Cut your spar and trial fit it to the cores. If it sticks up 'just a little bit', you'll have to sand the skins later and compromise strength. You might be planning to fly it with a 400 this season, but what about next year when you need a home for that new brushless motor? If the spar is recessed in the cores, then your glue has to do more of the work, not ideal.

Put the cores in the beds and sand the 'angel hair' off of them with a paper towel, no sandpaper here. Failure to do this will mean a poor bond and you know what that could mean!

Get a timer and set it for the rated pot-life of your glue. You'll need a glue with a pot-life of 20-30 minutes. If you are new to your glue, mix up a trial batch and see how long is stays liquid in the cup. If you find that it cures too fast, there are two things that work to fight it. Try reducing the hardener content by 10%, or pour the glue onto a paper plate. Epoxy glues have an exothermic reaction when mixed, meaning that they give off heat. Heat causes the glue to cure more rapidly, so spreading out the glue on the paper plate keeps it cool. Refrigerating the resin and hardener probably won't work for you.. I've tried it on HTR-212 and West Systems and it got too thick to mix.

Mix about an ounce(one pump each in my case) of the glue and mix thoroughly. Keep your fingers (they are warm, remember?) away from the cup as best you can and you'll be rewarded with a longer working life. That extra minute might be valuable when you are stuffing the wing into the bag, all taped together and in place when you realize that the cores are upside-down in the beds!

Get a timer and set it for the rated pot-life of your glue. You'll need a glue with a pot-life of 20-30 minutes. If you are new to your glue, mix up a trial batch and see how long is stays liquid in the cup. If you find that it cures too fast, there are two things that work to fight it. Try reducing the hardener content by 10%, or pour the glue onto a paper plate. Epoxy glues have an exothermic reaction when mixed, meaning that they give off heat. Heat causes the glue to cure more rapidly, so spreading out the glue on the paper plate keeps it cool. Refrigerating the resin and hardener probably won't work for you.. I've tried it on HTR-212 and West Systems and it got too thick to mix.

Mix about an ounce(one pump each in my case) of the glue and mix thoroughly. Keep your fingers (they are warm, remember?) away from the cup as best you can and you'll be rewarded with a longer working life. That extra minute might be valuable when you are stuffing the wing into the bag, all taped together and in place when you realize that the cores are upside-down in the beds!