Let's start with epoxies.
"Low Quality" Epoxy
Low quality epoxy is the term I give to epoxies found at most hardware stores. Many of these are in disposable syringes or squeeze bottles. "Low-Quality" epoxies are mixed in a 1-1 ratio of resin to hardener. Fillers are added in the manufacturing process to achieve this 1-1 ratio. These added fillers decrease breaking strength and thicken the epoxy.
I have a set of BSI 8oz epoxies and use them quite often. The BSI epoxies come in 5minute, 15 minute, 30 minute and 20 minute (laminating). 5min is excellent for quickly "tacking" parts together or field repairs. 30minute works fine for fillets and has been my most used epoxy so far.
Even with the decreased strength these epoxies are perfect for almost any application. The bond well to almost any surface and are decently durable.
Epoxy like this is a must for any workshop.
Use for: Fiberglass, cardboard, Phenolic, Balsa, Most Plastics, and metals. 20min laminating epoxy is acceptable for small fiberglass layups.
DO Not use for: Parts requiring very high structural strength, very high heat applications.
"High Quality" Epoxy
"High Quality" Epoxy is more difficult to come by. You will not find it at most hardware stores and is usually ordered online. High quality epoxy is usually meant for fiberglass and carbon fiber layups. It is usually not mixed in a 1-1 ratio (with the exception of Aeropoxy). "HQ" Epoxy is typically sold by the quart or the gallon, rather then by the ounce. Most of these epoxies have a low viscosity and are ideal for soaking into parts. Many Higher-end epoxies are around 4 times stronger then the epoxy above (source.)
These epoxies can often be thickened with an additive such as Phenolic Microballoons, Colloidal silica, or even carbon fiber. With these fillers the epoxy can be used to create smooth fillets.
Manufacturers include:
West Systems
Aeropoxy
US Composites
and many more
Use for: Everything
Do NOT use for: Applications that are under intense heat.
Wood Glue
Surprisingly, wood glue is one of the strongest adhesives for wood-wood and wood-paper applications. Using wood glue on wood-wood joints is usually stronger then high quality epoxy. Wood glue works by soaking into the wood and hardening, this binds the wood together in a bond that will usually outlast the things being glued. I use wood glue for all of my engine mount assemblies and fin attachment. Wood glue shrinks as it dries so it should never be used for fillets. Woodglue should never be used on anything other then wood and paper. It will not bond to things like fiberglass, metal, or plastic. Besides that, it's great. You can work with it with your hands and washes off with a little water.
Use for: Wood, paper
Do NOT use for: plastic, fillets, fiberglass, metals,
Cyanoacrylates (CA)
CA is also known as super glue. CA is a necessary adhesive to have around the shop. I use CA for tacking in all of my fiberglass or carbon fiber fins. CA dries very quickly, making it ideal for tacking in fins and joining parts that need to be bent. These joints should be reinforced later with wood glue or epoxy. CA comes in super thin, thin, normal, thick, super thick, gap filling, odorless and others. The main reason CA is not used more is the cost. CA costs 5x more then epoxy.
Use For: Quick bonding, fiberglass, wood, metals, plastic. Do NOT use for: structural joints
JB Weld
JB weld is a type of specialty epoxy adhesive. JB weld is intended to be used to "cold weld" metal structures togeather. Because of this, JB weld is very heat resistant and hardens like steel. In rocketry, JB weld is often useful for tacking in fins on minimum diameter rockets or securing motor retainers. JB weld is strong but it's loaded with fillers that decease strength and increase heat resistance. When deciding an adhesive for a strucural purpose that will NOT go under intense heat, it's best to go with a good epoxy instead. JB weld is also expensive, even expensive epoxies are much cheaper.
Use for: Retainers, Fin on Minimum diameter rockets
DO NOT use for: Things that epoxy could be used for.
In the field of engineering, epoxy adhesives are frequently used for attaching two surfaces together. This is often done for dampening sound and reducing movement between joints. This cementing agent is also used as structural glue for completing bonding jobs where using nails is not possible. One of the most fascinating features of this glue is that you can use it for attaching two objects permanently or semi-permanently depending on your needs. Often when we use nails to attach two objects together, separating them becomes impossible; at times, this makes epoxy adhesives a more useful alternative of nails.
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