spinnakers

[Cherod]

i believe mono hull second hand sails are not suitable for multi hulls as the multi hull sail is cut flatter ( as i understand it ) ,, but what about off wind sails, eg, , spinnaker Asy / Sy / code 0 , etc,, as these would be for predominately down wind would they be suitable / useable,, ta R

[44'cruisingcat]

Yep, the spinnakers are usable. A spinnaker made specifically for your cat might be a bit bigger in the foot, but a mono spinnaker will work.

[Bean Counter]

Have run an ex mono asymmetric 1500 sq ft and a 2000 sq ft symmetric - both work well.

[Tornadosailing]

Just bought a used symmetric from Masthead Supply. Can't wait to fly it.

[Cherod]

right , thanks boys for the good news,, ( looks like the wallet might be a little lighter soon )

[thinwater]

Originally Posted by Cherod

i believe mono hull second hand sails are not suitable for multi hulls as the multi hull sail is cut flatter ( as i understand it ) ,, but what about off wind sails, eg, , spinnaker Asy / Sy / code 0 , etc,, as these would be for predominately down wind would they be suitable / useable,, ta R

It's not NEARLY that simple.

• Many (most?) monos are faster to windward than cruising cats, thus, their sails are flatter. What drives sail shape is windward requirements, and most multies are not fast to windward. Look at the flat sails on a 12 meter. I've had used mono sails that were flatter than my original sails, and I liked them. But as a rule, windward sails are generally blown out when sold as used.
• Off the wind the chutes generally work, though not always at the same true wind angles. It depends on the multi and what you want to use the sail for. Some multies are better on fast reaches down wind, and some go as deep as monos. So it depends.

Don't think mono-multi, think performance on a given course.

[Cherod]

Originally Posted by thinwater

It's not NEARLY that simple.

• Many (most?) monos are faster to windward than cruising cats, thus, their sails are flatter. What drives sail shape is windward requirements, and most multies are not fast to windward. Look at the flat sails on a 12 meter. I've had used mono sails that were flatter than my original sails, and I liked them. But as a rule, windward sails are generally blown out when sold as used.
• Off the wind the chutes generally work, though not always at the same true wind angles. It depends on the multi and what you want to use the sail for. Some multies are better on fast reaches down wind, and some go as deep as monos. So it depends.

Don't think mono-multi, think performance on a given course.

thanks ,,, but i had not considered using the spinnaker for windward sailing, my intensions would be using it for downwind stuff..

[Sparx]

How does one choose the appropriate size for a cruising catamaran spinnaker?

The cat rig can certainly stand up to a seriously large spinnaker. But big is not better. For cruising it seems more important to be easily managed by a small crew. This includes having broad shoulders so the sail is stable in a variety of winds.

For an assymetrical intended to carry at 140 AWA in up to 17 knots of wind, how many square feet are appropriate? I know boat size and weight matter, so let's say 38 foot waterline and 4 tonnes displacement.

[thinwater]

Originally Posted by Sparx

How does one choose the appropriate size for a cruising catamaran spinnaker?

The cat rig can certainly stand up to a seriously large spinnaker. But big is not better. For cruising it seems more important to be easily managed by a small crew. This includes having broad shoulders so the sail is stable in a variety of winds.

For an assymetrical intended to carry at 140 AWA in up to 17 knots of wind, how many square feet are appropriate? I know boat size and weight matter, so let's say 38 foot waterline and 4 tonnes displacement.

Personally, I always thought this depended on the weight of the boat. A heavy cruising cat will benefit from a big chute and will sail deep. A performance boat can use a smaller, flatter sail, since it won't need it once the wind gets up. It also depends on what else is in the sail inventory (reacher, big genoa etc) and the use (racers and cruisers need to go deep, some people like to reach back and forth all day).


I had a full masthead kite on the PDQ, but I had 7/8 reaching kites on my beach cat and Stiletto. My F-24 has a nice reacher, but I'm pondering what chute I should get.

[Bean Counter]

Originally Posted by Sparx

How does one choose the appropriate size for a cruising catamaran spinnaker?

The cat rig can certainly stand up to a seriously large spinnaker. But big is not better. For cruising it seems more important to be easily managed by a small crew. This includes having broad shoulders so the sail is stable in a variety of winds.

For an assymetrical intended to carry at 140 AWA in up to 17 knots of wind, how many square feet are appropriate? I know boat size and weight matter, so let's say 38 foot waterline and 4 tonnes displacement.

A spinnaker for a cruising cat. A determining factor is the luff length (I) Then there is the foot (J) -150 - 180% that will determine the square footage roughly. If you want a bigger kite you may need to go to a mast head and have running back stays to support it. For ease of sail control many use a paraglider or wingaker but are quite expensive and hard to find used. For a 38 footer an asymmetric of around 1000sq ft+ would be good. For use in 17 knots I would go for a nylon cloth weight of over 2oz.



