Neil

IP: 92.233.237.49

Apr 25, 08 - 3:56 PM

Main Sail Trim Confusion

Dear All

I have now gracefully accepted that keeping the boat flat is a good thing, and therefore hiking out, whilst sitting on a knife edge peering at the water below on the OTHER side of the boat is a bad thing. No matter how exciting it feels!

Similarly, I have also now realised that both crew and helm sitting at the rear of the boat deep in conversation (as I did with Ravi last year) with bow in mid-air, is also not conducive to moving fast over the water. No matter how convivial!

Given my reluctant acceptance of the flatboat mantra I have now moved on to unravelling the mysteries of sail trim with the help of a book called "Illustrated Sail & Rig Tuning by Ivar Dedekam". Its a great read, although its a lot to digest.

Anyway the point is that he recommends to reduce heeling by: "opening the leech of the main(adding twist)" but don't you do this by easing the kicker and if so does that not go against another one of his other recommendations to reduce heeling by "flattening the sails".

Can anyone explain.

Cheers

Neil

Richard

IP: 80.254.146.4

Apr 25th, 2008 - 4:22 PM

Re: Main Sail Trim Confusion

Neil

All this is totally unnecessary. You simply control the heel of the boat by ensuring the picnic basket is moved to the windward side of the boat during a tack/gybe.

Richard

IP: 80.254.146.4

Apr 25th, 2008 - 4:33 PM

Re: Main Sail Trim Confusion

Please note this less effective after lunch!!!

Tony

IP: 82.39.103.162

Apr 25th, 2008 - 4:42 PM

Re: Main Sail Trim Confusion

Neil,

Does the authors name have have any bearing on your crew?....read backwards...there seems to be a subliminal message..Make dead Ravi?????

Strange......see you out here!

Tony

Neil

IP: 92.233.237.49

Apr 25th, 2008 - 4:58 PM

Re: Main Sail Trim Confusion

Amazing...how on earth did you notice that !
Spooky

Neil

Mike

IP: 83.67.105.75

Apr 25th, 2008 - 6:13 PM

Re: Main Sail Trim Confusion

That's funny

Re. the original question, it does sound a bit confusing.

Assuming you are going upwind and over-powered, I think the usual advice is pull on kicker, cunningham and outhaul to the max and keep playing that mainsheet (hard work). In an Osprey you would have raked the mast back and/or put some more bend in it. Only if it is so windy that the boom is out at 45 degrees all the time might you consider letting the kicker off.

However, unless you have a very powerful kicker, the top of the leach will probably be being blown open anyway. A streamer at the end of the top batten pocket helps tell you what's going on.

Viola

IP: 83.67.105.75

Apr 25th, 2008 - 6:16 PM

Re: Main Sail Trim Confusion

Yes, set the kicker and cunningham and PLAY the mainsheet. You will frequently see our boom end off the centre line - flatter is absolutely faster.

Neil

IP: 92.233.237.49

Apr 25th, 2008 - 7:28 PM

Re: Main Sail Trim Confusion

Thanks for all the replies, even the more spurious ones !

Basically, keep the sail as flat as possible and just play the main sheet. Unless it is so windy, in which case you let the kicker off a bit to open the leech.

Or alternatively always sail with a large picnic box and shift to windward when necessary.

Thanks

Mike Charlton

IP: 86.151.226.100

Apr 26th, 2008 - 12:15 PM

Re: Main Sail Trim Confusion

Sometimes not keeping the boat flat helps. If it is a very light wind day healing the boat to leeward helps as it reduces the wetting area and reduces 'stickyness' of the boat.

If you are a bit low of a mark as you get next to it, healing the boat over can give you a quick lift to windward and might just be enough to lift you around (mostly works on keelboats).

Also on a dead run in most winds the opposite sometimes helps, particularly on lasers/topper type boats. Healing the boat right over to windward sticks the mainsail further into the wind, reduces amount of boat in the water and you go faster.You need to lift the centreboard right out and have the bottom of the boat virtually out the water (technique taught to me by a world champion I used to sail with). Mind you, it takes a bit of bottle in a strong wind as one mistake and you gybe, splash!

Neil

IP: 92.233.237.49

Apr 26th, 2008 - 5:07 PM

Re: Main Sail Trim Confusion

Thanks for that Mike, and particularly for explaining the theory behind it all.
I will keep the topper tip for the Little Americas Cup - since as I normally end up in the water anyway I have nothing to lose !

