Spinnaker Area
Printed From: Laser 28 International Class Association
Category: Laser 28 General
Forum Name: General Forum
Forum Description: All the topics that don't fit elsewhere
URL: http://www.laser28.org/forum/forum_posts.asp?TID=401
Printed Date: 23 November 2024 at 7:16am
Software Version: Web Wiz Forums 11.03 - http://www.webwizforums.com
Topic: Spinnaker Area
Posted By: jez rees
Subject: Spinnaker Area
Date Posted: 13 August 2010 at 7:34am
With the arrival of the asymmetric spinnaker I'm investigating how to best get rated in IRC. IRC likes unmodified boats so I was looking at the standard data.
Are the class kites really 62.2m2 (670ft2)? We're currently 42m2 on ours and using a 3m long pole rather than the 3.45m class pole. Basically I'm looking to see if we can add a short retractable bowsprit without too much loss on our rating.
IRC calculates spinnaker area as SPA = ((SLU+SLE)/2)*((SF+(4*SHW)/5)*0.83
SLU = spinnaker luff longest
SLE = spinnaker leach
SF = spinnaker foot
SHW = spinnaker half width
Another 20m2 to the spinnaker area would be a phenominal presumably big shouldered running kite. Does anyone know whether this is a calculation issue or reality? Has anyone got an IRC rating with the long pole and big kite? Are there smaller kites being used in PHRF?
Thanks
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Replies:
Posted By: frfletch
Date Posted: 13 August 2010 at 2:07pm
By your 2009 phrf cert I see you carry a code 8 spinnaker which is already cut down from the class size kite and pole. I wonder what code the class spinnaker is. Looking at the list I see that Aussie Rules carries a code 7, which is smaller again.
It is interesting that Number Cruncher has a 4/8/4 inventory. I can't imagine the reason for a code 4 main.
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Posted By: dmarkc
Date Posted: 13 August 2010 at 2:59pm
Jez
I am running an IRC certificate with SPA of 40.71 and a STL of 3.11. I too can't see how one could get another 20m2 bigger than my kite. We get overpowered as it is!
I shortened my pole last year to reduce the rating and it made very little difference - perhaps 3 points. My understanding is that a bowsprit that is no longer than the pole has no effect on the rating.
Very interested in your asymmetric experiment. If yu see another one going cheap, I would be interested in having a play!
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Posted By: Chris Ross
Date Posted: 14 August 2010 at 9:01am
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Ask the Canadian quantum sail makers... I bet they know more about laser 28 sails than anyone else in the world. I would really like to know the answer to this too.
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Posted By: Chris Ross
Date Posted: 14 August 2010 at 9:06am
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As for the Asym experiment, a melges 24 asym is 670 sq feet. So, in Phrf, you shouldn't take a rating hit for using it. Haven't been able to get my hands on one yet, I think that would be the one to try, You can fly asyms deep off of a pole, jybing them can be tricky though. It takes an extra control line in heavier air, so it is a bit more complicated...
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Posted By: jez rees
Date Posted: 16 August 2010 at 4:32am
Thanks guys. Hopefully the sailmakers will read this post and be able to advise.
frfletch - that'll be the other Farr Out. We're in the UK and don't really even know how phrf works..
dmarkc - interesting that Zorra has a longer pole and smaller kite. Have a scan of the Laser SB3 forum for a second hand ayso. We're so pleased that we're thinking of getting another one without the VW branding which is illegal in jog.
Chris - I need to ask the Melges in our club if we can have a hoist of their kite on a clam day. I think it's too big at 11.3m luff length but I suppose this would depend on the length of your prod, the SB3 kite at 10.6m luff length seems about right to fly off the bow roller on a tack line. At 670 sq ft with the kind of wind we have around here I think that you'd need to deepen the rudder and get some heavy guys on the side it would be fun though and definately give you that nice hum off the foils!
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Posted By: Chris Ross
Date Posted: 01 September 2010 at 8:36am
Usually the max girth of a symmetrical chute is 180% of the pole length. If our max girth was 6.9 meters a 62.2 square meter spinnaker would be quite possible. I think somewhere along the line the spinnaker size must have been reduced, maybe for a better rating?
Under our LMPHRF rules we can carry a spinnaker that is 180% of our pole length, so a 62.2 square meter symmetrical spinnaker is legal for us, and an asym of similar area is also legal. Bowsprits are another matter.
Under LMPHRF, a 1 foot bowsprit can be used without penalty, but every additional foot costs 3 seconds a mile, up to a total of 3 feet. (that is, if I'm reading the rule correctly)
usually, an asym is the 160% of your J dimension, so when you add a sprit you are adding length on the foot of the sail.
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Posted By: Chris Ross
Date Posted: 01 September 2010 at 8:54am
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maybe the spinnaker area was reduced so the rudder wouldn't have to be altered?
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Posted By: Bill Brock
Date Posted: 01 September 2010 at 11:16am
The chute on a Laser 28 is substantially over sized as the pole is noticeably longer than the “J” dimension. In very light air this is a big plus. I have a North Code 0 symmetrical that I really like that allows me to make the boat move and even point above a Beam Reach on those days when everyone else is dead in the water. It appears to me to be much more effective than a light air No. 1 in those conditions, probably in part because it extends forward of the forestay and has excellent shape when boat is heeled slightly.
