Materials and Hardware used for RC Modelling Part 3 - Glues

Glues used for Model Building.
  • Glue is a mainstay in this hobby.
  • Glue, we use it for just about everything in our radio control hobby. 
  • There are a variety of adhesives available.
  • The big question for a newbie to the hobby is which glue is best for my application?
  • Each has a useful purpose as well as things it definitely should not be used for.
  • I will try to explain properties of common adhesives used in model-building and give guidance on selecting and using the correct adhesive.
  • If you know what each glue's properties are, then selecting the correct glue for your use is a simple task.
  • If you are a beginner, do not worry much about glues.
  • A good wood glue or CA and some epoxy will get your trainer built.
  • Use the right stuff to stick those parts together!
Type of glues - Mostly there are two types:
  1. Evaporation Types -Glue is solvent or water-based and dries by evaporation of the solvent.
     2. Chemical cure types.
  • These glues cure by chemical process.
  • They comes down to one or two-part glues.
  • Two-part glues must be mixed in some ratio before the glue can be used.
  • Two-part chemical-cure glues do not shrink significantly.
  • One-part types may or may not shrink.
  • Excess glue can be wiped up with solvent while wet or scraped off with a razor blade after it is cured.
  • Larger quantities can be mixed in a disposable container such as plastic cups, cans, etc.
  • Some glues may melt plastic,so check before mixing.
  • One-part glues that cure include Cyanoacrylates(CA) (brands such as Super Glue, Fevi Quick , Flex Quick) and silicone sealant.
  • Two-part glues include epoxies. (brands such as  Araldite, Bond Quick ,etc..)
Terms related to glues.
  • The terms  "dry" and "cure" mean the same thing about glues.
  • Strength - Normally stronger glues tend to be heavier.
  • Therefore, select a glue that is strong enough to do the job but do not go over-board.
  • Slow drying glues tend to be stronger than fast drying glues because they have more time to soak into the wood.
  • The important problem with fast-drying glues are that they tend to be brittle.
  • Materials it can bond - Most glues are intended for certain materials.
  • Using the wrong glue can cause a variety of problems including excess weight, difficult finishing and some times failing of glue joints.
  • Fuel-proof - If you are using IC engines select fuel proof glues for construction.
  • Easy sanding - Many times we have to sand a glue joint between two pieces of wood.
  • If the glue is significantly harder than the surrounding materials, the glue will not sand away at the same rate as the materials it is bonding.
  • This results in an unsightly ridge that will be seen under the final finish.
  • Pot-Life - How long the glue stays usable after it has been dispensed or mixed in an open container.
  • Working time - This is not the same as glue kept in a pot.
  • Glues that cure tend to heat up.  In the pot, they will cure faster than in a thin film.
  • So many of these glues can still be worked after being applied to a part even though the glue in the pot is too thick to use.
  • The time given for epoxies is the working time, not the curing time - For example, 5 minute epoxy has a 5 minute working time.  Cure time is usually 30-60 minutes depending on the brand and climate.
  • Cure time - How long a glue takes to fully harden.  The time given is for practical purposes, most glues that cure tend to continue the chemical curing process for long times.
  • Shelf-life - All glues have a shelf life.  This is how long it can sit on the shelf before it goes bad. So look for the date of manufacture before buying.
  • Set (Tack or Grab) - When the glue "grabs" but not when it is fully dried or cured.  For solvent and water based glues this is when the glue reaches a state where the parts are firmly held in place, but could be taken apart , possibly without damaging anything.
  • For adhesives that cure, it is the stage where the glue has cured to the point where the parts are firmly bonded in place, but has not fully hardened.
  • Surface Protection - Sometimes an adhesive is used to protect a surface.
  • This property can take precedence over bonding characteristics.
  • For example, if you want a smooth, long lasting surface to mount a servo using foam tape, then epoxy is a good choice.
  • The strength of epoxy is irrelevant in this case.  What is important is that exposed, cured epoxy withstands exposure to the environment better than many other adhesives while creating a non-porous surface that foam tape adheres to well.
  • Carpenter's glue is a bad choice because it shrinks as it dries so the surface won't be as flat and smooth as desired and it also breaks down if too exposed.  
1. Spray adhesives

