Beneteau 373 -Assemetric Spinnaker

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Kinsale373

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Hi All,
Im considering buying an assemetric spinnaker to improve down wind performance on my 2004 Beneteau 373. I'm leaning towards an assemetric from reviewing other posts on this forum and the fact that we normally cruse the boat with two on board. I'm not sure how to specify the dimensions of the sail. I have the original Rig specifications , ie , Height , Forestay Length etc, Is there a rule of thumb for assemetric design based on this? Anyone any ideas?

Regards, Kinale 373
 
I'd suggest measuring the forestay or 'halyard sheave to bow roller, mast to bow roller and sheave to deck. So you have proper dimensions for the foretriangle.
An asy will generally not be set with the luff taut. It will normally be flown on a tack line to at least clear the pulpit. So the length along the luff tape could be a bit longer than the forestay, but generally is shorter.
Personally if I were ever to spend proper money on a brand new asy, I would seriously consider a little bowsprit to take the tack forwards clear of the pulpit.
I would be looking at the biggest asy I could fit on the boat, because my use of them is all about making progress down wind when everyone else is using their engine.
If you sail somewhere windy and you want to reach fast, then something a bit smaller might be optimum. You might also look at heavier cloth.
Having got those dimensions and thought about what exactly you want from the sail, talk to a couple of sailmakers and ask what dimensions they propose and ask to see photos showing how full a sail.
Asy's vary from almost triangular to very full at the top.
I do know of people just ordering a 'cruising chute to fit XYZ AWB' and not getting what they really wanted.
People ideas differ, I expect my wishlist would be different for a quick ocean crossing compared to a typical summer of coastal cruising.

Personally I'd look at secondhand sails too, because if I'm not racing, I can live with used sails if the price is right and the dimensions are near enough.
 
Kinsale373 said:
Hi All,
Im considering buying an assemetric spinnaker to improve down wind performance on my 2004 Beneteau 373. I'm leaning towards an assemetric from reviewing other posts on this forum and the fact that we normally cruse the boat with two on board. I'm not sure how to specify the dimensions of the sail. I have the original Rig specifications , ie , Height , Forestay Length etc, Is there a rule of thumb for assemetric design based on this? Anyone any ideas?

Regards, Kinale 373
Click to expand...

There is no standard size or even type. There is a wide range of different styles of assymetrics and it is worth going onto the websites or a few sailmakers and read up about what is on offer and the pros and cons of each type. You will then be in a better position to discuss your expectations with more than one sailmaker to see what they propose.

In addition to different types of sails you need also to consider whether you want to fly it free (with or without a snuffer) or use a top down furler. For many boats a short sprit is useful or even essential to get the tack clear of the forestay and the sail as far forward as possible.

I went through this process last year and settled on a top down furler with a 1.4oz cruising chute a bit smaller than the maximum because I sail single handed. I also fitted the Selden furling line guides and jamming double block so I can set and furl it from the cockpit. So far worked well - but if I had a regular agile crew I would probably have gone for a bigger chute on a sprit without the furler (which would have been less than half the price!).
 
lw395 said:
Personally I'd look at secondhand sails too, because if I'm not racing, I can live with used sails if the price is right and the dimensions are near enough.
Click to expand...

The first question I'd ask is about your budget? If it's a big number I'd talk to a few sail makers; doubtless they would give hardware advice, too.

Otherwise, I'd follow lw395 advice and look for second hand. Ebay very regularly has near-new cruising chutes for sale. Set-up a search and wait.........

I have 2 on my 41 ft AWB. One is slightly heavier cloth and slightly smaller than optimum. It's advantage is that it's easy to fly and douse short handed. I can also easily adjust tack and head lines for balance. I'm sure that racers/purists would be unimpressed, though. I also have a lighter weight cloth, huge thing. Guaranteed to put a smile on your face once it's flying.

I've used a snuffer but it now resides in a shed in disgrace. I plan to sell it when I get round to it. I have difficulty in getting all of the sail out without twisting the lines. Work of the Devil! A launch bag is far easier.

My boat doesn't have a bowsprit and my tack line is adjusted via a block on the bow roller.

Your post says that you want to improve down wind performance. Neither of my 2 sails fly deep, they are more reaching sails. Down wind is usually associated with symmetrical spinnakers. My AWB has a fat arse and swept back spreaders so I tend to go down wind broad reach / gybing.
 
