How to Set a Genoa Sail Car

Joe · Sep 12, 2016

If you extend the line created by the sheet from lead block to clew all the way to the mid point on the sail's luff... i.e. bisecting the clew angle... your jib lead will be in a neutral trim position. Mark the mid point... or estimate it if you can't measure.. tension the sheet...check the alignment. Do this for a couple of reef positions and mark on the track. Chances are they will not vary that much.... The various positions on the jib/genoa track are more often used for shaping the headsail.. if you get a good sail trim guide such as the one offered on this site by Don Guillette.... you'll improve your confidence rapidly.

My recommendation to you is to use both your sails... it makes the boat much more balanced. If you reef the main before you go out and sail with a reefed genoa... you'll be able to balance the helm and use the mainsheet or traveler to handle the gusts rather than messing with the roller furling.

BTW.... call it a block, not a pulley.

dlochner · Sep 12, 2016

Joe gives good advice, especially about using both sails.

Another indicator is looking at the tell tales, those strings that flutter along the front of the sail. When the sail is trimmed properly the upper and lower tell tales will move in unison. Moving the block (sometimes called a fairlead) forward or aft will cause one set of tell tales to stream aft and the other set lift or drop. Experiment with them.

A properly set headsail will look even. The curve of the foot of the sail will look similar to the curve of the leach. Tension on the foot and leach should be even. If the fairleads are too far forward the leach (aft edge of the sail) and will look very tight and straight, while the foot of the sail will have a big curve in it and not be tensioned. If the fairlead is too far aft the foot will be straight and tight, the leach will curve and fall off to leeward.

The point of sail you are on also has an effect. Closer to the wind the fairlead will need to come back, off the wind it needs to go forward.

If all this sounds like too much work, do what most of us do set the fairlead in a compromise position, a place where you get good sail trim on a beam reach and leave it there unless you have long windward or downwind legs when having the fairlead more precisely set will make a big difference in getting to your destination.

Most of all, enjoy sailing, enjoy the lifelong learning that you will do.

Brian D · Sep 12, 2016

Moved this to the Sail Trim forum. Don, who is our subject matter expert on sail trim, can help you out. He has also written a book on sail trim that comes with some very good charts. I recommend that you get the book. I can tell you that the book helped me immensely.

Good luck.

Anonymous 121765 · Sep 12, 2016

Cat,

My first boat was a C22 & here is what I can pass on to you pal.

First of all, the boat is more tender & fast reacting then a boat with a fixed keel. I hated my dropdown centerboard. I did however like it when going aground. A simple crank up & I was free.

The centerboard being narrow in length will allow your boat to roundup quickly with a mere wind gust.
Sailing with just a headsail can be fine IF the conditions are right.

When first learning to sail by the seat of my pants, I first read how-to sail books. There are many good ones out the that simplify the how too's.

Using a main along with the headsail lessens the rounding up tendencies. Simply put, sailing is nothing more then flying sideways while balancing the wind's effect on your boat. The only real difference is that you add water.

As for car positioning & knot knowing what size sail you have, try putting your boat about 60° off the wind.
Now, move your car so that your sail has an equal camber all around (you don't see stretch lines). You don't want to set it too far forward creating a pocket effect while sailing to windward. Too far aft, the foot will be too flat & you will choke wind between the high pressure side of the headsail & the low pressure side of the main. I call this the slot. You want the wind passing between the sails to flow smoothly.

Here's a handout I give to beginner sailors. It's a quick visual of approximate sail positions that will be a quick reference for you to hone your skills. I suggest to folks to put this in a plastic sleeve for use in the cockpit without getting wet.

Remember pal, you want to sail smart...not hard.

CR

Joe · Sep 13, 2016

Instructions on how to set your jib/genoa lead block will be found in every basic sail trim guide. The neutral position is the point where the tension on the sail's foot (bottom) and the sail's leech (following edge) are equal. Once set to the neutral position, shifting the car forward or backward will change the tension balance between the two edges... and ... is part of the headsail trimming process.... But the idea is to get it neutral first, then trim for conditions. Again, this information is part of any basic sail trim guide.

