Broken Fin Fillet Repair help needed!

[Hyak]

I have a LOC 2.36" Tomahawk [38mm] that I managed to break a fin fillet today when the shock /kevlar line snapped just above the motor mount at somewhere about 2k+.

This resulted in the bottom half landing hard dead-smack in the middle of a dirt road, causing my wife to yell "Stop! Stop" before we ran over it! and cracked - not hairline - both outer, inner but maybe not the motor tube joint.

The fins is firmly loose, meaning I can wiggle it, the damage is visible, but I can't pull the fin out or flex it too much.
(Busted my L1 re-certification flight because of this actually)

I probably could haves simply applied some 30min epoxy and clamped it hard, and flown again BUT, I want to fix this as well as possible, not a temp "filed type" repair.

As info, the existing fillets are all RocketPoxy. The fins ae 1/8" Birch and not cracked.
While I would not rule out FG, that's not my first choice if avoidable.

So, anyone have any thoughts on how to go about fixing this??

(I have to also replace the shock cord mount, but for that I will epoxy in a new ring with ring hardware just about the MMT.)

If anyone is curious, the upper half landed quite happily under chute, another ~4,500' away on the other side of a ridge in Sage brush. No one would have EVER found it, but I had a Featherweight GPS tracker in the nose and walked right to it. Despite it not being visible from even 98' away!. I will NEVER fly a rocket again without one onboard!

Anyway, I digress! Fin Help please!

 

[jqavins]

In just one person's opinion, not an especially expert person, so probably wrong...

Fillets are not repairable. Period, end of sentence, don't even try, thank you for playing. You could force the crack open and get some fresh epoxy inside, then close it up and apply a fiberglass strip over the top, but that'd be a patch, not a repair.

Get out the Dremel, grind the original fillet away, apply a whole new one. I don't guess it's really necessary to grind away every little bit of the old epoxy from fin and tube; if you just look at old epoxy as "warts" that will covered up by the new fillet it'll be fine. But grind away what you can without damaging the material below, then apply new.

 

[jqavins]

Wow, I get the last word? What'd I do to deserve that honor?

 

[aerostadt]

Can you get away with using very thin CA and let it seep into the joint? This might work for lower powered rockets. I'm not sure I would do this for high-power. If you went the hard way, you would need a Dremel tool and start using different attachments to remove the old fillet. Then build a new fillet. Digging out the old fin, would also be hard. There is stuff on the Apogee website, but I am not sure you would find anything that help your particular situation.
https://www.apogeerockets.com/Advanced_Construction_videos/Rocketry_Video_354

 

[jqavins]

For the record, I wrote Dremel, but one can do it with a file (or better a couple three files of different shapes). And the OP only mentioned the fillet being broken, not the fin.

I shall now take my self-confessed non-expert voice out of the matter.