Twist

[Don Guillette]

We've discussed twist many times but as new mates enter the world of sailor this subject will tend to come up time and time again. I wrote this on a Catalina30 I frequent. Hopefully, new sailors on this forum will find the info helpful. A C30 lister (actually a lurker) called me today regarding twist. He wanted to know how to recognize it and thought it was too silly a question to ask of the list. I thought if he had the question some others might also. Actually, on any given sailing day probably half the sailors are sailing with a very twisted sail and don't know any better. They are spilling power all over the place. Twist is the leeward sag of the top of the sail. What that means is the top of the sail is on a beam reach and the bottom part is closehauled. You can see it by standing in the cockpit and look up the leech of the sail. The C30 lister thanked me and said he'd look for it the next time he was sailing. I told him not so fast - you have to learn how to set it correctly for the wind condition your sailing in. Here's the steps you follow:step 1: sail closehauled.step 2: position traveler so boom is near the center of the boat.step 3: trim the mainsheet until the top batten is parallel to the boom. The top telltale should stream. If it curls, ease the sheet.step 4: ease the traveler down while observing the top and bottom of the leech. If the top of the sail breaks first - trim the sheet in (too much twist). If the bottom breaks first ease the sheet out (not enough twist).step 5: pull traveler up to center the boom and ease it down. There should be no break in the leech.step 6: twist is now set for the conditions your sailing in. step 7: pull the traveler up to induce 3 to 5 degrees of weather helm. *** note when I say "ease" I mean just that and not 5'!!  There are 2 sail trim controls for TWIST and they are the mainsheet and the boom vang. A lot of boats don't have a boom vang or don't use it if they do have one. The Garhauer rigid vang makes twist a snap. If you have a boom vang, in step 3 tighten it so the boom is horizontal. After you get the hang of adjusting twist you can play the boom vang and mainsheet like a twist fiddle!!

 

[GuyT]

Vang usage and sail trim on beam reach

I struggle a little between the vang and the sheet since they have similar roles - its like they work in parallel in some points of sail. It seems that they co-play most when I am trimming from a close haul to a beam reach. Here's my scenario - I adjust the vang and sheet like you instruct on a close haul. Now lets say I want to go to a beam reach and let my boom out. I cant just let the main sheet out without also letting out the vang because of the tension on the vang.Which one do I let go first and how do I trim vang and sheet for twist when boom is out or should I even care about the vang when the boom is out?Thanks for your help - great post!

 

[Don Guillette]

Beam Reach

Guy T: Your right, the mainsheet and the boom vang do work together just like the 2 jets on a carb. I asume you have a soft vang. Either way it does not matter but the rigid vang is a massive improvement over the soft vang. The problem with the soft vang is that on a reach and a run the boom wants to go up. With a rigid vang it can't no matter how hard it tries.Mates, assume the wind speed, sea condition etc remains the same and all Guy has done is change the direction he is sailing in (in effect he has just spun the boat on its axis) what else can he do before he messes with the vang and the mainsheet?

 

[Brian M H23]

Not always necessary...

I don't believe, if you have a traveler, that any vang is really necessary if the boom is over the boat. It may have some fine tuning effects, but as long as the mainsheet car is below the boom, the boom isnt rising up (Though, I have heard that some people use the vang for all main control upwind! - this definitly stresses things a lot, especially the boom) Off the wind, the vang becomes important because the sheet can no longer provide a downward pull. This "downward pull" is what removes twist from the sail. The mainsheet is more effective than the vang as doing this, because it is closer to the leech. another thing to look out for - on a normal straight traveler, as you depart from centerline, the sheet also gets tighter.

 

[Don Guillette]

Sail Trim Controls

GuyT: Every sail trim control on the main and jib is there for a reason. Sailors invented them for a reason and that was to improve the shape of the sail.When you change your point of sail the sails don't even know it. The way the wind is hitting the sails has not changed. I'm going to over simplify this but picture this - the boat is on a stand, with a dowel through the keel, on your fireplace mantel with the sails set for closehauled. Now pivit the boat to beam reach. The way the wind is hitting the sails remains the same. All that has changed is the direction of the boat. So, the first thing you want to do is drop the traveler to compensate for the new direction. Dropping the traveler (see another thread above regarding the traveler) does nothing to the shape of the sail. Do not adjust the boom vang either at this time. The next thing you want to adjust is the mainsheet to compensate for the new direction. I've seen this a million times with middle to back of the pack racers (cruisers make the same mistake when they try to turn the boat). The boat is reaching a windward mark and the skipper is preparing to turn the mark. The mainsheet/traveler trimmer does nothing as the skippers tries to turn the mark but he is having trouble. What is happening is the mainsail is like a giant barn door and wants to keep the boat going straight. The giant barn door of a mainsail is acting like a rudder amd is overpowering a rudder. What the mainsail/traveler trimmer should have done is ease the traveler down so the boat can turn. Once the boat has made the turn then the sail is trimmed for whatever point of sail they are on.

 

[Dick Westwood]

No traveller

What, though, if you don't have a traveller?In my case, I have my sheet and a Garhauer rigid vang. But no traveller.

 

[Don Guillette]

No Traveler

Dick: Lots of boats do not have a traveler or they have a little travelers (Catalina25) that are useless. There are 2 controls for ANGLE OA ATTACK and they are the traveler and the mainsheet. So if there is no traveler then a mate uses the mainsheet. Unfortunately, when you use the mainsheet you are also adjusting twist and draft position so you have to be careful.