Topping Lift - Mainsail Trim - Light winds...

[2Wind]

Today, it was very light winds out on the bay - 3.5 to 5 kts. Not ideal conditions for my boat.

It was a fabulous day and as I was sailing solo without an agenda or timetable to consider, I busied myself trying to tease out every last bit of speed I could. I know, I've heard it all before, "Lagoons are not designed with speed in mind...." Anyway, I decided to try.

With a heavily roached 85sqm 8 batton main, made of relatively heavyweight Hydranet, I have found in the past that when there is little pressure in the sail by virtue of light wind, the top third of the sail effectively has a reverse twist due to the leach tension generated by the sail weight and the boom weight being in excess of the twisting moment of the light wind pressure. As you ease the main sheet, the boom moves upward and to leaward, but fails to really address the lack of twist. So you end up with either sheeting and positioning the traveller to optimize the top of the sail or alternatively you can optimize down low, but you can't have both!

Enter the topping lift! It was like one of those moments when you suddnely think you have come across something that all the world has known about for years and you're the last to find out! Maybe so, but I'm not so proud that I can't bare my sole on CF.

So I found that I could more precisely anchor (no boom "wander" as you get when loose sheeted) and position the boom in both vertical and horizontal axises. By adjusting the topping lift and tensioning against it with the mainsheet and in comjunction with the optimizing the traveller position I could achieve ideal trim for the lower half of the sail and by ensuring that the leach was not excessively tight by tensioning the toppinglift, I could also optimize the upper half.

Here is a picture of my instruments showing true wind speed and direction, the iPad GPS SOG and the tridata boat speed. In 4 kts of breeze, what I did was worth about 0.5 to 1.0 kt which, bearing in mind the slow pace, was a 25% gain.

Did I mention that I had fun too!

[arsenelupiga]

amazing discovery !

thanks for sharing, I will try that too.

not bad speed you achieved

[seandepagnier]

why don't you use a spinnaker? I found it's faster to drop the main in very light winds as it interfears with the spinnaker and provides little drive.

[2Wind]

Originally Posted by boat_alexandra

why don't you use a spinnaker? I found it's faster to drop the main in very light winds as it interfears with the spinnaker and provides little drive.

The true wind angle was 80 degrees, that would have been about 50 apparent, I guess. might have been able to fly the screecher at that angle in light wind, but as you can see in the plot, I had a tight track to follow with shallows either side coming up.

[Benz]

My topping lifts are sized for that very purpose, and are the easiest way to tweak the trim and get the most out of the sail. I rarely bother with the clew outhaul, since the lift is a lot easier.
Good on you for experimenting!
Ben
zartmancruising dot com

[seandepagnier]

ok, you win.

I have symmetrical spinnaker good to 90 degrees, and asymmetric good to 60, but closer than that I am without specialized light air sails for pointing.

I have heard of people who have nylon main sails good up to 15 knots which hold a much better shape in light air

[arsenelupiga]

i just ordered laminated gennkaker that should be good to 55 true, according to sailmaker.

Want to see how this goes in 6 kn of wind, huh!

[2Wind]

Originally Posted by arsenelupiga

i just ordered laminated gennkaker that should be good to 55 true, according to sailmaker.

Want to see how this goes in 6 kn of wind, huh!

Make sure you write up your experience. Many will be interested. I have a nylon screeched/gennaker that will do 60 apparent in light conditions under 7 kts but 70 -75 as the wind gets up. It's size prevens it sheeting inside.

To get 55 do you plan to sheet inside the shrouds?

[2Hulls]

Good on ya, 2wind.

A question of curiosity:

Originally Posted by 2Wind

With a heavily roached 85sqm 8 batton main...

85 m2? Best I can find, the typical 440 sail on the tall rig (70.25ft/21.4m) is 74 m2. And 8 battens? Wow. Do you have an even taller rig? - or a longer boom? - or so "heavily roached" that no only is it a sq top, but a big rectangle?

Dave

[meirriba]

Originally Posted by Benz

My topping lifts are sized for that very purpose, and are the easiest way to tweak the trim and get the most out of the sail. I rarely bother with the clew outhaul, since the lift is a lot easier.
Good on you for experimenting!
Ben
zartmancruising dot com

Aren't you mixing foot tension (outhaul) with leech tension (mainsheet & topping lift)?

[meirriba]

Originally Posted by boat_alexandra

why don't you use a spinnaker? I found it's faster to drop the main in very light winds as it interfears with the spinnaker and provides little drive.

IMHO there is no need to drop the mainsail. Even symmetrical spinnaker would not work properly directly downwind in light wind conditions. In light wind you are forced to sail much higher and as wind picks up it is possible to point further down. It is rather strong blow that allows to sail directly before the wind.
With an assymetric, the above will be even more pronounced (i.e. apparent wind angles will be lower and no wind will be strong enough to sail directly dead down without danger to sails long before.
Taking the above into consideration, the mainsail may be (or should be) left deployed. If it still interferes with the spi - it may be moved on the traveller towards the middle of the boat, higher than you will normally expect, up to the point that it will no longer influence the spi. The exact point will be found by playing the traveller up and down. What we do is starting with the traveller very close to the middle of the track, than trimming the spi, than easing the main down on the track while looking at the spi. When we reach the point where the spi tells us that it is not happy, we take the mainsail up a little.

One more thing - when the wind picks up - the mast will not be happy with spinnaker only (without main), as there is no backstay on a cat and the pressure on the mast in forward direction goes higher and higher without the backwards equalising tension of the main, it may become dangerous.

[2Hulls]

Originally Posted by meirriba

One more thing - when the wind picks up - the mast will not be happy with spinnaker only (without main), as there is no backstay on a cat and the pressure on the mast in forward direction goes higher and higher without the backwards equalising tension of the main, it may become dangerous.

This is commonly repeated and may be supported by certain manufacturer's advice (including Lagoon) never to sail a spi w/o the main. But it seems to me that whatever "support" a loosely or tightly sheeted main might provide can be far exceeded by a tight topping lift + sheet tension without the main whatsoever. Further, it also seems to me that if forces on the mast and rigging can get so high as to be dangerous that the weak link will be the spi itself. It should blow up long before it pulls the rig down. (This logic may not apply for mast head spis on fractional rigs.)

I fly my sym spi almost exclusively w/o the main and the mast is quite happy.

Dave

[2Wind]

Originally Posted by 2Hulls

85 m2? Best I can find, the typical 440 sail on the tall rig (70.25ft/21.4m) is 74 m2. And 8 battens? Wow. Do you have an even taller rig? - or a longer boom? - or so "heavily roached" that no only is it a sq top, but a big rectangle?

Dave

Dave, you are absolutely right. 75 sqm it is NOT 85!
No excuses, just stupidity.

[2Hulls]

Originally Posted by 2Wind

No excuses, just stupidity.

Maybe better to blame it on rum? that's usually my story and I'm sticking to it....

[44'cruisingcat]

That's a great tip! I've been using different holes on my main's headboard to either open or close the leach at the top of the sail. Works OK, but the problem is if the wind changes much I have to drop the sail to change.


This looks a much easier way.