asymmetrical spinn v. twin foresails

[roverhi]

The beauty of a twin headsail rig is it is really easy to set up for sheet to tiller steering. Run each sides sheet to the tiller and let the pressure on the sails drive the boat. May not work for wheel steering but then wheel steering is it's own hair shirt. Typically, the twin headsals are too small to get optimum speed so not the most efficient rig. Seem to do almost as well reaching off with a largish headsail poled out and the main, wing and wing, running DDW.

Reaching for some boats, like multi hulls and surfers, is way more efficient for miles made good as 'uncivilized' says but it doesn't work for all boats or crew. Sailed for 2,000 miles DDW wing and wing with a 135 genoa poled out. Had to jibe once and other than a collapsed whisker pole didn't have a damn thing to do for 14 days, pleasantly bored. No drama, no rolling, no having to live on the side of the boat. Averaged slightly over 140nmpd on a 25' water line. May have been a knot faster on a reach but doubt if I'd have made up the extra sailing distance for the discomfort.

If you have a downwind sled or multihull reaching off rather than running DDW may be smart but think for most cruising boats, the benefits of straight line DDW outweigh any gain tacking downwind.

For what it's worth, almost all the boats in the Transpac end up running DDW with the chute. Probably because of the surfing with the following seas and the large spinnakers they can handle with large crews.

[moseriw]

please skip thinking of spi's
this construction is really the bare future!

downwind you do not need a pole and as this thing, due to it's foil, is really flying a bit upwards you do not have a problem with both poles and the waves. It is simply up and above in front of your boat.

Some guys made the barefoot route Kanaries to Carribian by simply setting it at the Kanaries and stroked it on the other side of the pot.

Home - ISTEC - The Downwind Company - Home of the Parasailor and the Parasail - Spinnaker, Gennaker, Downwind Sail

[knockabout]

we run 3 headsails on furlers and use combinations of twin sail depending on wind strength and angle works very well for us / easy to reduce sail they will furl with the poles on / have experimented with small spinnaker one side, genoa the other / configuration worked well in some flukey wind conditions / only in Australian waters twin poled out smaller headsails downwind in the southern ocean worked very well and less tiring / when the wind died down a bit and the sea rose we settled this small boat down by towing a styrene mooring float on 50metres of 10mm anchor rope with tiller locked in position steering by adjusting the sheets as the wind swung around more to the south / moved the drogue rope across to the starboard side to help stay on course / the boat stayed relatively smooth we were able to cook meals etc, as the wind dropped down slowly scaled up to larger headsail and ended up with small spinnaker port side, genoa starboard, main furled and the mast braced against the topping lift with the main sheet / some clothes were being dried on the boom brake lines for a while and the next low caught up and so back to reefed small twin headsails / small wooden keel boat G.L Watson design and sails well upwind using one or two headsails in very strong wind. back to your question it's similar to what anchor to use / twin poles work very well and so do large spinnakers / we carry both

[sheldon957]

This diagram is simple and excellent. You can simply click on the green bar at the various TWA and see the boat speed change in the instrument at the bottom.

It shows 5.1 at 180 vs. 8.6 at 130.

How to read a polar plot for sailboats | Sailing Blog by NauticEd

[lamadriver]

When I re rigged the boat last year I got rid of the stay for the second head sail.

I personally dont like running DDW and find you really dont have to, I agree with Uncivilized on most of what he is saying.

I have a small asym on a sock but since buying the CCZ I harldy use it. When it all goes smooth its great but Ive have had a few exciting moments with it.

I really like the CCZ over the asyem,. Its super adjustable and far more versatile ( it will fly at 50 deg apparant). I u a barber hauler and I'll often run a boom preventer , with the boom out and run a snatch block off the end effectively poling out the CCZ with deep wind angles. I love this sail. Its on a top down furler ad was one o fmy best boat purchases.

I can comfortably run it up to 15 konts+-


I have also played with poling out the headsail with the CCZ up , in the right scenario it works pretty good. Kind best of both worlds.

Another set up that has yet to be mentioned is a Twizel rig. One stay , two headsails for DDW sailing. I have a friend with 100K miles and a few laps under his belt who swear bye his twizel rig.

ld

[sy_gilana]

We sail downwind with a twin-genny system and love it. BUT its not DDW, we usually do 10-15 degrees off.

We have a twin groove foil, We pull both gennys up on one halyard.
We pole out the windward one only.
The windward one has one sheet.
The leeward one is sheeted so the clew is aft of the windward clew by about 2-3 metres.
The main is double reefed and sheeted almost midships, as a roll damper and to be able to deal with squalls.

When a squall approaches from astern we adjust course, as the hour or so wont make a difference on a long trip.
If the winds go wide, or on the nose, the single sheeted Genny is allowed to pass inside and lies inside the regular sheeted Genny. The pole stands naked and fixed. and we can beat or reach, or heave to.
Both Gennys can be furled one inside the other, so if the tailwinds go up high, we only have to reduce the size of the sails by furling, the sail trim remains set.
We have done many thousands of miles like this, rolling is reduced by the asymmetrical trim that we set up.
If they are both sheeted identically, and DDW it can feel rolly.
Hope this helps...

