Symmetric or Asymmetric Spinnaker for Simplicity?

[Chotu]

after trying to figure everything out myself all this time, I’m thinking the spinnaker sock length at the head of the sail is already accounted for in Richard Woods instructions.

The spinnaker has to curve and make a rounded belly. Maybe that’s exactly where the extra needed to curve comes from.

[fxykty]

Originally Posted by Franziska

Interesting, could you explain more why that would be an issue?

In case of a symmetric spi, the foot is flying lose when the sail is hoisted.
The sail "bulges" upwards, so the luffs are not straightened/fully stretched (unless oversheeted), hence I can not see a big issue with that length being taken up by the sock at the top.
When the luffs are sized at an equal length as the forestay as Richard writes the clews will always fly higher than the lowest point of the forestay.

Appreciate your comment. Or are you referring to an assymetric in a sock, which is a different story?

It’s a symmetric. In light winds the sail droops and the foot is very near the deck when hoisted from just above the (originally designed) hounds. In stronger winds the clews need to be restrained by both guys to prevent the spinnaker rising too high.

I’m not a sailmaker, so maybe the spinnaker sock doesn’t matter in the luff (or should it be “leech”?) measurements. But I will note that traditionally spinnakers are flown without socks and the head is expected to be near the halyard block, so effectively extending the head 1m away from the halyard block must make some sort of difference. Or not?

[Franziska]

Originally Posted by fxykty

It’s a symmetric. In light winds the sail droops and the foot is very near the deck when hoisted from just above the (originally designed) hounds. In stronger winds the clews need to be restrained by both guys to prevent the spinnaker rising too high.

I’m not a sailmaker, so maybe the spinnaker sock doesn’t matter in the luff (or should it be “leech”?) measurements. But I will note that traditionally spinnakers are flown without socks and the head is expected to be near the halyard block, so effectively extending the head 1m away from the halyard block must make some sort of difference. Or not?

I do not think that it would make a huge difference as to really impact the performance of a cruising boat.
We compromise most of the time anyway between comfort and precision trimming.
The sock is largely a cruising boat item. A racer would not want that bulged up material high up anyway, due to windage and weight.
When deployed the sock is bundled up over a piece of halyard aloft anyway and not over the spi itself after all, no? Meaning the spi itself is not hoisted all the way to the sheave.
A symmetric spi is less dimensional critical than an asymmetric as all sides are free-floating in the air anyway.

[Chotu]

I have some questions about sizing. I used the Richard Woods method.

His method is as follows:

Forestay length = leech of spinnaker

.8 x LOA = foot of spinnaker

My forestay is 52.5ft long approximately.

My boat is 50, but .8(50) is a 40ft foot. I thought that sounded a bit crazy, so I put in the original size of the boat which has more to do with the beam. And it still comes out to a 36ft foot.

So what size is the foot of your spinnaker? Because this isn’t making much sense to me. All of the ones that are for sale with a 52-53ft leech have a foot of about 30ft max.

Am I missing something here? This was the part I was most confused about because it is a circle essentially.

I do know my bow cleats are 19.5ft apart.

I’m attaching a rough sketch that I did only for myself. But the numbers are on here so it might make some sense to put the sketch in the thread.

I realize some of you may not be able to follow my high-tech CAD system due to not being technical enough to understand it. . Ha ha.

[Chotu]

I am also having some additional worry as I am reading a little bit more online about boats speed on catamarans in relation to flying spinnakers.

Given my boat’s performance (does 3-4 knots without a rig or engines just drifting in the wind, does 7-8 knots with a single 30hp outboard ) Is it possible that I’m not going to have apparent wind coming from aft so that I actually need to use an asymmetrical?

I do plan to get the bowsprit eventually, as living out here is actually feeling pretty good.

[rslifkin]

If you want to sail close enough to DDW, you'd still have apparent wind from behind, I think. I'm pretty sure much of the "fast cats move the apparent wind way forward" thing is predicated on you never actually sailing DDW and just tacking downwind instead.

[fxykty]

We have a performance sailing cat. When we want to go within 30* or so of DDW to get somewhere in light to moderate winds we can’t be bothered and don’t have an asymmetric spinnaker large enough to make gybing worth it. Though our screecher takes us down to 120-130* AWA in mid to strong winds and can be a ton of sometimes frightening fun.

So we just throw up our spinnaker, usually without a main. We generally go 60% TWS right up to when it gets scary and we replace it with our jib (as in, holy sh*t, it’s blowing 30 knots and nobody noticed because the ride is so smooth).

