I'm trying to find out if this crack in the fin box is something to be concerned about, or not. Any ideas?
yes, it will be a problem because the screw won't tighten enough. You might have to add some Loktite to the screw to stop it from vibrating out and losing the fin. Chances are that it won't happen, but it will get wobbly and worse over time. You can fill the screw hole with wax, then put a glass patch over the section of fin box and sand it out. There might be a few other techniques but without a plastic welder and a retap I don't know what else you could do without having to replace the box. If you do have to replace it, it's not a hard job either, just a pita.
I had one like that that held for years. Dont worry about it.
Thanks for the advice!
The grub screw tightens nicely (taking care not to over-tighten).
I guess if I bottom out or hit something then there's maybe a higher chance of the fin pulling out.
It seems to still be nice and solid.
Hi Dafish - it's not that the screw is loose, just that there is this crack (which doesn't open as the screw is tightened).
My view is that for the fin to pull out it'd have to be a pretty hard impact - hard enough to effectively cause the grub screw to smash through the plug (as there isn't any opportunity for the crack to 'open'), if that makes sense?
In that case - I guess it's no different to if the crack didn't exist (i.e. such a hard impact would probably wreck any box).
...or would you disagree?
I'm wondering what caused the crack to form in the first place ...and if it is a common issue with these boxes?
there is more pressure on a fin box for kite surfing than there is on a normal surfboard. It could have been a manufacturing error that was only noticed as it got dirty. The fact that the screw still holds is good. When mine cracked it went all the way through, yours looks about 3/4 through. As Vespa mentioned, not to worry, as long as your screw tightens and holds it should be fine. And no, I would not say it's common as I have had plenty of boards with Futures and they are pretty solid. But everything breaks when you hit reef or sand banks ;)
I'd still put a bit of superglue on the crack and let it soak in. (with no screw in box......)
If it gets loose later you may then save it by oiling screw very lightly and reinstalling with some JB Weld on it.
After that its cactus. Futures is not a hard replacement tho