gaff rigged? Full Battened Marconi?

[jbarros]

Hi all.

I was wondering about the pro''s and cons of gaff rigged boats and of the wind-surfer esq sails I see on some of the new 12 meters.

Regarding the gaff rig: It seems that the lower center of force you could get for the same sail area would be cool; helping you stay level etc, but I would think that the extra weight aloft would nullify that, as it''s got leverage and would bring you over, as well as loading up the rigging. I also cant help but get nervous about having one more thing to break somewhere not easily accessable.

I''ve noticed that the Americas cup boats have realy long, battened mains, which seem to have the almost square shape, with none of the extra weight aloft, nor most of the complexity. What am I missing that this isnt done more in "regular" (read: cruising) boats. What major downside to this am I not seeing?

Also, with the exception of once, when I was 10 and dont remember a thing, I''ve never sailed anything but a Marconi rig, so if I''m way off base, feel free to let me know.

Thanks.

-- James

[paulk]

Downside to a square-topped sail and/or gaff rig is the backstay. AC boats have crew & tackle to handle the running backstays, and the mast stays up (most of the time). Lonely cruisers often don''t have lots of crew, so permanent backstays are a bit safer. With a permanent backstay in place, the super-roach" that long battens permit has to be tempered with not getting the sail caught (and chafed) too much on the backstay. You pays yr money & takes yr choice.

[jbarros]

Does this apply to gaff rigged boats as well? I''ve seen a few gaff riggers, and none of them seemed to be setup to require a racing crew. How do they do it? Just set the shrowds far back?

-- James

[jbarros]

also... I''ve heard from a couple people that gaff rigged boats dont go to weather as well?

And while I''ve not heard this, I would presume that since they''re getting their air lower, they''d not sail as well in light airs where the top of the mast is getting more breaze than the surface. Is this an appropriate supposition? or am I guessing out my arse?

Thanks agian

-- James

[thomasstone]

http://www.greatsoftware.net/voyage/voyage1.html James, just sailed a Gaff rigged boat from Daytona to NYC. While I think nothing looks better, Im glad my own boat is not. We had a crew of three so the running backstays were not that bad but shorthanded it could be a real pain. Point to weather forget about it. Wind was of our quarter the whole way so the Gaff did pretty well. When reefing or raising or lowering sailyou have two halyards(the throat and the peak you also have to deal with). No winches on the main you had to sweat the line. I have met people that swear by it though-thomas

[Jeff_H]

There are a lot of reasons why Gaff rigs are not as weatherly as Bermuda rigs. To being with going up wind is always a battle to keep drive high and drag low. Going up wind the drive comes from the leading edge of the sail and much of the aerodynamic drag comes from the spars and the trailing surfaces of the sail. The ideal upwind sail profile would be a tall narrow sail on a single tiny spar where the drive is maximized and the drag is minimized. But of course it would be diffucult to keep a proper shape in the sail without a trailing edge and so sails have a leech area. All other things being equal, for a given sail area a Bermuda rig has more leading edge and less spar area than an equal sail area gaff rig and so is more efficient in terms of drive to drag.

But that is only a piece of the puzzle. In order for a sail to be effective going to windward, it is important to control the shape of the sail and the angle of attack of the sail over the entire span of the sail. In some ways, having the combination of throat and peak halyards allow a lot of control of a gaff sail''s shape but in the big picture it is much harder to control depth and placement of camber on a gaff sail. This makes it a little harder to properly flatten a gaff sail when going up wind and still end up with a proper shape.

The other and far more serious problem is twist or angle of attack. On a Bermuda rigged mainsail twist is very easy to control with a high degree of precision using the mainsheet and traveller. On a gaff rig it is pretty much imposible to control twist without either using spencer vangs (think of them as windward and leeward sheets that control the end of the gaff and have to be tacked or jibed), or else negatively altering the sail shape in other ways. Spencer vangs are really not all that effective and are best used on a multimasted rig run from the peak of the gaff aft to the hounds of the mast aft of it. Of course multimasted rigs are inherently poor to windward as well so spencer vangs really do notbuy you much.

So gaff rigs are challenged by lower aspect ratios (or higher heeling if the aspect ratio is kept constant), higher spar drag, poorer section shape control, and poorer angle of attack control. The deck is pretty well stacked against the gaff rig going to windward.

Jeff

[jbarros]

hate to show my ignorance, but I suppose it''s better to show (still more of) it with chance at remedy, than to keep it hidden, but still with me.

Whats a bermuda rig? asanother term for a Marconi rig? (triangular sail?)

Thanks agian.

-- James

[Jeff_H]

A Bermuda Rig is a generic term for, more or less as you put it, any rig with triangular sails attached to its mast instead of gaff sails attached to its mast. Traditionally, a Marconi rig is a specific type of Bermuda rig that has spreaders and as orginally used was a boat with a multiple spreader rig that resembled Marconi''s radio towers. To help clarfify this distinction by way of example, the boats that Freedom builds are Bermuda rigs but not Marconi rigged. Most modern rigs can be called either.

Jeff

[dameware]

“I''ve noticed that the Americas cup boats have realy long, battened mains, which seem to have the almost square shape, with none of the extra weight aloft, nor most of the complexity. What am I missing that this isnt done more in "regular" (read: cruising) boats. What major downside to this am I not seeing?”

Main sails with a big roach area need battens to maintain the shape and are very common on catamarans because cats don’t have or need a backstay. A backstay will get in the way of a full roach.
The advantages are more sail power and longer wear due to less flogging. Downsides are greater cost and a bit more weight aloft.

I would definitely use a fully battened main on a cruising boat, if I had a cruising boat.

Why don’t more cruising boats have them? Very good question…

[jbarros]

> cats don’t have or need a backstay

eh? how is it that one can cary sufficient sail area, and not need a backstay? I would think that, especialy traveling downwind, it would be essencial, to ensure that your mast ist bent (or broken) to the fore?

-- James