December 18

Adhesives for RC Planes

modelling glues

There is a wide variety of adhesives types available for repairing and building RC planes.  They all have a useful purpose but it is important to know what they should not be used for.

Inevitably you will have to use some kind of glue or adhesive in the future, either to build your own model or to effect a repair following damage to any of your RC planes. You will need to be prepared for this eventuality and it will be helpful to understand what types of glues are best for the particular requirement you have.

Glue Properties

There are certain things you need to understand about the properties of any glue that you decide to use.  This understanding will help you select the correct glue for a particular task

Glue Types

Most glues used to build model airplanes fall into one of two types:

  • Evaporation Types

These glues are solvent or water-based and dry and set by evaporation of the solvent.

  • Chemical Cure Types

These glues involve a chemical process that causes them to cure and set.

Chemical types can be further broken down into One or Two-Part glues.

Two-Part glues rely on the mixing of the two parts in a specific ratio before the glue can be used.  These glues do not shrink significantly and have good filling properties. Two-part glues include Epoxies.

Multi-Part adhesives should be mixed on a non-porous surface or in a similar container. Porous surfaces such as cardboard and untreated wood will prevent the glue from being mixed in the proper proportions as some of the components will soaking into the surface.  This could result in the glue not curing properly and compromise its final strength.

One-Part types may or may not shrink. Such glues that cure wnen exposed to the atmosphere include Cyanoacrylates (AKA Super-Glue or CA) and Silicone Sealant.

Excess glue of both types can be wiped up with an appropriate solvent while wet or scraped off with a blade after it is cured.

The expressions “Dry” and “Cure” will be used to describe the process of setting and hardening. For all practical purposes these mean the same thing.

Properties

Strength

Generally speaking, the stronger the glue, the heavier they are.  It is important to select a glue that is strong enough to do the job without adding excessive weight.  There is no good reason to use epoxy when gluing wing sheets together but good reasons not to.

Slow drying glues tend to create a stronger joint than fast drying glues because they have more time to soak into the wood.  Fast-drying glues tend to create a more brittle joint.

Matching Adhesives to Materials

Most glues are intended for use with certain materials.  The use of a wrong glue for a particular job can cause problems that include excess weight, difficult finishing and joint failure.

Fuel-Proofing

Fuel tanks can and do split open as a result poor assembly, defective moulding, bad design or as a result of a crash.  It is essential that the fuel tank compartment be coated with something fuel-proof such as epoxy resin or polyurethane (paint).  On a Glow/Nitro powered model all firewall joints should also be glued with a fuel-proof glue.

This precaution is not so necessary in electric powered models as the possibility of impregnating the structure with fuel is most unlikely.

Ease of Sanding

Often you will need to sand across a joint between two pieces of wood.  If the glue used is significantly harder than the surrounding materials, the glue will not sand away at the same rate as the materials it is bonding. This can result in an unsightly ridge that will be visible through the final finish or covering.

Pot-Life

This expression refers to the useable life of the glue after it has been dispensed or mixed in an open container.

Working Time

It is important to understand that glues that cure tend to heat up.  In the pot, they will cure faster than in a thin film.  This means that many of these glues can still be worked after being applied to a part even though the glue in the pot has become too thick to use.

The time given on epoxy packaging is the working time, not the curing time.  So, a 15 minute epoxy has a 15 minute working time.  Cure time is usually 30-60 minutes depending on the brand and climatic conditions.

Cure Time

This describes how long a glue takes to fully harden for practical purposes.  Most glues that cure tend to continue the chemical curing process for months.

Shelf-Life

This is the length of time a glue or adhesive can be stored on the shelf before it goes bad. Some glues last better than others so do not buy any more glue than you can reasonably use within about one year after you purchase it even though manufacturers make claims that their glues have shelf lives of years.  Shelf life is strongly affected by the climate (heat, humidity, UV light, etc.).

Surface Protection

Sometimes an adhesive is used to protect a surface. An epoxy resin coating on wood will provide a smooth, long lasting surface to mount a servo using foam tape.

