The Main Man

Stu Jackson · Feb 7, 2010

Install tell tales (mid sail and leach) and learn how to use them, do not over trim and make sure your outhaul works. After that it's the mainsheet, traveler and all the other wonderful controls Don's book and charts teach you.

BobM · Feb 7, 2010

Don't forget the outhaul and the cunningham for flattening the sail when there a lot of wind or bellying the main for light air.

Don Guillette · Feb 8, 2010

Ducati: There are a couple of things we need to know about your boat? To save time I’ll assume it is in the 30’ range and as mainsail trimmer you are adjusting the mainsheet, traveler and boom vang. I also assume your boat is middle of the pack or farther back.

Time and space here does not permit a full explanation so I’ll give you the basic info and you can go from there. It would be nice if a mate could become a good mainsail and jib trimmer by reading a few sentences but it doesn’t work that way.

The first thing you have to know is what are the above sail trim controls adjusting. The traveler is primarily adjusting angle of attack along with the mainsheet. The boom vang is primarily adjusting twist along with the mainsheet. The mainsheet is also one of the controls involved with adjusting draft position. As mainsheet trimmer you also need access to the outhaul so you can adjust draft depth (belly). You need to have a complete understand of draft depth, draft position, twist and angle of attack or sail trim will never make any sense.

As you can see, you asked a simple question but the answer is a bit more complicated. There is a specific setting for each of your mainsail trim controls for each wind condition and point of sail and you need to know what these settings are or your just guessing. Additionally, you have to be able to read your telltales.

I assume the boat is a masthead rig. The engine one these boats is the jib. As mainsail trimmer you have to WAIT for the jib trimmer to trim FIRST and then adjust your sail accordingly. If his trim is no good you could trim the mainsail all day and your wasting your time.

Switching trimming positions is not a good idea. It is like trying to switch a little league player from second base to the outfield and then back again. That is not a good idea but it is done all the time. It is not a good idea because it is hard enough to learn one position.

At the Catalina30 National events I always work the mainsail – for a couple of reasons. The first reason is that I know that position and the second reason is the jib trimmers job is too much work!!

One suggestion would be to locate a good mainsail trimmer in your fleet and have him show you the ropes.

Todd Smith · Feb 8, 2010

Ducatti,

I assume that you are racing a Beneteau first 36.7 that your signature lists ? If so, go to http://www.beneteaufirst367.org and read the forum, there might be specific trimming hints there.

I support switching positions for practice or minor races. That way the team can understand how to best work togethor. You can also gain new skills and maybe find a better fit in another position. For the big races, keep the players in their strongest positions.

I will assume that you understand Don's 4 elements of sail trim and also understand how you can adjust them. With that asumption, here are some tips.

For upwind:
1) Trim the main for full power, but ease the traveler to control heel.
2) Play the traveler in the puffs to control heel and weather helm. The boat heeling and making the helmsman turn the rudder slows you down.
3) You will probably have a bubble in the luff from the jib. Get used to it.

Downwind
4) There is not a lot of playing the main downwind, ease it out all the way at the top mark.
5) Unless you are surfing waves, then you will need to trim in when you accelerate. Ease back out when the surf stops.

Have fun
Todd

Don Guillette · Feb 8, 2010

After reading Todd's post I've changed my mind. I like the idea of changing position during practice so everyone gets the idea of what is going on. In fact, during "on the water seminars" I conduct that is exactly what I do. Everyone gets a chance to experience every position for every point of sail.

Bubble in the main: this is my personal opinion. i don't like the bubble in the main, which is caused by backwind from the jib but lots of mates don't mind it. I think it disrupts the flow of air but maybe not enough to matter. Being a purist I don't want to look at it. How you get rid of it on a masthead rig is by adjusting the mainsail. You don't want to mess with the jib if you have it powered up. On a fractional rig you ease the jib because the mainsail is the engine.

Ducatti: If the race boat you're talking about is yours (I just assumed it was someone elses) and if it is a fractional rig then the mainsail trimmer has the bigger job because his trim sets the tone and he should know his onions.

Years ago I worked with an all gal crew from Shoreline YC in Long Beach, Ca who were preparing for the Newport to Ensenada race. I assigned positions based on where they worked best. That was a fun experience but the best one was another all gal crew that was racing in Newport Beach. They wanted to whip up on the all guy crews who were always giving them smack about being there in the first place. After about 2 weeks of practice with assigned positions they got very, very good and were easily winning against the guys. Every time they won or even came in second you'd think they won the America Cup!!

