I recently aquired a Coreban Rockett 10'6 x 30". I took it out this morning in some punchy beachbreaks and every time I caught a wave, the fin would make quite a loud humming noise. The fin is a sort of long thin hatchet shape and I have it set slightly forward of centre in the box. This is a photo of it.



Does anybody know what is causing the fin to hum and is it a bad thing and how could I stop it?

Cheers

Th0m0

its the trailing edge shape that is doing it.
either its too sharp or too blunt.

i suggest sanding the trailing edge untill its its almost 1mm thick (maybe more) square to the fin. once this is done, on one side only of the trailing edge shape a slight 45deg bevel by sanding the TE a few times. the bevel must not be the entire thickness of the TE though.

basically the fin is humming coz of the way its shedding vortices. once it starts humming the drag generated is huge and basically applies a hand brake. If you cant fix it by some sanding scrap the fin.

sand the back edge of the fin, thin it down sounds like it too thick back there ,thats the main reason for fins to hummmmmmm

Agree with Bertie: Trailing edge is too rounded.

Either sand it square or put a chamfer on it.

Nope, IMHO if that is possible the base of the fin is flexing which gives you the hummer thingy

Where's bloody Lacey when you need him, oh he's on the stick sk8er thingy going past my house [}:)]

lacey said...

62mac said...

Nope, IMHO if that is possible the base of the fin is flexing which gives you the hummer thingy

Where's bloody Lacey when you need him, oh he's on the stick sk8er thingy going past my house [}:)]

hummings ok,i would be worried if it started singing mac the only big stick i need is the one that's good at whacking you over the head with

I love the old hate love relationship you do know I through a few guy's over the VW bug that sat in the Playroom
No but with all your testing on boards and products, you would be the guy I would value now hit me with that big stick

AHHHHH the old humming caper! It seems some are on the right tack. In my experience this problem was always caused by the back of the fin being too blunt or thick. Easily fixed! Sand it or return it.

Hey Thomo

Coreban's are hitting WA this week and my brother is keen on the 10.6
Besides the hummer, how does the rest of the board go

Heard the 9 6 was very good Might be stronger than you previous board.


Yea with the extra litres the 9.6 could be a better onshore board. I am down Rocko on Monday for work so may go have a look of they are in
May in-CREASE my water time over the banana
Are you up this weekend. Half a chance Sunday morn

Twimby said...

Hey Thomo

Coreban's are hitting WA this week and my brother is keen on the 10.6
Besides the hummer, how does the rest of the board go

I've only had 4 sessions on it and am a bit reluctant to draw conclusions with such limited experience on it. But so far I am very impressed with it. I am 86kg and bought this as a board for really crappy, windy or fat days. I tested in those conditions on the weekend and was very happy with it. It is super stable at my weight and paddles very nicely. Glides into waves easily and turns really well on the wave. It has a v through the bottom running almost the full lenghth of the board which makes it go rail to rail really well but can also make it a bit wobbey when you paddle for a wave in the surfing stance. It is a little slow to swing around for a wave, I think due to the wide tail and long fin, but nothing that can't be easily adjusted to. The real surprise for me was when I took it out in some punchy beach breaks. This day all the guys that normally ride sups took their short boards out and there were barrels aplenty. I nearly didn't paddle out because I thought I would get smashed on such a big board. But I bit the bullet and was glad I did. I didn't get any barrels but the board performed really well in conditions I didn't think it was suited to. So, bearing in mind my limited time on the board, I would say it's very versitile. A great beginner board for the lighter person or a good capable allrounder for the intermediate medium to heavy weights.

CMC said...

I used to work for a fin company and you get this from time to time. The boys are exactly right, it's the trailing edge. It sounds scary but it will take about 30 seconds to fix this fin. You dont even need sandpaper. Any sharp blade works fine, scissors, knife, razor etc. Just hold the angle and run it in even strokes top to bottom removing some of the clear coat off trailing edge.

Carbon fins are notorious for humming. The manufacturer gets a bit carried away with the clear coat to make them look shiney. Leaves a blob and you got yourself a hummer.

The blade is clean, only affects a small area and keeps it very even. Sandpaper is less accurate.

Cheers, I like that idea better than the sandpaper.