Cheers

Neil

Paul

IP: 81.151.162.36

Apr 26th, 2008 - 5:32 PM

Re: Main Sail Trim Confusion

Hi Neil

Come & see us next time the 49er is on the slip. It's the best boat to demonstrate sail controls, as the changes are very obvious. There is also a previous thread on the same topic, from around a year ago.

What you do & don't do as the wind build also depends on your specific boat.

Peter

IP: 86.129.13.235

Apr 28th, 2008 - 9:54 AM

Re: Main Sail Trim Confusion

Hi Neil,

Here's my take of the kicker thing (sorry if this is utterly patronising, but it took me a long time to get my head around this stuff)...

First thing to note is that a mast with no rig tension is pretty straight, but the front edge of your sail is curved. When you hoist the curved edge up the straight mast the sail goes all dish-shaped. When the mast is bent so that it follows the curve (or "cut") of the sail, your sail will be flat.

The kicker does 2 things...

1) it holds the boom down, which stops the back edge of the "dish" from opening up when the wind flows across it.

2) it pulls the boom forwards, which causes the mast to bend.

In light winds, a sail that is too dish shaped (or "full") will kill the air flow: you want a fairly flat sail, but you also want the back to be open so that the air can escape, so kicker is not good. You generally need to bend the mast without using the kicker to get a sail that is both flat and "open". You can do this with spreaders & rig tension and even a little cunnigham, but don't use the kicker!

In medium winds you should use the kicker to stop the wind from lifting the boom and spoiling your lovely dish shape. As the wind builds you will need more and more kicker to hold the boom down. On a wayfairer, you can prevent the kicker from bending the mast in medium winds by adding chocs in front of the mast at deck level. The key to medium wind sailing is that when your sail is correctly sheeted you should do everything in your power to achieve a fully-hiked position. If you are not hiking out in 6 knots, then try adding mast chocs and pulling on some kicker. If you are hiked, then you have more power and more speed.

In strong winds, you need to get your sail flat, so out with the chocs and on with the kicker (and cunningham) to bend the mast. The cunnigham bends the mast without pulling in the leach, so is better in some respects when you are first overpowered. Once you have everything on tight, use the main sheet to keep the boat flat. It doesn't matter if the boom is not on the centreline. Lots of kicker will allow you to sheet out without the sail flogging.

If really strong winds, and especially in gusty or wavey conditions, then less kicker allows the boom to rise in the gusts and spill wind automatically, but this technique can make the boat difficult to handle, so I generally save it for survival / coming ashore etc.

Don't get me started on Rake

Mike

IP: 83.67.105.75

Apr 28th, 2008 - 10:17 AM

Re: Main Sail Trim Confusion

Excellent scholarly response from Peter.

Worth noting that on some boats, beating in light to medium conditions where you are not having to sheet out in gusts but are searching for every ounce of power, you use the mainsheet instead of the kicker to control the leach tension because it is more precise - you can keep the leach just on the verge of stalling, top streamer streaming straight most but not all of the time.

Viola

IP: 83.67.105.75

Apr 28th, 2008 - 12:04 PM

Re: Main Sail Trim Confusion

Peter,

Can we have your views on rake, please.
What you have done with bend is great - in fact, we should go through this forum and make a collection of advice as a resource. Anyone with a few hours to spend? I had better not this week

but would support and encourage a volunteer

Steve

IP: 86.131.203.141

Apr 28th, 2008 - 1:11 PM

Re: Main Sail Trim Confusion

If someone collects together the best (and correct) advice I can make a page out of it on the website.

Steve

Peter

IP: 86.129.13.235

Apr 28th, 2008 - 1:46 PM

Re: Main Sail Trim Confusion

OK, but i'm going to get into trouble cos I'm supposed to be working...well it is kinda lunch time I guess...

Raking the mast backwards does lots of things to help in heavy weather...

1) reduces the overlap (looking from the side of the boat) between the main and the jib. This overlap is called the "slot" and air squeezing through it speeds up and therefore increases mainsail power. A short slot means less power.
2) Tilting mast backwards also tilts the top of the jib backwards, but the bottom of the jib stays where it is (between the bow of the boat and the tight jib sheet). If you think about it, you can see that this is just like the boom lifting up on the mainsail: the back edge of the jib will open up and become less "dish shaped". This makes the slot wider, so once again it is not squeezing the air onto the main as much.

