Rigging an inside shroud upwind screecher on a cat

[arsenelupiga]

i fly symmetric spi and mainsail wing on wing up to 20 app wind. Was surprised as it has not collapsed down to 160 app angle on both sides.

[arsenelupiga]

Originally Posted by Tupaia

I have had 3 screechers. The first was Cuban and designed by Gary Martin. Spectacular sail terrible material. The second was a Doyle NZ, Genesys string sail, too heavy, terrible shape, terrible material. The 3rd was made from a material called Code Zero by Dimension Polyant from a batch that was made for a one off campaign and sadly no longer available. I has a very light taffeta on a single clear net reinforced membrane.

They were all used in the tropics, the Cuban lasted 9 months, Doyle Genesys 1 year, CZ is 12 years old and due for replacement but still useable, just.

The key to upwind sailing with a screecher is to keep everything light, the boat, the sail, the sheet(s). IMO it should not have UV protection, this makes it too heavy. Take it down when not in use. I use a single line drum rather than a continuous furler as it is easier to deploy and stow in my case into a dedicated front apron locker. I also have a net on my bow prodder to make access easy. I only use one sheet on the screecher as it cannot be tacked or gybed. If you were racing maybe this would be different but it is easy to furl it, tack, walk the sheet round and unfurl it.

Size wise mine is a tiny bit bigger than the main and gives a good balance once in the groove you can let go of the wheel. It is only useable up to 10 knots (12 knots gusts) apparent. It is possible to get down to 30° AWA but performs best at 34-35° AWA in the right conditions we can exceed TWS.

With your mast further aft, an arrangement better suited to off the wind, you may have to experiment a bit so I see your need to understand before spending out. If the screecher is a lot larger than your main there may be a tendency towards lee helm.


I have PM'd you a link with some pictures.

interesting that sailing in 8 kn wind at 35 app at 8 kn boat speed produces 10 % better VMG than doing 4 kn boat speed in 8 kn true at 35 app. - this is what we manage so far.

[davecalvert]

Originally Posted by BigBeakie

Thanks Dave, and I would like to investigate CZ90 Silver further and compare to some other materials. Is Warp Dacron pretty much like Hydranet Radial, or what is the difference? What about heavier Stormlite?

I think we've got the strength built in, for the sail. Our halyard is 2:1 and so is the continuous furler tack which can be pulled down by our capstan easily. The prodder is a boom section (not pretty, but strong & functional) and the nacelle longeron & composite forebeam are built strongly and engineered to spread the loads.

Warp dacron is a woven polyester with the straight fibers in the weave on the warp (The length of the roll of material) . This construction is similar to Hydra Net but, without the "NET" of Dyneema fibers inserted into the polyester weave. Stormlite, is a 4 oz. to 5 oz. Contender Sailcloth's balanced weave polyester big boat spinnaker material. It would be good for a Code 0 but, too stretchy for a screacher. I would recommend a good 6 oz warp dacron or a laminate with high modulus fibers for a screacher on your size cat.

[Tupaia]

Originally Posted by arsenelupiga

interesting that sailing in 8 kn wind at 35 app at 8 kn boat speed produces 10 % better VMG than doing 4 kn boat speed in 8 kn true at 35 app. - this is what we manage so far.

If you look the TWA for the faster boat will be greater. But you are talking tiny VMG and is only applicable if you are in fact sailing directly to windward. If your destination is at 70 degrees being able to pull an app of 35 degrees and sail directly there at 8 knots is much faster than the boat that can only achieve 4 plus knots in similar conditions. A quick look at polars for various boats will show this.

[BigBeakie]

Originally Posted by davecalvert

Warp dacron is a woven polyester with the straight fibers in the weave on the warp (The length of the roll of material) . This construction is similar to Hydra Net but, without the "NET" of Dyneema fibers inserted into the polyester weave. Stormlite, is a 4 oz. to 5 oz. Contender Sailcloth's balanced weave polyester big boat spinnaker material. It would be good for a Code 0 but, too stretchy for a screacher. I would recommend a good 6 oz warp dacron or a laminate with high modulus fibers for a screacher on your size cat.

Thanks Dave, great summary.

Upon thinking on it a bit more, and going back to first principles of "What is the use case for this boat & our cruising plans?", the Admiral and I think durability will be more important than perhaps we'd first thought. For example, regarding UV resistance, it is not only that the sail has a UV cover on the leech & foot for leaving it up when furled, because we anticipate that in the tropics we'll be using the screecher a lot. Probably every day and for several hours. So the material itself will need to be UV resistant. For example a heavier nylon with a lightweight UV edge strip would not be a good, lasting solution.

I like the shape holding/stretch resistance of laminates ( hence interest in finding out more about CZ90 Silver), as long as the mildew issue in the tropic humidity does not kill the sail. I know 3Di would handle this requirement, but out of budget I believe.

[davecalvert]

The Dimension-Polyant line of CZ Silver Code 0 cloth is a fairly durable option. With a taffeta on one side only, the mildew issue is not bad. Because of the weight, less than 5 oz., a light weight UV strip is best like the 4 oz. adhesive backed UV dacron material or the 6 oz. Weathermax.
Of course, warp dacron, with a 6 oz. Weathermax UV strip, would be another good option for leaving it rolled up with lots of UV exposure.

[BigBeakie]

Originally Posted by davecalvert

The Dimension-Polyant line of CZ Silver Code 0 cloth is a fairly durable option. With a taffeta on one side only, the mildew issue is not bad. Because of the weight, less than 5 oz., a light weight UV strip is best like the 4 oz. adhesive backed UV dacron material or the 6 oz. Weathermax.
Of course, warp dacron, with a 6 oz. Weathermax UV strip, would be another good option for leaving it rolled up with lots of UV exposure.

Yes, agreed on the UV strip. But it appears that the CZ90 Silver still has a mylar film as the core layer, so if that is the case wouldn't mildew still grow because the sail cannot breathe, and the humidity gets trapped when it is furled?
And it seems the mildew attacks the structure of the mylar layer or at least how the layers are bonded together, so the sail delaminates. That's my understanding. Someone said the fused laminates do not have this issue anymore, so would the CZ material be considered a "fused" laminate sail ( ie melted together under heat) ??