Its strength is irrelevant in this instance. Exposed, cured epoxy withstands exposure to the environment better than most other adhesives while creating a non-porous surface that foam tape adheres to well.

 

Aliphatic Resin (Also called Carpenters Glue)

Aliphatic resins are most useful, inexpensive, light and strong. Super Aliphatic Resin It is the primary adhesive I use to build Balsa and Plywood based flying model aircraft.  Its longer working time lets me make adjustments to ensure everything is as it should be before the glue sets hard.

This glue is water-based so it allows me to create neat joints. The excess glue is easily removed using a damp sponge or paper towel before it starts to set.

Features

  • Not Fuel Proof – They are fuel resistant to a point but will not withstand continuous exposure to raw fuel.
  • Clean-up – Use water while wet, Acetone when dry.
  • Use for – General construction.
  • Do not use for –

Non-porous surfaces,

High-stress areas (firewalls, landing gears, etc.),

Edge joining sheets of balsa — it does not sand as easily as soft balsa and will leave a nasty ridge when you try to sand the sheet flat.

Laminating broad areas — it will cause severe warping.

 

Cellulose-Based Glue (Balsa Cement)

This glue comes in a tube and is used for balsa wood models. Balsa Cement It is fast-drying and lightweight.  The solvent in this glue has a strong odour and should only be used in a well ventilated area.

Balsa cement is ideal for joining sheet wood together.  It sands very easily and makes a strong edge to edge joint.

Features 

  • Fuel proof – They are fuel proof to low nitro fuels.
  • Clean-up – Dope thinner or acetone even after it has dried.
  • Use for –

Stick and tissue model.

Edge joining sheet wood because it is very easy to sand.

Gluing some types of plastic parts to wood models.

Sealing dissimilar grains to make sanding easier.

  • Do not use for –

Non-porous surfaces with the exception of some plastics that it are capable of melting in order to create a bond.

High-stress areas (firewalls, landing gear, etc.).

 

Contact Adhesive

Contact adhesive is heavy and has very limited uses in model-building. contact adhesive The one benefit is that it doesn’t warp sheeting badly enough to cause problems.

It is applied to both surfaces and allowed to dry to the touch. The manufacturer will advise the best time for this to occur either on the container usage instructions or leaflet. The two parts are brought into contact with each other and they are instantly and permanently stuck together.  You do not get second chances to align things when using contact cement.

Features 

  • Fuel proof – Unknown.
  • Clean-up – Lacquer thinner, mineral spirits or a dedicated thinner.
  • Use for –

Laminating broad contact areas (fuselage doublers, creating your own balsa ply sheets, etc.).  If you use contact cement to glue sheeting to a foam wing core, be sure the cement is foam-safe.  Most contact cements you see in hardware stores will melt right through the foam and ruin the core.

  • Do not use for –

Anything else.

Cyanoacrylate Adhesive(CA)

Also called Super Glue

CA glue will instantly bond almost anything to anything else and indeed it is very versatile. CA Adhesive The only substances that resist it seem to be some soft plastics.

It is very good for bonding hard plastics, resin and metals to each other. It is not easy to use and should perhaps be avoided by novices and children. The thin formulas cure in one or two seconds and often seem to stick fingers to the components to be glued much better than it sticks the parts together.

Although cyano will stick most things together, the quality of the surface is important.  Any dust or grease on the surface will substantially reduce the strength of the bond.  Roughed surfaces stick better than smooth ones, so a light sanding of the surfaces that are to be bonded is worthwhile.

Excess should be immediately wiped off with a paper towel.  Any residue should be left to harden and then scraped off with a sharp knife.  If fingers, or other human tissue is accidentally bonded, it should be carefully separated with superglue debonder If you decide to use Cyano always have a debonder available for such incidents.

Once open, CA deteriorates quickly and it very easily blocks the nozzle of the bottle.  To reduce this problem, always wipe the end of the nozzle, gently tap the bottle on a hard surface to encourage any glue on the inside the nozzle to go back down and put the top back on straight away.

If you are not going to use a bottle of superglue for some time, the shelf life can be extended by putting it in the fridge.