  • A spray adhesive is a contact adhesive based in a solvent that is applied by spray.
  • When using spray adhesives, it is important that you apply in a well-ventilated room.
  • After spraying your project, allow the solvent to completely evaporate before mating for immediate bond. 
  • Once mated, you cannot re position your substrates.
  • Spray adhesives can be used with paper, foam board, fabrics, photo, and felt.
  • Specialty contact adhesives are also available in a can to roll or brush on for larger, more demanding projects that involve wood, metal, and plastic sheet laminates.
  • Application example: Spray adhesives are an excellent choice for adhering photos or fabrics to a foam board back.
1. Spray Adhesive: Claire Mist
    Do NOT Use With: Closed-Cell Foam, Use With: Open-Cell Foam
    This includes all densities, colors, and firmness values of: Poly Foam,  Super Soft Foam,   Dryfast Foam,  Rebond Foam,  Acoustic Foam, Speaker / Filter Foam, Polyurethane Anti-Static         Foam, Dunlop Latex Foam,  HD36 Foam: Regular and High Quality,  Lux Foam: Regular and         High Quality,  Charcoal Foam: Regular and Firm,  Memory Foam.
2. Spray Adhesive: 3M Super 77
    Do NOT Use With: Expanded Polystyrene Closed-Cell Foam (EPS)*
    Use With: Most Closed-Cell Foams AND All Open-Cell Foams**
    This includes all densities, colors, and firmness values of: Polyethylene Foam, Polyethylene Roll,       Cross-Linked Polyethylene (XLPE),  Neoprene, Gym Rubber
    *3M Super 77’s formulation can physically melt EPS foam varieties, damaging and/or destroying         the material.
  **3M Super 77 bonds more strongly with open-cell foam than Claire Mist but is costlier. Claire              Mist is the cost-effective  choice for all but the most demanding open-cell foam projects.
3. Spray Adhesive: Camie 373
    Do NOT Use With: Open-Cell Foam OR Most Closed-Cell Foams***
    Use With: Expanded Polystyrene Foam (EPS)
    1LB Expanded Polystyrene Foam (EPS)
    2LB Expanded Polystyrene Foam (EPS)
    3LB Expanded Polystyrene Foam (EPS)
***Camie 373 is specially designed for use with Expanded Polystyrene Foam (EPS) to prevent                 damage that other adhesives may cause.
      For foam you will need the odorless CA. that is fine with foam. The regural stuff will eat the               foam like acid..

2. GORILLA GLUE
  • As far as strength and (light) weight go, Gorilla Glue takes the cake. 
  • It dries white and sets in about 30 minutes. 
  • It foams up a little to fill gaps, something many modelers dislike because it tends to squeeze out of joints and onto clean surfaces. 
  • An easy fix is to cover the surface with clear tape right after gluing. 
  • This not only helps keep the foamed-up glue in, but it also hold the two parts together until the glue dries. 
3. FOAM-SAFE CA
  • Cyanoacrylate (CA) adhesives are among the most common used in modeling. 
  • They are fast-setting and hold a decent bond. 
  • For the ever-growing foam business within RC, new foam-safe CA glues have appeared in the last few years. 
  • They come in various viscosity like thin, medium and thick. 
  • Most commonly used is the thick, slow-curing CA. 
  • This is due to foam’s porous properties and the need to fill the gaps in it. 
  • Foam-Safe CA is worked onto one surface with a long tip and a toluene-based activator is applied to the other. 
  • When both surfaces are joined, there are only about 3 seconds until the glue sets. 
  • Since CA doesn’t hold the strongest of bonds, it is not the best choice for models that will endure high speeds or stress on the airframe. 
4. HOT GLUE

