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Adhesives used for Model Building

September 12, 2011



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Airfield Models (http://www.airfieldmodels.com/)Adhesives used for Model Building

There are a variety of types of adhesives available.  Each has a useful purpose as well as things it definitely should not be used for.  This page is intended to outline the most common adhesives used in model-building and give guidance on selecting and using the correct adhesive.

If you are a beginning kit builder, then the short answer is that you will need Carpenter's Glue, Slow-Cure Epoxy, and a small bottle of Thin Cyanoacrylate (CA).

If you are assembling an ARF, then you will need Slow-Curing Epoxy and Thin and Medium CA.  The other glues listed here can be purchased as needed.

 
 

Glue Properties

Typical adhesives used to build models.

These are things you should understand about any glue that you use.  If you know what each glue's properties are, then selecting the correct glue for a task is a fairly simple matter.  On the other hand, if you are a beginner, do not get hung up about glues.  A good wood glue or CA and some epoxy will get your trainer built.

Type

Most glues are of one of two types:

  • Evaporation Types

Glue is solvent or water-based and dries by evaporation of the solvent.

  • Chemical cure types

These glues cure by chemical process.  They are further broken 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 yogurt cups, tuna cans, etc.  Some glues will melt plastic, but I have not had any problem mixing epoxies in plastic containers.

One-part glues that cure include Cyanoacrylates (AKA Super Glue or CA) and silicone sealant.  Two-part glues include epoxies.

If you happen to say "dry" when you mean "cure" someone will undoubtedly correct you.  Even though he's right, feel free to ignore him.  For all practical purposes, "dry" and "cure" mean the same thing the glue hardened about as much as it's going to and it isn't wet any more.

Note: Multi-Part adhesives should be mixed on a non-porous surface or container.  Cardboard and other porous surfaces will prevent the glue from being mixed in the proper proportions due to the glue soaking into the surface.  This may result in the glue not curing properly.

Strength

As a rule of thumb, stronger glues tend to be heavier.  Therefore, select a glue that is strong enough to do the job but do not go over-board.  For example, there is no good reason to use epoxy to glue wing sheeting together but a lot of reasons not to.  Slow drying glues tend to be stronger than fast drying glues because they have more time to soak into the wood at least that's the reason most commonly given.  It's a true statement but there is another important problem with fast-drying glues.  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 glue joints failing.

Fuel-proof

Fuel should not be able to get inside the airframe and fuel-proofness is not much of a consideration for general construction.  Fuel tanks can and do split open from improper assembly, defective molding or design or a crash.  The fuel compartment should definitely be coated with something fuel proof such as epoxy or polyurethane (paint).  Joints around the firewall should also be glued with a fuel-proof glue.

Sanding ease

Often you will need 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.  Usually this results in an unsightly ridge that will be seen under the final finish.

Pot-Life

How long the glue stays useable after it has been dispensed or mixed in an open container.

Working time

This is not the same as pot-life.  Glues that cure tend to heat up.  In the pot, they will cure faster than in a thin film.  Therefore, 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.

Tip: The time given for epoxies is the working time, not the curing time.  For example, 15 minute epoxy has a 15 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.  Note that the time given is for practical purposes.  Most glues that cure tend to continue the chemical curing process for months.

Shelf-life

All glues have a shelf life.  This is how long it can sit on the shelf before it goes bad.  My advice is to not buy any more glue than you can reasonably use within a year or so after you purchase it even though some glues have shelf lives of years.  Shelf life is strongly affected by the climate (heat, humidity, UV light, etc.).

Set (also 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 irrelevent 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.

 
 

Gluing Techniques

Tip: A round bamboo skewer with the end cut at a bevel is a great scooper to remove excess glue that squeezes from a joint without smearing it everywhere.

Double-Gluing

Double-gluing is a technique that should be used whenever gluing end-grain wood.  End grain needs to soak up a certain amount of glue to make a strong joint.  If you apply glue and immediately put the part in place, most of the glue will be forced out of the joint and the end grain will soak up the glue that is left leaving very little glue in the joint.

What you should do is put glue on the end grain and let it soak in for a minute or so.  Fit another part while you are waiting.  After the glue has soaked into the grain apply a little more glue and put the part in place.

What I actually do is squeegee the glue back and forth for a minute or so using a popsicle stick or toothpick to force the glue into the grain.

