Laser 13 rig settings
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Technique
Forum Discription: 'How to' section for dinghy questions and answers
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=13927
Printed Date: 06 Aug 25 at 6:28am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: Laser 13 rig settings
Posted By: Sam.Spoons
Subject: Laser 13 rig settings
Date Posted: 08 Apr 22 at 6:06pm
|
A mate has a L13 and, as he has just had the misfortune to break his mast, (replacement will be claimed for) I though it would be worth getting some settings so that when we rig the new mast it'll be in the right place. Can anybody help with rake and tension numbers please? It's not for serious racing but we just want the boat to be as manageable as possible over a range of wind strengths.. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Replies:
Posted By: The Moo
Date Posted: 08 Apr 22 at 8:32pm
Just interested. Under what conditions did the mast break? I always thought the L13 and its kit was pretty robust. |
Posted By: Sam.Spoons
Date Posted: 08 Apr 22 at 8:54pm
|
Forestay failure parked up plus gale force winds. The mast foot was bolted to the step and it's torn the rivet holes out of the tube. Probably fixable if we cut an inch off but if the insurance will pay...
That said it's just a standard section and they do break, though I reckon the hull will be around for the cockroaches to sail after the apocalypse
 ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Grumpycat
Date Posted: 08 Apr 22 at 10:44pm
|
Its possible to get a new Laser 13 mast .? Wonders will never end
------------- |
Posted By: Oinks
Date Posted: 08 Apr 22 at 11:50pm
|
I know nothing about Laser 13s. But as a rough guide in the absence of anything else for starters.. Big main, small jib ...mast step..mid setting ...put the mast up ...hoist jib ....pull rig tension to abt 350 lbs ...mast rake...tiny jib big main so it probs need to be a little bit aft of upright ....spreaders....so that shrouds are maybe prodded slightly aft of in line, but make sure squared across the boat And make sure the mast is properly upright and not bending off to one side. Hope thats helpful! |
Posted By: Sam.Spoons
Date Posted: 10 Apr 22 at 10:05am
|
Thanks gents, It's mostly how much rake will give the best balance. I'll go and sail it with him and experiment a bit. I can't see a problem with getting a new mast unless it's an obsolete section, it's un-tapered I think and it'll almost certainly be a common stock section. But I reckon it's an easy fix if not.
------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Oatsandbeans
Date Posted: 10 Apr 22 at 11:46am
| I don’t think that rake and or mast foot position affect the balance of the helm directly, but they do affect mast bend which has a big affect on helm balance. Normally setting it up so there is some 1 to 2” of prebend is a good start. If you get over bend creases at that straighten it up a tad. |
Posted By: Sam.Spoons
Date Posted: 10 Apr 22 at 5:59pm
I'm a windsurfer and our primary means of steering is mast rake  but the range of movement is rather more than mast rake in a dinghy. But rake must affect the helm balance?------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: 423zero
Date Posted: 10 Apr 22 at 6:15pm
|
While it won't be as exaggerated as a windsurfer, it does make a difference, I prefer a bit of weather helm. ------------- Robert |
Posted By: Oatsandbeans
Date Posted: 10 Apr 22 at 6:17pm
|
Mast rake in a dinghy is complex, but the thing it doesn’t really do is change much the position of the CoE of the rig surprisingly. It does change the geometry of the spreaders and how the mast bends.This is why raking the rig will depower the rig by reducing the camber in the main which will thus reduce weather helm. ( the opposite way to what you would think)
Boards are different as the mast foot can be moved a lot and the centre of lateral resistance changes massively as you go from using a centreboard fully down to raked and then onto fully retracted and using the fin 100% .With a board the one thing that is constant throughout all of this is the rig that is unaffected by all these changes.But with both boards and dinghies the aim is the same , in a breeze to balance the rig and foil forces and to minimise drag from both. |
Posted By: Sam.Spoons
Date Posted: 10 Apr 22 at 6:20pm
|
I agree, a little weather helm is good, ideally not much when the boat is flat (that said most people don't keep the boat flat enough, me included). ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: 423zero
Date Posted: 10 Apr 22 at 6:32pm
I have found that I think I am keeping flat, but when you look at a video, nothing like flat, even using a bubble indicator. Difficult to keep up the concentration in a blustery strong wind, I am too busy sailing the boat, so, Sam is right, very rarely can you do anything other than trying to keep flat  hence a touch of weather helm, I think it gives you quicker feedback on what the boat is trying to do, just my opinion though. ------------- Robert |
Posted By: Oatsandbeans
Date Posted: 10 Apr 22 at 6:44pm
| There’s one reason why weather helm is good - having the rudder at a small angle of attack means that it is generating lift as well as the centre board -a bit like a gybing board .So a few degrees can be good. The reason why some sailors have weather helm as it gives them “feel “ this feel is often at the expense of boat speed as it adds drag-so if you develop better “feel “ by having a more balanced set up you can sail with a lighter helm (which is faster!) |
Posted By: Sam.Spoons
Date Posted: 10 Apr 22 at 9:29pm
|
The more vertical the rudder the less 'feel' you have (or the lighter the rudder, it's one of the reasons why I dislike the Laser) but having a vertical or balanced rudder does not affect 'weather helm' as such it just reduces the effort required to combat it. A boat with too much weather helm will mean you need to angle the rudder to correct it which is slow. Weather helm caused by not keeping the boat flat is the usual cause but if the boat is unbalanced even when flat you still have the problem of the angled rudder acting as a brake. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: 423zero
Date Posted: 11 Apr 22 at 6:12am
|
Does the weather helm create the same amount of drag as rooster tail? ------------- Robert |
Posted By: Rupert
Date Posted: 11 Apr 22 at 7:35am
|
Weather Helm- when you fall over in the boat, do you want it to round up towards the wind, or bear away and speed up? It's to do with where the centre of lateral resistance is compared to the centre of effort.