  • Hot Glue comes in solid “sticks” of various lengths and diameters and is melted with an electric gun that also squeezes it out of a nozzle tip.
  • Many modelers like hot-glue for building with foam.
  • It holds a strong bond and is easy to work with but it stays a bit flexible  which might be a good thing in a few applications, but not most.
  • Make sure the gun is set to low temperature and you won’t damage the foam.
  • With Hot-melt Glue you’ll get a strong, inexpensive bond in seconds. 
  • The melting and cooling of polymers provides the methods of delivery and adhesion for hot melt adhesives.
  • Hot glue is most commonly applied using a glue gun and comes in low (250°F) and high (380°F) melting options.
  •  Many varieties and performances are available depending on the polymer type. 
  • Hot glue can be used on porous and non-porous surfaces.
  • Because of its high viscosity, it can bond uneven surfaces together and is great at filling gaps. 
  • Hot glue is not typically used in high strength applications. And, it will not survive elevated temperatures near the application temperature.
  • However, it provides a very quick setting option for a variety of crafts and substrates.
  • It’s a great all-purpose craft glue for quick set up and execution, but it’s not for use by children.
  • Hot tip: With hot glue, you can trace patterns to form bead designs on surfaces for texture and paint over it for a 3D surface effect.
  • Hot glue is often used to add flower or ribbon embellishment on wreaths, headbands and picture frames where stiffness and strength is not such a concern.
5. Glue Sticks

  • Glue sticks are great for kids!
    They are a low bonding adhesive, but do provide a permanent bond on various types of paper to include cardboard, foam board, and poster board.  Glue dries clear. 
  • Application examples: sealing envelopes, applying labels, paper crafting, art projects, scrap booking
6. EPOXY
  • Epoxy is a popular, strong and inexpensive adhesive but it adds a bit of weight to models.
  • We love, we hate it - epoxy.
  • It smells, it's messy, it's a pain, but it can't be denied it's place in the pantheon of ultimate glue solutions. 
  • Epoxy has it's place in the world of RC modeling.  
  • There are a large selection of Epoxies to choose from. 
  • Most users like 5-minute Epoxy since it sets quickly. 
  • It comes in two chemicals in gel form. 
  • You mix the two by way of a stick or paddle and apply it to the surfaces with such tool. 
  •  You can use epoxy on foam but it's heavy and will yellow after time. 
  • For more strength you can try 30 minute epoxy.
  • Bonds - Metal,  Wood,  Concrete,  Glass,  Ceramics,  Just about anything.
  • Epoxies are generally two part systems designed for high performance bonding.  
  • Epoxies have excellent gap filling properties due to their high cohesive strength.
  • While epoxies can be formulated to suit many applications, they are generally very hard, durable adhesives that bond to many substrates successfully in more extreme environments.
  • Epoxy adhesives can exhibit a range of flexibility and clarity as well as cure speed.
7. OTHER GLUES
  • Lastly, other popular glues for building RC planes with foam. 
  • The list includes Ultimate RC Foam Glue, Fab-Tack (very similar to URCFG), some Elmer’s glues, silicone caulking (very heavy!), UHU Por, UHU Creativ and an endless list of adhesives that dominate the modeling world.  
  • If you aren’t happy with this, try reading through the RC Groups.com and RC Universe.com forums for other ideas and stories.
8. CA-Super Glue (also known as cyanoacrylate adhesives)

  • Before you got into the hobby you called this super glue. 
  • The great part about CA is that is wicks into the fibers of balsa making a strong joint. 
  • It is also light. While it dries super fast it can be brittle. There is no give to CA. 
  • Bonds - Wood,  Fiberglass,  Aluminum,  China,  Cloth,  Metal,   Most Plastics,  Pottery,  Rubber.
  • Cyanoacrylate adhesives bond very quickly and to a range of substrates. 
  • They form a very strong bond and dry clear.  
  • The surfaces to be mated must fit together well to achieve good bonding.  
  • You can buy super glue in a variety of viscosity which enable in gap filling performance. 
  • However, super glues can be finicky with respect to surface contact and coverage- too much or too little can affect the bond.
  • In general, super glues are not good for foamed plastic, unless specified on the bottle.
  • Cyanoacrylates work best in tensile applications that have low impact strength requirements.
  • In their uncured state, you can use an acetone solvent wipe for cleanup.
  • However, once cured, solvents can no longer dissolve the adhesive.
  • Cyanoacrylates work particularly well for balsa wood projects.  
  • Carpenters often use a two part cyanoacrylate to quickly bond mitered wood trim.
  • Cyanoacrylates can set in seconds to minutes, depending on formulation. 
  • It dries clear and is waterproof.
  • Cyanoacrylates are good for projects involving: wood, metal, ceramic, leather, glass, and some plastic where bond line is very tight.
9. Foam-Tac

