Mainsail reefs, where to put them?

[Quandary]

My boat came with a North mainsail with three reefs. The reefing intervals are enormous compared to anything I have had before. So far we have never used the second reef though we have not been out in steady wind much above F6 and the conditions that would require the third reef inshore in a UK summer (F8 or 9+?)are so unlikely that we have never bothered to reeve the line for it. I was having the sail modified last winter and asked the sailmaker to put in a new first reef halfway to the existing one, he persuaded me instead to install a lens foot to make the outhaul more effective, he told me that flattening reefs were now old hat and booms tend to be higher now. Certainly I feel happier looking up at the boom than seeing it at knee level. Looking around it seems that a lot of recent cruising boats now have these very high reefing cringles
His explanation of the very big reefs were that unless the boat carried a trysail it was now required that the sail area can be reduced by a stated percentage. I think that this may have related to getting a CE cert or it may have something to do with one of the rating systems.
Does anyone know what the score is here? I suspect that if it was more widely understood that it would be better to buy a trysail than have these distorted mainsails, or at least the issue of reef placement should be discussed when taking an order for a sail.

 

[dt4134]

The only rules I know about that specify reefing points are the RORC rules for offshore racing.

If you've got a fractional rig you can de-power the main a great deal without reefing, so that is probably why your first reef is so big. I've found the first reef to be often too small on cruiser-racers. By the time you've used up the controls to flatten the sail and still need a reef you need a big reef, so your arrangement sounds good to me.

I'm also a great believer in three reefs on a cruising boat. F8 or F9s do happen. A trysail is great in theory, but unless you have suitable arrangements (such as a separate mast track) it would be pretty difficult to switch to it when you need it.

 

[flaming]

The only rules I know about that specify reefing points are the RORC rules for offshore racing.

Specifically, for cat 4 racing you don't have to carry a trisail if your mainsail is reefable to 40% of its luff length.
Can't remember off the top of my head if that applys to cat 3, but for the more serious stuff you have to have a trisail.

 

[snowleopard]

I would say keep the 3rd reef and reeve the lines. If you ever found yourself wanting to beat off a lee shore in heavy weather you wouldn't be wanting to climb out to the end of the boom to run a line through.

I came across a mainsail recently where the sailmaker hadn't allowed for the height of the stack of slides and, having failed to put the reef cringle midway between slides, the cringle couldn't be pulled down to the gooseneck without taking some slides out of the track. If you put in an intermediate reef you could hit this problem.

 

[Deleted member 36384]

The 3rd Main Sail Reef Is Useful

I have sailed close hauled in a F6 with the 3rd reef and a bit more head sail rolled out quite often. It offers a more comfortable beat and allows the old roller reefing head sail to set a bit flatter.

I have also used the 3rd reef to sail slowly in blustery conditions for close quarters boat handling when the head sail is rolled away.

So the 60% reef is in my opinion a requirement for a mainsail slab reefing system.

If you don't want to rig up a 3rd reefing pennant. You can rig a mouse line between the 2nd and 3rd reef. I use 3 mm shock cord. Feed the line through both reefing clews and tie it together to make a loop.

If you put in your second reef and believe that the wind will increase, then undo the first reefing pennant and tie it to the mouse line loop with a clove hitch. I assume that you don't actually have a 3rd reefing pennant installed. Then just pull the 1st reefing pennant up and through the 3rd reefing pennant and make off.

 

[Quandary]

Mainsail reefing

The point I am trying to raise is that if the reef intervals were not so great the boat could be sailed faster and far more efficiently in stronger winds. If you are ordering a mainsail for performance it is worth thinking about, particularly if like me you expect the reef positions to be based on optimising the boat performance in the conditions you are likely to sail in. When I raced and cruised Sigmas, the reefs in the sails were proportionately much smaller, yet I can only recall using the third reef once or twice out in the North Channel in close to survival conditions on long offshore races. However we did have a choice of four headsails.
On the Finngulf using roller reefing headsails all the time (it is a through deck system) I now only carry two headsails, a 140% genoa, and if it is windy I switch this to an approx. 100% blade. (when only my wife and the dog are with me, I admit I tend to use the small headsail in F4 or above as this is an easily driven boat.) I rarely reef the headsails as the shape is lost and you loose all control of luff tension. If I had been more specific when ordering the boat, rather than accepting the standard reef positions, I would asked for the first reef cringles to be about 1/2 m. lower, the second down about a metre and the top ones down at least 2m. With this arrangement I would be happy to reeve all the reefing lines in the boom and would have something useful to do with all the rope that is already there. I don't sail offshore in winter or anticipate being allowed to visit the Southern Ocean or even the N. Atlantic, the west coast of Ireland is the worst I expect to experience now.
By the way, the third reefing line is rigged and stowed at the mast, just not run away up to near the top of the sails, the top cringles are so far up that they are well inboard if I thought I ever needed to use them, if they were permanently reeved all that rope dangling around would be a real nuisance.
I recognize that a lot of skippers reef for the worst conditions anticipated rather than those encountered and that this is exacerbated by conservative inshore weather forecasting, but we have a single line system and don't even need to go to the mast to put in or shake out a reef.
If I replace this sail I will make sure that the reef positions are fully considered.

