Confusion on sail trim chart

[Scott21120]

Don,On the Sail Trim Chart, Main Sail, Page 1, under Quick Reference it states that for Heavy Air Trim, twist should be increased. In the book, it states the two controls that affect twist are the mainsheet and the vang. In order to increase twist, it seems that the vang would have to be eased, or the mainsheet eased, and yet for the heaviest air listed on the Windward chart (15-18 kts) and in the Heavy sections of the Reach and Run charts, the settings call for maximum vang and mainsheet. (Medium for Mainsheet on Reach in Heavy air.) That doesn't seem to make sense to me - can you clarify?Thanks!

 

[Alan]

Scott

You are correct. As main sheet and vang tension is increased, twist is decreased. As the wind strength increases more and more main sheet and vang are required. If the heel or helm become unmanageable after those adjustments the traveler is lowered.If still further relief is required, the main sheet and vang are then eased to spill air out of the top of the main. This decreases the heeling force in the top half of the main but at the same time decreases the forward driving force. The entire procedure is a progression of adjustments ending with the spilling of air out of the main. Of course the next step would be to reef the main. This starts the cycle over again.....full main sheet and vang are reintroduced.

 

[Ken]

Sail Trim

I don't have a copy of the sail trim chart, but I'll try to explain what it is trying to tell you. Sail trim for each point of sail is different. The purpose of adjusting the trim is to keep the boat under control while maximizing speed. In heavy air going to windward you want to increase twist to reduce the amount of heel/weather helm. You do this by easing the mainsheet/vang as you correctly stated. For Reaches because of the wind angle, heeling/WH is less of a problem, tighten the mainsheet to medium. For Runs neither heel or WH is a problem. Increase the vang/mainsheet tension to keep the sail flat to maximize the available sail area. Don't forget you can also use the traveller to adjust the angle of attack to reduce heel/weather helm. All the trim controls work in concert, don't fixiate on one or two. Sail trim experts, please correct me if I am wrong.

 

[Alan]

Ken

There is truth in your statement about going to weather in heavy air. But there isn't one single adjustment for any given point of sail or wind condition. Yes, there is a time to ease main sheet and vang to spill air from the main, but not before flattening the main as much as possible and lowering the traveler. Only after taking these steps would you resort to twisting off the main.I believe this is where the confusion is coming from. In the progression of trimming, the main is made increasingly flat and the angle of attack is decreased. Only after achieving this level of adjustment would the main be twisted off. The next step would of course be a reef.

 

[Don Guillette]

Confusion

Scott: There problem I encountered in developing the Sail Trim Chart was if I included everything I wanted it would, and was, about 8 pages long. Everyone who has developed any kind of a chart runs into this problem. When you start cutting down on info you run into problems. I wanted twist and the flat sail to be in the quick reference for the reasons you'll see below. Here's what I was trying to get across. The sail trim setting for light winds (very flat sail) is the same as for heavy winds (very flat sail). When you start out sailing in light wind and the wind starts to pipe up you gradually induce draft depth, draft position and twist plus deal with angle of attack. At some point in the wind speed, depending on what a sailor is comfortable with, you gradually start to reverse the situation and flatten out the sail.Assume it is starting to blow like stink and I'm having trouble controlling the boat. What I'll do is induce as much twist in the main and jib as it will take and hopefully I'll get the boat on an even keel. If that doesn't work I'll depower both sails by making them as flat as possable. A flat sail is a less powerful sail. If the flat sail doesn't do the job then it is time to furl the jib and reef.

 

[Don Guillette]

Adjustments

Alan has it right again - there isn't one single adjustment for each point of sail and wind condition because the wind condition plus the state of the seas are every changinging. Well, there kinda is a single adjustment and my Sail Trim Chart indicates what it is but that just gets you into the ball park. You have to tweek and fine it from there because of the variable conditions you run into every time you go on the water. In other words, if your sailing in 10 knots and you have no draft depth and your draft position is wrong your boat will SAIL and move through the water but it would sail so much better if you had the proper setting for the main and jib.If you are a middle to back of the pack racer and you do not constantly adjust your sails for the changing conditions you will never move out of that pack. Save the race fee and put it into something else. What I just said presupposes the racer knows which way to adjust the sails in the first place. Many don't.For a cruiser, you can get away with raising the main and rolling out the jib and not adjusting anything but you would get so much more enjoyment out of your boat if you learned the simple steps of sail adjustment. Sail trim is not brain surgery - if I can learn it anyone can. It is so simple I've reduced it to about 65 pages in my book. Leave the book in the bathroom at home and after about 3 trips to the head (depending on how fast you read it make take 6 trips) you'll move from beginner to high intermediate.A mate bought a sail boat to sail it and I can explain how to sail the boat in very simple terms anyone can understand.I think I went off on a tangent here so I'll just stop before I go way off the deep end.

 

[Bob]

Perspective

Someone described sailing as being like driving a car when someone else's foot is on the gas. Every sailboat has a wind speed range it likes best - BELOW that range, its skipper is trying to capture as much of the wind's power as he can, because the boat can handle more power; AT that RANGE, he is using all the power of the wind and trimming for balance and max boatspeed; ABOVE that range he is bleeding off the extra power that gives him no more boatspeed and only serves to unbalance and slow the boat down by forcing excessive heeling or weather helm or rounding up. For different boats, these optimum wind ranges vary, depending on what the boat was designed to do. So knowing what windspeeds your boat "likes" is a big part of knowing when to power up the sails, when to trim for max speed, and when to depower.