Like other light displacement boats, however, in higher wind conditions, particularly with gusting conditions, a class chute this sized becomes uncontrollable. In those conditions you really need a Code 4 or 5 symmetrical. These boats and most other light displacement boats just do not have enough rudder to handle anything larger. Some new sailors think they should be able to carry an oversized chute directly down wind, but the reality is the boat becomes very dicey and may start to oscillate (roll rail to rail) even in relatively flat water. On some occasions my boat has just rounded up with no warning. On other boats I usually get some sort of warning. I may feel the rudder stall before the round up. With this boat sometimes there is no warning.
In any kind of wave action you will have problems keeping enough rudder in the water to maintain control without adjusting the chute. I would suggest you try to easy out the chute as you go up the wave (as the rudder starts to come out of the water) and then sheet in very quickly as you race down the wave. It is exhausting for your crew, but it can be done.
When sailing on the edge of the upper wind range with the chute it is important for the new sailors to remember to go deep in the puffs (steer slightly down wind) and come back up in the lulls, otherwise you will most likely run out of rudder and broach. In conditions like this you need to maintain a substantial distance to other boats. I would recommend at least two or three boat lengths separation. If you broach in those conditions you can cover that distance in a matter of a few seconds.
There are other suggestions for heavy air sailing on other parts of this Forum.
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Posted By: Bill Layton
Date Posted: 01 September 2010 at 12:07pm
Some very good point Bill
Here in Montreal we have so many L28's racing One-Design , whoever doesn't hoist in big winds finds themselves out of the race fast. Our technique in big winds is to tweak down the tweakers all the way. This prevents the chute from oscillating and really helps keep the keel under the boat. We sail the boat dead downwind in anything over 12 true. We have broached many times in conditions above 22 knots and have sailed the spinn in winds as high as 37. With the chute we once planed downwind with a boat speed of 18 knots. You can imagine how heavy the helm gets in that situation. We found in the super heavy stuff to never have the pole to low, as it can drive the bow down and plow more water and make steering alomost impossible.
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Posted By: fatjohnz
Date Posted: 01 September 2010 at 12:17pm
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Do you fly spin with the halyard fully hoisted or eased a bit?
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Posted By: Bill Layton
Date Posted: 01 September 2010 at 12:21pm
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Must be full hoist or else it will oscillate in big winds.... from a class boat perspective
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Posted By: Guests
Date Posted: 01 September 2010 at 12:26pm
We agree with Bill's comments on heavy air spin work. Impact does a fair number of offshore and overnight races on Lake Ontario.
Big wind downwind is great for us.
Full hoist halyard
tweakers fully down both sides
Pole forward and up a little if needed.
Drive aggressively down in the puffs
some crew weight behind the helmsman
In big squalls we have been really fast with Spinnaker up and a reef in the main to keep her under control in big waves
Dousing the kite is always fun in 25+ knots. Bowman will release the guy snap shackle and we retrieve under the boom. If too crazy for weight on the foredeck, release the guy while the foot is gathered behind the main or letterbox between foot of main and boom. Halyard is the last to go in these conditions.
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Posted By: jez rees
Date Posted: 01 September 2010 at 12:41pm
Is it correct then that the class chute is 670 ft2? Not having an oversized sail like this could account for our poor downhill speed in the light stuff. I'm very happy with our 42/43m2 kites in the breeze!
Does anybody have luff / leach, foot and half width dimensions for a code 0 chute?
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Posted By: Chris Ross
Date Posted: 02 September 2010 at 1:10pm
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I saw the 670 square foot size on the brochure... but after playing around with a spinnaker design program I found I can't get to 670 using the PHRF max girth either... well, I can get to 670 but the sail doesn't look right. I'll see if I can paste a jpeg or bitmap. I'm curious about that symmetrical code zero chute... I'm having a hard time imagining what that looks like. I have seen asym code zeros before, but never a symmetrical one.
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Posted By: Bill Brock
Date Posted: 07 September 2010 at 10:59am
Hello Chris,
My North Code 0 symmetrical looks like other symmetricals, except it just has a flatter cut. Send me an e-mail at wmabrock@msn.com and I will send you a photo.
Note also that the 670 sq. ft. in the brochure is incorrect. I don't remember the exact number, but to the best of my memory it is in the range between 500 and 600 sq. ft.
Bill
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Posted By: Bill Brock
Date Posted: 07 September 2010 at 12:24pm
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My oops. I called it a Code 0 and it is actually a 1S iaw North designations.
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Posted By: jez rees
Date Posted: 05 May 2011 at 7:54am
Hi Guys,
Can I re-open this subject? I'm thinking of running a test certificate under IRC to see what effect reverting the spinnaker and pole length to class size would have.
I can buy a second hand 3.45m pole but what we really need to know is what the class running kite (1S) dimensions are: leech/luff, foot, and half width. Can anybody help with this?
On Farr Out currently we only use a symmetrical spinnaker for running and an asymmetric for tighter angles and we do feel underpowered dead downwind especially in the light. The kites which came with the boat are all wearing out now so now's the time to make the jump if it's worth it. Spinnaker area is quite cheap under IRC.
So if anyone has this info to hand or can run a tape measure over their class chute for us I'd be really grateful.
Thanks
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