traveller down vs twist off?

[DHV90]

Got a question about trim in gusts or building wind strengths, something I've wondered over for a while!

My instinct has always been to gradually blade out the main (halyard/outhaul/backstay) as wind builds and play the traveller through gusts, and gradually drop the traveller if wind continues to build and play the sheet when at the end of the traveller, before taking a reef.

Recently I have sailed with a crew who asked me, when getting overpowered, to traveller up and twist off the main in gusts to spill wind. To me, traveller up and sheet eased is a low gear/powered up mode, but I got thinking about the sailplan overall and it's standard to move the genoa car aft as wind builds, twisting it off, so that seems to contradict my instincts on main shape.

Im guessing theres merit to both approaches and both have their place in different conditions of gusts/chop and different boats etc. it just confuses me how opposite some of the approaches are, like to me traveller up feels like light winds mode, so how can it be effective in heavy airs unless youre dumping the main so far that you're basically luffing half of it?

I appreciated the difference between twist and depth so maybe a flat but twisted sail is a totally different effect to a full and twisted shape?

If someone who knows this kind of stuff give me some insight I'd really appreciate it! Just curious really, probably of little practical benefit but its just something I haven't got my head round yet.
Thanks!

 

[flaming]

Quite a big topic... And it does depend on the boat to an extent. But...

If you are keeping the leach on hard, and dropping the traveller in the gusts, then what you are doing is closing the slot. However if you are keeping the traveller up, easing the sheet to depower in gusts, then you are only closing the slot at the top, and as you say you have probably started to drop the car back to open it up anyway.

If your boat is quite a traditional boat with a big overlapping genoa and quite a wide sheeting angle, then the 1st approach can be quite effective, as the tight leach allows you to keep your height whilst the relatively open slot is less susceptible to being closed. However, if your boat is quite modern, with a non overlapping, high aspect ratio jib that is inhauled to a small sheeting angle, then dropping the traveller is just going to shut off the flow too much and kill a lot of drive. In this case you will be better going with the sheet unless you need to dump the traveller quickly just to keep the boat on its feet.

We did an experiment one windy day, and figured out that for us playing the fine tune was the best method, with the traveller up above the centre line and available for an "oh bother" type dump. This was definitely quicker for us.

 

[TLouth7]

Setting aside actual sail shape considerations for a second, we dump with the traveller for two primary reasons. Firstly it is more ergonomic with a nice pull angle on the control line and greater effective purchase, and secondly it makes getting back to the correct trim after the gust easier as twist is not affected. Note that our yacht is the first type described by Flaming, so dropping the main has little effect on genoa drive.

 

[DHV90]

As ever flaming that is a really clear informative response and answers all of my questions, thanks for taking the time to respond.

Out boat is 80s and fractional, just swapped from an overlapper to a high aspect, close sheeted jib so a swap of tactics may be in order. Ill have a play around!

What is the overall consideration over width of the slot, is it just about keeping it clear and even to aid flow?

 

[flaming]

As ever flaming that is a really clear informative response and answers all of my questions, thanks for taking the time to respond.

Out boat is 80s and fractional, just swapped from an overlapper to a high aspect, close sheeted jib so a swap of tactics may be in order. Ill have a play around!

What is the overall consideration over width of the slot, is it just about keeping it clear and even to aid flow?

If your underwater profile is quite "conservative" don't be too tempted to shut the slot down too much. You can get all sorts of height out of the rig, but unless your keel can cope with the angle of attack you won't go anywhere.
We have found with our high aspect ratio Jib (also after swapping from overlappers) that with our mid 2000s L shaped but fairly moderate keel we cannot inhaul much inside the turn of the coachroof without killing the speed, and that the fastest way is often with more twist in the setup than you'd initially think sensible.
Certainly if you're not getting the speed you want and are in any doubt open it up and add twist.

 

[lw395]

On a sail with a decent amount of roach, it often seems to pay to let the top twist off some when overpowered.
Easing the sheet with the vang fairly light will allow the top to twist off first, but limited by the vang. Then the boom will go out some.
In reality, the two axes of control for the boom (in/out, up/down) generally both want adjusting, so although we spend a lot of effort to separate these into either sheet/vang on a dinghy or sheet/traveller on big yacht, the ideal is possibly to have the sheet do both in a balanced way, at the point where we are operating in puffy wind or being stopped by waves.

But in many yachts, the vang and boom are simply not strong enough to sail it like a dinghy. Luckily these boats normally have more minions to fiddle with sheets and travellers.

I think the real key is to get get back into 'normal mode' smoothly and progressively as the gust recedes/the boat accelerates.

 

[flaming]

The other thing worth mentioning is that the experience of the helm will also have an effect. A really good helm will not allow a gust to reach the boat with all the telltales streaming. As the gust arrives the good helm will have inched up, so that you are "inside the jib" with the inner telltales just lifting. This allows a much smaller ease than would be the case if the gust had arrived with the boat fully powered up with all telltales streaming. If you're the trimmer and you know your helm can do this, then the twist method of dumping is more attractive as you're much less likely to need a great big release of power. If however you helm is not that experienced, then start off by using the traveller, as you're much more likely to be able to keep the boat on its feet with the traveller if you get hit by a gust when the boat is too powered up.
And then again, even if your helm is top notch there are days when the gusts are so much stronger than the normal wind that traveller is going to be the only way to keep the boat on its feet.