Double Gluing Technique:  First, apply glue to end grain. Glue is applied to end grain wood and allowed to soak in for a minute or two.  I usually squeegee it back and forth instead of just letting it soak because it is faster, but either way works.
Allow glue to soak in to the grain. Note the small amount of glue that is left.  Apply a little more glue and then put the parts together.

You can see that the wood has cupped slightly.  The wood was like that before the glue was added.  Weight will be used while the end cap dries to help flatten it out.  It will not fully resolve the problem, however.

This is the reason I make some parts from thicker wood than called for on the plan.  It allows the part to be sanded flat but not end up with a part that is too thin.

Apply more glue and attach part. The stabilizer end cap glued in place.  I almost always use caps on plank tail surfaces to help prevent the wood from cupping.  I also use end caps on built up tail surfaces to cap the end grain spars making it more attractive under transparent coverings and easier to cover with any iron-on film.

Another type of double-gluing is when using Solvent glues (Airplane glue).  These glues dry so fast that when you put glue on one piece it is dry by the time you join it to another piece.  It actually is not dry but has gelled.  The answer to this problem is to add glue to both pieces.  When you join them the solvent that is trapped under the gelled glue will dissolve the gel long enough for the pieces to adhere to each other.

Tack Gluing

A part is tack-glued knowing that it will be broken or cut loose later when there is no other practical way to hold the part in place temporarily.  Use only the smallest amount of glue necessary to hold the part so removing it is not more difficult than necessary.

This technique is usually used for shaping parts in place that you will want to remove later.   Clamps and pins are not feasible because they will be in the way when it comes time to sand.  Examples are wood cowls, wing tip blocks that will be hollowed after they are shaped on the airframe and ailerons shaped in place on the wing.

 
 

Aliphatic Resin

Also called Carpenters Glue

Aliphatic resins are inexpensive, light and strong.  Carpenter's glue is the primary adhesive I use to build flying model aircraft.  Its longer working time allows me to ensure everything is as it should be before the glue sets up.

Because it is water-based, aliphatic resin also allows neat glue joints because excess glue removes easily with a damp sponge or paper towel while the glue is still wet.

In addition to common aliphatic resins, there are also so-called "sandable" resins.  I do not use them because the additive to make them sandable probably weakens the glue.  I do not know this for a fact, but it makes sense to me.  Carpenter's glue sands easily enough that it is not an issue in most cases.

  • Fuel proof

    No.  They are fuel resistant to a point, but extended exposure to raw fuel or exhaust residue will break them down.

  • Clean-up

    Water while wet.  Acetone when dry.

  • Examples

    • Titebond
    • Elmer's Carpenter glue

    • Pica Gluit

  • 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.  These glues are water-based and dry by evaporation.  If you place the part under a lot of weight until it has dried thoroughly then it might work for laminating, but I wouldn't do it.

      However, it can take several days for it to dry even longer if you have put plastic on both sides to prevent the part from sticking to the bench or whatever weight is used.  Generally it is a better idea to use a different type of adhesive for laminating parts.

 
 

Traditional Solvent  or Cellulose-Base Glue

Also called Airplane Glue or Tube Glue

This is the type of glue that comes in a tube and is used for wood models.  It is fast-drying and lightweight.  The solvent in this glue has a noxious odor and it should only be used in a well ventilated area.

This type of glue is the best thing going for joining sheet wood together.  It sands very easily and is more than strong enough for the task.  First, trim the two pieces of wood so they mate squarely.  Then use a few short pieces of masking tape to hold the pieces together.  Only tape one side at first.  Next, open the joint and run a bead of glue down the joint.  Place the wood with the masking tape side down on the board and press it flat.  Wipe up any glue that has squeezed from the joint and then tape this side and allow to dry.

  • Fuel proof

    Yes.  They are fuel proof to low nitro fuels.  I do not know at what nitro content they are no longer fuel proof.

  • Clean-up

    Dope thinner or acetone even after it has dried.

  • Examples

    • Ambroid

    • Sigment

    • UHU

  • Use for

    • Stick and tissue models

    • 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 is capable of melting in order to create a bond.

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

Another use of this type of glue is to seal grain so that it does not fuzz when sanding.  For example, I was recently working on a part that had laminated edges that butted against a stick.  The stick was radiused on the end making it go from end grain to face grain.  What happened was that I could never get the radius smooth when sanding due to the different types of grain the end grain kept "fuzzing."

