Asym Size, and Use

[BungalowBill]

I am in the market for an Asymetrical Spinnaker for my H33.5, at least until my wife says 'No that's too much to spend'. I checked my rig measurement specs and my 'I' is 39' 2" and my 'J' is 11' 8". I have read that most folks fly these sails tacked 4 feet or so off the bow. So now I am wondering what size should I get? 39' - 4' = 35' for my 'I' measurement? I checked this website store and they do sell one for my boat but it takes over 3 weeks to order a new one and if I wait that long the opportunity may pass me by, so I am checking the used 'on the shelf' market.

Also I would love to hear from anyone who has one of these sails on my model boat (H33.5) or even a similar sized boat. Just wondering if you use it often and how you like it and if you use a dowsing sock. Thanks a bunch.

 

[Clark]

The best dimension to use is max luff. You can measure it yourself with a line or strong tape measure tied to your spinnaker halyard. Run it up to max hoist and mark/measure to the point on the deck or anchor roller where the spinnaker tack would attach. It should be something close to this: Max=SQRT("I"sq + "J"sq). The foot should be around 1.6x - 1.8x your "J". You can work with those dimensions +/- a couple of feet. Ideally, you'll want the tack adjustable but that is not required. Looking for a used one is kinda frustrating since 90% of what you'll see listed are symmetrical spins.

We have one for our 280 and our Capri22. We've used one on our 280 several times and enjoy it - just don't try it in heavy winds or tight quarters.

 

[RichH]

What Clark said ....
You or the sailmaker REALLY NEED to take actual luff length measurements so that the asymm. luff can occasionally be drawn VERY tight. .... AND you also have to subtract the ACTUAL 'as deployed' sock/chutescoop dimensions from the ACTUAL luff length dimension to insure that the luff on an asymm. is correct.

 

[Alan]

From reading your post I get the impression you think that the "I" dimension is the length of your forestay but it is the height of the forestay from the bottom of the mast to the point where it intersects the mast. As Clark points out you can calculate the luff length from the "I".
I have several asymmetrical kites of varying sizes for my 35.5. You can find very good deals on used ones for a fraction of the cost of new. I just checked Bacon Sails and they have a very good used one for $795. Catalog Number: 88-HECH-105

 

[BungalowBill]

Alan, you are right. I had the 'I' measurement concept wrong. Thanks for the reply, I will check Bacon.

 

[COOL]

There can be broad variation in an asymmetric spinnaker design,
depending on what wind velocity and apparent wind angle you hope
to carry it in. It could be a small flat reacher or a massive runner.
Since your boat has a fractional rig with a small fore triangle,
you will want to maximize your spinnaker area as much as
possible. Your spin halyard exit may be a bit above your
forestay, which would be a good thing.
Standard dimensions for a racing asymmetric for
your boat would be something like:
Luff 42' Leech 39' Foot 21'
If you plan to use a sock, the luff will
need to be a foot or so shorter.
The only time you would want the tack up
4', would be if you were trying to run deep.
If you are reaching you will want the tack as low as your
set up allows, and preferably projected as far forward
as possible, perhaps on an anchor roller.

 

[Joe]

Also check North Sails Direct. They have a selection of pre made sizes one of which will fit your vessel... there is a sizing chart on the site. But it is easier to just call them and they will send you the correct size for your boat..Luff length is the critical sizing dimension. I bought mine from these guys when they were called CruisingDirect about 8 years ago and it took them about a week to get the sail to me... they might offer overnite, too. Good quality sail for the price.

http://www.nsd.northsails.com/entit...y/categoryid/22/sename/gennakers/default.aspx

 

[sinnettc]

Tried one yesterday . . .

We tried out a borrowed Cat 22 assym on our Capri 22 tall rig last night. It's maybe a bit smaller than we need but it was the first time I've ever tried a spinnaker of any kind and was an . . . interesting . . . experience. :neutral:

Wind was very light when we started; we got it hauled up, raised the snuffer, and off we went - not too bad I thought. About 10 minutes later I decided to try jibing as we were getting into an area where the wind picks up and I wanted to stay in the wind shadow of the hill near the marina. That didn't go so well as I couldn't get the clew to fly beyond the forestay. Sent my son, who'd come along with his girlfriend, up to try and sort things out as the wind was really starting to pick up. Finally just had him douse it with the sock and we put it away. Turned out I'd not led the windward sheet in front of the forestay. By the time we figured that out the wind was blowing way too hard to try again.

