unless someone is clever enough to give the formula assuming an elliptical curve.

One of the few advantages of an inmast mainsail is the straight line from head to clew!

 

[Chiara’s slave]

One of the few advantages of an inmast mainsail is the straight line from head to clew!

I presume you’re thinking of marking the foot of the sail to give a guide to reefing? We have done that on our jib.

 

[Robih]

Yes, exactly that. As we furl we can of course infinitely vary the sail size but we find references on the foot of the sail very helpful when reefing. Without something one is guessing and invariably after completing a reefing maneuvere it is bigger or smaller than was imagined.

 

[Chiara’s slave]

Yes, exactly that. As we furl we can of course infinitely vary the sail size but we find references on the foot of the sail very helpful when reefing. Without something one is guessing and invariably after completing a reefing maneuvere it is bigger or smaller than was imagined.

our reasoning precisely. Our handbook refers to ‘reef 1’, ‘reef 2‘ etc on the jib, so after finding out what this meant, we marked then on the jib in matching colours to the mainsail reef lines.

 

[SaltyC]

Yes, exactly that. As we furl we can of course infinitely vary the sail size but we find references on the foot of the sail very helpful when reefing. Without something one is guessing and invariably after completing a reefing maneuvere it is bigger or smaller than was imagined.

I've found the full length vertical battens in the new furling sail are an excellent measure for the first 3 reefs.

 

[mjcoon]

If the sail were a triangle, then those numbers would just be doubled to give the area taken away, ie 25% at the first reef, but of course the curve of the roach changes things, unless someone is clever enough to give the formula assuming an elliptical curve.

Surely you cannot be trying to convince us that 50% on linear measure is 100% by area?

 

[capnsensible]

Without being sarcastic(!) I'm sure the best people to ask are sailmakers. Better than best guessers on here.

With all due respect to those that are trying to be helpful.

 

[scottie]

Without being sarcastic(!) I'm sure the best people to ask are sailmakers. Better than best guessers on here.

With all due respect to those that are trying to be helpful.

That goes against forum rules does it not
I understood that experts were only allowed to reinforce opinions when challenged

 

[johnalison]

Surely you cannot be trying to convince us that 50% on linear measure is 100% by area?

Er, no. 50% equates to 25%. I’m not sure what I was thinking. It was a long time ago.

 

[Chiara’s slave]

Without being sarcastic(!) I'm sure the best people to ask are sailmakers. Better than best guessers on here.

With all due respect to those that are trying to be helpful.

That was the resource we turned to. They were able to tell us where each mark on the foot should be for the sail to correspond to the handbook recommendations. Obviously it’s more significant on a multi.

 

[Robih]

Without being sarcastic(!) I'm sure the best people to ask are sailmakers. Better than best guessers on here.

With all due respect to those that are trying to be helpful.

If you can get a sailmaker to respond. We asked for reef marks to be fitted at manufacture, they ignored that and added a hull number instead that we specifically asked not to be fitted. Don’t talk to me about *&@/-^€ sailmakers…..

 

[capnsensible]

Have you tried the designer? Or the boat builder? I found a Jenneau agent in the UK when I needed a third reef for a coded yacht.

Good luck.....and not all sailmakers are the same!

 

[johnalison]

Does it actually matter? I'm not a student of fluid dynamics but I would doubt that the forces exerted are proportional to the sail area, or even easily predictable. Unless you have a continuous system such as a furling main, the reef is always going to be a bit too little or too much. All I need is a reef available for the strongest I am likely to be out in and either one or two reefs available for the intermediate blows, which may as well be evenly spaced for aesthetic reasons.

 

[Roberto]

Very helpful, thanks.

The sailmaker should be able to give you a full set of measurements like this, it also includes the foot length of each reef.




For the precise positioning of reefing lines I waited for a windless day then positioned everything quite precisely, I put tape strips where the 1st reef clew arrives, the 2nd uses a friction ring kept in the right position with a strop from an attachment point on the boom; tape again for the 3rd.
This was my 2nd mainsail from a different sailmaker, the positions of marks for the reefing points had all to be moved somewhat.

 

[Fr J Hackett]

If you can get a sailmaker to respond. We asked for reef marks to be fitted at manufacture, they ignored that and added a hull number instead that we specifically asked not to be fitted. Don’t talk to me about *&@/-^€ sailmakers…..

I had a sail made which when it was finally ready for collection (late) it turned out to be considerably smaller than specified, on talking to the owner of the business who was a very nice chap, he assured me that he would find out who was responsible and take him out and shoot him. I don't suppose he did but it took the edge off the conversation.

 

[SaltyC]

Does it actually matter? I'm not a student of fluid dynamics but I would doubt that the forces exerted are proportional to the sail area, or even easily predictable. Unless you have a continuous system such as a furling main, the reef is always going to be a bit too little or too much. All I need is a reef available for the strongest I am likely to be out in and either one or two reefs available for the intermediate blows, which may as well be evenly spaced for aesthetic reasons.

No! It is knowing the boat. With slab reefing, the percentage is dictated at tge time of build.
With in mast it is infinitely variable and down to experience and knowledge of your boat.
We were advised with full vertical battens to reef until the batten was in the mast, with 4 battens that gives us 3 reefs and an 'I shouldn't be out here'
The 3rd reef brings us down to a handkerchief and suitable for F8.