I have a thruster fin that keeps coming loose, Both grub screws are an issue. They don't seem stripped as they do back up tight so I'm thinking a bigger grub screw wont help.

I tried a bit if thread tape this morning to see if that would help grab but they were loose again mid way through a session.. luckily I attached a fin key to my leash now.

I'm not sure what to try next? There are groove marks on rhe fins so I'm wondering where the screws are causing grooves which is causing play?

Any suggestions?

Medium threadlock the blue stuff.

Interesting problem. I suspect that part of the issue may be that the two tabs in the fin box may not be snug enough when you first put them in? If so, try to tighten them up a bit with either a shim or a bit of tape on the tabs. If the tabs are sloppy in the box before you tighten the screw they will gradually loosen the screw.

Bob

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FRP said..
Interesting problem. I suspect that part of the issue may be that the two tabs in the fin box may not be snug enough when you first put them in? If so, try to tighten them up a bit with either a shim or a bit of tape on the tabs. If the tabs are sloppy in the box before you tighten the screw they will gradually loosen the screw.

Bob

I was thinking of something similar to that do a couple wraps with some electrical tape to see if it tightens the fin up. I'll have a look later to see if there is any noticeable play in the fin.

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Nugdam said..
I was thinking of something similar to that do a couple wraps with some electrical tape

Same, but I would use some incompressible material: bits of radiographic film, water bottle...
If it works, superglue them to the tab.

never had much luck with lock nut ,so i use to dip them in glue on my naish boards ,they still all wind out ok .

Had that problem with a futures box. Sliced beer can strips in the box and a grub screw a little longer than stock.

Voila! Just like downtown!

Re Screws, most supplied are stubby, not allowing much thread turns to grip . Your local surf shop may have longer screws for longboard side fins or checkout your local Nut n Bolt wholesaler, to get longer length screws in your current thread pitch. Compare what's your best bet for oversized whilst you're there. ENJOY