To solve the problem, I put some Ambroid on the end grain and rubbed it in with my finger.  I did this twice more and then it was easy to finish sand using 400 paper.  If you rub the glue in with your finger until it is dry (about 20 seconds) you can sand immediately.

Soft balsa can be difficult to sand smooth.  Use airplane glue or dope to harden the wood prior to sanding.

After sanding

 
 

Contact Cement

Contact cement is heavy and has very limited uses in model-building.  Doesn't tend to warp sheeting badly enough to cause problems.

Contact cement is applied to both surfaces and allowed to dry to the touch.  Then 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.  I do not use contact cement at all.

  • Fuel proof

    Don't know.

  • Clean-up

    Lacquer thinner, mineral spirits or dedicated thinner.

  • Use for

    • Laminating broad contact areas (sheeting on foam wings, fuselage doublers, 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 (CA)

Also called Super Glue

Any time there are a zillion tips in magazines on solving a problem, the real message is that there is a fundamental problem with the item that will probably never be solved.  Clogged tips on CA bottles are a great example of this kind of problem.

I generally avoid cyanoacrylate glues because they are expensive, make messy joints, skin from my fingers almost always ends up on the structure somewhere, and the fumes are horrible.  Cyanoacrylates also allow builders to make mistakes faster which are very difficult to correct.  When this happens the time savings over the use of a slower adhesive are more than nullified.

I have noticed that CA joints on some of my older models started to disintegrate by turning into some white, powdery substance.

Lastly, many people have extreme allergic reactions to these glues.  The manufacturers of CA try to capitalize on our inherent impatience by selling the "speed" of these glues.  Impatience and model-building do not go well together.

In spite of their short-comings, cyanoacrylates are fast and strong.

  • Fuel proof

    No. They are fuel-proof to 0% nitro fuel (FAI fuel), but nitro methane dissolves cyanoacrylates.

  • Clean-up

    Acetone or nitro-methane.  Some companies make debonders that are a mix of these items.

  • Examples

    • Satellite City Hot Stuff

    • Pacer Zap

  • Use for

    • Hardening threads cut into wood.

    • Gluing fiberglass or carbon fiber (epoxy is preferred)

    • 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 fiber to wood.

  • Do not use for

    • High-stress areas.

    • Areas exposed to raw fuel.

    • Clear plastic parts.  CA can fog the plastic.

    • Foam.  CA dissolves foam.

An item made for use with cyanoacrylates is called accelerator.  It sets CA glues instantly and is made for people who think that waiting 60 seconds for a microwave to cook a hotdog is too long.

 
 

Double-Stick Cellophane Tape

Double-Sided TapesAlso called Double-Sided Tape.

Double-stick tape is used to join multiple blanks together so they can be shaped and machined at the same time to make matched parts.  It is fundamental to the way I build so not having it on hand can be a real problem in my shop.

This type of tape is made by Scotch and others and can be purchased from office suppliers.

There are several types of double-stick tape.  Some of them are surprisingly tenacious.

Important Points

  • Sand then vacuum parts with a brush attachment before applying the tape.

    The tape will let go at the worst possible moment if it's stuck to dust between the blanks rather than the blanks themselves.

  • Do not use too much tape.

    Some of these tapes are very strong.  The force required to separate the parts may damage or destroy them.  This is an easy problem to avoid.

  • When separating thin pieces, peel them apart slowly.

    At times I used too strong of a tape or too much I managed to get the parts separated by being patient.  I pulled the parts as much as I could safely and waited for the tape to release which can take longer than you think.  But it will let loose.  Parts break when you pull too hard.  Parts get damaged when you try to wedge something between the blanks to separate them such as a spatula or knife.

Types of Double-Sided Tape

  • Removable Cellophane

    This is definitely the type to use for most purposes when stacking thin, delicate parts such as light ribs or thin sheeting.  It is also good for large parts (fuselage sides, for example) that will need several small pieces to keep the parts from bending and bowing differently while shaping.  When parts in a stack can move individually you get individual parts not matched parts.

    It will hold the parts securely while being cut and sanded but will release without the parts breaking.  If you use rough sawn parts the tape may not stick at all or may seem to stick and then come apart when you start working on the stack.  Sand and vacuum blanks before taping them together.

  • Permanent Cellophane

    The word "Permanent" by tape manufacturer's standards and builder's standards do not have the same meaning.  Do not use permanent tape as an adhesive for anything your models.  It's not that permanent.  It's permanent in that it will hold together two pieces of cardstock and will tear the face from the stock if you try to separate it.