  • Foam based planes are everywhere now. 
  • From home made foam planes to highly detailed planes, foam is used for a lot of what we fly.
  • In the early days of foam a lot of us figured if CA was good for balsa then it would be good for foam. 
  • Then we found out that CA melted foam. 
  • The good news now is there are more than a few great glues out there for the foamy pilot. 
  • Bonds - Depron, EPP, EPO, Styrofoam, Insulating Foam, Balsa, Carbon Fiber
10. Canopy Glue

  • You have worked long and hard on your plane and now your are down the cockpit. 
  • You use CA and then you realize that you just fogged the clear plastic with the fumes of the CA!. 
  • There is a solution. 
  • Horizon sells a glue called RC56 that will keep you from doing this. 
  • You can also use this glue on fiberglass and MonoKote.
  • Bonds - Wood, Fiberglass, Paint, MonoKote.
11. Weldbond
  • Some nice things about Weldbond is that it is non-toxic and fume free. You can use it on smooth and porous surfaces. It also doesn't become brittle. It is foam safe. 
  • Bonds - Depron,  Poly-Styrene, Most foam, Plastics
12. White Craft Glue

  • This is the most common craft glue for porous lightweight materials such as paper, cardboard, cloth, and kids’ crafts. 
  • Water is the carrier; this means easy clean up and low toxicity.
  •  Keep in mind that the glue must dry before strength is significant and the project often requires clamping to hold it in place until the glue is completely set and dry.
  • This also means that white craft glue should not be used in applications that require water resistance.
  • White craft glue dries clear and is somewhat flexible. Get creative and add fillers, like fine glitter, pigment, or water-based food coloring for decorative effects. 1 hour set time, with final cure in 24 hours.
13. Yellow Wood Glue

  • Yellow wood glue is also water based and is made of the same vinyl acetate polymers as craft glue. 
  • It is designed to work with wood and is immediately tacky for better hold in the uncured state. 
  • It is also generally more rigid, hence it is easier to sand. 
  • Some wood glue can also be white and dry clear.
  • Make sure to read the labels.  Again, you can add sawdust or another powdered filler for special effects. 
  • Wood glues set in less than 1 hr.   That said, it could take as long as 24 hours to reach full strength. 
  • Three types of wood adhesives are available: 
  • Type-I exhibits some waterproof properties.
  • Type-II will perform better in exterior conditions.
  • These adhesives generally have a longer open time and can bond at colder temperatures. 
  • Both types I and II can be used for exterior applications, such as outdoor furniture and trim.
  • Type-III is not water resistant and is designed for interior use only. Type-III is good for interior woodwork and trim projects.
  • Note: True water resistance for immersion in water requires a marine glue.
14. Pressure sensitive adhesives (PSA)

 
  • PSAs are available in sheets and dots and can be used in a multitude of craft projects to include substrates such as lightweight paper, plastic, metal and glass.
15. Fabric adhesives

  • Fabric adhesives can be liquid white glues like polyvinyl acetate (PVA) types.
  • A variety of products cover lightweight to heavyweight fabric bonding, so it is important to get the correct product to match the hand or drape of your project.  
  • Some versions are safe for washing and dry cleaning, but it’s important to read the glue’s label first.
  • There is an expanded selection of non woven tapes and fusing adhesives in rolled good form, which range from highly flexible to stiff for fabric and leather projects and garment construction.
  • These can be found in sewing and fabric stores and can bond permanently without bleed through for a very durable craft.
  • Fabric adhesives can be used to fix a hem that is falling apart and for DIY projects like making headbands or constructing fabric/foam laminated computer sleeves.
16. Polyurethane