Getting a new asymmetric or cruising chute can be expensive and you may find it does not do what you want without having a bowsprit to move the tack forward.
I would suggest an easy starting point is to look for a second-hand sail of roughly the right size either online or through send hand sails suppliers.
That way you have an economical way to see if it does what you want or not. I have done the same and actually sold the first one having used it for a bit over a year for more than I paid. I then had a better idea what I needed.
 
Just to add a bit to the "downwind" question. It is difficult to get any asymmetric to work deeper than 160 - you need a symmetric for dead downwind. Different cuts can give you a wider or narrower range. For example the large lightweight genoa types can work as low as 70 up to around 140. The general purpose cruising chutes usually have a range of around 90-160. They are good at filling the gap on the now common large main, small jib rigs where the job gets blanketed once you get past a reach and can usually be flown in winds up to 15 knots or so.
 
As Tranona says, sailing with the wind less than about 30deg from dead astern is difficult as the main creates a shadow.
However, in these situations we sail dead downwind and goosewing the asymmetric and this works well; but be sure to put a preventer on the main. We have also sometimes just used the asymmetric without a main if going downwind with a gentle breeze for a long period. This works very well though if the wind gets up it can be difficult to get it down. You don't have the wind shadow of the main to depower it but you can unfurl some genoa to make it easier.
 
Tranona said:
Just to add a bit to the "downwind" question. It is difficult to get any asymmetric to work deeper than 160 - you need a symmetric for dead downwind. Different cuts can give you a wider or narrower range. For example the large lightweight genoa types can work as low as 70 up to around 140. The general purpose cruising chutes usually have a range of around 90-160. They are good at filling the gap on the now common large main, small jib rigs where the job gets blanketed once you get past a reach and can usually be flown in winds up to 15 knots or so.
Click to expand...

I don't think vague guides of what TWA a sail will work over are very helpful.
To get to the essence of the cruising chute you need to get a feel for the vectors.
In light airs, a fair sized kite will bring the apparent wind forward usefully, if the hull is easily driven.
In 6 knots of breeze and 5 knots of boat speed this is far more pronounced than in 12 knots of breeze and 7 knots of boat speed.
The vector triangle is a whole different shape.

What 'entropynow' says is a good point. Once you have played with an asy on your boat, you will know how a sail of a certain size powers the boat in a certain breeze.
Boats vary. You will notice the difference made by a fixed prop or a bottom that needs a scrub.
 
lw395 said:
I don't think vague guides of what TWA a sail will work over are very helpful.
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Why not? In my experience when buying such a sail this is one of the first questions the sailmaker asks, or one of the first points made when explaining the different types of sail they can offer. The point I was making for the OP is that there is a choice of working range.

Most people only buy one sail so choosing the style and size that most suits the way you want to use it is crucial and looking at the potential range of wind angles is part of that decision making.

You are right that using the sail is key to getting the best out of it for the boat and your style of sailing. Of course if you have more than one sail available you have greater choice, but otherwise you have to accept your compromise and work with it.
 
entropynow said:
This works very well though if the wind gets up it can be difficult to get it down. You don't have the wind shadow of the main to depower it but you can unfurl some genoa to make it easier.
Click to expand...

This is where having a furling sail is advantageous, particularly if the furling line goes through a double jamming block as you have much greater control over the sail.
 
Thanks for all the useful inputs guys.
I'm currently considering an offer of a suitable Assymetric with snuffer for around £1200 which seems ok compared with new pricing.
When I look at the sailmakers sites they often state that an Assemetric crusing shute offers a great improvement off the wind to modern rigs with Large Main and small self tacking jibs and I can see how this works. My rig has a smaller In mast roling main with a large 140% furling jib. will I see much of an improvement using an assmetric crusing shute . Interested to hear your thoughts on this point.

Regards, Kinsale 373
 
No direct experience of using a chute with a rig like yours, but the main advantage I think would be better offwind performance in light airs because of the greater sail area. Would guess it is likely to be around 80 sqm, well over 50% greater than your current genoa.
 
Thanks for that Tranona, and I suppost that being a lighter material , it should be easier to fly in lighter winds and be useful when the Genoa is too heavy to use. I don't use a whisker pole or spinny pole.


Regards, Kinsale 373.
 
entropynow said:
The performance will depend on how much bigger in area the sail is compared to your genoa.
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And also what shape it sets to.
A good all-round asy will set to a full, powerful shape, with a high shoulder rotated to windward when desired.
A flatter one will have less power reaching due to less camber, and it will expose less overlap due to being more triangular with a straighter luff. Which makes it more optimised for tighter reaches in more wind.

There's also the question of how the sails interact. Getting the kite to work with the main, directing flow around the lee side rather than having half the main stalled.
 
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