    That said, permanent tape has a much more aggressive bond and should not be used on delicate parts.  Use it for holding small but strong parts that don't have much surface area such as hardwood blocks.  Also use for holding plywood parts. Again, this tape is very strong so a few 1/2" squares of it strategically placed will make separation much easier.

    If the parts you want to hold together need a better bond than removable tape but not as strong as permanent then you can try not sanding the parts first and then use permanent tape.

    Do not leave parts together any longer than necessary when using permanent tape or you'll regret it.  In other words, don't tape parts together this weekend that you plan to work with next weekend.

  • Poster Tape

    I purchased this tape when I couldn't find removable tape locally.  Its strength falls in between removable and permanent tapes.  It's more expensive than either of the other tapes and more tedious to use because it has a backing that must be removed.

  • Carpet Tape

    I use carpet tape for various purposes around the shop.  There are several brands of this tape and they're all different.  Some are reinforced having rovings through it that appear to be fiberglass.  Others are simply adhesive on both sides of a plastic strip.  Some of the adhesives are gooey and others aren't.  My problem is that the carpet tapes I've purchased that I like aren't marked inside the roll so I can never remember what to buy.

    The main purpose I have for carpet tape is making sanding blocks.  I now consider my home made blocks to be disposable because they're super inexpensive to make and my old method of using spray glue and then removing it to replace the paper was very time consuming and just not worth the effort.

    Now I use carpet tape to attach the paper and throw the block away when it's worn out.

 

 
 

Epoxy Glue

Epoxy is strong but heavy and expensive.  Epoxies are used for bonding high-stress areas as well as items that no other adhesive will bond together.  Additionally, epoxy can be used for applying fiberglass cloth and making fiberglass parts.

There are two kinds of epoxy resin that I know of.  The most common type is used as an adhesive.  The second type is used for laminating and tends to be thin in consistency.  There are also various epoxy putties, etc.  This section pertains only to the adhesive.

Use slow-drying epoxy (30-minute to 4-hour working time) whenever epoxy is called for.  5-minute epoxy is of little use except in special circumstances.  It is heavy and weak, does not cure properly and gets brittle with age.  You really shouldn't make field repairs which is a common use of 5-minute epoxy.  Generally, epoxy should only be used on load-bearing components.

If the part that breaks is not a load-bearing member, then using epoxy adds unnecessary weight.  If the part is a load-bearing member, then it is probably important enough to get it repaired right that the repair should be made in your shop and not at the field.

The sort of "special circumstance" I would use 5-minute epoxy for is to create a smooth, non-porous surface for servo tape.  Place a sheet of waxed paper on a flat surface and apply a thin coat of epoxy to it.  Then put a piece of 1/32" plywood that is approximately the same size as the servo directly over the wet epoxy.  Put another piece of waxed paper on top of the plwood followed by a thicker piece of scrap wood as a clamp block.  Clamp or weight the piece to the table.

After the epoxy has cured, peel the plate from the waxed paper and trim off the excess epoxy.  Allow the epoxy cure fully (at least over night) and then give it a wipe with alcohol to remove any residue before applying the servo tape.

Locate the plate in the fuselage and glue it in place with the cured epoxy side out.  You now have a smooth, non-porous surface that servo tape will stick to very well.

  • 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.

  • Use for

    • High-stress areas.

    • Applying fiberglass cloth.

    • Fuel proofing firewalls and fuel tank compartments.

    • Bonding fiberglass and carbon fiber.

    • Mix with micro balloons (microscopic glass beads) to make a putty that can be formed into fillets and sanded easily.  I also use epoxy with micro-balloons to make perfect fitting wing saddles.

    • 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

I have seen some ARF's that were assembled using hot glue.  They are the sloppiest looking model aircraft structures I have ever seen.  I do not believe strength is an issue with hot glue, but it is very heavy.  I would never use it on any part of a model.  I do use hot glue for miscellaneous tasks around the shop.

For example, I may use hot glue to hold a runner in place on a shelf so it does not move when I drive screws into it.  Other than things like that I do not find hot glue to be very useful.

  • Fuel proof

    Don't know.

  • Clean-up

    Contact Manufacturer.