 

[srm]

Some owners have strange ideas - we set and hoisted the newish mainsail on my 'new' boat for the first time only to find it was a bit short on both luff and foot. However, the biggest surprise was the reef points - first reef where I would expect the second to be and second in the normal 'deep reef' third position. I appreciate the arguments for taking in a first deep reef on a cruising yacht but bringing the head of the sail down to the upper spreaders can be a bit much when simply balancing the rig for the Monitor gear.

I will dust off the trusty 'Reeds Sailmaker' machine (anyone remember them?) to fit reef patches and cringles for a more conventional first reef this winter.

 

[Deleted member 36384]

I think that for a boat to be coded for say charter (definitely for a sailing school boat), you have to have this 60% reef option (or a Tri Sail), so that may be the reason why the default setting is now so big as you observe i.e. it comes with the order.

I have seen main sail reef positions quoted as a standardised reduction of 20% area for each reef. Certainly there would be milage in trying to match the mainsail reefs to optimise your slot geometry for the 140 and 100 which would then address your performance requirement.

The head sail is made more efficient by the presence of a mainsail (no surprise there), so by using your head sail choices your should be able to optimise reef points to maximise the lift. The mainsail increases the head sail efficiency by diverting more air to leeward of the head sail so that the combined effect of both sails is greater lift.

I think you would be looking to keep your head sail leach just aft of the mainsail deepest point of camber as I believe this is the most efficient slot flow.

Hence as you point out by the time you reef to your 100% blade you may only want a relatively small reduction in mainsail height for subsequent expected wind strengths.

Maybe this optimised reefing position can be simulated on a calm day by hoisting your mainsail luf to establish slot geometry with the desired head sail hoisted with a good sail maker on hand to mark up the positions.

This is an interesting post because today there is a lot of standard stuff around because its, well standard stuff! If you come up with a revised reefing arrangement based on any logic, perhaps you could update this post.

 

[Twister_Ken]

"The mainsail increases the head sail efficiency by diverting more air to leeward of the head sail "

Could you explain the physics of that?

Yours, Bear of little brain.

 

[Deleted member 36384]

"The mainsail increases the head sail efficiency by diverting more air to leeward of the head sail "

Could you explain the physics of that?

Yours, Bear of little brain.

Its to do with the flow of air over a single air foil, the head sail in this case. There is an area of "stagnation" to the lee near the leech on a head sail only which limits the efficiency of the foil shape.

Add in a mainsail and it alters the air flow across the wind ward side of the head sail. The stagnant point of the head sail moves back beyond the leech of the mainsail. The combined head sail and mainsail are now behaving more as a single air foil which as we know is far more efficient way of powering a sloop under sail.

What happens in the two sail scenario is the slot causes the air flow across the windward side of the head sail to be some what choked (compared to no mainsail being there) and this resistance is what diverts more of the effective air around the head sail to leeward than would other wise happen in the single head sail case. For the correct angle of attack to the wind (say close hauled) this air has to move faster so causes the pressure on the leeward side of the head sail to drop more than it would by itself only.

Its the same reason why allowing a mainsail to back wind in heavy airs before reefing can be a good thing. It may be why a Bi-Plane upper wing is slightly forward of the lower wing i.e. the upper wing, slot and lower wing working in unison provide more lift than say just one big wing in the days when aerodynamics were just beginning to be understood. I am not sure about this bi-plane analogy, just added it for interest.

 

[Quandary]

Mainsail Reef

Blowing Old Boots,-thanks, yes, I agree with you very succint (is that the word) analysis of the issue, however with three reefing cringles already; the sailmaker (Chris Owen who knows all there is to know about performance) advised me not to add more and they recut the mainsail instead. While an improvement I regard it as a compromise but as the main is only two (light) seasons old I am reluctant to order a custom replacement yet.
My purpose in posting was to warn others ordering boats or sails not to assume anything as the design criteria used may not suit their intended use, I am kicking myself now for not being more specific with North Finland before they cut the sails. I suspect that like most things nowadays a conservative attitude to safety is at the back of this problem.