Tech Tip: Canopies and Vapor Fumes
By Don Snedden
I surf the Internet and almost drown when the monthly bill arrives. Frequently I come across the same two questions being asked. How to clean canopies suffering from vapor fumes and how to rig biplanes. Once I suffered from vapor fumes but, instead of finding a method to clean off the fumes I worked on how to stop them happening.
After wiping several eggs off my face and cleaning up rough methods the answer proved to be very simple and easy. The basis is to find the “tacky time” of the glue you use. This time is last possible second that the glue will still glue before it becomes too dry to work.
Put some glue on a piece of plastic and then count off the seconds steadily saying “one and” “two and” “three and” so on is accurate enough. For super glue and MEK I find about two seconds is long enough with polystyrene taking about seven seconds. Press a second piece of plastic onto the bit where you have glued. Let it dry and see if it comes apart. If it sticks firmly then increase your time until the pieces won’t stick together. Go back two seconds and you have found your tacky time. I prefer using the longer time of polystyrene.
Presuming you have dry fitted the canopy for a perfect fit so hold the model in a flying position enabling the vapor fumes to drift away from the model. Now glue the cockpit edges where the canopy will fit. Your tacky time starts the moment you put the first bit of glue onto the model. I find a succession of glue drops (super glue) or a line of polystyrene in the centre of the plastic prevents surplus glue oozing out from the canopy edges. In one swift movement, put your canopy into position, hold it firmly in place and swiftly turn the model upside down so any fumes left will drift away from the canopy.
Before gluing I recommend very strongly practicing the swift movement until you have it perfect. It is the secret of preventing vapor smears. The next time you glue a canopy you must go through finding the correct tacky time. Maybe the plastic you are using is not quite the same, maybe your glue has dried out a little. Taking a bit extra time is much easier than trying to unstick a canopy. Later on I will answer on how to rig biplanes.