Todd Smith · Feb 8, 2010

Don Guillette said:
Bubble in the main: this is my personal opinion. i don't like the bubble in the main, which is caused by backwind from the jib but lots of mates don't mind it. I think it disrupts the flow of air but maybe not enough to matter. Being a purist I don't want to look at it. How you get rid of it on a masthead rig is by adjusting the mainsail.

Yeah, but how ? If we trim in the main sheet or traveller, then the boat slows down. If we ease the jib, we slow down or lose point. Maybe a little less draft ? But this typically happens when the wind is up and we have already flattened the main as much as possible. I would love a way to get rid of the bubble, but sometimes it seems the fastest way.

Ray T · Feb 8, 2010

I was always told that a bubble was fast. I do know on my Cal 227 even with a new main when hard on the wind I couldnt eliminate the bubble. It sounds like you are finding this out. My advice is dont worry about the bubble and concentrate on other things to increase your speed.

Ted · Feb 8, 2010

I generally agree that a bubble near the luff of the main is still fast. For that matter the bubble can extend a few feet aft of the mast with no reduction in boat speed. Each boat sets up differently. If you want to get rid of the bubble you can try moving the genoa lead outboard to the toe rail if you have one on your boat. This will open up the slot between the main a genoa leech. It may do the trick unless you are at the upper end of the sail range. In that case it's time to change to a smaller headsail. Closely monitor your knot meter and make subtle adjustments. Ugly can be very fast.

Joe · Feb 8, 2010

According to Tom Whidden, the bubble is irrelevent, that's why you never see tell tales on a mainsail luff... power comes from the front half of the headsail and the back half of the main... Think of both sails as one continous entity. Air flows over the genoa luff and exits over the main's leech. This is especially true with masthead rigs and large overlapping genoas. Watch your speed log... that will tell you what's fast. Trimming your sails just to eliminate the bubble will slow you down.

RichH · Feb 9, 2010

Don Guillette said:
Bubble in the main: this is my personal opinion. i don't like the bubble in the main, which is caused by backwind from the jib but lots of mates don't mind it. I think it disrupts the flow of air but maybe not enough to matter. Being a purist I don't want to look at it. How you get rid of it on a masthead rig is by adjusting the mainsail. You don't want to mess with the jib if you have it powered up. On a fractional rig you ease the jib because the mainsail is the engine.

A bubble along the luff of a mainsail isnt necessarily 'detractive' vs. speed, as the 'flow' in the slot is poorly misunderstood, by most. A 'happy bubble' is usually because the leech of the genoa is too close to the mainsail, so either flatten the main (assuming that the {typically}aft end of the second from the top mainsail batten is already parallel to the boat's centerline, etc.) or open the genoa an inch or two. If that doesnt work, then take the genoa to a sailmaker and consider to get the genoa's leech recut .... cutting more 'hollow' into the leech of the genoa will usually correct an errant 'happy bubble'. In most practice a small 'happy bubble' at the luff is simply ignored .... but not the speedo/VMG.

So for the most part, ignore any 'happy bubble' if the speedo (and/or VMG) is indicating a higher value than without the 'happy bubble'.

Sails 'cut' for cruising have a more 'rounded' luff entry shape than race-cut sails with a flat 'entry' (requiring VERY precise angle of attack) and such rounded entry sails can easily adversely interact with the flow coming off the leech of a large overlap (or with not enough 'hollow' cut into the leech). Also, the more halyard (or cunningham) tension you put into a mainsail, the more forward the position of maximum draft ... and the shape at the luff may no longer aerodynamically correctly 'match' the shape of the genoa/jib's leech. Not to worry - set up the boat for maximum speed and ignore any small 'happy bubble'.

Joe · Feb 9, 2010

It is my understanding that the bubble is not created by the headsail leech as much as it is caused by the mast's wind shadow. So... the best way to eliminate it is to rotate the mast. A rotating mast is a common (as in necessary) feature on catamarans with their small headsails and huge powerful mains. Not so common on conventionally rigged production boats. Again..... that's why you never see luff tell tales on the main.