[StuM]

All this talk about polars saying DDW is slow!.

In the context of this thread - can anyone show me a polar derived for twin headsails and no main?

[Snowpetrel]

I am more in the DDW camp, gybing downwind works well for some race boats, but for trundling across an ocean its pretty hard to beat a winged out headsail and a more or less downwind course if the wind is right aft. It can be worth hotting up 10-20 degrees at times to reduce roll or align with the wavetrains better. And in light airs it can be faster and more importantly less slating to hot up the angles slightly, but overall I would definately go poled out headsail and wind aft over an asymetric and sailing the angles myself for wind right aft situations.

Its also probably faster with the wind dead aft on most crusing boats rather than gybing all over the ocean on a boat limited to hull speed for the most part.

Even on my brothers racing boat he finds its often better to sail DDW. He often beats the "sail the angle" crowds to the bottom mark in the right conditions.

From Sun Fast 3600 Racing’s SSANZ Race Report

"Higher ground a few others had gone really wide doing big angles, this didn’t look like a good thing to do and we just wanted to do the shortest distance possible. Our crossover is a solid 25kts before we put the bow up and take the speed gains for a better VMG but any breeze below that we are best to just cover the least distance and keep the bow down. Feels sluggish but 9-10kts directly at the mark has proved to be the best for us."
https://vimeo.com/174001549

This is on something way higher performance than your average loaded ocean crossing cruiser, coming from a seriously good racing sailer, so its good enough for me.

[Suijin]

Originally Posted by StuM

All this talk about polars saying DDW is slow!.

In the context of this thread - can anyone show me a polar derived for twin headsails and no main?

If anyone actually captured those polars for their boat I'd be...well, I'd be laughing. Because if you sail DDW with twin headsails, you're not concerned about polars, you're concerned about a stable easily managed rig.

Just for comparison, even a symmetrical kite is slower DDW than it is heated up to @ 120-140. There's no question that DDW is slower. But that's not the issue. It's what's manageable and comfortable on a long, week+ passage.

[donradcliffe]

Originally Posted by sheldon957

This diagram is simple and excellent. You can simply click on the green bar at the various TWA and see the boat speed change in the instrument at the bottom.

It shows 5.1 at 180 vs. 8.6 at 130.

How to read a polar plot for sailboats | Sailing Blog by NauticEd

Since you know how to read polars, you must also know about VMG. If you need to go somewhere which is dead down wind, how much faster (or slower) will you get there if you sail 130 vs 180???

[Snowpetrel]

http://www.yachtingmonthly.com/saili...downwind-31806

This is interesting. They found the difference in a real live test with matched boats was 3% between spinnaker sailing angles vs poled out headsail DDW. Farrs calculated theoretical polars showed 10-12% faster in 5-10 knots and 7% faster in stronger winds 15+.

I have found it not worth the hastle of sailing angles downwind most of the time when offshore except in very light airs and sloppy sea states where you need all the apparent you can get to stop everything slatting. Realise that to make sailing the angles work you really need to have an active crew, adjusting angle and sails to match the rapidly changing apparent wind. Its not a set and forget solution. Not good for average AP or windvanes.

[StuM]

Originally Posted by donradcliffe

Since you know how to read polars, you must also know about VMG. If you need to go somewhere which is dead down wind, how much faster (or slower) will you get there if you sail 130 vs 180???

Ooooh, I love these questions

Let's take a 100 miles DDW destination.

Sail at 180 and you cover 100 miles at 5.1 knots = 19.6 hours

Sail at 130 and you cover 155.6 miles at 8.6 knots = 18.1 hours
So about an hour and a half faster over 100 miles or 8% faster sailing 130 vs 180.

But even better:
At 140, it's 8 knots and 130.5 miles for 16.3 hours which is 3.4 hours or 17% faster.

(At 150, it's 6.9 knots and 115.5 miles for 16.7 hours.)

[40 South]

No comment on DDW or polars….just an image foe you all to enjoy.

Some of us sail real boats!

[robert sailor]

Originally Posted by StuM

Ooooh, I love these questions

Let's take a 100 miles DDW destination.

Sail at 180 and you cover 100 miles at 5.1 knots = 19.6 hours

Sail at 130 and you cover 155.6 miles at 8.6 knots = 18.1 hours
So about an hour and a half faster over 100 miles or 8% faster sailing 130 vs 180.

But even better:
At 140, it's 8 knots and 130.5 miles for 16.3 hours which is 3.4 hours or 17% faster.

(At 150, it's 6.9 knots and 115.5 miles for 16.7 hours.)

What sized sails were used in this example?

[StuM]

Originally Posted by robert sailor

What sized sails were used in this example?

No idea, just took the numbers from the polar under discussion - see posts #19 and #25.

But I bet that polar isn't for twin headsails downwind - I'd guess it is for a basic main + genoa.