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Old 24-03-2012, 06:18   #31
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Re: Mainsail - two reefs or three?

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Originally Posted by Bill Balme View Post
So (Eric!), if one goes with a deep second reef, how deep is deep? What percentage of sail area do you reduce for each reef or is it strictly a linear measurement of the hoist?
The standard that sailmakers have been using since mankind can remember is the 12.5% of luff rule, first reef is at 12.5% of the luff, second at 25% and third at 37.5% sometimes you will find a fourth reef which will be around 50%. This is luff length, not reduced sail area!

Reduced sail area with this standard rule is:
1st: 20%
2nd: 35%
3rd: 55%
4th: 75% (is approx trysail size)

The reason that they use this rule is that the structure of the sail is really well balanced with number of battens in the leach versus location of reefs, battens and reefs are usually not good friends.

With our second reef configuration we have:
1st reef: (at 27% of luff) is a 40% area reduction.
2nd reef: (at55% of luff) is a 75% area reduction.
Trysail is approx 85% area reduction compared to full main

This looks like putting a reef is an extreme measure, but the reason one is reefing is too much propulsive power produced by the sails that the boat needs to get rid of. I found that the reductions in sail area as I made in our mainsail do reduce the power enough to have a pleasant comfort level aboard without slowing the boat down.

Of course there is an interaction between two or even 3 or 4 sails that are working at the same time. So in my opinion you should look at the absolute sail reduction rather than reduction in the size of the mainsail only.

Our largest upwind headsail (105% LP) is about the same size as the mainsail, so when we put our first reef, the total sail area on the boat is reduced with 20% only, second reef is only a reduction of 37.5%.

I found for our selves, this is of course personal preference and is different from one sailor to another, that reducing the sail area in steps of 20% of the existing sail area is working very well for de-powering without slowing down. What I mean with this is that the first reef reduces the total sail area from 200 sqm to 160sqm (20%), the next step is another 20% reduction, but not counting with 200sqm as the basic, but the "new" surface of 160 sqm. So next step should be a reduction to 128sqm and so on. We are currently sailing without a headsail furler and we have 3 headsails, the whole de-powering process is based on reductions of 20% of the sail area before the reduction that you are going to make. And it works great for us. All the clients that I introduced to this system of de-powering are very happy with it and do not want to change back to the "standard" system.
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Old 24-03-2012, 06:38   #32
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Re: Mainsail - two reefs or three?

The more reef points you have the easier it is to reef, trying to put in a very deep reef can be a handful on a big sail..
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Old 24-03-2012, 06:40   #33
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Re: Mainsail - two reefs or three?

But also the more you have to work because you will put a reef much more often. It takes about 1 minute for us to reduce the luff with six meters.
To be honest, I do not see why it is more work than a standard reef height?
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Old 24-03-2012, 10:36   #34
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Re: Mainsail - two reefs or three?

One thing about a third reef is that the sail stack up on the boom gets so large that it's a bit of a mess. That flat top of the sail is pretty much useless it seems to me except as a riding sail.... but I gues that can be of service.
If you think about it, the reefs should be predicted by the size of the head sail to be used for each reef. ie: the boat should be balanced properly at each reefing point. So with one reef maybe you should have a 120% genoa up. With 2 reefs maybe a 100% jib etc etc. If you really want to get into it, figure out where your furling headsail looks good partially rolled up. Run the numbers for the sail area and boat balance and predict the reef point to match... :>)
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Old 25-03-2012, 07:21   #35
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Re: Mainsail - two reefs or three?

Erik,
Great explanation - thanks.
I don't want to bring you out of retirement (!) but if I could ask a little further... Our boat has a relatively large main (580sq ft) compared to upwind jib (393sqft), and so reefing it has more impact on total sail area than a smaller main would have (I think).

As planned, my reefing on the upwind sails would be as follows:
Main and Jib: 973sq ft
1st reef main + jib: 847sq ft
2reefs in main + jib: 702 sq ft
2 reefs main + reef jib: 643 sq ft

(Planned trysail will be 175sgft)

Does this all sounds sensible to you?
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Old 25-03-2012, 08:25   #36
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Re: Mainsail - two reefs or three?

Hey bill,

I wish I was retired! I only changed career because the income as a sail maker is not that great with all the competition from the far east. I'm active as a yacht designer now, that was actually what they tried to teach me at University. (I'm only 30 years old now)

Anyway, it depends on what you want to do with your boat. For coastal cruising it sounds good. For offshore sailing you do have a big gap between double reefed mainsail and trysail. you can either place the reefs a little further apart, that would be my preference or, add a third reef.