In Catalanc's case... he simply wants to know how much he should move the car when he reefs his sail. I suggest that he mark the neutral points for each reef on the track ahead of time... so he can preset the car when he decides to reef. This is more easily done at the dock.... where he can extend a line that bisects the clew's corner angle down to the track... and use this as his neutral trim point for each reef. You can create this line with a protractor or sighting from the clew to the mid point on the sail's luff (leading edge) .... It's basic geometry.

In any event.... a little time spent with Don's book... or any other basic sail trim guide will make it crystal clear. Some of the comments here obfuscate the question.

pwhitmore · Sep 19, 2016

Hey cec,
I learned to sail on Dillon and can support the earlier comment to reef your main before going out and enjoy the wind. gusts and direction changes are constant and often quite strong. stay out of the water tho...

normofthenorth · Sep 19, 2016

While I agree with the folks who recommend using BOTH sails if you can, there is a KISS advantage to using just the Genoa. Specifically, when reaching or beating with Main & Genoa, the Genoa has TWO functions, and the perfect sail shape ("fairlead" position) to optimize one function may not optimize the other. First, the Genoa is a good-sized sail, and it will propel your boat forward by deflecting or "bending" the wind, from the wind's initial direction to a different direction that is more aft. In effect, the Genoa (or any sail generating LIFT) is "throwing air" backwards, which has the same Newton's Laws effect as throwing bricks or sandbags over the transom -- it pushes the boat forward. And making sure that the jib-luff yarns, top and bottom, are behaving the same, means that the shape of the Genoa ( the sail's "twist") exactly matches the varying direction of the wind (the wind's "sheer") from the deck to the top of the Genoa.
But with the Main up, the Genoa also has a second function, which is to funnel air into the "slot" between the two sails, increasing the wind velocity the Mainsail "sees". In general, that function is optimized when the shape of the two sails are similar. Sometimes adjusting the jibsheet-block car so the yarns act identically top to bottom will also optimize the "slot", but not consistently or reliably. The good news when you're sailing on Genoa alone is that you don't have to think about that second function at all, because there IS no slot!

But if you follow the advice above -- e.g., setting the car so the jibsheet angle bisects the angle of the Genoa at the clew -- or follow Don's chart, you'll be Close Enough for Cruising, with or without the Main! But if a different position makes the boat go faster, or increases your progress ("VMG") to windward when sailing close-hauled, then that position is better!

dlochner · Sep 19, 2016

normofthenorth said:
While I agree with the folks who recommend using BOTH sails if you can, there is a KISS advantage to using just the Genoa. Specifically, when reaching or beating with Main & Genoa, the Genoa has TWO functions, and the perfect sail shape ("fairlead" position) to optimize one function may not optimize the other. First, the Genoa is a good-sized sail, and it will propel your boat forward by deflecting or "bending" the wind, from the wind's initial direction to a different direction that is more aft. In effect, the Genoa (or any sail generating LIFT) is "throwing air" backwards, which has the same Newton's Laws effect as throwing bricks or sandbags over the transom -- it pushes the boat forward. And making sure that the jib-luff yarns, top and bottom, are behaving the same, means that the shape of the Genoa ( the sail's "twist") exactly matches the varying direction of the wind (the wind's "sheer") from the deck to the top of the Genoa.
But with the Main up, the Genoa also has a second function, which is to funnel air into the "slot" between the two sails, increasing the wind velocity the Mainsail "sees". In general, that function is optimized when the shape of the two sails are similar. Sometimes adjusting the jibsheet-block car so the yarns act identically top to bottom will also optimize the "slot", but not consistently or reliably. The good news when you're sailing on Genoa alone is that you don't have to think about that second function at all, because there IS no slot!
But if you follow the advice above -- e.g., setting the car so the jibsheet angle bisects the angle of the Genoa at the clew -- or follow Don's chart, you'll be Close Enough for Cruising, with or without the Main! But if a different position makes the boat go faster, or increases your progress ("VMG") to windward when sailing close-hauled, then that position is better!

Ah, if only life and sailing were simple.

Besides the obvious making the boat go forward, the main and genoa serve another function, steering the boat. The main will tend to make the boat turn towards the wind and the genoa will tend to make the boat turn away from the wind. When both are properly trimmed these opposite turning tendencies cancel each other out and the boat sails in a straight (more or less) line without any attention from the helm.

