Association Forum - Keel Vibration/Hum

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Keel Vibration/Hum

New Topic

Topic Locked

Printer Friendly

Author

Topic

LeighMarie
Navigator

Member Avatar

USA
188 Posts

Initially Posted - 05/23/2002 : 08:30:09

We took our 1985 swing keel C25 on its first run undersail Tuesday night and everything worked like it should! When we got in the 4.9 - 5.4 knot range (actually I'm not sure if the speed indicator is reading mph or k/h as it read about the same as my GPS which indicates mph - but that's a later issue for us to unravel) we had a very distinctive hum that came from the keel. Will I always have that? Even at the slip I have yet to hear any keel clunking, nor have I heard clunking while under way, but that hum is definitely there. I didn't know if raising or lowering the keel a bit help that? I have read about shims for the keel pin, and is that the only way to get rid of that? You can talk above the hum, but you have to talk a bit louder. The wind didn't get any higher to push the speed up so I don't know if it abates as one gets faster.

Dave & Sharon on "Leigh-Marie"
Hull #5128

Edited by - on

tinob
Master Marine Consultant

Members Avatar

USA
1883 Posts

Response Posted - 05/23/2002 : 08:49:32

Hi Dave,
The hum is from the keel cable when taut. To be rid of it you need only to slack the cable, that is to lower the keel all the way and then unwind the cable a little further producing slack in the cable, or wind up the keel till it stops.
Val on "CALISTA" #3936
quote]
We took our 1985 swing keel C25 on its first run undersail Tuesday night and everything worked like it should! When we got in the 4.9 - 5.4 knot range (actually I'm not sure if the speed indicator is reading mph or k/h as it read about the same as my GPS which indicates mph - but that's a later issue for us to unravel) we had a very distinctive hum that came from the keel. Will I always have that? Even at the slip I have yet to hear any keel clunking, nor have I heard clunking while under way, but that hum is definitely there. I didn't know if raising or lowering the keel a bit help that? I have read about shims for the keel pin, and is that the only way to get rid of that? You can talk above the hum, but you have to talk a bit louder. The wind didn't get any higher to push the speed up so I don't know if it abates as one gets faster.

Dave & Sharon on "Leigh-Marie"
Hull #5128
[/quote]

Val Bisagni

Edited by - on

Champipple
Master Marine Consultant

Members Avatar

USA
6855 Posts

Response Posted - 05/23/2002 : 08:55:02

The Hum comes standard on most if not all C-25 Swing keel models. Its the cable, not the keel. People have tried or claimed over the years that they slack the cable, others take up the tension, etc and so forth...I really don't think it is entirely removable or that thier methods removed it.

The only way to really get rid of it is raise the keel all the way up, or go slower...your choice, personally I prefer the hum, it lets me know I am going fast. It comes up right in the window your talking about and sticks around up to and above Hull speed. You will come to enjoy it....

As for your knotmeter, most can calibrate to MPH and or knots, as do most GPS's. Either use the GPS to calibrate the knotmeter or sail alongside someone...remember the GPS has a lag from your actual speed (usually 3 seconds or so)...

DW

Duane Wolff
"The Flying Wasp"
C-25, #401 std,sk
Chief Measurer C-25/250 National Assn.
<img src="http://im1.shutterfly.com/procserv/47b2dc20b3127cce9cd2f45b211a0000004010" border=0>

Edited by - on

LOREN SOUERS
Navigator

Members Avatar

USA
100 Posts

Response Posted - 05/23/2002 : 16:35:16

I have a fixed keel C25 and I get a slight hum when going fast. I figured it was kind of a good sign. I thought it was generated when you were approaching maximum hull speed.

Any other thoughts out there?

Loren Souers, aboard
Nimue,
The Lady of the Lake

Edited by - on

dlucier
Master Marine Consultant

Members Avatar

Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/23/2002 : 19:38:37

As my old swinger picked up speed, the cable would start to vibrate and hum, and being a Beach Boys fan, the song, "Good Vibrations" always came to mind. And after reading some of the lyrics, they do seem to apply to sailing.

