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#1274933 - 09/07/08 06:19 PM Humming fins - advice?
bandini Offline
Michael Peterson status
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Registered: 01/22/02
Posts: 2202
Loc: SF
Just got a sweet board that rides real nice. First time I've had bamboo glass-on fins, but when I develop any speed at all on a wave, they hum REALLY loudly. Is there any method to turning this down? I've heard sanding the fins, but don't really want to try that 'til I've heard some more advice.

Am sure this has been a thread on the design forum before, so if anyone knows a link to past threads, would happily take that too. Thanks.

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#1274934 - 09/07/08 06:37 PM Re: Humming fins - advice? [Re: bandini]
seb70 Offline
Grom

Registered: 09/29/06
Posts: 90
maybe a bead on the trailing edge of one of them... check it, sand it.

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#1274935 - 09/07/08 08:46 PM Re: Humming fins - advice? [Re: seb70]
TRI FINS ARE DANGEROUS Offline

Tom Curren status
***

Registered: 01/10/02
Posts: 13157
Loc: Pavement, CA USA
Yeah, there is a small bead or chip or something on the trailing edge. The smallest little thing will make them hum.
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Surfboard Blog: Surfy Surfy

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#1274936 - 09/07/08 08:58 PM Re: Humming fins - advice? [Re: TRI FINS ARE DANGEROUS]
stu dog Offline
Duke status
**

Registered: 01/15/03
Posts: 33199
Loc: CA
doesn't humming mean your maxing out the fin
that's at least when I start to hear the hum/whistle when on a super fast wave where it feels like I'm BARELY holding the fin in


Edited by stu dog (09/07/08 08:59 PM)

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#1274937 - 09/07/08 09:05 PM Re: Humming fins - advice? [Re: bandini]
R3W Offline
Phil Edwards status
***

Registered: 02/19/02
Posts: 6852
Loc: Frisco
Is the humming louder than the voices in your head?

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#1274938 - 09/07/08 09:49 PM Re: Humming fins - advice? [Re: bandini]
silentbutdeadly Offline
Duke status
***

Registered: 09/26/05
Posts: 22363
Loc: Tower 13
My Pavel has glass ons and it humms. I haven't really had the desire to sand them though. It let's me know I hit 5th gear!
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"The size / dimensions don't matter. What does matter is that it's flammable. Because you should set it on fire and get a real surfboard" Witchipoo

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#1274939 - 09/07/08 11:50 PM Re: Humming fins - advice? [Re: silentbutdeadly]
20W-50 and blood Online   mad
Duke status
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Registered: 02/04/04
Posts: 21657
Loc: SOCAL
Buy my fins...they are quiet as hell and fly like demons.

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#1274940 - 09/07/08 11:52 PM Re: Humming fins - advice? [Re: silentbutdeadly]
jcb619 Offline
Grom

Registered: 01/11/08
Posts: 60
Loc: Alta California
cleaning up the trailing edge as well as the leading, round entry with a fine exit! If the entry is too fine that can cause cavitation as well.

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#1274941 - 09/08/08 04:39 AM Re: Humming fins - advice? [Re: bandini]
walrus Offline
Billy Hamilton status
***

Registered: 04/01/07
Posts: 1355
Loc: NJ
humming fins is the sign of improper foiling of either the fin or it's base...as water flows over and around the fin it forms eddy's and boils---robbing energy from both the board and the water in motion---get going fast enough and the system will rip apart(never happen in surfing , wrong Reynlods numbers) the fins need to be touched up a bit with sand paper and have the foil improved. Or, leave it as it is and enjoy the sound of drag and poor workmanship....
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if your not having FUN, get out of the water!

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#1274942 - 09/08/08 05:34 AM Re: Humming fins - advice? [Re: bandini]
blakestah Offline
Phil Edwards status
**

Registered: 09/10/02
Posts: 6139
Quote:

Just got a sweet board that rides real nice. First time I've had bamboo glass-on fins, but when I develop any speed at all on a wave, they hum REALLY loudly. Is there any method to turning this down? I've heard sanding the fins, but don't really want to try that 'til I've heard some more advice.

Am sure this has been a thread on the design forum before, so if anyone knows a link to past threads, would happily take that too. Thanks.




Humming can have two causes.

By far the most common is a small bead of resin on the trailing edge. You should be able to feel it with your finger pretty easily, and sand it off. This can also happen if the rear edge of the fin is not thin enough. It needs to be under a mm, around 3/4 mm thick is right, thin enough not to hum, and thick enough not to slice your legrope or feet.

The less common reason, which might apply in this case, is if the fin is too flexy or thin. It will wobble with speed, and that causes a hum. The only cure is adding glass layers to the outside and re-foiling.

Could be worse. Get a bead on the leading edge of a fin and it whistles. In some cases very loudly.

hth

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#1274943 - 09/08/08 07:29 AM Re: Humming fins - advice? [Re: blakestah]
SurfZombie Offline
Tom Curren status
***

Registered: 06/29/04
Posts: 14250
If you get beads everywhere - it's like an orchestra.



Aloha

Bryan

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#1274944 - 09/08/08 11:05 AM Re: Humming fins - advice? [Re: SurfZombie]
bandini Offline
Michael Peterson status
**

Registered: 01/22/02
Posts: 2202
Loc: SF
Thanks for the tips, I appreciate it.
Will let you know the results next time I take it out.
--B

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#1274945 - 09/08/08 01:06 PM Re: Humming fins - advice? [Re: bandini]
bobsurf Offline
Tom Curren status
**

Registered: 01/10/03
Posts: 10684
Loc: Blue Oyster Bar
Teach em the words.

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#1274946 - 09/08/08 03:01 PM Re: Humming fins - advice? [Re: bobsurf]
bandini Offline
Michael Peterson status
**

Registered: 01/22/02
Posts: 2202
Loc: SF
Quote:

Teach em the words.






Thank you, I'll be here all week...

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