Sail Area: How Much and How to Distribute It

How Much Sail?

Question: How much sail area do you think an offshore boat should have for a given weight?

Answer: Our boat, Morgan’s Cloud, has a comparatively high sail area displacement ratio for her type, of 16.5. This combined with good sails and her very easily driven hull shape means that we can sail in quite light airs without resorting to substantially overlapping sails. I think that cruising boats should have as tall a mast as possible, within reason, without compromising stability. High aspect ratio foresails are easier to handle and roller reef better. Propper sail area makes for faster passages and the shorter the time you are at sea, the less chance of severe weather.

How to Distribute Sail Area

Question: What is your thinking on how sail area should be positioned between the fore triangle and mainsail on short handed cruising boats?

Answer: I think there are two ways to go: The first is to have a big mainsail and a small fore triangle so that the jibs are small, and to be a sloop. The second is to have a bigger fore triangle and be a true cutter—one that carries the staysail all the time with a jib topsail (Yankee). I think that the first is better for inshore sailing since the boat is easily tacked but the second is better for offshore since, particularly if both staysail and jib topsail are on roller furlers, it gives more flexibility.

Morgan’s Cloud is a cutter with a large fore triangle. Her relatively tall mast and large sail plan allow her to sail well in as little as 6 to 8 knots of apparent wind and we can go all the way to heaved-to in gale force winds without making any sail changes using our two foresails on roller furlers and 3 deep reefs in the main.

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Meet the Author

John

John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

7 comments… add one
  • Dick Stevenson Aug 15, 2012, 5:29 am

    John, I continue wandering the site. I have essentially the same rig/sail set up and concur with all your points. Getting the jib top tacked through the foretriangle is made easier by leaving the staysail backed (hove to position) allowing the jib to slide along the backed staysail and through the slot smoothly & quickly. We then tack the staysail once the jib is through the slot. Leaving the staysail backed for a short period is no problem as the sail power of the other sails dominate as you get things sorted. With 2 people this goes quite quickly. Dick Stevenson, s/v Alchemy

  • John Aug 15, 2012, 9:18 am

    Hi Dick,

    Very good point.

    We tack in exactly the same way, which works well for us too. Of course a sloop will be much easier inshore when tacking frequently, but we don’t do that much and when we do”Morgan’s Cloud” sails quite well, as long as the water is fairly smooth, with just the staysail and main, in which case tacking is very easy.

  • Stuart Finlayson Nov 28, 2014, 12:03 pm

    John, We have just bought a Contest 46 which is sloop rigged with a 150% Genoa. I note you state that a 150% genoa has no place offshore as you believe it to be dangerous. Could you please explain to me why it is dangerous. I am planning to add a removable inner forestay to allow us to rig a staysail and a storm sail if required. Have you any suggestions as to what we should do to make this rig safe for offshore?

    • John Nov 29, 2014, 9:48 am

      Hi Stuart,

      I have to confess to a certain amount of hyperbole here, inspired by the loads on a 150% genoa on our 26 ton boat, which would certainly be dangerous for a two person crew.

      Having said that, large overlapping headsails as part of the working rig are really not a good idea offshore, in my opinion, for a bunch of reasons including, but not limited to, visibility, poor reefing and furling, the need to move the lead when reefing, and poor shape when reaching.

      If it were me, for offshore work with your boat with her quite large foretriangle, I would consider a high cut jib topsail (yankee) of 100 to 115% and a staysail. You could then add light air sails, if you wish. More info here, and here.

  • David Higgs Jan 11, 2015, 2:35 pm

    I’m in the process of putting a new rig into a Hylas 54, partly inspired by John, and so I guess membership of morganscloud.com has cost me far more than the membership fee….
    Hylas’s have Selden in mast reefing which I’ve not been happy with, and then the motor failed and I didn’t want to throw any money at it. So I’m going slab reefing with a carbon mast and canoe boom, and dare I say single line reefing. Increasing the size of the main by 20% to get a better balance at the helm. I was thinking of reducing the jib from 135%, but in conversations with North Sails I’ve been advised that 135% is what she was designed around and I should stick to it. The sails are 3Di, and the other thought was that with the foam luff the genoa should hold its shape better when furled. The 3Di is going to be interesting, I guess many would argue here they are for racing, but the deciding factor was not having to worry about UV, their durability (2x the mile) along with ease of repair. It has put my sail area to displacement ratio into the 22 area which could prove “interesting”, but the Bal./Disp is 41.35% for a standard 54 which is good and the weight out of the rig can but improve this.

    • John Jan 12, 2015, 1:52 pm

      Hi David,

      That’s sounds like a really nice rig, albeit powerful! I will be really interested to hear how the 3Di work out. I’m also wondering if you will end up with a smaller jib, despite what North say, but there maybe balance issues. If it were me, I would rig a boat that big with that much sail as a cutter with a 100% high cut jib top. But that is very much a personal preference and which is “better” depends a lot on the type of sailing you are doing.

  • David Jan 14, 2015, 4:20 am

    Like so many of these decisions it’s a launch into an unknown in regard to performance and balance. How do you quantify a benefit that is pretty difficult to measure/compare in the field, let alone looking at numbers sitting at a desk before hand. Asked the sail designer, and that’s what came back. As I’m heading south think this will be ok as I get used to the new rig. Suspect though in a few years you might well be proved right. The 3Di sails are going to be interesting. It’s been said to me that they’re racing sails which is indeed where they are used extensively. For me they are the ultimate cruising sail for the reasons outlined earlier. I’ll let you know……

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