Nothing to do with rudder shape or angles. If you sail heeled, it is hull shape causing the boat to round up, meaning you have to counteract by bearing away the "weather helm" the rudder feels. In a yacht designed to be sailed heeled, the rudder will be neutral at the designed angle of heel, if the designer got their sums right. In a Laser 13, the mast position is set, so mast rake will alter your CofE, so with no cheat sheet, trial and error will give you your answer, though I doubt a couple of holes on a chain plate will make much difference. ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: Sam.Spoons
Date Posted: 11 Apr 22 at 8:44am
This was my point above, but the effect/feel of weather helm is dependent on the shape/angle of the rudder, basically how close the CoLR of the blade is to the pivot. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Rupert
Date Posted: 11 Apr 22 at 8:32pm
|
A nice barn door rudder will turn a slow, heavy boat nicely where a narrow blade would simply not have enough bite.
Still doesn't explain why the Laser will happily change masts, sails and controls, but not the rudder. Should have done it 49 years ago. ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: Sam.Spoons
Date Posted: 11 Apr 22 at 10:11pm
^^^ This... ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Sam.Spoons
Date Posted: 11 Apr 22 at 10:14pm
|
Actually just allowing the blade angle to be free would be a virtually no cost mod that would improver the feel of the boat immeasurably. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: Grumpycat
Date Posted: 11 Apr 22 at 10:46pm
The option of a larger/better rudder was put to a class vote sometime in the in late 80s/early 90s ( back when I was a class member ) . It failed and I don’t think this option has been put to the class since .
------------- |
Posted By: Grumpycat
Date Posted: 11 Apr 22 at 10:48pm
So true . ------------- |
Posted By: Oatsandbeans
Date Posted: 12 Apr 22 at 6:07am
I remember a story about the first IACC America’s Cup. Before race 1between America cubed, and Il Moro de Venezia they both had to remove the skirts to show the world the underwater appendages. When the US designers saw the size of the Italian rudder they realised that one of the designers had got it wrong. The Italian rudder was double the area of the US one. The larger rudder was slow and draggy. The US boat was faster but the sail trimmers had a big input into what the boat was doing-. It is the same for dinghies. |
Posted By: Guests
Date Posted: 12 Apr 22 at 6:15am
I’ve done quite a bit of research and analysis on this. As a first approximation, to minimise drag you want the lift to be shared between the daggerboard and rudder in proportion to the square of their spans. For example if the daggerboard is 1m deep and the rudder is 0.7m deep: 1^2 = 1, 0.7^2 = 0.49, so ratio ~ 2:1 (i.e. the rudder should take one third of the total load). In reality the rudder is surface piercing and in the wash of the daggerboard so the relationship changes a little. In this example, if the rudder is less than one the total foil area then it can only provide one third the total force if angle of attack on the rudder is increased by pulling the tiller towards you. The boat therefore needs to be set up with some weather helm to keep it tracking straight.
|
Posted By: Gordon 1430
Date Posted: 12 Apr 22 at 7:41am
The angled rudder on the laser helps no end with rowing in the starting area. ------------- Gordon Phantom 1430 |
Posted By: Oatsandbeans
Date Posted: 12 Apr 22 at 5:09pm
| Yes -I am sure that’s why Bruce did it-(can’t think of any other good reason for it!) |
Posted By: 423zero
Date Posted: 12 Apr 22 at 6:50pm
|
Probably already had the rudder from another boat. Not forgetting he didn't design it to be the racer it became, designed to carry two people and was going to be called the Weekender. ------------- Robert |
Posted By: Sam.Spoons
Date Posted: 13 Apr 22 at 11:13am
|
More likely that a 'swept back' rudder blade would look racier in the eyes of a non sailor. ------------- Spice 346 "Flat Broke" Blaze 671 "supersonic soap dish" |
Posted By: 423zero
Date Posted: 13 Apr 22 at 12:20pm
Should have gone for stripes and a matt black foredeck ------------- Robert |