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Fin sanding
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adywind



Joined: 08 Jan 2012
Posts: 201

PostPosted: Tue Apr 16, 2013 6:55 pm    Post subject: Fin sanding Reply with quote

How smooth /grit #/ would you wet sand an old fin and in which direction?
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DanWeiss



Joined: 24 Jun 2008
Posts: 1928
Location: Connecticut, USA

PostPosted: Tue Apr 16, 2013 7:49 pm    Post subject: Reply with quote

600 grit in the direction of flow after any repair or paint removal. Or, use a "normal" 3M pad for more common cleaning which is so very important to performance.

Others will chime in that they never bother to clean their fins and it goes fine, but from testing I can tell you that a fin with salt crystals and/or oil from one's hand will not perform nearly as well as one simply prepped with a 3M scrubby.

It's the same as keeping the bottom of boards very smooth and clean. It's a serious difference.

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U2U2U2



Joined: 06 Jul 2001
Posts: 3056
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Tue Apr 16, 2013 9:02 pm    Post subject: Reply with quote

depending on the action being taken, if you are removing nicks or more, I use a sander, and progressively go down with wet sandpaper to mirror fine, like 1000 grit.

not so certain which direction matters when you use above, but water flow direction on the last few series cant be wrong

try to maintain the original shape , even if you make it smaller

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keycocker



Joined: 10 Jul 2005
Posts: 3222

PostPosted: Tue Apr 16, 2013 10:36 pm    Post subject: Reply with quote

600 is likely better. Notice there are not many shiny fins on the market?
It goes against instinct but a lot of winning watermen swear by 600 in the direction of flow creating less drag than mirror finish of any kind.
Same on your bottom and your Hobie, and raceboat.
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adywind



Joined: 08 Jan 2012
Posts: 201

PostPosted: Tue Apr 16, 2013 11:39 pm    Post subject: Reply with quote

Yeah, that's the dilemma I'm having: mirror finish or 600 like the bottom of the board? Does the finish play a role in how much grip a fin has ?
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tramontana00



Joined: 15 Feb 2010
Posts: 152

PostPosted: Wed Apr 17, 2013 2:11 am    Post subject: Reply with quote

Yes it does. Mirror finish will make it easier for water to detach from the fin and it will be more prone to spinouts.
Sand with 600 or 400 grit and keep your fin clean. Direction of sanding is not important.
Water flows around fin in layers (millions of layers). Goal is to create a surface that will keep water layers attached to the fin and friction between water layers rather than between water and the fin itself. There is most optimal sanding grit for every speed.
Don't believe it. Ask sharks. They have gritty skin and swim faster with less effort compared to other fish.
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norcom



Joined: 16 Jun 2008
Posts: 129

PostPosted: Wed Apr 17, 2013 8:01 am    Post subject: Reply with quote

I keep damaging my fins on the beach/oysters. Mad I repair them but they look pretty bad afterwards; though they still seem to work ok. I'll try the boardladys advice next time with the glass instead of epoxy but I have a feeling that'll be even worse. Maybe the edge will look better though.
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adywind



Joined: 08 Jan 2012
Posts: 201

PostPosted: Wed Apr 17, 2013 9:47 am    Post subject: Reply with quote

norcom wrote:
I keep damaging my fins on the beach/oysters. Mad I repair them but they look pretty bad afterwards; though they still seem to work ok. I'll try the boardladys advice next time with the glass instead of epoxy but I have a feeling that'll be even worse. Maybe the edge will look better though.

Im using JB Weld for fin repairs.Its easy to work with, takes like 12 hrs to dry and then just wet sand it 400 grit and you are ready to go. Its strong enough to not having to use glass or anything, cheap-what not to love about it?! Just make sure to leave the fin hanging upright when drying, because although its very thick and holds its shape it still may deform some.
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U2U2U2



Joined: 06 Jul 2001
Posts: 3056
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Wed Apr 17, 2013 10:33 am    Post subject: Reply with quote

I use Gorilla epoxy for ding repairs on FINs. If it has a large area I would probably add fiberglass or carbon.

the 600 grit or smoother debate.....

whatever floats yer boat

How smooth are the Americans Cup boats

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zirtaeb



Joined: 03 Jul 2009
Posts: 2312

PostPosted: Wed Apr 17, 2013 11:33 am    Post subject: Reply with quote

I talked to America's cup crew and National level Aussie18 crewman.
Most say finer than 600, cross hatch about 30 degrees from direction of water flow.
If you're using a freestyle, wave, or freewave board, it makes no difference to you.
If you spend the 200 bucks on Tetonic's blades, then make sure it's done.
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