I'm pickin' up good vibrations
She's giving me excitations
I'm pickin' up good vibrations
(Oom bop bop good vibrations)
She's giving me excitations
(Oom bop bop excitations)
Good good good good vibrations
(Oom bop bop)
She's giving me excitations
(Oom bop bop excitations)
Good good good good vibrations
(Oom bop bop)
She's giving me excitations
(Oom bop bop excitations)

Gotta keep those lovin' good vibrations
A happenin' with her
Gotta keep those lovin' good vibrations
A happenin' with her
Gotta keep those lovin' good vibrations
A happenin'

Ahhhhhhhh
Good good good good vibrations
(Oom bop bop)
(I'm picking up good vibrations)
She's giving me excitations
(Oom bop bop)
(Excitations)
Good good good good vibrations
<img src=icon_smile_cool.gif border=0 align=middle>

Don Lucier, Northstar
C25 SR/FK

Edited by - dlucier on 05/24/2002 01:51:05

Edited by - on

LeighMarie
Navigator

Members Avatar

USA
188 Posts

Response Posted - 05/24/2002 : 09:46:16

Very appropriate song, Don! I would not have thought it was the cable humming. It's OK to have it there as long as I know there's not something wrong. I frankly don't know how far down to let the keel cable. Does it go slack at some point? I replaced my keel cable this past Spring, and my greatest fear is that if I let it all the way down that it will slip all the way out of the winch and then of course I would be in trouble. I tightened down the clamp holding it on, so it should be OK, but I just haven't dared let it all the way out yet. I leave about 2 - 3 wraps on it. In the slip we're in I can't let it out all the way to see what it would do. But, I'll give it a try and let it out all the way. Cross your fingers!

Dave & Sharon on "Leigh-Marie"
Hull #5128

Edited by - on

John V.
Admiral

Members Avatar

USA
559 Posts

Response Posted - 05/26/2002 : 08:55:52

The hum reminds me of the warp drive sound effect from the old "star trek" show. The hum increases in pitch as the hull speed increases. It always made me feel as though I was really cooking.....

Slacking the cable works for me, though there are situations when the hum would return when there was a change of heel angle or coming around from close hauled to a down wind run.

John V. Nin Bimash II
77 C25 sk/sr #153

Edited by - on

Mike Vaccaro
1st Mate

Members Avatar

77 Posts

Response Posted - 05/27/2002 : 06:28:03

Unfortunately, there's no way to get around physics, and the cable will always hum, although the speed at which it does varies with tension on the cable. A slack cable will delay the onset. Sufficient slack may prevent vibration completely at sailboat speed, but I'm not sure whether the cable is long enough. If you try to slack the cable to mitigate hum, recommend that you always keep at least two turns around the winch drum to ensure the winch works properly.

If your cable is properly sized, there is plenty available to lower the keel completely and leave several wraps on the winch. There is a very distinct change in feel in the winch handle when the cable goes slack. Don't continue to winch down with the cable slack, because you'll develop a "birds nest" (i.e., mess of unwound cable) around the winch. If this happens and the keel is subsequently retracted, it's possible to get a "line over" which may impede lowering the keel next time (i.e., this is similar to geting a line over on your sheet winch), or result in a cable slipping during lowering. If the later happens, there will be a distinct "klunk" as the keel is lowered. This puts a good bit of stress on the cable/winch/companionway/sole and is best avoided by not "over lowering" (pardon the German grammer) the keel.

We actually find that if we lower the keel, and then take up the slack, the cable hum begins at approximately 3 knots, and increases in intensity to approximately 6 knots. The amount of hum/vibration is a good seat-of-the-pants speed cue that we find to be pretty handy during racing.

The bottom line is that this is a quirk of a swing keel boat.

Cheers,

Mike Vaccaro on the "Swoose"
84 TR/SK #4707

Edited by - mike vaccaro on 05/27/2002 06:29:45

Edited by - mike vaccaro on 05/27/2002 06:36:35

Edited by - on

tinob
Master Marine Consultant

Members Avatar

USA
1883 Posts

Response Posted - 05/27/2002 : 15:16:13

Hi Dave / Sharon,

There are a few things worth mentioning regarding the swing keels songs. When I converted my swing to a wing keel Three important things changed, the keel cable stopped humming, the keel stopped clunking and the boat stopped sinking. Not in the order of importance but worth mentioning at any rate.
Val on "CALISTA" #3936
'83 Tall/wing
Patchogue,N.Y.

Val Bisagni

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.