Forestay vibrating in high winds

[northoceanbeach]

The past two days have been pretty windy, over 25. I noticed going upwind sometimes my forestay would bang or vibrate a bit. I just tuned the rig myself using a tension gauge to about 14% or breaking as recommended. I don't know if that is related or not. I hadn't been out in high winds on this boat before tuning so I don't know if it did it before or not.

I seem to remember other boats I have owned doing this as well. Is it bad and what can I do to fix the problem? Thanks.

[skipmac]

Not sure why you're getting the noise but I don't recall ever having this problem on any of my boats.

My first guess would be too much slack in the forestay?

[s/v Beth]

Tuned my rig this spring- it hummed at about 25kts wind, went away after a few good blows. Not sure why.

[northoceanbeach]

It's not very slack, though maybe it is too slack. I have a tension gauge and iit is set to about 14% of breaking.

[UNCIVILIZED]

Everything has a natural harmonic frequency, & I highly doubt that this is anything to worry about. You may have had a much looser forestay prior to your rig tuning, & thus it wasn't tight enough for this to occur in the wind ranges which you experienced before.
For example, tight bow strings, or guitar strings have a lot more twang than loose ones. And in the case of a stay, the wind takes the place of a finger plucking things.

I gather that on your boat, this is happening with a bare forestay? And I'm assuming that you aren't running a TuffLuff bolt rope setup on your headstay, also.

With either setup, you can always have a sailmaker make you a small "micro jib". Like 1' or so on each side.. And with a grommet @ the top & bottom on the leading edge, plus one on the aft end.
Then you just hoist it up like a jib, bt with a downhaul in the lower grommet, & a "sheet" through the aft grommet. Pull it up about 1/3 the height of your forestay, until all of the lines are tight, & it should stop any vibrations & such.

That, or you could use an aluminum carabiner on the stay, with a downhaul line. And run a halyard through the 'biner, & back to a pad eye or deck fitting, somewhere aft of the stem. It should work to the same effect as a "micro jib", & the aluminum 'biner is soft enough not to hurt the stay or the halyard.

The "micro jib" is a solution which racers use on boats with foil headstays like the TuffLuff system. As with the foils, there's enough surface area to start the foil "sailing" around on the stay when there's no sail up. So the aft pulling tension stops this.

You'll also see some (race boats) with square "micro jibs" on bare foils, & the grommet in the aft top end of it is connected to the topping life. Plus a "sheet" in the lower aft grommet. Thus there are then 2 lines pulling aft on the foil/headstay to pull it aft, & stop the vibrations.
This of course should also work on a bare wire or rod headstay too.

If you walk around the docks, & keep your eyes open (looking @ race boats) you'll see what I'm talking about/describing.

[northoceanbeach]

No tuff luff, but it is only happening with the sail up. It's more of a banging around than a vibrating. It may just be part of the sail is luffing and causing the forestay to bang. My other boats, when the jib luffed, didn't cause the forestay to bang around and vibrate. I'm having trouble describing it.

[UNCIVILIZED]

Yes, then a better description would be key in terms of diagnosing things. Are you getting leech flutter, from an improperly tensioned leech cord? Or true luffing of the jib?
Either one can cause vibrations in the stays or rig.

You can also play with altering the tension of the headstay, backstay, & various shrouds, by a few percent, & see what happens.
Going several percent either direction from where they're at now shouldn't hurt anything. Especially as, generally speaking, you don't cause any permanent deformation in most alloys used for rigging, until you got up into the range of 50% of their breaking strength. By which point, other items like chainplate attachments, bulkheads, & some hulls, etc.may become overstressed.

[northoceanbeach]

A better description is in order.

I tuned my rig for the first time.
I tightened and balanced everything a good deal.
I sailed in high winds for the first time(on this boat)
When the sail starts to luff it cause the forestay to go "bang, bang, bang"
not a fast guitar string vibration, but maybe a bang twice a second.

I didn't notice any leech problems.

I've seen luffing before, and this could be how my new little jib boom headsail luffs, but it was just weird, the way it jarred the forestay back and forth. Didn't look good for the boat.

[UNCIVILIZED]

If you didn't have a jib boom until now, that could likely be the key issue right there. Because anything that's attached to a sail when it starts to luff is going to want to slam back & forth too.
The boom on a mainsail would do the same thing when a main luffs too, except that it's attached to the mast. And even attached as it is, if you luff violently enough, the boom will wrack & slam regardless.

I don't know what, if anything your jib boom is attached to, but if it's a new piece of gear, you might want to start your diagnostics there. Like say, go up forward, & physically restrain the forward end of the jib boom. Maybe even by sitting in the pullpit & facing aft, if you can manage it. And then hold it firmly, while your helmsman intentionally luffs up, to varying degrees.

You might even go so far as to stand up, next to the headstay, & put your foot on your jib boom, so that you can exert a lot of pressure on it, & then, again, have your helmsman luff up.
Plus, assuming you can do so safely, try restraining the jib boom @ it's aft end, when intentionally luffing. Even if it's via a line tied on to it's aft end, that's run through a block, say, on the leeward rail, & then belayed to something solid, to tension it.

You can also try sailing without the jib boom, luffing up to varying amounts, in different wind speeds, & see what kind of results that produces, also.

Can you describe, & or post pics of the jib boom setup please. It'd help with diagnosing things.

Also, if it's not too big a deal, check everything on the headstay, from the stem, all the way up to the masthead. And check everything else on the spar while you're at it. If naught else, it'll give you peace of mind that nothing's awry, or has shaken itself loose up there.

On that, I always take/tell folks to take a camera up the rig with them, & snap multiple shots of everything (from different perspectives & angles). That way, you don't have to recall from memory what you saw, plus you can always show the various suspect components/areas to others, afterwards.

Plus, & this is key, it lets you take pictures of/view remotely, areas of the masthead which are nigh on impossible to view from a bosun's chair/climbing harness. Because you can position the camera at all kinds of heights & angles, above, & along side the masthead & hounds. Recording all of the details of components that are normally only usually viewable when the mast is pulled out of the boat.

One other idea which just came to mind. Take a small block & tackle up forward, when you're under sail. And hook it up to the tack cringle, & to a hard point on deck near the stem. Then use it to add varying degrees of extra tension to the luff of the sail, while your helmsman intentionally luffs up, to see if that'll stop the noise.
Also, try the same thing, only on the jib boom's forward end too.