[Chotu]

Originally Posted by fxykty

We have a performance sailing cat. When we want to go within 30* or so of DDW to get somewhere in light to moderate winds we can’t be bothered and don’t have an asymmetric spinnaker large enough to make gybing worth it. Though our screecher takes us down to 120-130* AWA in mid to strong winds and can be a ton of sometimes frightening fun.

So we just throw up our spinnaker, usually without a main. We generally go 60% TWS right up to when it gets scary and we replace it with our jib (as in, holy sh*t, it’s blowing 30 knots and nobody noticed because the ride is so smooth).

Happens to me all time too. Ha ha. A relaxing downwind afternoon turns into a howling, bouncy mess when you arrive at the destination or waypoint. Lol

So thinking carefully about your post (I think our cats perform similarly - I've watched some threads with you and Grit discussing), the typical wind angles may be important.

For the near future, I'm staying within an about 1600 nautical mile area. In the USA, Canada and maybe Bahamas.

My downwind sailing direction here is generally north and east. Not so much northeast, but kegs of mostly north and mostly east. The prevailing winds are southwest in season. Out of season, all of this reverses, but the angles stay about the same.

I'd also like to fly the Spinnaker by itself for simplicity and so it's smooth and easy for the autopilot to handle things.

So 60% of TWS out to 30 degrees off DDW?

If you stretch things to 45 degrees off DDW, sail collapses? or does it just require more wind strength for it to work properly at less efficient angle?

I have a main and blade jib in addition to whatever Spinnaker.

Just trying to cover as many sailing angles as I can until I do a bowsprit.


Definitely not a gybe downwind kind of guy. I'm way more lazy. Ha ha.

I'm a "set the course for the day, engage autopilot, then set the sails to match the course" sort of guy. But I'm concerned that between 150 AWA and 100 AWA, when the blade and main start to shine, I'll be caught out with no sail to handle it.

Especially in light winds which are very common up and down the east coast of north America.

Yet with the asymmetric I'll be caught out between 170 and 190 with no sail to handle that, right?

In the future I see a screecher also. But not yet. So maybe the gap is best addressed with a second cheap, beat up asymmetric Spinnaker? Or?

[fxykty]

Originally Posted by Chotu

Happens to me all time too. Ha ha. A relaxing downwind afternoon turns into a howling, bouncy mess when you arrive at the destination or waypoint. Lol

So thinking carefully about your post (I think our cats perform similarly - I've watched some threads with you and Grit discussing), the typical wind angles may be important.

For the near future, I'm staying within an about 1600 nautical mile area. In the USA, Canada and maybe Bahamas.

My downwind sailing direction here is generally north and east. Not so much northeast, but kegs of mostly north and mostly east. The prevailing winds are southwest in season. Out of season, all of this reverses, but the angles stay about the same.

I'd also like to fly the Spinnaker by itself for simplicity and so it's smooth and easy for the autopilot to handle things.

So 60% of TWS out to 30 degrees off DDW?

If you stretch things to 45 degrees off DDW, sail collapses? or does it just require more wind strength for it to work properly at less efficient angle?

I have a main and blade jib in addition to whatever Spinnaker.

Just trying to cover as many sailing angles as I can until I do a bowsprit.


Definitely not a gybe downwind kind of guy. I'm way more lazy. Ha ha.

I'm a "set the course for the day, engage autopilot, then set the sails to match the course" sort of guy. But I'm concerned that between 150 AWA and 100 AWA, when the blade and main start to shine, I'll be caught out with no sail to handle it.

Especially in light winds which are very common up and down the east coast of north America.

Yet with the asymmetric I'll be caught out between 170 and 190 with no sail to handle that, right?

In the future I see a screecher also. But not yet. So maybe the gap is best addressed with a second cheap, beat up asymmetric Spinnaker? Or?

Our symmetric spinnaker, relatively heavy (I think 1.5 or 2 oz nylon) goes up to 90*AWA in light to moderate winds (up to 15 knots TWS). In stronger winds the highest possible angle goes up (e.g. 20 knots TWS highest angle is about 130* AWA). So, symmetric can sail higher in lighter winds - but there’s too much sail area up high to be efficient in stronger winds at those higher angles.

You can definitely sail a symmetric 150-100* AWA. Towards the 130* and more AWA in stronger winds and up to the 120-90* AWA in lighter winds. You’ll be just fine with a symmetric.

