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Attaching fiberglassed fins to a fiberglassed body tube?

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RocketRoll

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Pardon the rookie question, I've never used fiberglass before...

I'm looking to fiberglass a rocket for the first time. I'm planning on using US Composites 3 oz E glass and 635 thin epoxy resin with a 3:1 medium hardener. I plan to glass the body tube and fins separately.

How do I then join the fins to the tube? What epoxy/adhesive/magic should be used to join two fiberglassed parts together?
 

DGBrown

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Assuming that you are surface mounting to the body tube, sand both surfaces, then clean. Tack the fin on with CA then use your 635 thickened with cabosil to make fillets.
This is what I would do, but there are plenty of methods for doing this. Look through some of the minimum diameter build threads on here for other techniques.
 
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REK

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What diameter rocket is this?


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RocketRoll

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Assuming that you are surface mounting to the body tube, sand both surfaces, then clean. Tack the fin on with CA then use your 635 thickened with cabosil to make fillets.
This is what I would do, but there are plenty of methods for doing this. Look through some of the minimum diameter build threads on here for other techniques.
Thanks. I’ve read that CA becomes brittle over time. Perhaps epoxy? I’m currently looking at JB Weld's PlasticWeld Epoxy, it says it’s for fiberglass, but it does seem rather thick.
 
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DGBrown

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The CA is just to hold the fin in position so you can lay down the epoxy fillets. The fillets are what is providing the strength for holding the fin on. There's no problem using epoxy to tack the fins, the CA just sets faster. Just make sure you sand and clean all the surfaces that you are bonding.
 

timbucktoo

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Most people use JB weld to tack fins on MD rockets. Gives you plenty of time to get alignment right.
 
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