humming rudder

why does the rudder make that hummin noise? what i gotta do to fix it?

Submitted by kawaikapu on Mon, 03/08/2010 - 4:42pm



take a file to the back edge and make it sharp,


#1 Mon, 03/08/2010 - 4:49pm


With all due respect, to correct the humming problem you'll need to do more then make the back edge sharp. I am no expert, but I kinda understand the dynamic of foiling a rudder or fixed fin. If you are on o'ahu, the man you want to see is Brian Bills. He builds fins and rudders for all types of surfboards, paddleboards, skis and OC1 and 2. I have one of his BC Rudderz on my Mahoe OC2. If I understood him correctly, a molded rudder or fin cannot be foiled properly. Maybe Keizo can add to this. Like I said, I am no expert on the matter.


#2 Mon, 03/08/2010 - 5:18pm


Kawaikapu,

What kind of rudder is it ? Shape, manufacturer, etc. would help diagnose.

KGB ... Molded rudders 'can' be near perfect, but not the norm.

aloha,
pog


#3 Mon, 03/08/2010 - 5:43pm


its a pueo rudder.


#4 Mon, 03/08/2010 - 7:35pm


Slow down... you going too fast you Pueo riders......rutters can't keep up....:)

Ask Keizo
Rambo


#5 Mon, 03/08/2010 - 8:57pm


I kinda liked the humming, its almost like a pueo howling.


#6 Mon, 03/08/2010 - 9:21pm


Are you sure it is the rudder itself making the noise ? Could it be that the rudder shaft has some spiel and transfers vibration unto the hull ?


#7 Mon, 03/08/2010 - 10:26pm


Simple, take it off and install another. If still get hum, then do as KGB says: go get a custom one from Brian.


#8 Tue, 03/09/2010 - 2:57am


Had the same problem last year. Keizo told me to file just ONE side of the trailing edge. A little at a time. I don't know why, but it works. Try it. Cheaper than buying custom.


#9 Tue, 03/09/2010 - 7:42am


Pueo ???

Not gonna bust Keizos balls on this ( his ) forum.

I bet he knows why rudders hum ... If not, he can ask me.

aloha,
pog


#10 Tue, 03/09/2010 - 8:56am


i had the same problem with my scorpius when i first got it. i attributed it to my paddling. it happened for a couple of days. mostly at a slower pace. once i figured the boat out the noise went away. no sharpening of the edges just getting the boat to have a nice flow. does anyone have a way of contacting Brian Bills?


#11 Tue, 03/09/2010 - 9:20am


FYI... I just did a google search for "Brian Bills" and it resulted in a valid number for him. I just spoke to him about my own rudder issues and he can build me a new one for $100.


#12 Wed, 03/10/2010 - 2:13pm


kawaikapu,

The vibration comes from a complicated interaction between the flow and the rudder. Without fundamentally changing the design of the rudder, the easiest way to fix it is like everyone else said -- alter the trailing edge. Attached is an image from Larsson and Eliasson, Principles of Yacht Design about how the trailing edge influences vibration levels. Typically all the rudders out of Kamanu Composites are beveled similar to case 7 or 8. This seems to have fixed the problem in most cases, but clearly not all. You can do it yourself, just use some 220 grit sandpaper and a block. But be careful not to sand too much. If you go through the carbon, you could end up ruining your rudder.

http://www.ocpaddler.com/files/rudder_trailing_edge_vibration.jpg


#13 Wed, 03/10/2010 - 4:21pm


I wonder if Keizo ever looks in the mirror and says "Keizo Gates: super genius". He should if he doesn't already : )


#14 Wed, 03/10/2010 - 5:11pm


He actually does... While flexing.


#15 Wed, 03/10/2010 - 8:12pm


this is why i have such a hard time carrying on a conversation with Keizo. i just know every time i say anything he's laughing inside about my feeble brain. all the while thinking about his flexing mirror image.

edit: i've just learned that everyone does that when i talk... not just Keizo.


#16 Wed, 03/10/2010 - 8:40pm


It vibrates ok, but why does it hum ? Great rudder, imo.


#17 Fri, 03/12/2010 - 1:12am


I hope that we are talking about the rudder now, and not Keizo....
and he is pretty great too....


#18 Fri, 03/12/2010 - 4:44am


Isn't hum just a higher frequency vibration?


#19 Fri, 03/12/2010 - 6:18am


Hum = resonance? Anyway, any island kid getting accepted to RPI is quite a remarkable achievement. You got to know your math and science. Go ask the honcho of HECO, also an alumnus.


#20 Fri, 03/12/2010 - 6:41am


The rudder on my mako6 was twisted. Looking at it from the front you could see the left side of the base and the right side of the tip...
Cheap and fast fix : I added some fiberglass and resin on both sides and foiled it by sanding. It does not Hum anymore.
I intend to order a new one from Jude at Huki. The Fenn rudder looks like a wart on a beautiful face.


#21 Fri, 03/12/2010 - 9:34am


I plan to use a Pueo rudder on my surfski - if it hums, I will talk to Keizo !

Can you get rid of the humming by having less/no play of the rudder shaft ?


#22 Fri, 03/12/2010 - 2:08pm


Maybe, maybe not, because in the old days (before fin boxes), my glassed on skeg for my surfboard use to hum loudly until I glassed on a different one.


#23 Sat, 03/13/2010 - 8:34am


if you are going fast enough on a surf board even a fin in a fin box will hum.


#24 Sat, 03/13/2010 - 10:40am


the logical answer for a rudder humming is it is not foiled right. as one who has glassed and sanded over 1,000 surfboards in my lifetime, if the fin is not foiled correctly, it will hum.


#25 Sat, 03/13/2010 - 11:14am


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