Flattening Sails to Depower

[Channel Sailor]

i am wondering if others have noticed this. In trying to put off putting a reef in the main, I can flatten the sail with backstay tension, outhaul tension and cunningham. Which does appear have the general desired effect. But if going upwind into a choppy sea then I appear to have lost the low down grunt power to keep the speed up. Also the flat sail appears to be less forgiving with helm control which results in a degree of wandering of the course mixed with varying heel. So a I put a reef in and the speed is about the same, consistent or even slightly better and importantly the yacht is easier to helm.

So my question is, can flattened sails be made to give a good result or is it a compromise one has to accept because you want the sail area when on the down wind leg? It could be the yacht is out of its sweet spot wind speeds so in a mixed fleet it is never going to do well anyway.

Decent cloth Dacron radial cut sails. Short handed sailing so not a lot of weight available on the rail.

i am wondering if a crew is needed to constantly adjust the flattened sail trim as the yacht’s slows down (due to choppy sea) and then accelerates, for example playing the backstay tensioner might be practical.

 

[flaming]

i am wondering if others have noticed this. In trying to put off putting a reef in the main, I can flatten the sail with backstay tension, outhaul tension and cunningham. Which does appear have the general desired effect. But if going upwind into a choppy sea then I appear to have lost the low down grunt power to keep the speed up. Also the flat sail appears to be less forgiving with helm control which results in a degree of wandering of the course mixed with varying heel. So a I put a reef in and the speed is about the same, consistent or even slightly better and importantly the yacht is easier to helm.

So my question is, can flattened sails be made to give a good result or is it a compromise one has to accept because you want the sail area when on the down wind leg? It could be the yacht is out of its sweet spot wind speeds so in a mixed fleet it is never going to do well anyway.

Decent cloth Dacron radial cut sails. Short handed sailing so not a lot of weight available on the rail.

i am wondering if a crew is needed to constantly adjust the flattened sail trim as the yacht’s slows down (due to choppy sea) and then accelerates, for example playing the backstay tensioner might be practical.

It strikes me that what you are describing is more likely to be the result of not changing your setup from flat water to choppy water in terms of twist and "forgiveness".

Think of it this way. If you are beating into "quite a lot" of breeze but in nice flat water, maybe in a sheltered bay for example, then provided that you can depower your main enough by flattening that you're not actually flogging it, that will be no slower than taking in a reef.
And in that flat water you can stand the leach up nice and straight, and obviously match the leach of the jib, to give you loads of height.

But... The trade off of a nice straight leach is that it narrows the "groove" that the helmsman has to work with. In flat water with a decent helm this is fine.

In chop however... Not so much. You need to move the jib car back a bit, and go traveller up with a bit less sheet tension (and kicker) to open up the top of both sails. This will give you more "grunt" to give the speed and ability to punch through the chop, but at the expense of the last few degrees of pointing. It also opens up the groove and makes the boat easier to drive.

If shorthanded racing I would go to a more open "twisted" setting earlier than when fully crewed with a dedicated main trimmer. But this is completely separate from how flat the sail is.
For example, if the wind then drops, but you still have the chop, then you can power up the sail by easing cunningham, backstay and a smidge of outhaul. but keep a bit of twist to allow for better ability to punch through the chop.

This article explains it well.

Full Power & Mix Of Power | North Sails

 

[Channel Sailor]

Ah, spotted one thing you have mentioned, twist. Probably not enough twist. I have been keeping the leech(s) fairly upright to keep the top tell tails flying (my plan there being to to get the entire luff of the main and genoa working for lift). Moving the genoa car aft a little is easy enough and it does exactly that. Putting twist into a “flat“ main I’ll need to experiment with and would be welcome because it will less effort on the hands/winches/boat fittings than trying to grind in the top of the leech. Interestingly at the same time, I noticed a slight lee helm which might indicate there was not enough power from the flat and upright main. Mostly the helm balance is fine so It seemed odd to look down to see the tiller pilot with slight lee helm. Cheers.

 

[flaming]

What type of boat is this?

 

[TernVI]

I find that different people have quite different ideas as to when a sail is 'flat'.
It helps a lot of you can put some numbers into the arm waving and talk about 5% camber or whatever.