Spinnaker hassles arise in rapidly increasing breeze and wind shifts so really it requires boat handling to bear off before it collapses and entwines itself in the spreaders. Once blanketed by the mainsail they are easier to retrieve with a sock or maybe better still a top down furler. If you can not get the sock down by just easing the sheet, blow the tack and it will take the pressure off, especially if sailing without the main up.


As an example the other day we were sailing off Cape Hatteras with a 2000 sq ft symmetric and no mainsail in 15 knots of N breeze with my wife and I only aboard. We put it on autopilot, started windward engine to maintain speed (this reduces apparent wind from astern) (and so as not to foul the leeward prop on a loose sheet) She eased the sheet while I pulled down on the sock, about half way down I blew the tack and the spinnaker slid easily inside the sock. She then eased the halyard and it was done.

[Sparx]

Bean Counter, Thanks. Your 150 to 180 times J confirms my intuition. Your description of dousing with a sock in a modest breeze describes a situation I could my wife and I being in and handling just fine. Good tip about using the windward engine, I might not of thought of that first time on my own.

I am thinking the assymetrical tack should be a few feet above the end of the sprit for clear sight lines under the sail ( cruising not racing). This then fixes the luff dimension of the sail. From there the total area is a matter of choosing J multiplier and the fullness of the sail.

So noodlng numbers using geometry, I am expecting an assymetrical sail around 1200 to 1400 square ft. Luff 46 feet, J to end of sprit is 20 feet. Gut feel tells me this will be plenty of sail for a cruising mind set and a light weight boat.

[Bean Counter]

Originally Posted by Sparx

Bean Counter, Thanks. Your 150 to 180 times J confirms my intuition. Your description of dousing with a sock in a modest breeze describes a situation I could my wife and I being in and handling just fine. Good tip about using the windward engine, I might not of thought of that first time on my own.

I am thinking the assymetrical tack should be a few feet above the end of the sprit for clear sight lines under the sail ( cruising not racing). This then fixes the luff dimension of the sail. From there the total area is a matter of choosing J multiplier and the fullness of the sail.

So noodlng numbers using geometry, I am expecting an assymetrical sail around 1200 to 1400 square ft. Luff 46 feet, J to end of sprit is 20 feet. Gut feel tells me this will be plenty of sail for a cruising mind set and a light weight boat.

We fly our spinnakers off an adjustable bridle attached to each bow, really good for turning your asymmetric into a virtual symmetric as you can haul the tack to windward, only issue is it will not handle a furling drum so need a sock, but we use the drum for a code 0 on the short pole. The good thing about the bridle is that it can be eased and the sail will lift giving great vision underneath. The I on our boat is 58ft, we have a 60ft luff symmetric, yet even using the shorter bridle (rather than windward sheet and tack haul) it flies high enough to see under from our fly bridge helm. Our Asymmetric had a 59ft luff and it flew nicely off the bridle at all angles from 170 - 80 - sometimes 70 - but then it tore in half at 25kn apparent

[thinwater]

Originally Posted by Sparx

How does one choose the appropriate size for a cruising catamaran spinnaker?

The cat rig can certainly stand up to a seriously large spinnaker. But big is not better. For cruising it seems more important to be easily managed by a small crew. This includes having broad shoulders so the sail is stable in a variety of winds.

For an assymetrical intended to carry at 140 AWA in up to 17 knots of wind, how many square feet are appropriate? I know boat size and weight matter, so let's say 38 foot waterline and 4 tonnes displacement.

IF you really mean 140 degrees AWA, a bridle will expose more area. I've had boat with sprits and bridles, some times trying both on the same boat.

A fast boat sailing hot angles is different.



As nearly as I can tell, bowsprits look cooler but bridles work better when you are going deep. The math is obvious.

[Cherod]

thats great Mr Beans,, 6' bow spit being fitted today and running back stays ready for fitting as soon as i can get at the top of the mast , hull fittings ready to bolt in,,, already got a big Sy and now looking for big Assy ...36' cat with 45 ' masthead , luff will be around 50+ with bowspit... 4 ton disp.. yeeh ha !! i would really like a code 0 on a roller but that a bit rare on the used market . i am not too bothered about the upwind as it is already pretty good at that ( i think ) .

[Cherod]

Originally Posted by Sparx

Bean Counter, Thanks. Your 150 to 180 times J confirms my intuition. Your description of dousing with a sock in a modest breeze describes a situation I could my wife and I being in and handling just fine. Good tip about using the windward engine, I might not of thought of that first time on my own.

I am thinking the assymetrical tack should be a few feet above the end of the sprit for clear sight lines under the sail ( cruising not racing). This then fixes the luff dimension of the sail. From there the total area is a matter of choosing J multiplier and the fullness of the sail.

So noodlng numbers using geometry, I am expecting an assymetrical sail around 1200 to 1400 square ft. Luff 46 feet, J to end of sprit is 20 feet. Gut feel tells me this will be plenty of sail for a cruising mind set and a light weight boat.

( out of interest for comparison sakes ) what kind of cat do you have ?