Boom Position

Don Guillette · Jul 25, 2010

The first part of your question is easy. The second part isn't. What you are describing is called "trimming to a point of draw" and is used in light air when close hauled.

When you're reaching and running the boom can't be in the same place as when you're closehauled.

Your sails, relative to the wind, stay the same and don't move - the boat does. Here's what I mean. Picture the boat sitting on a spindle and piviting. You start out close hauled and when you want to change direction you turn the boat to a beam reach. The sails don't know the boat has turned and they continue to take the wind as if they were closehauled. The above is highly simplified and not ment to be technical.

Maybe I don't understand the situation you're describing. I thought I'd heard just about every sail trim question known to man - some questions over 1000 times!! - but this one is a new one on me. Alan, Stu, Ron from San Diego, Rich H, what am I missing? Help me out here.

Stu Jackson · Jul 25, 2010

Don's right. What point of sail were you on when this happened? Where are the telltales on your main, in the middle or at the leech?

RichH · Jul 25, 2010

I 'think' I might know what dscibner is describing ... it is possible that his boom may be rising during the release of the mainsheet, and he is 'compensating' by pulling the boom back aft to keep the mid-panel midcord and aft tell tales flying correctly.

If that's so, instead of letting out or pulling in the mainsheet, try adjusting the traveller and/or vang and that will keep the twist more or less constant as you let out the mainsheet. What I mean by this is to as much as possible 'forget' the mainsheet and adjust the angle of attack primarily with a tight vang AND by pulling/easing the traveller. (If the traveller isnt controlled by "control lines", this will be very hard to do). The important thing to watch is that ALL the leech tell tales are 'flying straight back' when easing or tightening the mainsheet. ..... and that's my 'best guess'.

dscribner ---- do you have a vang and an easily adjustable traveller? You might want to briefly describe your 'set-up' and etc.

Bill Roosa · Jul 25, 2010

It is all about wind speed

I'm willing to bet that you are sailing in light (< 10 knots) winds. The boat speed is a significant fraction of the true wind speed and you get the apparent wind moving significantly forward. At 5 knots wind from the aft quarter and 4 knots boat speed the apparent wind will be well forward not aft. It is even worse if going to wind ward.
As the true wind speed picks up and becomes more than 150% of the boat speed you start to be able to get a beam reach set on the boom.
I know EVERYWHERE we go seems to be a beat until the wind gets to 12 knots.
FWIW

kloudie1 · Jul 25, 2010

Ahhh Haa an Injun Ear! SO what you are seeing is the vector sum of true wind direction and velocity, plus boatspeed direction and velocity.. as the boat speeds up, the wind resultant goes forward.. more % boat speed vs true windspeed, more forward is the apparent wind.. and so ya get to sheet in more..

Don Guillette · Jul 25, 2010

Dscribner: For the time being forget about midsail telltales - concentrate on the leech telltails. On the mainsail, the most important one is the top because it is your twist indicator. From what RichH says your boat handles a bit differently and since I'm not familiar with it I'm going to change tack - so to speak!!

I'm not an engineer. I'm just a common seaman and I approach things from that perspective. You had mentioned your leech line, boom vang, traveler etc and that is how beginner sailors start sailing. They deal with one sail trim control at a time and one sail at a time. That's like starting a basic engineering class in the middle of the semester!!

Most new sailors are confused with all the sail trim controls for the main and jib. We all were. The first thing you want to know is WHAT is it that all those controls are adjusting. They are ONLY adjusting 4 things - draft depth, draft position, twist and angle of attack. Unless you understand those 4 elements sail trim will never make any sense to you. Next you have to know which sail trim controls on the main and jib are used to adjust each of the 4 element. At this point you're half way home.

Next you have to learn the correct adjustment for each sail trim control on the main and jib for each point of sail and wind condition.