 

[savageseadog]

We definitely take the height in gusts with the helm if we can (Prima 38)

 

[Triassic]

Assuming we're talking about going to windward here so close hauled we try not to ease the main sheet unless it becomes absolutely necessary, i.e. we're coming out of the water......! We need sheet tension to keep both the mainsail shape and the forestay tension so we tend to depower in gusts by luffing slightly as Flaming was suggesting. There are usually subtle changes in wind direction with gusts but even if not the first thing you will notice is the apparent wind moving aft momentarily before the boat can accelerate. I always try and immediately react to this by heading up, and then easing off if I think we can handle the increase, or staying high if not. Having quite a roachy main with a square top the reality is there will always be a certain amount of twist off as the wind builds so we don't move the traveller until we are actually sailing lower angles. If the wind builds we reef the main early, this allows us to keep the shape and the boat is rarely slower.

 

[DHV90]

All really useful to consider, will definitely be beneficial to try and learn to get a bit higher up through gusts and use them to our advantage. Keel wise nothing fancy, but we're sheeting to the factory inboard no3 tracks which are well inside the shrouds but not extreme and presumably within the original design parameters. So far the main is a lot easier to play, and is more accessible from anywhere in the cockpit so makes more practical sense as the primary power control, which makes all of this very welcome information!

all starting to make a bit of sense to me know, so I've got plenty to experiment, with thanks all!

 

[savageseadog]

I assumed when I posted previously that we were considering beats, ie head up in gusts, part of the skill is in predicting and observing when those gusts are coming. Off the wind we try to ease both sheets in gusts which we find keeps best speed but the traveller is quicker when pressed.

 

[bignick]

Worth also considering water conditions.
Flat water means you can pinch higher in the gusts, which in turn requires more main leech tension on the main.
Nasty waves and chop require more drive, when twisting off the rig (both main and jib genoa) can be more effective.
I'm a big believer in looking at the rig as a whole, not two sails in isolation, which is why I always look at how well the leech of the jib/Genoa matches the twist in the main in dictating slot shape.

 

[Yealm]

Quite a big topic... And it does depend on the boat to an extent. But...

If you are keeping the leach on hard, and dropping the traveller in the gusts, then what you are doing is closing the slot. However if you are keeping the traveller up, easing the sheet to depower in gusts, then you are only closing the slot at the top, and as you say you have probably started to drop the car back to open it up anyway.

If your boat is quite a traditional boat with a big overlapping genoa and quite a wide sheeting angle, then the 1st approach can be quite effective, as the tight leach allows you to keep your height whilst the relatively open slot is less susceptible to being closed. However, if your boat is quite modern, with a non overlapping, high aspect ratio jib that is inhauled to a small sheeting angle, then dropping the traveller is just going to shut off the flow too much and kill a lot of drive. In this case you will be better going with the sheet unless you need to dump the traveller quickly just to keep the boat on its feet.

We did an experiment one windy day, and figured out that for us playing the fine tune was the best method, with the traveller up above the centre line and available for an "oh bother" type dump. This was definitely quicker for us.

Please could define the slot ?- i'm having trouble understanding - presumably distance between the sails in some plane or other?

 

[lpdsn]

Please could define the slot ?- i'm having trouble understanding - presumably distance between the sails in some plane or other?

It's the gap between headsail and mainsail that air flows through. Managing that flow is very important for optimum sail trim.

 

[Beelzebub]

Please could define the slot ?- i'm having trouble understanding - presumably distance between the sails in some plane or other?

The slot between the headsail and the main is crucial to the speed of the boat, particularly upwind. In low winds and a calm sea you look for a narrow slot to help increase the wind flow on the leeward side of the main. In stronger winds, you still want a decent flow over the leeward side of the main but you don't want to be overpowered so you open the slot a bit. On the X-99 we used to move the genoa traveller back two or three notches; other classes might move the headsail sheeting position outboard a little. This is an over simplification of the topic. There are many books offering good advice here.

 

[Birdseye]

Setting aside actual sail shape considerations for a second, we dump with the traveller for two primary reasons. Firstly it is more ergonomic with a nice pull angle on the control line and greater effective purchase, and secondly it makes getting back to the correct trim after the gust easier as twist is not affected. Note that our yacht is the first type described by Flaming, so dropping the main has little effect on genoa drive.

Sail shape is important and dumping the traveller in a gust makes it far quicker to get back to a decent shape at the right angle of attack than letting out the main sheet. But gust is the important word. If you are in the no mans land with average wind a bit strong but not yet reef worthy, then getting twist into the main is the way to go IMO. Or at least this seems to work with my boat.

The reason why the approach is different for the jib is that it doesnt have the same controls. Bit of a statement of the bleeding obvious I know.

 

[Kerenza]

lest we run the risk of perpetuating any myths, for those in doubt about slot theory:

https://www.google.co.uk/url?sa=t&s...FjAAegQICBAB&usg=AOvVaw2Whk47h4YxOS2-yJLwfxlv

 

[kof]

when racing we always played the traveller first. It kept the main driving but allowed for a quick de-power when needed, then back in again as the gust died. Easing the main sheet brings in a lot more twist to the sail but is more of a long term power down if you know what I mean.

So traveller first, sheet second. If it's still overpowered then 1) get some more meat on the rail, 2) reef 3) call it a day and go for a pint.