Features

  • Fuel proof – No. Nitro methane dissolves cyanoacrylates.
  • Clean-up – Acetone or nitro-methane.  Some companies make debonders that are a mix of these items.
  • Use for –

Hardening threads cut into wood.

Gluing difficult to clamp items when you do not want to hold the part for the two hours another glue would take to dry.

Use for some types of dissimilar joins such as carbon fibre to wood.

  • Do not use for –

High-stress areas.

Areas exposed to raw fuel.

Clear plastic parts.  CA can fog the plastic.

Foam.  Standard CA dissolves foam.

An accelerator is made for use with cyanoacrylates.  It sets CA glues instantly but tends to make the joint more brittle.

 

Epoxy Glue

Epoxy resins are strong but add considerable weight to the structure.  Epoxy glueThey are good for bonding high-stress areas as well as different materials that other adhesive will not bond together.  Additionally, epoxy can be used for laying up fibreglass cloth and making fibreglass parts.

There are basically two kinds of epoxy resin.  One is used as an adhesive whilst the other type is used for laminating and has a thinner consistency.

I advise using slow-drying epoxy (30-minute to 4-hour working time) whenever epoxy is called for.

5-minute epoxy should be used in special circumstances only.  It is heavier, does not cure well and gets brittle with age. Generally, epoxy should only be used on load-bearing components. It is probably important enough to get it repaired right correctly in your workshop and not at the field.

The only “special circumstance” I would use 5-minute epoxy for is to create a smooth, non-porous surface for servo tape. Allow the epoxy to cure fully (at least over night) and then give it a wipe with alcohol to remove any residue before applying the servo tape.

  • Fuel proof –Yes.
  • Clean-up – Lacquer thinner, acetone or alcohol before cured.  After cure, a heat gun will soften it so that it can be scraped off.  Soaking in a strong solvent will break it down eventually but could well ruin the component it is attached to..
  • Use for –

High-stress areas.

Applying fibreglass cloth.

Fuel proofing firewalls and fuel tank compartments.

Bonding fibreglass and carbon fibre.

Mix with micro balloons (microscopic glass beads) to make a putty that can be formed into fillets and sanded easily.

Bonding dissimilar items such as metal to wood.

  • Do not use for –

General construction.  It is heavy, stronger than necessary and difficult to sand.

 

Hot Glue

Hot glue is very heavy.  I would never use it on any part of a wood built HotGlue & Gunmodel other than to perhaps fix components within the structure where there is no load bearing implication. Once set it has good vibration absorption properties.

  • Fuel proof – Unknown.
  • Clean-up – Contact Manufacturer for advice.
  • Use for

Fixing RC components and other accessories inside the model

Building foam models used sparingly.

  • Do not use for

Model Building using traditional materials.

 

Silicone Adhesive

Flexible, relatively strong and fuel proof.  It can be bought in small silicone adhesivetubes large enough to complete smaller jobs. The types available from DIY stores in larger tubes will go off and set in the tube long before it gets used up.  There is a high-temperature variety that can be used to seal mufflers and other engine parts (with care).

  • Fuel proof – Yes.
  • Clean-up – A special silicone sealer remover can be purchased from hardware stores
  • Use for

Sealing holes that you may need to access later.  For example, if you do not want exhaust residue to climb up the landing gear leg and go into the wing, you can seal the landing gear area with silicone.

Attaching landing gear fairings so they flex instead of break when the landing gear flexes.

Sealing the seating between wing and fuselage sides.

Attaching servo trays inside the fuselage.  I have never done this, but have been told it works well.

  • Do not use for

General construction.

Load-bearing members.

 

White Glue

White glue is very economical and is strong enough for many modelling tasks. White Glues It looks very much like PVA glue, being white and water-based but it is more viscous.  It has limited use for most modelling applications, but is very good at bonding wood,

  • Fuel proof – No.
  • Clean-up – Water.
  • Use for –

Small wood or paper models.

  • Do not use for –

Plastic

Metal

High stress areas

 

Glues For Building RC Planes Using Foam Products

Electric RC planes and foam building material has revolutionized the way park-flyers are built. We are still exploring the hundreds of bonding materials to find those that do not damage our foam, have a strong hold and weigh as little as possible.

