How to Trim your Mainsail and Genoa – Basic Sailing Series

Getting great sail shape and trim on your sailboat can be truly challenging! In this clear and concise video we explain the basics of getting great trim on both your genoa and mainsail, which will ultimately help you sail faster.

Genoa Sail Trim

  • Close Hauled: sail in tight!
  • Close Reach: 1-2 feet outside lifelines
  • Beam Reach: 3-4 feet outside lifelines
  • Broad Reach & Run: genoa comes off furler at 90 degree angle
  • Use telltales to fine tune sail trim


Mainsail Trim

  • Close Haul: Boom down center line of boat
  • Close Reach: Boom points towards back corner
  • Beam Reach: Boom is over primary winch
  • Broad Reach & Run: Boom is eased out to almost hitting spreaders
  • Use telltales to fine tune sail trim

We already took notes!

We have included all of the things we said in the video here, so you can just copy and paste what you need for your notes.

Hey guys, sail trim is an art. In this video, we’re not going to go into the super advanced stuff. We’re going to give you the basic tools and tips to help you with your sail trim. This will help maximize your speed, it’s going to help you be better trimmed than 90% of the sailors on the water, and it’s going to help you get the most out of your sails.

Genoa Trim

Let’s talk about how to get perfect genoa trim first. On so many charter boats and boats that you’re going to be on, you’ll notice that the telltales are off, they’re missing, and so we’re going to give you a few tricks that are going to help you see where to put that genoa in relation to the boat for the different points of sail.

Let’s start with a close haul. A close haul is 45 degrees to the wind. It’s kind of the closest we can sail to the wind. Here our genoa is going to be really tight. It’s usually going to be just inside the lifelines or right over the lifelines, as tight as it’ll go.

Next point of sail down is a close reach. That is 60 to 75 degrees from the wind. And what we’re going to notice here is that we’re now easing our genoa out a little bit and the foot of the genoa at its widest point is one to two feet from the lifelines.

The next point of sail down is a beam reach, which is 90 degrees to the wind. We’re going to ease our genoa out a little bit more and here you’ll notice that the foot of the genoa is about three to four feet from the lifelines at its widest point.

After this, we go to a broad reach and a run. A broad reach is about 120 to 150 degrees from the wind. You’re going to notice that your sail trim on a genoa is very similar for a broad reach and a run. What we’re looking for here is we want the genoa to come off of the furler at a 90 degree angle. Some folks will over ease it, and as you ease out that jib sheet, you’ll see that the Genoa has a tendency to start going in front of the boat and that actually reduces the slot where the wind can catch the genoa. So really important, the genoa should be coming off at a 90 degree angle from the furler.

To really fine tune our genoa sail trim, we’ve talked about roughly where the sails go in relation to the boat. Now if you have telltales on your boat, which hopefully you will, you can really use your telltales to get precise and perfect sail trim.

Sometimes here it can honestly be a game of moving that jib sheet an inch to get perfect sail trim. You’ll notice that there are telltales on the insides of your sail and on the outside. The rule of thumb is if your inside telltales are luffing, bring it in. If your outer telltales are luffing, let it out. So in, bring it in, out, let it out.

You’ll also notice that there are rows of telltales on your genoa. Usually there’s about three if not four rows. We really want to make sure the bottom most rows are flowing back really nicely. That’s where we’re getting most of the power from in our genoa. The top telltales can be luffing about 50% of the time. If you notice that the telltales on the top of your genoa are consistently just going all over the place, one of the common mistakes here is that the jib car on the track is too far back. Try moving that forward a little bit and that will just help with the sail trim on that upper telltale.

Mainsail Trim

Let’s look at main sail trim now. Just like we said when we were talking about genoa trim on charter boats, often there may not be any telltales on your main, so let’s talk about where your boom should be in relation to the boat for each point of sail.

On a close haul, your boom should be right down the middle of the boat. On a close reach, your boom should be pointing towards the back corners of the boat. On a beam reach your boom should be right over the primary winch. When we go down to a broad reach and a run, we want to let our sail out as far as it’ll go. In an ideal world, we put it at 90 degrees to the boat, but with swept back spreaders on most modern sailboats, that’s not an option. So the trick here is to ease your sail all the way out. Your boom should be out as far as it’ll go without your sail hitting or chafing with that spreader. You don’t want it chafing on the spreader or it can slice and cut your main sail.

So that’s roughly where your boom should be for each point of sail. That’s going to get us really close. And now in an ideal situation, if you have telltales, we can use the telltales to get that perfect tuning on our main sail and to get perfect sail shape. You’ll notice like on the Genoa, there’s usually three to four rows of telltales on your main sail. The trick with telling main sail trim is those telltales are on the very back of your sail, on the back edge or on the leech. When those telltales point out, breakout or point towards, say, the port side, you want to ease your sail out to port. If the telltales are breaking in or pulling towards your starboard side, that shows that you need to bring your sail in. What you’re going to notice is on a perfectly trimmed main sail, your bottom telltales are all streaming beautifully back. Your topmost telltale should actually break or flutter about 50% of the time.

About the Video Series

New to sailing? We created this comprehensive basic sailing video series just for you! We know how difficult it is to find solid answers to your questions related to sailing fundamentals. As professional sailing instructors, we get it, and since we cover these topics regularly with our students, we knew we could help you too. We created these Learn How to Sail:Sailing Basics Videos, to be your ultimate sailing 101 video series. In them we cover monohull sailing for beginners from anchoring to steps to recovering a man overboard, all the way up to perfect sail trim!



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