Model Airplane Glue - Choose From Many Types
The benefits and limitations of modeling glues
When building an RC aircraft from a kit or a set of plans, model airplane glue is an essential part of the construction process. In the old days of model aircraft construction, wood was the predominant building material and there were just a few types of glue to choose from.
Today, RC models can be made from a wide range of materials to include foam, fiberglass, metal and wood. It is vital that the RC hobbyist have a clear understanding of the proper glue to use for each case.
Two types of glue
There are two types of adhesives - evaporation and chemical cure. Evaporation glue dries by the loss of a solvent. A good example is Elmer’s white glue. Evaporation glues take a long time to dry, at least overnight. A chemical cure model airplane glue bonds via a reactive process. Chemical cure glues can be further divided into one part glues (such as Cyanoacrylate or CA) or two part glues (epoxy). Chemical cure glue bonding times are anywhere from several seconds to 30 minutes.
Different types of glues have diverse strengths and characteristics. As a general rule, stronger glues, such as epoxy, tend to be heavier. Fast drying glues are also often brittle. The idea is to select the proper glue for the job. This is especially important for model airplane glue used on lightweight indoor flyers such as the Finch (free, full size plan here) or the Robin (full size plan here) where weight is an important consideration.
Use the correct glue for material being bonded
When building any model airplane, use the proper glue for the materials being bonded. Foam can be especially sensitive to certain types of CA glue. Evaporation glue is usually not effective when used with plastic or metal. Epoxy works on just about anything. Using the wrong model airplane glue can make it difficult to achieve a smooth finish. While not a consideration for indoor RC flight, some glue is not fuel proof.
Wood parts bonded by glue will eventually need to be sanded. If the glue is much harder than the surrounding wood, especially with balsa, unsightly ridges can develop as the softer wood is removed while sanding while the glue stays in place.
Cure time, or how long the model airplane glue takes to become fully hard, is an important building consideration. Evaporative glues typically bond overnight. Chemical glues, such as epoxy and CA, will completely bond parts together in a matter of minutes.
Safety is an essential consideration for today’s different types of glue. Many of the chemical glues are toxic, and either the glue or fumes can harm the modeler.
Always work in a well ventilated area. Consider using throw away gloves and long sleeved shirts when working with epoxy and CA glues. Avoid direct contact with these model airplane glues whenever possible.
For my modeling activities, I always use odor free CA glue such as the User Friendly Odorless (UFO) line of adhesives.
Cyanoacrylate is the most common glue modelers use these days. CA typically comes in one or two ounce sizes. For working on smaller RC model planes, the one ounce size usually works out the best. CA glue shelf life is unpredictable, and the one ounce size is usually enough for several modeling projects.
CA glue is available in a wide variety of types and brands. The first choice will be between thin and thick CA. Thin CA has the viscosity of water, penetrates very well, requires a very close fit on parts and dries almost instantly. Thin CA is useful for tight fitting laser cut wood parts and will tolerate no gap in the glue joint. Thin CA is very useful for soaking and strengthening model airplane parts such as thread wrapped around a landing gear balsa covering.
Thick and thin CA
Medium or thick grade CA is ideal for most model construction tasks. I use medium grade CA for the majority of my model builds. Medium CA can fill small gaps between parts. But most useful is the 15 to 30 second drying time medium CA allows for minor repositioning of the assembled parts as the glue cures.
Remember that tight fitting joints will always produce a lighter and stronger model than a gapped joint filled with glue.
One very important safety tip is that CA will bond skin instantly. Be as careful as possible to avoid any contact with the glue and your fingers, face, eyes, etc. Should you accidentally get some glue on your skin, have some CA debonder at the ready and seek assistance. Acrylate based nail polish remover can be used for this task as well.
Epoxy glue will be an essential part of your model airplane glue collection. For most everyday modeling jobs, five minute epoxy is ideal. Epoxy is mixed in two equal parts and it begins to cure immediately.
Epoxy bonds to a wide range of materials to include wood, metal and most foam. Epoxy is exceptionally strong but is heavy and essentially impossible to sand once cured, thus it should be reserved for your most demanding gluing tasks. Epoxy is well suited for mounting firewalls and landing gear.
Elmer’s glue (white or carpenter) was in common usage in the past. The drawback of Elmer’s glue is that it must dry overnight. Compared to the instant bonding characteristics of CA glue, evaporative model airplane glues are used infrequently today.
There are some specialty glues that are very useful. One good example is canopy glue. Canopy glue is available under several brand names.
An important aspect of canopy glue is that it bonds well to wood and plastic, is opaque white when out of the bottle, but dries completely clear. Thus, canopy glue is perfect for installing acetate windshields and canopies onto your model aircraft.
There are many types of glues that are used to construct model airplanes. In this day and age of ready to fly RC models, it is very useful to have these model airplane glues available, and more importantly, know when and how to apply them for either repairs or building tasks.
Author: Gordon McKay