mainsail leech flutter

[Megunticook]

Had a delightful sail Sunday afternoon on Penobscot Bay returning to Camden from the East Bay. 15 knot breeze out of the NNE, the boat was moving right along at 5-6 knots. Full main and working jib (any more wind and I'd have reefed).

The main's leech was fluttering against the mast quite a bit. What causes this and what's the cure? Sailcut doesn't match the bend in my mast? Not trimmed right? We had the boom vang set up at moderate tension, topping lift was loose.

Have a look at this video and tell me what you think: https://www.youtube.com/shorts/EUg42H3kJo4.

Thanks for any tips. For those of you still in the water here in Maine, this is absolutely the finest time of year to sail. I don't plan to haul until after Columbus Day (barring any hurricanes!).

[Jim Walsh]

Difficult to cure on that point of sail but to reduce luff flutter you can tighten the halyard and increase clew outhaul tension. Changing your point of sail and getting some tension on the main sheet can also help. I have had the same issue in strong winds and I altered course to minimize it.

[Megunticook]

Thanks--halyard and outhaul were tight as can be. My son was at the helm, I thought he had the mainsheet too tight for a beam reach but since we were flying along I didn't say anything. Tough to change point of sail as we were headed into port with rain coming so were making a beeline.

The flutter wasn't a big deal and not constant either, just mildly annoying.

[sloopjohnl]

a bit more tension on the downhaul might help

[wikakaru]

I think you mean luff not leech.

When the conditions are right (wrong?) both my Typhoon and CD22 both do this. There seems to be a certain apparent wind speed and relative wind angle that make it happen, as I recall a beam reach in around 15 knots of breeze. Under certain conditions the luff hums loudly. It is pretty annoying. I don't recall any of my other boats doing this. When I had a new mainsail built for the Typhoon I had the sailmaker put the grommets for the sail slugs closer together than the old sail thinking that might help. It didn't. I've thought of temporarily adding sets of small neodymium magnets as nodes along the spans to change the natural frequency of vibration but never got that far.

Your luff tension seems appropriate--I don't see any horizontal wrinkles radiating from the slugs, though I can't see from the video what's going on down at the bottom of the sail.

If anyone knows a sure-fire solution to solve this mystery I'd love to know, too.

Smooth sailing,

Jim

[Megunticook]

Yes, "luff" not "leech" is what I meant...sorry for any confusion.

Sounds like I'm not the only one that experiences this. Not the end of the world, just annoying.

[fmueller]

I get a little of this sometimes ... it's more like a buzz (than a flutter) between the a few of the track lugs mid mast. Usually remedied by tightening the halyard a bit.

or ....

If you have a traveler, add twist to the main by pulling the car to windward and easing the mainsheet a bit to twist off the top of the sail.

It's not uncommon to fly your mainsail fully twisted in light air, then flatten as the breeze picks up, but then twist again in heavy air to dump the top of the sail and reduce healing moment ... although this is generally when a reef is called for.

Actually viewing your video, you were well past the point of needing a reef !!!

Question - is your sail so stretched that you can't fully tension with your halyard ... ie the headboard tops out at the masthead ? You may not even be aware of this. It looks pretty close up there, although the sail looks fairly new to me ?? I s it ?

[Megunticook]

I get a little of this sometimes ... it's more like a buzz (than a flutter) between the a few of the track lugs mid mast. Usually remedied by tightening the halyard a bit.

Halyard was tight.

If you have a traveler, add twist to the main by pulling the car to windward and easing the mainsheet a bit to twist off the top of the sail.

No traveller on Typhoon Senior.

Actually viewing your video, you were well past the point of needing a reef !!!

No...boat was moving at top speed and not heeling excessively. Buoy data shows wind 13 knots gusting to 16 at that time. We were right on the edge--any more wind and a reef would've been the right call.

Question - is your sail so stretched that you can't fully tension with your halyard ... ie the headboard tops out at the masthead ? You may not even be aware of this. It looks pretty close up there, although the sail looks fairly new to me ?? I s it ?

No, there's still room at the top. Sail is not new, I've had the boat since 2013.

[Dick Villamil]

When you think you might be reefing do it! Most people tend to hang on to the full main way too long. Actually in that wind and point of sail a reefed main, will do much better. Also perhaps the genny or jib cars could be pulled aft a few notches to reduce backwinding the main. You were actually sailing under the jib because the main was not doing too much with that kind of backwinding. A roller furling on the genny could help also. Main downhaul and halyard tension will not be helpful when this much backwinding is in effect.

[John Stone]

It's just the wind being compressed between the mast and the luff. Maybe a little more halyard tension if you can get it. Try steering slightly different angles.

I think you would have benefited from a reef and not lost a bit of speed.

Also, I never let my main out so far the sail is deformed by the spreader. It will chafe the sail over time though it can be mitigated with wear patches.

So my thoughts are put a reef in the main and sheet in a bit. Apply some vang unless you are attempting to twist off the top of the sail in which case absolutely a reef.

[jamin66]

Tuck in a reef and balance the boat by adding / reducing headsail area. Apply just enough vang to keep the boom under control and the leech trimmed.