Practical Adhesives for RC Modeling

Practical adhesives for the RC modeler including their pros and cons

There are several different adhesives in use for the modern modeler. These all have their uses, and more importantly they all have different properties that make them either right or wrong for several different applications.  Please understand that this is a very general overview of this subject, and I may not be hitting on every detail of every adhesive.

All pictures “borrowed” from the manufacturer’s website.

Let’s start with the adhesive that is perhaps mentioned more frequently than any other here on Flite Test…

Ethylene-Vinyl Acetate or Hot Glue.

Like anything else, there are many different qualities of hot glue available, and just as many “applicators” or Hot Glue Guns. It’s important to obtain quality product in order to achieve quality results, so do your homework when selecting both. 

Hot glue is applied by laying a bead of glue from the nozzle of a glue gun that is up to temperature (can be up to 400f, so handle with care) then bonding the two surfaces before the glue has a chance to cool and solidify.  It’s a fairly straightforward process, and with a little practice it can be mastered.

Although Hot Glue has the ability to bond almost any two substances together, it is far more successful with a porous, natural material such as paper or wood.  Some items such as glass and plastic can see a successful bond, but may be prone to failure since hot glue uses a mechanical bond to adhere the surfaces.  Flat non-porous surfaces make it difficult for hot glue to get a good foot hold, and can eventually peel free.

Hot Glue is a reversible adhesive.  It can be reheated to soften, or use solvents such as Denatured Alcohol to relax the bond.  This, however, can only be done with certain items that are not heat sensitive, or that won’t be dissolved or otherwise harmed by the application of Alcohol.

Hot Glue is also a very good gap filler in that it can be forced into voids, then trimmed flush. It can’t however be sanded which limits its use in this capacity.

Pros – It is a fast and easy adhesive.  There are no precautions that need to be taken other than understanding that if you touch the glue or the applicator while they are hot you could get a nasty (although not life threatening) burn, and it can be messy if not attended.  You also need to take care to unplug/turn off the Glue Gun when not in use.  It is inexpensive, extremely versatile, flexible and water resistant.

Cons – Hot glue may loosen up in a hot vehicle or on very warm days causing surfaces to let loose or shift.  As a result of this it isn’t a good choice as a load bearing glue, or for use where temperatures can reach extremes in either direction.  Application on large surfaces can be difficult due to the rapid rate at which this glue cures.  It needs to be applied and the parts pressed together quickly to avoid issues.

Cyanoacrylate (CA glue or “Super Glue”)

Probably the most go-to adhesive that is available in the consumer market.  There are several different types of CA glue, each with a different purpose, the most widely used among modelers is the “instant” variety.  Used for everything from medical to forensics this adhesive truly is versatile. 

As an adhesive CA is fast.  The instant variety bonds, well, instantly while slower curing formulas can extend working time and be cured at will using an accelerator.  This accelerator generally shouldn’t be used with the instant cure formulas as it causes the glue to foam and become more brittle, weakening the joint.  Most commonly used by modelers for wood and plastic, it can also be used with varying success on almost any other non-porous materials like ceramic, glass and metal.

CA glue is a very effective gap filler. Thick formulas can be mixed with various substances such as baking soda or sawdust to fill voids such as small drill holes and gouges, then sanded flat.

Pros – It is an instant cure.  Generally there is no clamping time needed since the bond in most cases is instant.  Simply hold or pin the two surfaces together, apply CA, wait a moment and it’s done. It comes in a variety of thickness and cure times further extending its versatility.  It has an accelerator available making it easy to pinpoint when the adhesive cures.  It is rather inexpensive and goes a long way.  A very small bit will adhere two surfaces together, so items with little surface area can be securely bonded

Cons – There is some medium that can’t be bonded with CA.  Certain foams and plastics will dissolve when in contact with CA, so do your homework, or test it in an inconspicuous place first.  CA can generate a lot of heat when it cures, sometimes enough to spontaneously combust.  It also generates very unpleasant fumes, so use in a well ventilated area.  Bonds, especially those with minimal surface area, can be brittle and easily break.  CA will bond virtually everything.  This includes fingers, eyelids and lips, as well as anything it may come into contact with when it leaks in your toolbox or on your bench.  CA is, for the most part, irreversible.  There are solvents on the market, but they are hit and miss with their effectiveness.

Aliphatic Resin (Yellow glue or Carpenter’s glue)

This stuff is the yellow glue that was always on your Grandfather’s workbench.  Most commonly adorning the “Elmer’s Titebond” label today, this reasonably viscous glue is used almost exclusively with wood.  With almost every other glues out there, there are multiple formulas to address multiple uses.

Aliphatic resin is a water based glue that has a pretty long cure time and easily cleans up with water.  Generally surfaces need to be clean, flat and clamped for a minimum of 2 hours (longer in many cases) and left to cure for 24 hours.  Aliphatic Resin will only work with porous surfaces, so plastics, glass and the like should look elsewhere for their adhesive needs, it really is a tool for working with wood only. 