Here are some of the best glues to use on foam like Depron, EPP, EPS, EPO, paper-faced Foam Board, etc.

GORILLA GLUE

As far as strength and weight considerations go, Gorilla Glue is a great choice.Gorilla glue It dries white and sets in about 30 minutes.

It foams up a little to fill gaps, something you need to watch as it tends to squeeze out of joints and onto clean surfaces. Cover the surface with clear tape immediately after gluing. This not only helps keep the foamed-up glue in, but it also hold the two parts together until the glue dries.

To help speed-up the setting process, wet both surfaces to be glued right before applying Gorilla Glue.

FOAM-SAFE CYANOACRYLATE (CA)

For the ever-growing foam business within RC, new foam-safe CA glues Foam Safe CAhave appeared in the last few years.

They come in various viscosities 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.

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.

HOT GLUE

Hot Glue comes in solid “sticks” of various lengths and diameters and is melted with anHotGlue & Gun electric gun that also squeezes it out of a nozzle tip.

Many modellers like hot-glue for building with foam. It holds a strong bond and is easy to work with but it stays a bit flexible, a good thing in a some applications.

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.

EPOXYEpoxy glue

Epoxy is a popular, strong and inexpensive adhesive but it adds a bit of weight to models.

There are a large selection of Epoxies to choose from. It is sold as two chemicals in separate tubes or bottles in gel form. You mix the two by way of a stick or paddle and apply it to the surfaces with this tool.

 

Summary

The variety and range of glues and adhesives available from model suppliers, DIY and hardware stores is vast. Building or repairing RC Planes requires just a few specialised glues so you don’t need to buy lots of different ones.

My advice would be to invest in the following initially:-

Two part Epoxy

Super Aliphatic Resin

Medium Viscosity Cyano

These three will enable you to carry out most of the gluing jobs you will encounter unless you are using a foam material. In this case I would suggest you buy:-

Gorilla glue

Foam safe cyano

Epoxy resin

As and when you come across a job requiring something different, just refer to the articles above to decide which is the best option for your needs.

There is one specific area I haven’t discussed because it is such a specific application and that is gluing clear plastic components such as canopies.

Sticking clear plastic parts presents problems. The fumes given off by polystyrene cements and even cyano glues can make the clear parts become foggy.  It is very difficult to use epoxy resin glues on clear parts without smearing the glue on the parts.

A number of modelling suppliers have produced their own special glues specificallyCanopy Glue designed for clear plastic parts and these are generally called ‘Canopy’ Glues.  They tend to be of low viscosity so it is easier to apply them in small amounts using a fine brush

Not only do they not affect the clear parts but they dry completely clear so any excess is almost invisible The bond is not as strong as some of the glues in the previous sections, but it is normally quite adequate.

If you have any questions please feel free to contact me through the comment facility at the bottom here. Also if you have enjoyed this post please feel free to share it on any of your social media sites. You may also enjoy my main site www.rookiercflyer.com especially if you are just getting started in RC planes.

Till the next time, all the best.

Colin

 

 

 



Copyright © 2014. All rights reserved.

Posted December 18, 2015 by Colin Bedson in category "Modelling Skills

9 COMMENTS :

  1. By Boss Body UK on

    i have always been a fan of using two part epoxy products for those heart breaking moment s you snap something on an RC plane. i recently began to use gorilla glue due to its clear drying. which is your favourite products to use? i find gorilla glue can go a little bit brittle over time so i try my best to stick to two part if i am at home. but gorilla is my go to glue for quick needed fixes.

    Reply
    1. By Colin on

      Hi and thanks for your question.

      For general wood to wood (especially Balsa & ply) I favour White Aliphatic water based Resin but for ply to ply or stronger joints I use two part epoxy resins, usually 30 minutes setting types. I find that these allow better penetration and ‘wetting’ of the wood fibres with the longer setting time resulting in a much stronger joint. It also helps where adjustment of the positioning is required before they start to set.

