Plastic to Fiberglass

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While I have no experience working at that scale, I assume the standard of roughing up the two parts and crosshatching before joining with a quality high strength epoxy of your choice would work.
I would not have even chimed in, but see that you have not gotten any responses yet, so someones gotta' get the ball rollin'.
Perhaps after you join the two, you could use a layer of 5oz. cloth to cover and reinforce the seam on the outside.
 
Well, I surely have less applicable experience than Top does, but I'll keep the ball rolling with questions.

What kind of plastic? One's glue options are very different with, just for example, PVC, polystyrene, and polypropylene.

Would you consider mechanical fasteners like rivets? Or threaded rods that are anchored in a bulkhead inside the fiberglass airframe and extend through the centering rings in the fin can, with the fin can held in place by nuts on the rocket's bottom? In the latter scenario the same rods and nuts can hold a thrust plate.

How long is the shoulder? If there is not a lot of contact area then a glue that is pretty good (for the materials) may not be good enough.

Which piece has the shoulder? The fin can, I would suppose. I don't think this makes much if any difference, but when someone who has more experience with this responds to tell me that I don't know what I'm talking about maybe he or she will include useful information too.:wink:
 
Well, I surely have less applicable experience than Top does, but I'll keep the ball rolling with questions.

What kind of plastic? One's glue options are very different with, just for example, PVC, polystyrene, and polypropylene.

Would you consider mechanical fasteners like rivets? Or threaded rods that are anchored in a bulkhead inside the fiberglass airframe and extend through the centering rings in the fin can, with the fin can held in place by nuts on the rocket's bottom? In the latter scenario the same rods and nuts can hold a thrust plate.

How long is the shoulder? If there is not a lot of contact area then a glue that is pretty good (for the materials) may not be good enough.

Which piece has the shoulder? The fin can, I would suppose. I don't think this makes much if any difference, but when someone who has more experience with this responds to tell me that I don't know what I'm talking about maybe he or she will include useful information too.:wink:

I like this Idea of reinforcing the join mechanically for overall observable structural integrity. Perhaps a hybrid of the two methods would yield a solid result???
I assume that when you are playing at the 7.5" scale, and with a scale model like a V2, you are not exactly concerned about things like weight or the maximum achievable performance.
Epoxy and some fasteners followed by a wrap of glass sounds rigid enough in theory to me given what I know about V2s.
Less weight in the rear still means the less you need front, but you said this is a re-build anyway, right?
 
I used epoxy after roughing and also use machine screws through the tube and into the fin can shoulder....It isn't scale but looks good. If the motor tube goes up into the body tube and has a forward cr attaching to the tube/motor tube as well, that's even stronger.....I thought about just relying on the screws but when I looked at the recovery loads I wasn't 100% happy with all the recovery load being held by the motor tube joint, the top cr sort of butts into the plastic fin can andI didn't trust that joint to hold all the recovery load so I wanted a good fillet tying the top CR to the body tube as well as the motor tube. That fillet and the screws probably does more to hold the fin can and body tube together than just a surface joint of the shoulder/body tube.

Frank
 
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Rather than using epoxy, use plastic rivets. They can be removed for repair.
I used 4 for attaching my fin can on a 6in version. The recovery harness was on CR attached to MM tube so no stress problem.
 
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