Before I start talking about the other effects of rake, a little note about the jib...The jib is much more than the small sail at the front of the boat: it is the mainsail's turbo-charger. If you don't believe me try this test: sail close-hauled, then let your mainsail out a little so that it's luffing. Now without changing the direction of the boat, or the main sheet, let the jib out a bit and see what happens to the main...any guesses???

Less jib means less mainsail power.

On with the rake...

3) Raking moves both sails slightly backwards, so the boat will naturally luff up when hit by gusts (i.e. weather helm). This can have some nasty side effects (difficulty tacking), but as long as you are aware of them it can really help.
4) It moves the mainsail lower down so it has less healing force (but more "boom smacking you on the side of the head" force!).
5) It moves your spreaders further back with respect to the shroud plates, so the mast will bend more under tension and flatten the sail.
6) The angle of attack is less aggressive: this is aerodynamic mumbo jumbo, but it basically means that air can flow quickly over the sail without too much drag and other nasty stuff. Think about aeroplanes: jet fighters have their wings swept backwards for high speed, whereas airliners have more straight-out wings for lower speed. By raking, we are sweeping our wing back so that it can handle the higher air speed without stalling.
7) It makes your boat look cool

PH.

Viola

IP: 83.67.105.75

Apr 28th, 2008 - 2:29 PM

Re: Main Sail Trim Confusion

Peter,

I think you have an amzing talent for describing the complex in a way that is easy to understand! An excellent use of a lunch hour.

Richard

IP: 80.254.146.4

Apr 28th, 2008 - 3:42 PM

Re: Main Sail Trim Confusion

Is the theory to keep the slot tight to accelerate the wind over the back of the main?

If so when the slot is closed too much and "backwinding" (if that is the correct term)happens should you be letting the jib out or doing something to the main? Or should we just buy a new main sail that is not as slack as "yer grannies knicker elastic"?

Peter

IP: 86.129.13.235

Apr 28th, 2008 - 4:38 PM

Re: Main Sail Trim Confusion

Thanks Viola, If only I could remember all this stuff when on the water

re Backwinding: We bought brand new racing sails for the wanderer and took them out in a steady 10 knots: the only way we could get the main to set properly on the beat was to let the jib out by about 1". On reading the class tuning guide I discovered that is exactly how you are supposed to set it!

I would say blame the sails last of all: there are so many factors that influence sail setting that you should be able to solve it another way.

Peter.

Giles

IP: 217.154.255.161

Apr 28th, 2008 - 6:05 PM

Re: Main Sail Trim Confusion

Might I suggest that the first thing to do is know how your mast (rake) and rigging is set up. Most sail makers and classes can give you this information and all you need is a tape measure, white PVC tape, a marker pen and a rig tension gauge - if you don’t have a gauge I am sure you could borrow one and I always have one on the boat. Failure to set up like this means that you never really know where you started from, what changes you have made and how they have affected your performance.
As Mike Charlton says sailing flat is not always best. In light wind you need to bring in some heel to help get a good sail shape to ease the flow of wind. In these conditions we bend the mast forwards. As the wind increases and we both move to sitting on the windward deck we have neutral mast bend and then put bend back as the wind increases. The kicker is progressively applied. I like to see the 2nd top tell tale on the main leach stalling a bit and it is important to have a kicker that comes easily to hand and is easy to adjust. The same applies to the Cunningham and the main outhaul. When the wind gets strong, or you are being seriously overpowered you can reduce the rigging tension. Again you need an ‘easy to adjust system’ for this.
And don’t forget the jib fairleads. Move them back as the wind increases. These are the adjustments we use on the Fifteen and I am sure there will be variations from class to class but I suspect the basic principles apply to most of them.

Good Luck

Giles.

Richard

IP: 80.254.146.4

Apr 28th, 2008 - 6:42 PM

Re: Main Sail Trim Confusion

Can I be bold enough to suggest that prior to racing commencing on a given Sunday not too far away that someone gives us duffers a bit of time to show us exactly how to set our boat(s) up for average conditions and give guidance on what we need to change for other conditions.

If there is sufficient interest shown perhaps those in the know for each class could pass on knowledge/advice over a series of weeks (Ospreys first please)

Suitable inducements could be offered to those with the key to unlocking the secrets of rig tuning. I could possibly stretch to a Mars bar and a cup of something warming!!