When sailing on only 1 sail it becomes necessary to use the rudder to keep the boat on course. The less balancing force that is available from the main, the more the rudder must be turned to compensate. Anytime the rudder is not centered, it is inducing drag and slowing the boat down, which is generally not something we try to do.

And of course there is always the exception to any rule. In general, the further off the wind a boat sails, the less important the main becomes and the more important the genoa becomes. On a very broad reach or run, the main often interferes with the genoa by blocking the airflow to the genoa. Reducing the mainsail size by reefing or taking it down, increases the efficiency of the genoa thereby increasing speed. Because the genoa wants to turn the boat down wind and because that's the way you want to go, less rudder is needed, thus boat speed increases.

If you are only out for a lazy sail on a warm summer afternoon, then all of this is really immaterial, go with whatever is easiest.

shemandr · Sep 19, 2016

A mental device I use to remember which way to move the jib cart for changes in wind speed while sailing upwind is to think of the mainsail outhaul. Tight for higher wind, loose for light wind. The cart is analogous.
Lately, I've been using a different guide to determine the optional position of the cart. I look at the relative positions of the jib leech near the deck at the turnbuckles and at the spreader tips. They should be about the same. If at the spreader tip the leech is a foot away and at the turnbuckle it's 2 inches, move the cart forward and retrim. And vice versa. This would be true with or without the main up, which is why I've included it. Of course, remember there are times when you might want to depower the jib by having the cart more aft than optimal - like in higher wind.
One of these days I'd like a sail on Lake Dillon. It's elevation must be above 10,000 feet. What's that like?

Jackdaw · Sep 19, 2016

A sail DOES NOT move a boat by deflecting wind.

weinie · Sep 19, 2016

Yes it does. Unless you meant 'defecating' instead of 'deflecting'. Not sure which letter you left out.

Jackdaw · Sep 19, 2016

weinie said:
Yes it does. Unless you meant 'defecating' instead of 'deflecting'. Not sure which letter you left out.

Deflecting. Boats move forward when lift is created. And deflecting wind (turning it aft) is not lift.

shemandr · Sep 19, 2016

I'm still trying to wrap my head around how throwing bricks off my transom will make the boat go. And, I took Physics - 'though all I remember is F=MA and you can't push a rope. For me, all of these explanations are constructs to make something difficult to understand (Unless you understand aeronautics) understandable.

weinie · Sep 19, 2016

Of course it is... by Newton's third law.

weinie · Sep 19, 2016

SFS · Sep 19, 2016

Popcorn!

shemandr · Sep 19, 2016

So, like I said I'm not a aeronautics guy and can't play one on TV. But I have a few problems with all of these constructs. The first, the speeding of the flow over the the top of the wing has several problems. Some of which were covered in the video. But I'd like to add that the proposed foil shown is nothing like the shape of a sail. For that matter neither is an airplane wing. For a sail, which is maybe .5 mm thick, the distance the air flows on each side of the sail is virtually the same. You probably couldn't measure the difference. So the lift wouldn't be due to the differential distance the air flows on both sides of the sail. The Newtonian model I'm trying to grasp. I understand, from being a kid and, having my hand out the car window for hours, making different shapes and feeling the difference. Yes, if the angle of attack is up and the palm feels most of the pressure the hands wants to go up - and back. I don't get why that makes a boat go. I know the construct a la Arvil Gentry, and books, North U etc. about air flow around the sail, which I can barely grasp and doesn't really provide me with a usable model. What I do know is that the more attached flow and the less drag the better the sail performs. This is empirical not theoretical. Attached flow = boat go. Unattached flow = boat slow. Yes, the sail alters the flow of the wind over it by bending it. I'll stipulate that creates a pressure gradient. But we also want attached flow. So we want to bend the airflow enough to alter the airflow but not enough to cause separation and the dreaded drag. But, for the windward side, the bend is virtually the same (Remember we want tell tales flying on both sides of the jib) and the pressure gradient would be the same but in the opposite direction and I can't see any net difference. " 'plain to me please..."

weinie · Sep 19, 2016

Go to 4:45 in the second video.

Sure looks sail-like

Your hand experiment:

This is the only reason the boat moves forward:

Read more:
http://newt.phys.unsw.edu.au/~jw/sailing.html

How to Set a Genoa Sail Car

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