My wife's comment was "there are too many lines!" as we were dealing with the halyard, tack line, 2 sheets, 2 twings, and the line on the snuffer. While we didn't broach, which was my biggest concern first time out, I'm not sure she's convinced a spinnaker is something I should spend boat any bux on.

So, we pulled the trusty blade out of the cabin, ran it up (not without incident), and by the time we got that up we really could have used a reef in the main. The wind that had been blowing about 2-4 kts had to have been blowing in the mid-teens with gusts near 20. The Capri 22 Tall Rig really powers up when the wind blows so we spent a lot of time with 2 or 3 of us on the rail and the traveller all the way down. Still, it was a good sail and I'm glad we had 2 extra bodies along for rail meat.

Don't know where that wind came from but this weekend I'll be putting mast gates on to close the opening in the track and replacing the reefing lines the PO removed from the boom so we can adjust the sail quickly/easily without needing a screwdriver and 2 lengths of line to tie it off.

Whether we'll end up with an assym remains a question at this point but I'm not overly hopeful. Maybe I'll buy a tacktick wind system instead. :neutral:

 

[dscribner]

If you're adventurous, handy and welcome a challenge Sailrite.com sells kits for assyms. That's right, kits. You figure that a spinnaker is thin nylon (ish) probabkly not much thicker than a wind breaker jacket so sewing is no problem on Mama's Singer. The pressure on a sail, per square inch, is no great shakes so the real strength is needed along the edges. So, with a well designed kit, well marked pieces and some time, you could make your own. They are computer designed, precut pieces, well marked. I'm planning on doing it this winter. But, I'm like that anyway.

Fair Winds

 

[Ron20324]

From reading your post I get the impression you think that the "I" dimension is the length of your forestay but it is the height of the forestay from the bottom of the mast to the point where it intersects the mast.

Your statement is wrong, if I read it right. Your statement made me rethink what I knew about "I", so i went to the Bacon web whcih says:"The I on many boats equals the maximum luff, but it’s best to measure to insure a proper fit. Hoist your tape measure on your regular genoa halyard and measure to your regular tack fitting".

 

[RichH]

If this is your FIRST spinnaker (asymmetrical spinnaker) and you dont have much experience in spinnaker launching or handling, etc. I suggest you look for one that has a 'short' LP dimension .... say a 150% LP asymm. A 170% LP asymm can be a very BIG sail to handle. You'll have less opportunity to wrap a 150% around the forestay, less opportunity to form 'bubbles' wrapped at the top of the forestay, and will be MUCH easier to gybe or tack-through.

I'd also recommend "very light weight" spinnaker sheets.

BTW ... that asymm depicted in my avatar is a 175% and is 1750 sq ft.

 

[Alan]

Ron there is nothing in the Bacon quote that is inconsistent t with what I stated.

1) The "I" is, in fact, the height of the fore triangle.

2) "The "I" on many boats equals the maximum luff." This is true because although mathematically the length of the forestay is always longer than the "I" dimension room needs to be left for attachment fittings of the sail which will result in a shorter luff than the length of the forestay, many times that length will be the "I" .

3) A further quote from that same paragraph "The luff of the working jib is usually 80% to 90% of the I." This true for jibs that are not a full hoist.

4) ...also "it’s best to measure to insure a proper fit. Hoist your tape measure on your regular genoa halyard and measure to your regular tack fitting." That measurement is the maximum "luff" for a genoa.

 

[COOL]

"The I on many boats equals the maximum luff

The 'I' dimension on most boats is roughly equal to the the maximum SL( luff/leech)
of a symmetrical spinnaker. The forestay length would be a better guide for the luff
length of an asymmetric.

 

[Cayennita]

A spinnaker luff length is 95% of the I dimension. That's true for either type of chute. The I is taken measuring from the upper headstay pin to a point on deck directly in front of the mast plus the height of the cabin. The luff length then will of course be shorter and you will be able to play with the tack line on the asymm. The leach is over 2% shorter.
The max. girth is 1.8 times the J.
When jibing the asymm, the lazy sheet can be run inside the luff for an inside jibe or outside the luff for an outside jibe.
I race my J-36 in the Caribbean with an asymm. connected to the spin. pole. This will allow me to move the pole well aft for running downwind or reaching when required.
There is also the tack line connected as far forward as possible. We have one chute with multiple uses and no guess work as to what to put up.

 

[Cayennita]

In case of an asymmetrical the max girth is 1.8 times the length of the distance from the front of the mast to the end of the pole when you have a boat with a bow sprit or a pole that extends then to the end of that.