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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Old 10-12-2010
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Genoa not filling up...

We were sailing downwind on Sunday in around 10 knots, on a rather narrow course that demanded constant attention (we didn't have GPS maps for that area) and didn't allow for a broader angle to the wind.

Initially, our main was unable to go past 45 degree, as if the weight of the boom + sheets was pulling it aft. At the same time the genoa wouldn't fill with wind, actually it would collapse and then refill violently... not fun. So we moved the main in opposite direction, resulting in better speed but both sail would still misbehave.

We then lowered the main thinking that it was interfering with the genoa but to our surprise, the genoa would still do the collapse and refill routine.

After about 30 minutes of looking for a correct setup and despite the fact that we were keeping a correct pace at around 4.5 knots, we abandoned and fired the engine... a bit of a disappointment for our last sail of the summer.

So my two questions are: What should I check regarding the impossibility to setup my main close to 90 degree? (other boats were sailing beside us with their main properly extended near 90 degree) What could be wrong with my genoa? (other boats were sailing with headsail only and it seemed pretty stable)
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Old 10-12-2010
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Sebastian,

There could be a couple different possibilities here.

If you were sailing dead downwind, the mainsail would mostly blanket the genoa. Normally, dead downwind is not the most desirable course. Most folks prefer to reach a bit higher, and work their way downwind by jibing. But you were in a narrow channel and didn't have a choice.

So, under those circumstances, sailing downwind wing-on-wing is probably your best bet. Forgive me if you know this, but "wing-on-wing" means setting the mainsail and genoa on opposite sides.

This is easiest to do if you have a spinnaker or whisker pole that can hold the genoa out and prevent it from collapsing. But it can also be accomplished without a pole for the genoa. If you have a pole, it is best to set the genoa on whichever side is slightly favored as "windward". If you don't have a pole, it is better to set the mainsail on the slightly "windward" side.

In either case, you should always secure the mainsail with a preventer. This will help to hold the mainsail out at full extension, too. Another reason you may not have been able to get your main all the way out, is if the vang was too tight. In light air, you may need to ease the vang until the mainsail is fully out, secure the preventer, then snug the vang back up to help hold the boom down.

In light air, when sailing deep downwind, there is always the problem of apparent wind. The boat's speed is subtracted from the windspeed, making conditions feel even lighter. This takes pressure off the sails, causing them to collapse, and making the boat seem listless. It feels worse than it is, as evidenced when you discovered that you were still making 4.5 knots good. Sometimes, positioning some weight to leeward will restore some list and help the sails set better.

Another trick you can try with a roller furling genoa, is to take a few turns on the furler and "shorten" sail somewhat. This works especially well if you don't have any way to pole it out. Sometimes the weight of the big genoa alone, unsupported by a full breeze, causes it to collapse more easily. Shortening sail a bit leaves less weight and material to flop around.
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Last edited by JohnRPollard; 10-12-2010 at 03:53 PM.
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Old 10-13-2010
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Thanks a lot John for all the info. I like your suggestion about shortening the headsail a bit to balance its weight vs. the apparent wind speed.

My rigid vang was fully released, but even there the boom seems to point downward. I might have rigged it incorrectly (too short) at the start of the season, I'll look into that.

I've scanned the net and the few books I have regarding the setup of a preventer but most references either show expensive boom brakes or the use of a non-rigid vang moved to the rail. Is there a simple setup to use in conjunction with a rigid vang? Are there any rules on where on the boom and rail should the attachments be made?
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Sebastien,

I would definitely take another look at how that rigid vang is set-up. You may need to do some tweaking there. One way to test would be to disconnect it from the boom and see if you can get the mainsail to set better in light air when sailing deep.

Re preventer: A boom brake is ideal, but not too many people use those as they tend to be a bit more complicated and expensive to set up. Definitely worth the investment, though.

There are different ways to set-up a basic preventer. Some knowledgeable folks advocate for a system that takes a line forward to the bow from the outboard end of the boom. There are quite a few variations on this approach, each with its own merits/drawbacks.

I prefer the approach that takes a line and tackle down from the mid-boom (near the vang attachment) to near the rail or aft chainplate. There are so many different rig geometries out there, that its difficult to be categorical about where/how to attach the other end of the preventer, except that it should be a very solid point at deck level capable of withstanding loads comparable to or greater than that taken by the mainsheet system.

A line and tackle system similar to a soft vang (but beefier) usually works pretty well. It's also good to have some elasticity in the system, either with somewhat stretchy line or better yet a shock absorber (like Shockles) at the boom.
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If I understand correctly, you sailed downwind with both mainsail and genoa on the same side of the boat, and then you tried sailing wing and wing, and finally you tried sailing on genoa alone, and the genoa collapsed and re-filled repeatedly in all three cases.

When both sails were on the same side, I would guess that the mainsail was partially blanketing the genoa, causing it to collapse and refill.

When sailing wing and wing, there could be two explanations. Perhaps the wind was puffing and lulling, causing the genoa to fill and collapse. Setting a whisker pole to hold the genoa out should have helped in that case. If I understand the situation correctly, that's what I would have done.

Alternatively, it could be that the air that poured off the luff of the mainsail over-filled the genoa, and that the excess air spilled out over the leech of the genoa, backwinding the leech. When that happens, the leech of the genoa will lift, the genoa will collapse, and the sail will re-fill with a loud smack. Setting a whisker pole will also help in that case, but, if you trim the genoa aft a bit further, the excess air will spill over the luff of the sail, instead of over the leech of the genoa, and that might prevent it from collapsing to some extent. In this scenario, it usually takes somewhat more than 10 kts of wind to cause the genoa to collapse.

Last edited by Sailormon6; 10-13-2010 at 09:17 AM.
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