When using Carpenter’s glue, you need to apply generously and push the two surfaces together to create a “squeeze out”.  The excess is cleaned up, and the two surfaces are firmly clamped together for several hours.  Although this glue is viscous, it makes for poor and unsightly gap filler, so that job is better left to another substance.  The glue joints tend to be very strong, but not very flexible.  True this glue does have a little give in it when cured, it is only a very little give, and the glue buy itself (meaning cured, but not bonding two surfaces) is not that strong and rather brittle.

Pros – Non-toxic, and food safe when cured.  Creates no odor, and normally poses no risk of skin irritation.  Glue joints are reversible, but only with steam so sometimes that is impractical.  On items with a reasonable amount of surface area, when the glue is properly used, the glue joint is in most cases stronger than the glue itself.  Aliphatic resin can be sanded with the wood.

Cons- Not waterproof.  Poor gap filling qualities.  Must be clamped for long periods of time and needs 24 hours to fully cure.  Not very effective on areas of minimal surface area.  Does not accept stain or paint.

Gorilla Glue (original)

Gorilla glue is a fairly new adhesive (within the last 15 years give or take) It is a polyurethane based glue that will foam and expand to 3 times its size (according to the website) to fill every void between the two substances being fastened together.  As you can imagine, this makes for a great bond between almost anything.  I personally have glued a jagged rock to a piece of plate glass with this glue with surprising success.

Although this glue is effective, it is messy and fairly toxic. Best use gloves with this stuff. Uncured glue can be removed with acetone, but once it dries you have to cut, scrape or sand it off which can make cleanup very difficult.  In the unlikely event that this glue (in liquid form) makes it into your stomach or throat, it will cure very quickly (as moisture is a catalyst) and could result in blocking digestive passages and airways.  It really can be quite nasty.  Don’t let this scare you though, it just means that you shouldn’t eat it and keep it away from kids and pets.

Gorilla glue requires clamping since the foaming action will have a tendency to push the two surfaces apart.  Clamping time is about 4 hours, full cure in 24.  Once fully cured Gorilla glue can be sanded, stained and painted.

Pros – Excellent gap filler.  Dries flexible.  Can permanently bond almost anything to almost anything else.  Fairly light when cured.  Can be sanded, stained and painted.

Cons – Pretty toxic if ingested.  Needs to be clamped for a long period of time with significant pressure.  Dries to an unsightly yellow color.  Must be cleaned as it cures, which means you need to babysit the part for about 4 hours since this product foams out to many times its original size.  Gorilla Glue is a permanent adhesive, and cannot be reversed.

Gorilla Glue (White)

This glues is fantastic when it comes to working with foam such as EPP, Depron, Styrofoam and the like.  Much like its older brother Original Gorilla Glue, this substance expands to many times its liquid form when curing and can bond many different substances together, but it dries white and is very flexible when cured.

White Gorilla glue shares almost all the attributes of its yellow counterpart, but it cures much more quickly, and when filling gaps it cures and acts just like foam which makes it a lock for filling voids and for operations like permanently installing carbon fiber spars.

Pros – In addition to the pros from Gorilla Glue (original) it cures quickly and is very flexible when fully cured.

Cons – See list from Gorilla Glue (original) with the exception that this glue cures white instead of yellow.

Two Part Epoxy

Like most of the others, Epoxy has many different manufacturers and formulas.  Generally this comes in a two part formula, several being a 1:1 ratio mix and sold in a handy applicator.  Epoxy is most often used to bond multiple items or as a gap filler.  As it cures, it forms a solid plastic-like substances that freezes whatever it is touching in place.

Epoxy cure times can vary from 5 minutes to several hours and generally speaking the longer the cure time the stronger the material.  Epoxy must be mixed thoroughly according to the instructions, and is then applied to, or poured over the items to be bonded or filled.

The materials need to be held in place while epoxy cures, but not necessarily clamped with force.  Unlike aliphatic resin and Gorilla Glue, if clamped with enough force epoxy can be completely removed from between two items, giving very little adhesion and a poor bond.

The fact that epoxy will pool and self-level makes it an excellent gap filler for solid materials such as glue and plastic, but it is generally a poor choice for softer materials such as foam or balsa.

Epoxy is difficult to clean up, produces unpleasant fumes and can be a skin irritant and very harmful if ingested in its liquid state.  Once cured, it is an irreversible bond.  The curing process generates quite a bit of heat, and it’s not unheard of for this to cause issues with the items being bonded up to and including, in rare cases, combustion.

Pros – Easy to use, can dry in a variety of colors, can be sanded, excellent gap filler

Cons – Can be hazardous, produces fumes and heat, messy cleanup, not flexible and irreversible.

The above is a basic list of the more common adhesives used for our trade.  It is by no means all inclusive, since Adhesive technology is ever changing.  There are older tried and true adhesives that have not been mentioned, mainly because there are more modern replacements, and others that haven’t been invented yet.  This in no way is meant to discount the usefulness of any other adhesive available today, it really is up to you to find the best suited adhesive for your particular project.  I just hope that this will give you some insight on the somewhat more popular ones available on the market now.