Singing backstay

noworries · May 16, 2011, 04:34:34 PM

When the wind is aft of the mast our backstay sings... it's like a whistle or tone... it's driving me nuts!

When we did the sea trial it wasn't there, but after the survey (we had to remove the backstay during the survey for a crane to haul the boat) it's been "singing" ever since.

I'm not 100% sure it's the backstay... it's a weird tone and it's hard to locate exactly where it's coming from.

I don't know much about tuning the standing rigging, but has anybody had experience with this? Should I loosen something or tighten something or ???

Jim Hardesty · May 16, 2011, 05:15:28 PM

Try holding or feeling the lines and the stays when it's singing. I get a buzz from my bimni straps and a vib from my topping lift at times. But nothing from my backstay.
Jim

Ron Hill · May 16, 2011, 06:35:49 PM

No : I'm going to guess that your backstay is overtightened !?!

BTW, you don't have to remove the back stay when picked up by a smaller travel lift.
Have thetravel lift start to lift your boat up. If it looks like the back stay will hit the back cross member of the travel lift - then use this procedure:

Take a couple of dock lines and put them around the forward supports of the travel lift on each side Put those lines in your primary Genoa sheet winches. Equally winch the boat while in the straps forward so the back stay will stay clear of that cross bar!!

Most marina operators are not smart enough to figure this out, but I've done this a number of times!! A thought

Jim Hardesty · May 17, 2011, 05:23:16 AM

Ron,
Thanks for the lifting tip. I've been removing the forestay (furling) and moving the bottom back to the shrouds. It's quick when the sails and furling drum are removed for the winter. This year I plan on a midseason lift. Will give your way a try.
Always learning something here.
Jim

noworries · May 17, 2011, 06:59:56 AM

About the only thing I haven't tried is getting a mechanics stethoscope and touching it to various parts of the boat. It's a loud tone... I have no idea what the key is... but we sailed back from Catalina on a broad reach the whole way and 4 hours of a loud tone drove me a little nuts. You walk around the boat... it gets louder... ok I'm getting closer... then it gets quiter... keep going... it gets louder again... it's incredibly hard to pinpoint what part of the boat it's coming from.

We had to have the boat lifted by a crane because the rig that moves the railway-like cars around broke down the morning we wanted to use it. I don't think they would have let us do anything but remove the backstay.

Ken Juul · May 17, 2011, 08:33:43 AM

We have to back in to the slip at the travel lift we use. That gives plenty of clearance.

As to the noise. Vibrations are hard to track down by sound alone. Feel is the best. Wifes/girlfriends generally have more sensitive fingers, may want to enlist some help in your dectective work. Since it happened after you disconnected the standing rigging, that is probably the source, but it could be any of the strands. Suggest you borrow a Loos guage and reset all the stays.

tonywright · May 17, 2011, 09:32:08 AM

Is your transmission in gear (reverse) while sailing, or is there a chance that the propellor is spinning? Just a thought, if the sound is hard to track down...

Tony

scotty · May 17, 2011, 07:29:48 PM

You might also eliminate shrouds by tying them off with a line, which should change the tone if that stay is vibrating (like moving fingers on a guitar string). Try tying the backstay to a jib cleat. I know that dingies will vibrate when they are sailing at hull speed. I was surprised to find that our Cat34 sometimes has e a vibration when we are flying downwind. This is very subtle though, not like what you're describing.

noworries · May 18, 2011, 07:17:17 AM

Thanks for the feedback. I did try neutral vs reverse and it didn't make any difference. Will poke around some more next time I get her out

Jim Hardesty · May 18, 2011, 08:06:49 AM

One more thought. On my friends Tartan he gets a "howl" in some conditions even sometimes at the dock. His came from the extra line exit slots in the mast. Covering them stoped the noise.
Jim

Stephen Butler · May 18, 2011, 07:27:20 PM

We sailed a catamaran for 8 years that hummed when doing 10kts and over. Finally tracked it down to a very slightly worn rudder bearing. Perhaps rudder shaft wear is the culbrit? Good luck on your search.

Craig Illman · May 19, 2011, 08:27:56 AM

My hum was traced to the burgee line running from the port shroud to the spreader. It was like a piano string after shrinking over the winter or something.