With the area's that you wrote down, your first step in reefing is 13%, the second step is 17% and than 8%, changing to trysail in combination with reefed jib is 64% reduction. Which is good for coastal cruising with a trysail to get home if your mainsail is blown to rags.

If you want to sail offshore, I would divide it a bit more evenly.
For example:
Full sail: 973 sqft
First reef + jib: 820 sqft
Second reef + jib: 650 sqft
Second reef + reefed jib: 530 sqft.

Trysail seams allright, maybe a little bit big. The recommendations from the ISAF on trysails and storm jibs are large in my opinion, especially if you have a light displacement boat.

I consider a storm jib a must for offshore cruising if you leave the tropical area's and visit moderate or even high latitudes.
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Old 25-03-2012, 17:55   #37
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Re: Mainsail - two reefs or three?

Quote:
Originally Posted by Erik de Jong View Post
The standard that sailmakers have been using since mankind can remember is the 12.5% of luff rule, first reef is at 12.5% of the luff, second at 25% and third at 37.5% sometimes you will find a fourth reef which will be around 50%. This is luff length, not reduced sail area!

Reduced sail area with this standard rule is:
1st: 20%
2nd: 35%
3rd: 55%
4th: 75% (is approx trysail size)

The reason that they use this rule is that the structure of the sail is really well balanced with number of battens in the leach versus location of reefs, battens and reefs are usually not good friends.

With our second reef configuration we have:
1st reef: (at 27% of luff) is a 40% area reduction.
2nd reef: (at55% of luff) is a 75% area reduction.
Trysail is approx 85% area reduction compared to full main

This looks like putting a reef is an extreme measure, but the reason one is reefing is too much propulsive power produced by the sails that the boat needs to get rid of. I found that the reductions in sail area as I made in our mainsail do reduce the power enough to have a pleasant comfort level aboard without slowing the boat down.

Of course there is an interaction between two or even 3 or 4 sails that are working at the same time. So in my opinion you should look at the absolute sail reduction rather than reduction in the size of the mainsail only.

Our largest upwind headsail (105% LP) is about the same size as the mainsail, so when we put our first reef, the total sail area on the boat is reduced with 20% only, second reef is only a reduction of 37.5%.

I found for our selves, this is of course personal preference and is different from one sailor to another, that reducing the sail area in steps of 20% of the existing sail area is working very well for de-powering without slowing down. What I mean with this is that the first reef reduces the total sail area from 200 sqm to 160sqm (20%), the next step is another 20% reduction, but not counting with 200sqm as the basic, but the "new" surface of 160 sqm. So next step should be a reduction to 128sqm and so on. We are currently sailing without a headsail furler and we have 3 headsails, the whole de-powering process is based on reductions of 20% of the sail area before the reduction that you are going to make. And it works great for us. All the clients that I introduced to this system of de-powering are very happy with it and do not want to change back to the "standard" system.

Thanks Eric, this stuff is golden. I've been toying with the idea of mothballing my first reef and just using my 2nd and 3rd reefs. Your comments inspired me to do some crude calculations. Under full sail (main and 100% jib) and 20mph of wind I get 1014lbs of pressure on my sails.
Under 2nd reef (a 25% reduction in total sail area) and 25mph of wind I get 1184lbs of pressure on the sails.
So by skipping the first reef and going straight to the second reef I still see and increase of 170lbs pressure. I know reality is a lot more complicated, but I think I will give skipping the first reef a try. My next main will likely have the first reef just below where the second reef is now, and the second reef just above where the third reef is now.
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Old 25-03-2012, 18:33   #38
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Re: Mainsail - two reefs or three?

Quote:
Originally Posted by Erik de Jong View Post
The standard that sailmakers have been using since mankind can remember is the 12.5% of luff rule, first reef is at 12.5% of the luff, second at 25% and third at 37.5% sometimes you will find a fourth reef which will be around 50%. This is luff length, not reduced sail area!

Reduced sail area with this standard rule is:
1st: 20%
2nd: 35%
3rd: 55%
4th: 75% (is approx trysail size)

.
My new sail seems to stick well to this guideline. P is 35ft, and the first reef is 4ft up. The second is around 7 1/2 ft.

What is odd is the old main that this one replaced. It has two reefs at about 2 1/2 and 4 1/2 ft. Needless to say, putting the first reef in didn't have much effect.

I just wanted to point out that the effect of reefing a sail on heel is greater than the area reduction, as there are some consequencial effects :

You have lowered the centre of effort.
Moving the sail downwards lowers the mean wind speed it sees.
The sail is flatter.
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Old 25-03-2012, 19:32   #39
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Re: Mainsail - two reefs or three?