In general, as the breeze increases you can let the sail out further for the same true wind angle.
If it's choppy, then you may want a fatter TWA too.
But you may want more twist, so the boom and foot of jib might be further in, but from 1/3 height upwards, the sail is actually further out.

Sometimes it's much better not to depower too much, and play the sheets to keep the boat on its feet in the gusts.

There are always compromises to keep two sails working together.
A tillerpilot is going to mean quiter a lot of compromise I suspect?
It might do better reefed, to make the 'groove' as wide as possible.

 

[MikeCC]

Equally, if you're short-handed and lacking rail weight and/or someone to play the main, might be advantageous to just put the reef in when it's choppy and hoist again for downwind?

 

[TernVI]

Equally, if you're short-handed and lacking rail weight and/or someone to play the main, might be advantageous to just put the reef in when it's choppy and hoist again for downwind?

I've raced like that.
If you sort your reefing systems so you can get reefs in and out very quickly, it has its merits, although on balance I don't think it's a substitute for having the right number of bodies when racing.
When cruising, so long as you are not horribly underpowered in a choppy sea, reefing early helps keep the kettle in action.

 

[Channel Sailor]

Just a short update., so you know I have not gone away. This weekend, again short handed, upwind, into a chop for an hour on several tacks. Full mainsail, normally would have been reefed for the apparent wind speed.

with backstay, outhaul and Cunningham on hard, the boat felt bogged down still. Next time I will try it with a reef. lated i I noticed that when sailing on just the reefed genoa (while dropping the main) the yacht was going almost as fast and easier to sail. further up date after next windy ish day.

 

[RJJ]

Just a short update., so you know I have not gone away. This weekend, again short handed, upwind, into a chop for an hour on several tacks. Full mainsail, normally would have been reefed for the apparent wind speed.

with backstay, outhaul and Cunningham on hard, the boat felt bogged down still. Next time I will try it with a reef. lated i I noticed that when sailing on just the reefed genoa (while dropping the main) the yacht was going almost as fast and easier to sail. further up date after next windy ish day.

In Lasers, we didn't used to pull on the outhaul bar tight, but a couple of inches off (compared to 4-6 inches off when looking for power in F2-3).

Once the backstay and cunningham are maxed out, you might benefit from a little camber along the foot. Still a flattish sail, but with a little drive. That'll restore the weather helm you're lacking.

 

[Channel Sailor]

RJJ, thank you. I’ll try that too. On a 23 squ m sail with a 2:1 outhaul tackle, I have needed the winch to flatten the foot completely, often then needing the foot line (like the leech line but along the foot) punched up to stop the foot vibrating on the boom. Maybe I have been too heavy handed on the outhaul.

 

[MADRIGAL]

Singlehanded and therefore short of moveable ballast, my my priorities are keeping the boat on her feet and making as much ground to windward as possible. Since excessive heel kills our speed and increases both weather helm and leeway, I have found that sailing with a flatter main that luffs evenly from head to foot allows me to spill wind without having the sail flog in gusts, while still making decent progress to windward even when heading up at the peak of the waves and bearing off down the back of them. It’s tiring and means plenty of steering and mainsheet adjustments, but it seems to work. When it doesn’t, then it’s time to reef.
Sailing with fuller, more twisted sails should allow me to steer around waves without as much mainsheet adjustment, but I find it hard to keep the boat on her feet by myself in F3/F4 without hauling in on the Cunningham, the outhaul, the main halliard, and the kicker (for mast bend). I wish I could put numbers like degrees of camber on all this, but that would be quite beyond me.

 

[Bobc]

lated i I noticed that when sailing on just the reefed genoa (while dropping the main) the yacht was going almost as fast and easier to sail. further up date after next windy ish day.

My boat does that, so what I do is to basically lean on the genoa (i.e. sail to the genoa), and feather the main just so it's not lifting and backing. I also find that in that situation, moving the genoa cars back a bit to allow the genoa leech to twist off a bit and to flatten the foot, de-powers the genoa a bit (which helps you keep the main on), and also allows you to twist the main leech off without shutting the slot and stalling the rig.