21-03-2012, 07:55 AM
Most epoxy's are fine, but are a bit on the heavy side just as they are. (weigth is the enemy of the model airplane!!)
I like to use a 24 hour cure epoxy (west systems of FGI) unless Im doing a very small job
The reason for this is it has about 20 mins pot life, that allows me time to add "micro-lite" filler to make it much lighter. With this filler I can reduce the weight of the resin down to, less than 1/4 of what it was and still be as strong or stronger than the parent material. Lets face it we are mostly bonding balsa or foam. They are not overly strong parent materials. Also this filler can be mixed in to the resin to make it any consistancy. It can easily be made thick enough so it will take up gaps very nicely and not drool out like 5 or 15 min mixtures and it will still bond like a bastard!! I realy like that!!
There's a whole range of fillers you can use for different purposes with epoxys. If you want a realy super strong bond then you must use filler with your epoxy. But for most aplications in areomodeling you'll find that it will rearly fail the epoxy joint it will mostly fail right next to the joint in the balsa or foam.
Gazz is right about epoxy reson shattering I have had just a couple of instances where highly stressed joints have failed in the actual reson, the solution to this is to use fiber filler mixed with the epoxy, that increases the joint strength massivly. Reinforcing with glass cloth, carbon or my favourite, kevlar, is also an easy option with epoxy.
The longer cure resons do have a higher yield point, the interesting thing about epoxy is that it's adheasive strength is higher than the yeild strength of the unfilled reson. The beautie of it being a little elastic is that is can stretch and allow the load to be taken up on the fibers, if they are there.
For the most part tho', when my things fail, it's not the glue's fault, it's the nut behind the sticks that causes the problem
Epoxy is a magic material, you can do so much with it. Once you start getting into composite structures it's interesting and very versitile, just AWSOME stuff!!
I like to use a 24 hour cure epoxy (west systems of FGI) unless Im doing a very small job
The reason for this is it has about 20 mins pot life, that allows me time to add "micro-lite" filler to make it much lighter. With this filler I can reduce the weight of the resin down to, less than 1/4 of what it was and still be as strong or stronger than the parent material. Lets face it we are mostly bonding balsa or foam. They are not overly strong parent materials. Also this filler can be mixed in to the resin to make it any consistancy. It can easily be made thick enough so it will take up gaps very nicely and not drool out like 5 or 15 min mixtures and it will still bond like a bastard!! I realy like that!!
There's a whole range of fillers you can use for different purposes with epoxys. If you want a realy super strong bond then you must use filler with your epoxy. But for most aplications in areomodeling you'll find that it will rearly fail the epoxy joint it will mostly fail right next to the joint in the balsa or foam.
Gazz is right about epoxy reson shattering I have had just a couple of instances where highly stressed joints have failed in the actual reson, the solution to this is to use fiber filler mixed with the epoxy, that increases the joint strength massivly. Reinforcing with glass cloth, carbon or my favourite, kevlar, is also an easy option with epoxy.
The longer cure resons do have a higher yield point, the interesting thing about epoxy is that it's adheasive strength is higher than the yeild strength of the unfilled reson. The beautie of it being a little elastic is that is can stretch and allow the load to be taken up on the fibers, if they are there.
For the most part tho', when my things fail, it's not the glue's fault, it's the nut behind the sticks that causes the problem
Epoxy is a magic material, you can do so much with it. Once you start getting into composite structures it's interesting and very versitile, just AWSOME stuff!!
“The knack of flying is learning how to throw your machine at the ground and miss.”
"When once you have tasted flight, you will forever walk the earth with your thoughts turned skyward, for there you have been, and there you will always long to return." ~Leonardo Da Vinci