    Examples

    • 3M

  • Use for

    • General shop tasks

  • Do not use for

    • Model Building

 
 

Plastic Cement

Unless you've built a lot of plastic models, you probably are not aware of the choices available for gluing plastic.  Most of us are aware of Testor's tube glue and that's about it.

All plastic glues pretty much work on the same principle.  The glue contains a solvent (or is a solvent) that melts the plastic together.  In essence, the parts are welded together.  This is why more glue is not better unless your goal is to create a molten puddle of plastic.

Generally speaking, I like medium viscosity glues such as Testor's Model Master Cement.  When using this type of glue or tube glues, the glue is applied to one part and it is then joined to the mating part.

When joining parts having long, thin edges, such as cowls or wheel pants, I like watery-thin glues that can run along the joint (capillary action) after the parts are joined.  There are several glues of this variety as well.  I use Tenax.

  • Fuel proof

    Yes.

  • Clean-up

    This type of glue is a solvent and melts the plastic.  Therefore you should use as little as possible.  If you get a small amount of glue on a plastic surface then just allow it to dry thoroughly.

    If you happen to spill a larger amount on the plastic then carefully blot as much up as possible while it is wet but do not smear it around.  Allow the remaining glue to dry thoroughly.

    After the glue is dry the blemishes can be sanded and polished even from clear plastic.  In fact, I often sand and polish clear canopies for plastic models to improve their appearance.  A polishing kit for motorcycle windscreens includes very fine sandpapers and polishes that will make the canopy blemish free and crystal clear.

  • Examples

    • Testor's plastic cement

    • Tenax

    • MEK (Methyl Ethyl Ketone).  Note that MEK is a carcinogen.

    • Model Master cement

  • Use for

    • Compatible plastic-to-plastic bonds.

  • Do not use for

    • Materials other than plastic.

 
 

Polyurethane Glue

I use polyurethane in many situations where I have used epoxy in the past.  For example, I use it whenever I want a bond that has more strength than an aliphatic resin, but epoxy seems to be too much.

I do not use polyurethane for general construction because it is messy and expands out of the joints.

The main thing I use polyurethane glue for is to laminate parts.  It does not cause severe warpage (if weighted).

I have read that these glues have a short shelf-life.  My first bottle of Gorilla glue lasted about 18 months before it was too thick to use.  My shop is not climate controlled and generally very humid because I live on the Gulf coast of Florida.  18 months did not seem particularly short to me.

  • Fuel proof

    Don't know.

  • Clean-up

    Lacquer thinner or acetone.

  • Examples

    • Gorilla glue

    • Elmer's Pro-Bond Polyurethane glue

  • Use for

    • Laminating.

    • Bonds needing more strength than traditional glues, but not as much strength as epoxy.

  • Do not use for

    • General construction.  Polyurethane glue is heavy and very messy

 
 

Silicone Adhesive

Flexible, relatively strong and fuel proof.  It comes in quantities that no modeler will ever use and most of it ends up being thrown out when it goes bad.  The glue cures in the tube and is hard to remove to get at good glue.  The high-temperature variety can be used to seal mufflers and other engine parts (with care).

Recently a person told me he uses silicone to glue his servos in his planes.  He wraps the servo with heat shrink tubing and then cleans the tubing with alcohol.  A healthy dose of silicone is applied to the heat shrink and the servo is placed in the structure on a non-porous surface (see epoxies above for a method to create the surface).  He claims he has never had a servo come loose.

I used silicone for the first time to attach radio components inside my JGRC Aggressor.  It has held up fine so far, but at the time of this writing, the plane only has a handful of flights on it.

  • Fuel proof

    Yes.

  • Clean-up

    Contact manufacturer.  I have not found anything that removes silicone glue before or after it has cured.

  • 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.

    • Wing saddles

    • 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.

 
 

Spray adhesive

Basically aerosol contact cement.  Very convenient around the shop.

I use spray glue for a lot of tasks in the shop, but not on my models.  I have noticed that it hardens and crumbles after a year or so.  I do not want my models falling apart in the sky.  Some people say you can use spray glue to attach sheeting to a foam core.  Conversely, I have heard several stories about the sheeting delaminating after a while.  I do not know either way because I have never tried it.

Generally I use spray glue for attaching sandpaper to sanding blocks, patterns to wood, etc.  When attaching patterns, I spray only the pattern with a light coat and let it dry for several minutes.  Then I attach the pattern to the wood.  The pattern will peel off easily after the part is cut out.