Mike

IP: 83.67.105.75

Apr 28th, 2008 - 6:52 PM

Re: Main Sail Trim Confusion

Richard,

I (and Viola I'm sure) would be very happy to look over your Osprey. We are away next weekend but will be at Kielder (at last) the 2 sundays after that.

Mike Charlton

IP: 81.132.168.132

Apr 28th, 2008 - 7:01 PM

Re: Main Sail Trim Confusion

There is a huge variation from class to class but I have to agree with Giles re seting the boat up. If you don't have your rig tensions etc right to start no amount of fiddling will make you go quick.

It is suprising how many boats don't even have a mast square and even in the boat! This is easy to check, just use the main or spinny halyard. Fix it off when the end that normally hanks onto the sail just touches the deck by the shroud plate (or where they go into the deck), then without undoing the length, it should touch the other side with the same tension(hope that makes sense, if not see me at the club). If it does not touch the deck or overlaps then the mast is leaning one way or another. Its a quick way to check if your mast is straight.

You can also let the kicker off on a dead run in certain winds to give the mainsail a bit of bag, drop the jib (or roll it away) is good if you are on a free spinniker leg, but not on a spinny reach. As with all these things you have to remember to put things back on again, not easy in the middle of a tight,crowded mark rounding!

Mike Charlton

IP: 81.132.168.132

Apr 28th, 2008 - 7:13 PM

Re: Main Sail Trim Confusion

Also in reference to Peters comments about the jib, don't choke the slot, over sheeting or heavy handness on rake etc can slow you down. A simple tip is to get on a beat before the race starts to set the boat, get as far back on the boat to leeward as you dare and look at the shape of the jib leech against the main luff, they should mirror each others shape.

I will stop now as this could go on forever! Also the more tips you give, the more abuse about how rubbish you are you will get when your last!

Neil

IP: 92.233.237.49

Apr 28th, 2008 - 7:47 PM

Re: Main Sail Trim Confusion

Hi

I have another question...but it can wait till another day.

I will now proceed to a darkened room to try and absorb all the excellent advice. I suspect it is with the latter comments that I need to begin - I currently don't know how my boat is set and have no way of measuring any adjustment ( I even suspect I can't change on my boat many of the things mentioned e.g my outhaul is not adjustable on the water). Peter's point regarding changing his jib by an inch set alarm bells ringing - I just don't how to measure that on my boat!
It has certainly clarified some of the apparent contradictions in the book I have got - poor Ivar Dedekam could become redundant at this rate.

Cheers everyone

Neil

Steve

IP: 86.157.6.10

Apr 29th, 2008 - 9:17 AM

Re: Main Sail Trim Confusion

Neil - next time you are at the club one or more of us will provide a rig tension gauge and the club tape measure and look over your basic setup with you and show how to measure things. With a class guide we can then go on from there to get a basic class setup for the day's conditions and see how that works for you and your crew's combined weight (which will affect the setup in areas not yet talked about!).

With a basic correct setup you can then concentrate on good seamanship and sail the boat to the best of your ability.

Steve

Neil

IP: 92.233.237.49

Apr 29th, 2008 - 9:53 AM

Re: Main Sail Trim Confusion

Thanks for that Steve. Karen and I will be concentrating on sailing the Wayfarer this season so it would be great to get it set up properly.

We have set ourselves the target of becoming spinnaker competent by the end of the year (this will be no mean feat considering we have never used one before).

However, I suspect we will sell both the Fireball and Wayfarer and buy a shiny new boat for next season- not sure what though !

Cheers

Neil

Steve

IP: 86.157.6.10

Apr 29th, 2008 - 12:06 PM

Re: Main Sail Trim Confusion

This link will get you to the clas association tuning guide. Get a copy printed off (and possibly laminated) and bring it with you to the club for when we set up the boat. I am probably not there this weekend (it is the cruising weekend) but will be the next.

Steve

Ruth

IP: 217.23.231.69

Apr 29th, 2008 - 12:18 PM

Re: Main Sail Trim Confusion

Of course the Wayfarer would be the perfect boat for you to be joining in the cruising weekend in! Nothing improves boat handling like epic sea battles and close range passing the chocolate hobnobs manouvres (sorry for possible poor spelling but that's as close as I can get!), in fact tactical warfare is very similar to the racing startline. Full details can be found on the forum!

Also, be careful...if there is one thing we like more than technical questions on the forum it's the perennial "What boat next?" debate. I will be first to chip in with a pair of supernovas, for obvious reasons.

R xx