Proper adhesive selection

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Lugnut56

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What is the best way to join plastic to a body tube? I had one of the plastic fins come off my Dark Zero on it's first launch. It was attached with contact cement at the top/bottom thru the wall lugs, but the ejection charge blew out the top contact hole. causing the fin to come off ( I want to join the entire length of the fin to the body tube). I'm also now building a MAXIALPHA 3, and have read some reviews where it was recommended that instead of just attaching the fins to the upper and lower plastic rings, the fins should also be attached the full length of the fin to the body tube. Will CA glue work, or do I need to use epoxy? Also on the workbench is a U.S. Rockets "Duel 18mm Rear Eject" model, and I want to make sure the nose cones do not blow off.
 

Micromeister

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What is the best way to join plastic to a body tube? I had one of the plastic fins come off my Dark Zero on it's first launch. It was attached with contact cement at the top/bottom thru the wall lugs, but the ejection charge blew out the top contact hole. causing the fin to come off ( I want to join the entire length of the fin to the body tube). I'm also now building a MAXIALPHA 3, and have read some reviews where it was recommended that instead of just attaching the fins to the upper and lower plastic rings, the fins should also be attached the full length of the fin to the body tube. Will CA glue work, or do I need to use epoxy? Also on the workbench is a U.S. Rockets "Duel 18mm Rear Eject" model, and I want to make sure the nose cones do not blow off.
+1 for Epoxy but there is also a technique used in applying epoxy between Body Tube and most plastic fin materials. "the epoxy rivet method".
This method and others are explained in detail in one of my Tech Tip-017 "Working with Plastics" This Article and the accompaning captioned photos give an in depth study of various material substrates and adhesives. If you'll visit www.narhams.org look at the left hand menu for the library click on the Tech Tip folder. All these Tech Tips are free downloads in pdf format.
Hope this helps a little.
 

Lugnut56

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Thanks for the info ( I have the site saved for future reference--lots of good info there).
 

Micromeister

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Plastic to paper? An MMA adhesive. Standard epoxy does not stick to most plastics - that is why the rivet method is sometimes used. Example: https://www.homedepot.com/p/Loctite-0-85-fl-oz-Plastic-Epoxy-1360788/100371824
While your observation that Epoxies do not bond with most plastic is correct, they do however in fact Stick and hold many plastics like styrene and Polycarbonates. The Epoxy rivet method greatly increases the strength of these joints. I have all kinds of Odd-Rocs using all manor of Plastics to cardboard with 0 joint failures over the last 40+ years. I use almost exclusively Devcon 5 and 30 minute epoxies for such projects. While Loctite Plastic Epoxy is a wonderful product, I don't generally use it alone for Model Rocket construction as it does not retain much flexibility after cure. It might be OK if used with the Epoxy Rivet method but only with fins that have a planform that reduce landing impact.

Plastics-6a_Epoxy rivet materials & tools_01-02-10.JPG


Plastics-6b_Polycarbonate-Polyproplene epoxy rivet fin_01-02-10.JPG


Plastics-6c_Styrene-Polypropylene epoxy rivet fin_01-02-10.JPG


Plastics-6d_Acrylic-Polypropylene epoxy rivet fin_01-02-10.JPG


Plastics-6e1_Best polycarb-anything epoxy rivet joint_01-02-10.jpg


Plastics-6e2_Polycarb-cardboard epoxy rivet & fillet joint_01-02-10.JPG


190a-sm_CoffeeCream&Sugar_08-15-96.jpg
 

caveduck

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Also check out Plasti-Zap, an unholy mix of CA and plastic solvent. I use it quite a bit for mixed-material bonding and have never had an unexpected problem. It has the viscosity of gap-filling CA (similar to the Zap green label stuff).
 
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