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What is odd is the old main that this one replaced. It has two reefs at about 2 1/2 and 4 1/2 ft. Needless to say, putting the first reef in didn't have much effect.
Maybe you had a racing main? or a second hand sail from a boat that was used for racing? For regatta's this is/was pretty much the standard.

Quote:
You have lowered the centre of effort.
Moving the sail downwards lowers the mean wind speed it sees.
The sail is flatter.
You are completely right there!
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Old 25-03-2012, 20:44   #40
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Re: Mainsail - Two Reefs or Three ?

I'm gonna vote for 3 (deep) reefs as well. We haven't used the 3rd reef all that often, but when we have needed it, we've been glad to have it. Personally, I'd rather pull in a 3rd reef than get the main down & secured, boom down & secured and a trisail set.
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Old 25-03-2012, 21:37   #41
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Re: Mainsail - Two Reefs or Three ?

This is a timely discussion for me. I have just placed an order for delivery sails including storm sails and a lazy jack bag for a Beneteau First 44.7 which I will be delivering to Australia from the US North East coast to Australia via the Panama. I am process of finalising area of Trysail and storm jib and deciding on 2 or 3 reefs and reef percentage. Mainsail area is 59.2m2. 135% furling Genoa is 56.9m2. The storm jib and trysail calculated to comply with Cat 1 ISAF offshore regs are 14m2 and 18m2 respectively. Thre storm jib equates to 25% of genoa area (75% reduction) and trysail 30% (70% reduction) for a total sailplan reduction of 72%. Are the storm sails too large? The boat will be used as a short handed race boat following delivery so will be pushed hard in its future life and the storm sails will be used as part of the racing sail wardrobe.
Was tossing up between 2 or 3 reefs in the main but had almost decided on 2 given that the boat is set up with 2 reef lines and they could be converted to single line reefing. I will consider Erics reefing percentages but that does beg the question of storm trysail size. My thoughts had been to go a medium deep #1 reef a deep #2 reef (close to trysail size) and then trysail.
I have 3 reefs on my 30 footer which is a lightweight trailable keelboat. The third reef is used while cruising but is a real nuisance to rig if under way with only 2 reef lines. I do tend to skip the #1 reef when cruising and rig #2 and #3 only but might be better to go #1 and #3.
Anyone have an opinion on single line reefing. Is it worth the spahgetti factory?
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Old 26-03-2012, 05:34   #42
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Re: Mainsail - Two Reefs or Three ?

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Anyone have an opinion on single line reefing. Is it worth the spahgetti factory?
It's not... (in my experience) the problem is that it seldomly happens that there is a balanced tension on the reefline at the clew end and the one at the tack end.
Usually this results in damage to the sail with ripped off sliders or even torn cringles.

The maximum trysail size that ISAF allows for racing is 17.5% of lufflength of mainsail multiplied with foot length of mainsail (17.5% of triangle, not of real main surface) and I find it big for cruising. I usually advise not to go over 70-75% of the ISAF regulations, especially if the boat has a realtively large mainsail to start with.

As for the storm jib, the ISAF regulations are 5% of the forestay height squared as maximum size. Again, 70-75% percent is plenty for cruising, you only need it to keep some speed in the boat to be able to manouver.

Our boat is 22 ton (50') and the ISAF rules maxim-ze our storm jib to 24.2 sqm. I made a jib of 17 sqm and we usually run upwind at 5-6 knots in a 55 knot breeze, faster than that is also not desired when cruising. The risk of not enough sail is that the boat does not accelerate fast enough when stopped by a wave, if not accelerating quickly, you might loose steering control and risk a knok-down.
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Old 26-03-2012, 06:45   #43
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Re: Mainsail - Two Reefs or Three ?

i have a 40 sqm main and ordered it with 2 reefs. i ditched the normal first reef and started with the normal second reef position and have another at the position of the norma third reef. the normal 1st reef is neglectible for cruising. for me it is a very good compromise
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Old 26-03-2012, 07:15   #44
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Re: Mainsail - Two Reefs or Three ?

Forgive me for a beginner question, but what would be the downside of going to the second reef, and just easing the mainsheet a little?
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Old 26-03-2012, 10:07   #45
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Re: Mainsail - Two Reefs or Three ?

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(...) Anyone have an opinion on single line reefing. Is it worth the spahgetti factory?
As already responded by another member.

IMHO it may work on smaller boats. But it did not work as advertised on the bigger boats I sailed.

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