      I only use Gorilla Glue where some filling of the joint is needed. Good preparation of the joints should make this unnecessary but occasionally it can help.

      Colin

      Reply
  2. By Carlos McCauley on

    I have a rocket that is encased in two foam shells about 1/2″ thick. They are held together by silicone adhesive which is rather strong. The motor mount was damaged when I extracted the motor after it had absorbed some water after being lost for a number of days. That was in January, so, I stopped at that point, not knowing what to do next. My hobby knife is inadequate; solvents may dissolve the foam; I was thinking,, a hot knife (wire with a current running through it) might work to cut through the foam, but what can I do about the adhesive on the foam and cardboard surfaces? Can I cut through or is it better to go around. I plan to discard the cardboard tube and replace it. I suppose I can replace the foam too if I have to.

    Reply
    1. By Colin Bedson (Post author) on

      Hi Carlos,

      Thanks for taking the time to contact me regarding your problem.

      This is a tricky one not having visual access to your rocket. I think your suggestion of using a ‘hot wire’ cutter is probably the best option. If you can remove the cardboard tube, which you intend to replace, then maybe you could cut the foam top to bottom rather than across the structure. This way you will not need to cut through the silicone adhesive. If you make your cut down the sides close to the existing silicone joint then re-joining the two halves can be done using a similar silicone adhesive.

      I hope I have read your question correctly and that this information is helpful to you.

      Colin

      Reply
      1. By Carlos McCauley on

        Thanks for your input. You have answered what I have described. My description though, is erred. The foam she’ll is actually a tiny bit thicker than 1″, and almost 14″ long. I just took a picture of the pertinent part of the instructions pertaining to gluing the two halves around the motor mount and body tube. One thing I neglected to describe is a plastic end piece which helps lock in place the half shells and locks the motor mount in place. 1/2″ overlaps the back end of the half shells. My thought is to take a hot knife to that also, and pass as close as possible to that plastic end piece; a regular hobby knife would chew up the foam beyond repair. I have also taken pictures of the afflicted rocket, but I don’t see an option for attachments. I could post them on Facebook. Thanks again for your input. As I look at this and read your words, rather than cut lengthwise, as I originally planned, I should cut across and remove the tail end, remove and replace the motor mount, then reglue the tail section over the new installation. That would simplify the operation and probably look better (than my initial thoughts). Putting my thoughts down on paper and sharing them with someone has helped. Thanks.

        Reply
  3. By Nichole on

    Wow there is way more glue than I thought! Thanks for going through all of them. I do have a couple planes that I would like to put together someday and this article is very helpful.

    I never even would of thought of putting anything around the fuel tank but totally makes sense for sure! Thanks for the great post.
    Cheers
    Nichole

    Reply
    1. By Colin on

      Thanks for your great comments Nichole. I hope you get round to building your model planes soon. If you ever need any help be sure to ask via any of the comment facilities on my website http://www.rookiercflyer.com.

      Colin

      Reply
  4. By Boniface on

    Hi Collin
    That’s quite a nice article and the information in it is quite on point and helpful.
    Adhesives, it seems, are in a lot of variety and one needs to have good information on the type to use in RC planes. Are there adhesives that could trigger auto-immune reactions either if inhaled, ingested or in contact with skin? What are the possible antidotes/first aid approaches?
    Keep writing more as such wonderful content is quite engaging to the reader.
    Boniface

    Reply
    1. By Colin on

      Hi Boniface,

      Thank you for your comments and questions. So far as I know there have been no cases of auto-immune reactions from the use of glues. This does not mean that sensible precautions should not be taken when using any chemical substances.

      It is always advisable to use some kind of protective gloves to protect the skin on the hands especially when using two-part epoxy adhesives. Also working in a well ventilated area when using contact adhesives and Cyanoacrylate glues is advisable, they do give off some unpleasant fumes. Water based glues do not present any real hazard but washing your hands after using them is always a good thing.

      I hope this helps. if you want to read more about subjects on a similar theme be sure to visit my main site http://www.rookiercflyer.com.

      Kind regards,

      Colin

      Reply

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