Humming / ringing question

S

Steven

New Member
It may have been answered in an earlier post, but what causes that high pitch hum when on a reach? Sounds like someone is playing the rim of a crystal wine glass.
 
pure speed, i think it is the centreboard.

i know when my centreboard was repaired but wasnt sanded properly the sound was much louder
 
i dunno, but it did it in the laser2 i sailed too, and it only happins when your going fast so im always glad to hear it :)
 
it caused because the trailing edge of your rudder or centreboard is uneven which causes it to flap at high speed. You need to sand the edge to make sure it is fair. I also have this problem and have done the sanding but it still hums and vibrates the tiller
 
it is the centreboard or rudder vibrating, you need to make a tiny flat in the trailing edge of the vibrating board, this should fix the problem, it has fixed the problem with mine.
 
What they are trying to say is the trailing edge of your centerboard should be flat about 1/8", not faired to a fine edge. The humming comes from water turbulence off of the trailing edge of your centerboard. This causes your centerboard to vibrate or move rapidly (osscillate) side to side. It only occurs when your on a plane usually when reaching or dead downwind. I also think how well your centerboard fits your trunk can affect it. Another factor that could or does cause it is if your centerbard has a flat spot on one side or the other. I believe it is also referenced in Dr. Laser's maintenance section.
Best Regards,
FishingMickey
178894/150087
 
its kind of strange, because it only happens when you are going really fast, but the vibration means you are not going your max-fast, by a tiny margin :)
 
the huming sound is called harmonics. its when the boat is reaching its highest speed. usualy!! its all about how thick the hull is and stuff that makes it vibrate because the water going over it does somthing. my uncle told me this sometime or another! but yes it is a good thing when it does hapin!
 
yachtie2k4 said:
it is the centreboard or rudder vibrating, you need to make a tiny flat in the trailing edge of the vibrating board, this should fix the problem, it has fixed the problem with mine.
Click to expand...

I'm surprised to hear that. In big boats, the high speed alarm is typically addressed by filing the trailing edge to an assymetric angle e.g.: longer on one side

I would think a square edge would not quiet the harmonic. Most big boat foils already have a squared off trailing edge.

Surprised to hear that your fix worked !
 
I am a new Laser sailor (new to Lasers and was lucky to be able to get a new Laser; I got a radial rig b/c I am a wee-man at 5'6" and 120lbs). I was in Galveston Bay off the Texas City Dike a few weeks ago and noticed the harmonics (I know about harmonics from my violin playing) when I was really moving fast on reaches. I knew it was something vibrating related to my speed but then I had no idea what it was. I called the GM at KO Sailing in Seabrook, where I got the boat, and the store manager (who is also my telephone tech help person, too) and after hearing my description, she said, "That's a good sound!" She said it was my centerboard, and then asked if I ahd my centerboard all the way down. Newbie-me said, yes, and that's when she reminded me to raise it up about halfway on reaches. (Ooof!) I haven't been able to get up to the same speed since then (winds have been lighter lately when I have gone out) to see if the harmonics happen as frequently with the centerboard up more; my guess is a different (likely higher) speed is needed to get the "shorter" board to vibrate at the same frequency as the boat.
I have learned so much from the members of this forum...Thanks a million!
 
dell todd said:
I'm surprised to hear that. In big boats, the high speed alarm is typically addressed by filing the trailing edge to an assymetric angle e.g.: longer on one side

I would think a square edge would not quiet the harmonic. Most big boat foils already have a squared off trailing edge.

Surprised to hear that your fix worked !
Click to expand...
I learned this from a boat designing book, you don't make a huge flat, just a tiny one, or you make it like a 45 degree angle, but you don't want a razor sharp edge on the end. my mate who was a world champion in the Tasar has also told me this, & knows a lot about this stuff.
it happens when you are going at a really fast speed, faster than hull speed, its when your up & planing that it happens, can't remember what cause's the vibrations though, whether its the water actually vibrating the trailing edge of the foils, or the whole thing.
 
it is only conceptually possible to get rid of this vibration. it will always vibrate a bit. the less board in the water, the lsee vibration though due to less play in the c-board trunk. it also helps when screaming in heavy air because you won't trip over the board and are less likely to heel of capsize and, as we all know, a flat boat is a fast boat.
 
yes it will vibrate, but, when it makes the humming it is vibrating more, which isn't good, this is caused by the trailing edge, which if you put the tiniest flat in it, or a 45 degree angle on both sides, this stops it, vibrations are caused by turbulance, which is slow, get rid of the humming, that means that you have less vibration, but you should have the centre board up anyway because you are on a plane.
 
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