In lighter winds you may have a gap like we do 60-90* AWA and in moderate winds 80-120* AWA. We plug this with our screecher. In stronger winds the jib is fine to 140* AWA with the mainsail and all the way to DDW without a main. An asymmetric won’t help much in any of those cases as it will only go about 20* higher than the symmetric.

[Chotu]

Thank you!

That's exactly what I didn't know about the performance of the symmetrical spinnakers on performance cats.

It's settled!

Symmetrical it is!

Thanks so much for taking the time to explain all these details to me. Now I'm confident it's the right decision. That's pretty good coverage.

[malbert73]

Originally Posted by fxykty

Our symmetric spinnaker, relatively heavy (I think 1.5 or 2 oz nylon) goes up to 90*AWA in light to moderate winds (up to 15 knots TWS). In stronger winds the highest possible angle goes up (e.g. 20 knots TWS highest angle is about 130* AWA). So, symmetric can sail higher in lighter winds - but there’s too much sail area up high to be efficient in stronger winds at those higher angles.

You can definitely sail a symmetric 150-100* AWA. Towards the 130* and more AWA in stronger winds and up to the 120-90* AWA in lighter winds. You’ll be just fine with a symmetric.

In lighter winds you may have a gap like we do 60-90* AWA and in moderate winds 80-120* AWA. We plug this with our screecher. In stronger winds the jib is fine to 140* AWA with the mainsail and all the way to DDW without a main. An asymmetric won’t help much in any of those cases as it will only go about 20* higher than the symmetric.

I second those general wind angles with my symmetric albeit on a performance monohull. Definitely can fly symmetric at 90-120 in lighter stuff.
Also Chotu- used symmetric is cheapest route so Id get that, sail the boat for a while and then see what you are missing. I think you should learn more about its performance so you know what you REALLY need

[Chotu]

Originally Posted by malbert73

I second those general wind angles with my symmetric albeit on a performance monohull. Definitely can fly symmetric at 90-120 in lighter stuff.
Also Chotu- used symmetric is cheapest route so Id get that, sail the boat for a while and then see what you are missing. I think you should learn more about its performance so you know what you REALLY need

Agreed!

I also have to keep the title of the thread in mind. I am creating a little bit of scope creep here. Trying to be perfect. I shouldn’t be doing that. I should be keeping it simple.

Getting the symmetrical Spinnaker today.

and I guess I don’t have to worry about the foot of the sail being too small?

they seem awfully narrow when I plug them into Richard Woods formulas.

does anyone have the measurement for the foot of their spinnaker so I can make sure I get the right thing? Doesn’t matter what size your cat is. I can just scale it.

I am worried that they are more narrow for monohulls and wider for Catamarans and I’m only seeing monohull spinnakers for sale. That is a concern.

[MicHughV]

Interestingly, I find the modern day monohull boat is rarely equipped with a spinnaker pole, mast track, and all the other bits and pieces required to fly a spinnaker.
The spinnaker itself is a rare item. Those items are typically an "add one" and usually only seen on racing boats or cruising boats that like to race.

For this reason alone, I think the asymmetrical spinnaker, if there is one at all, is the more logical choice for most modern boats, as it does not require all this paraphernalia.

Sailing dead downwind is so 50's.....sailing on a broad reach is so 90's...kind of thing and while a symmetrical spinnaker can be flown at wider angles, the asymmetrical would seem to be the more practical choice.

Off course, a cat with it's wider beam does offer more possibilities, but the fly in the ointment is usually the fear of an accidental jibe threatening to take your head off.

My vote goes for an asymmetrical.

[malbert73]

Chotu- I wouldn’t worry too much about width. I think they generally are sized “appropriately” regardless. If you had a spinnaker as wide as your cat that may be a bit ridiculous from a shape/aspect perspective. But I’m not a cat owner. Your ability to sheet it to the whole width, or partial width, of your bow is key, and fantastic.
MicHughV- I use my spinnaker without the pole much of the time- for example deep reaching at 130-140AWA. It’s a myth that symmetric spinnakers require a pole for sailing. Even more so with cats.
I use my pole mainly for 160-180AWA where an asymmetric is nearly useless anyway. But I’ve also gone without mainsail and flown chute DDW without the pole

[MicHughV]

Can't say I've ever flown a spinnaker without a pole....
mind you..when jibing the spinnaker, it is " poleless" for a brief period, but from my perspective, it just didn't seem happy during that transition.

I kinda like the pole, as it allows me to set the bottom of the spinnaker...and also controls the luff/leech tension...

Pole also good to keep the genny out, running downwind. I've seen twin poles keeping two headsails out...a poor man's spinnaker..

But...to each...his own...