When attaching sandpaper, I spray the paper and the block and attach the paper when it gets tacky.  I have to remove it with a heat gun and then use solvent to clean up the glue.  Spray glue is expensive, so I try not to use any more than necessary.

I recently priced these glues in a Home Depot store.  The 3M 77 cost approximately three times more than the Elmer's for the same quantity.  Because I only use it for gluing sandpaper to sanding blocks, templates to wood and similar non-critical bonds, I stick to the cheaper glue.

  • Fuel proof

    No.

  • Clean-up

    Lacquer thinner, mineral spirits, acetone or MEK.

  • Examples

    • 3M 77

    • Elmer's spray adhesive

  • Use for

    • Attaching paper patterns to wood by spraying the template only and allowing to dry just beyond a tacky state.  Apply the pattern to the wood, cut the part and peel off the pattern.

    • Attaching sandpaper to sanding blocks by spraying the back of the paper and the block and attaching the sandpaper when both are tacky.  Generally the sandpaper must be removed with a solvent such as lacquer thinner.  I use a heat gun to remove the paper and thinner to remove remaining glue.

  • Do not use for

    • Any part of model construction the stuff crumbles after about a year.

 
 

Thread Locking Compounds

Unless you have a reason not to use it, always use the type that is called "Removable."  I think it is the "Red" formula, but I could be wrong about that.  It comes in a red bottle, but the compound is actually blue.  In any case, do not use the permanent kind especially for set-screws or you will never get them out again.

If you can put the part in an oven or have a torch then you may be able to heat the part enough to get it loose, but if it is inside your R/C car, I doubt you will want to put your car in a 300 oven.

  • Fuel proof

    Yes.

  • Clean-up

    Contact manufacturer.

  • Examples

    • Loctite (various formulas)

  • Use for

    • Any metal hardware that you do not want to come loose.

  • Do not use for

    • Plastic hardware such as nylon fittings.  The bottle specifically states that thread locking compounds can attack plastic.

 
 

White Glue

White glue is very economical and is strong enough for many modeling tasks.  Small rubber-powered aircraft can be built entirely with this type of glue.  I personally wouldn't use it for anything larger than 1/2a size models.

  • Fuel proof

    No.

  • Clean-up

    Water.

  • Examples

    • Elmer's school glue

  • Use for

    • Small wood or paper models.

  • Do not use for

    • Plastic

    • Metal

    • High stress areas

 
 

Adhesive Additives

  • Chopped fiberglass

    Mix with epoxy to strengthen joints.  I sometimes mix chopped fiberglass with micro-balloons and epoxy when I am building up wing fillets to strengthen the fillet.

Chopped fiberglass comes in various lengths and weights Chopped Fibeglass comes in various lengths and weights.  This fiberglass is cut from rovings and will break down into fine filaments.

Always mix the resin before adding anything to it.

Mix the fiberglass thoroughly to wet it and break it into small filaments Add chopped fiberglass to resin.  Mix it thoroughly to wet out the strands and to separate the rovings into smaller filaments.
Chopped fiberglass and resin is much stronger than resin alone. In cases where resin is used outside a joint, the addition of chopped fiberglass will make the reinforcement much stronger and less brittle than resin alone.
  • Micro-balloons

    These are microscopic glass beads that look a lot like baking soda.  They are generally used with epoxy to create an easily sanded putty.  The gotcha here is that when you use them on balsa, some of the epoxy will soak out of the mix into the balsa and still create areas that are difficult to sand.  It is not a big problem, but just something to be aware of.

    When I need something extremely easy to sand, I mix micro-balloons with tube glue (Ambroid).  It dries very fast so I only mix small amounts and use it immediately.  Working time is something like 30 seconds, so obviously it can not be used for big jobs.  Basically I use it to fill in small seams between sheets of balsa or similar tasks.  It can be sanded after about 10 minutes.

  • Talc

    Essentially used for the same purposes as micro-balloons.  Talc makes a putty that is smoother, denser and has fewer pits than micro-balloons, but is also heavier.  Talc can also be added to some paints to create a sanding sealer or filler.

  • Thickeners

    Various thickeners are made for epoxies.  I have had no reason to use them so I also can't give any real guidance to using them.  I would guess that these would be needed when applying epoxy to a vertical surface so that it doesn't run.

    If you think you may have a use for a thickener, then contact the manufacturer for guidance as to what will be appropriate for your application.

 
 

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Copyright 2002 Paul K. Johnson