  • Polyurethane adhesives bond a variety of surfaces. They bond to textile fibers, metals, plastics, glass, sand, ceramics, rubber, and wood.
  • Polyurethane is a multipurpose glue that comes in one part and two part options.
  • Polyurethanes can work well on a wide variety of wood species, particularly on woods with high moisture content or on oily woods, where other glues are not as successful.
  • Clamping is required until strength is built; a few hours.
  • Full strength is achieved in six to eight hours for a very strong and tough bond.
  • Before completely cured, polyurethane adhesives can be removed using solvents such as mineral spirits or acetone.
  • Dried glue can be sanded.   
CRAFT GLUE TIPS
  • Not all glues are created equal.  There are many variations within each category and from one manufacturer to another. Read the labels for information on toxicity, ventilation, recommended handling and use, as well as durability in a variety of environments. 
  •  Apply adhesive evenly and remove excess quickly.  Immediately clean and cap the adhesive container to maintain shelf life and performance.
  • For optimum bond strength, it is imperative that the surfaces are residue and dust free. If possible, clean surfaces prior to bonding with a lint-free rag dipped in isopropanol.  Let them dry thoroughly before applying adhesive.
  • For crafts and repair projects requiring some durability and strength, you can often aid adhesion by roughening the surfaces with fine grit sandpaper to provide “teeth” for adhesives to interlock.  If you cannot abrade the surface, try wiping with isopropanol or acetone before applying adhesive.  This is particularly helpful for smooth, glossy surfaces that can be harder to bond. 
  •  Experiment with the glue on scrap pieces of your project.  Check for appearance, adhesion and and resulting bond strength.
ADHESIVE SELECTION - Adhesive selection involves the following considerations:
  • Substrates:  What are you trying to bond?  Are the surfaces the same or dissimilar, porous or smooth?  Are you covering a large area? Do you have heat or solvent sensitive surfaces?
  • Application restrictions: How do you intend to apply the adhesive- examples: spray, roll, heat gun, cartridge, squeeze bottle?  
  • Use Requirements: How does the bonded piece get used? How much strength is required? For example, bonding wood requires much more strength than decorative paper crafts do. What kind of environments might it see?  Will it experience temperature extremes or water/steam?
ADHESIVES & SEALANTS OVERVIEW
  • The world around us, and hence our lifestyle and the way we work, are changing at breakneck pace.
  • Who would have thought just 20 years ago that computers and mobile phones would now be a part of everyday life?
  • Who could have imagined a 3-litre car engine? And who could have dreamed of detachable adhesive strips which do not tear away the wallpaper when a poster is removed?
  • The constantly increasing requirements being put on new consumer products is the driving force for technological progress: Nowadays, each new product that is developed must – as in the past – not only be better and more favorably priced than its predecessor, but must also meet the requirement of sustainability.
  • The consideration of environmental aspects means that the development of new products is becoming ever more demanding and that manufacturers must take into consideration more complex requirements for their new products. 
  • The increasing requirements put on products has since time immemorial been the key driving force for the development of advanced and new materials.
  • In addition to the classic metals, these materials include special alloys, plastics and also ceramics and glass.
  • So-called composite materials, produced by combining different materials, have played a major role in this development.
  • Reinforced concrete is a well known composite material that has been around a long time. 
  • Newer composite materials are glass-fiber reinforced plastics and carbon fiber reinforced plastics which are used, for example, for constructing speed boats and yachts and increasingly also for car, rail vehicle and aircraft manufacture.
  • Another good example of the development and use of new materials is the wheel and tires.
Conclusion
  • These are just a few glues.
  • There are multiple types of CA, epoxy and everything else.
  • There are as many opinions on glues as there are glues to choose from! 
  • Experiment, search RC Groups and talk to your RC friends about what they use.