Sounds like a lot of work doesn't it? It isn't. I could teach you all you need to know about sail trim in 3 hours in a class room and then top it off with 2 hours on the water putting into practice what you learned in class. At that point you would be a high intermediate and know more about sail trim than 75% of the sailors worldwide. You would have a solid foundation to build on. You wouldn't be at the level of some of the lister on the forum such as RichH, Alan, Stu, Joe for San diego and some others but you'd know exactly what they are talking about and more importnatly you'd be able to pass your sail trim knowledge on to others who are going through exactly what you're going through..

Joe · Jul 25, 2010

It is perfectly clear that you are paying way too much attention to the mid chord tell tale. Until you get your leech tales flowing it makes no difference about the middle ones. If you scan back a week or so you will find a thread on this subject. The mid chord tales have very little to do with twist, or angle of attack. If you peruse RichH's excellent discussion on this you'll find those tools to be more useful to determine draft depth and position.

My suggestion is to learn to set twist, then practice maintaining it by manipulating vang, sheet and traveller. Inside the range of the traveller track, the sheet will control twist... outside the range the vang is more effective at twist control and the sheet takes over angle of attack duties from the traveller.

Once you're comfortable with that process... using the mid chord tale to adjust your draft depth and position with outhaul, cunnigham, backstay and halyard will make more sense.

Bill Roosa · Jul 25, 2010

The bicycle analigy

Imagine that you are on a bike going 10 knots. In still air the wind is directly in your face at 10 knots. If the wind is going with you at 10 knots you will not feel any wind on your face. If the wind is against you at 10 knots you will feel a 20 knot wind directly in your face. So you are riding your bike in a large circle and the wind is blowing (lets say) from the north at 10 knots. you will feel wind at 20 knots when riding north and 0 knots when riding south. At ALL other times you will feel the wind from one side or the other but ALWAYS from ahead.
Go try it, I'll wait.

OK so now consider a 40 knot wind and the same situation. You can now get wind from every direction even blowing from directly behind you.

When you sail in light winds you will be beating. That just the way it works.

Don Guillette · Jul 26, 2010

Dscribner: I don't know why your head hurts? Maybe I do. Obtaining info from a forum like this is like getting knowledge through a fire hose - you get a lot of info at once and probably a good portion of it is hard for you to understand because you don't have a foundation to build on but you're not alone. We all started that way.

There are many videos available. Four that I used are "Learn To Sail" by Steve Colgate, "Sailing In Heavy Weather" by Neil Pryde Sails, "The Shape Of Speed" by North Sails and "Starting Tactic" by J world, which you should skip for the time being. The problem with the videos is that they are like a computer manual. I understand the first chapter and then they get technical and I have no idea what they are talking about.

In other words, if the video started referring to draft depth, draft position, twist and angle of attack would you know what they are talking about? If they told you to set your draft position at 50% and your draft depth at 20% or they referred to apparent and true wind in regard to angle of attack would you know what they are talking about? If you can answer these question you're way ahead of the game. If you can't then you have a problem and you have to expend the effort to learn the terminology. Otherwise, you'll be like about 25% of the sailors worldwide who just raise the main and roll out the jib and call it sailing. They guess at sail trim adjustment. Sail trim guess work give me a head ache!!

This is a minor point but you indicated your are NOT an engineer. Didn't you say a few messages ago "I'm in engineering so A+B+C rings true to me". What else were we to think?

Space and time does not permit this forum to make you an intermediate sailor but there is a solution. Please note the info under my signature. I wrote THE SAIL TRIM USERS GUIDE and developed THE SAIL TRIM CHART. Do yourself a favor and buy both from this web site. They are cheaper than a 24 pack of Sam Adams and we all know where the Sam Adams goes. With the book and chart at least you'll retain the knowledge. I've sold over 8000 charts and over 5000 books worldwide and have never had one returned but if you're not happy with either product I'll refund your money. Actually, I did get one compliant and it was from a MIT engineer who liked the material but felt the laminate was too thin. I learned from it and switched from 3 mil to 5 mil.