rpmtech
Posts: 584
Joined: 3/14/2002
From: green valley,
AZ, USA
Status: offline
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Composite materials have several little tricks that need to be learned to use them successfully. One of them is bonding, bonding them together, or bonding them to other materials.
If you need to install a plywood former, firewall etc,
here is a successful way to achieve a good bond:
After making sure the part/s fit correctly:
First, clean surfaces are your friends. Clean from ANY and every type of contaminents, including your grimey little fingerprints.
Put on some gloves and clean the surface using Acetone and a new rag and thouroughly wipe down the area.
Next, with gloves still on, scuff the mating surface with 80 or 120 grit sandpaper, and the wood part/s also. You want a scuffed surface everywhere the Epoxy will be.
Again repeat the cleaning process. after everything is cleaned, You need to do what is called a "hot coat". A hot coat is when you brush on some Epoxy to the mating surface with no thickener {Cab-O-Sil or Colloidial silica} added yet. The Idea is that the thinner epoxy will penetrate all of the pores and scratches left from the scuffing up step. This step is especially inportant for parts that are porous{wood, foam etc}.
Now mix the epoxy with the Cab-O-Sil. You just want enough thickener so that it does not run from the mixing stick, A mixture in beteween mayonnaise and peanut butter thick. Do NOT add Microspheres or Microballons or glass bubbles or what ever name you want to use for these into this mixture, These were not designed to use to thicken resin for bonding. You can however if you want the ultimate strength, although usually not necessary, is add some Milled fibers or kevlar pulp.
If you are using the Aeropoxy style glue, the hotcoat still applies.
Position your part/s next and then try and make a nice fillet wherever you can. I say try because it takes some patience to get a nice looking fillet for a bulkhead or whatever the part is.
After you clean up thats it! very easy but sometimes these steps are overlooked. One of the drawbacks of improperly done composite bonds is that it will appear to hold well, then all of a sudden in will break totally free. Not a good thing for a flying machine!
Good luck and have fun
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My model shop: www.rpmodeltech.com
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All Forums >> RC Airplanes >> Composites Fabrication And Repair >> How to bond: glass to glass, glass to wood... 
How to bond: glass to glass, glass to wood... - 
How to bond: glass to glass, glass to wood... -