Glue

Glues Explained

Written by David Niedzielski and Stephen Niedzielski.

A quick explanation of the different glues used to build model airplanes.

Ambroid cement is readily thinned and cleaned with acetone. It works well for gluing wood to wood and is somewhat flexible. Joints can be softened for repairs at a later date. Sands well during finishing if not globbed on. This is a waterproof glue. Seldom used by modelers today, it can be purchased from boat building suppliers.

Yellow woodworker's or aliphatic glue, available from most craft and hardware stores. Thin this with 25-40% water. It holds well for gluing wood and tissue, but will take hours or overnight to dry. Yellow glue is quite flexible depending on how much you thin it. It can be easily cut through with a sharp razor knife and sands well. This glue is water resistant but not waterproof and requires doping the surface to improve water resistance or for outdoor flying.

Instant glue known as CA or cyanoacrylate glue, comes in different viscosities and reacting speeds - thin, medium and thick, with cure times of 5 seconds to 2 minutes. Most model builders use CA glues. We use JET CA Glues. Applying this type of glue can be done via a small diameter tip on the end of a bottle allowing a tiny drop to be placed where you want it or by placing several drops on some plastic and dipping the end of the wood to be butt joined into the glue followed by putting the piece into it's location. The thin type of glue works best with the applicator tip, however the dipping method is better for the thicker glue. Thick cyanoacrylate glue is heavier but very strong, the joint is stiff, it does not sand easily, but it is waterproof. Jet SET accelerator can be sprayed where you have just finished applying the glue or by putting the glue on one piece and spraying accelerator on the other surface to be jointed. Make sure you are ready as the joint sets very quickly. Cyanoacrylate glue does not work for applying tissue.

Glue sticks. To apply tissue we use glue sticks which are a permanent glue which dries clear. Just spread it evenly along the wood, lay the dampened tissue on carefully and pull taut. Another option involves using thinned white glue. You paint this on the wood, then lay the dampened tissue in place. Finally seal and water proof the tissue. Clear Krylon spray paint is our choice for water proofing. It does a great job of sealing the tissue with minimal fumes.

Dope. Yet another technique is to paint several coats of dope on the frame. After it dries, damp tissue is laid in place and then dope is brushed on along the wood structure through the tissue. After the tissue dries seal it with several coats of dope. Dope can be purchased in colors or clear. Ventilation is mandatory when using dope.

Foam Safe CA Glue. For building models that contain foam parts UFO Odorless glue is the most effective. An added benefit is practically no fumes.

On a final note: Always remember to read the manufacturer's warning label and follow their instructions.

Gluing Up Your Model

There is an easy way to insure that wing ribs, and fuselage clam shell type construction formers are held at a 90 degree angle to the building board while the glue dries. All that is needed is a supply of triangles that can be pinned on either side of the rib, or former. To make these triangles you will need various widths of 1/8" strip wood, a razor saw, and a miter box. For wing ribs I recommend 1/8" X 3/4", and for fuselage formers I recommend 1/8" X 1", and 1/8" X 2". Simply measure along the length of the wood, and mark off sections equal to the height of the strip. Thus you will have marked off 3/4" squares on the 3/4" wood, 1" squares on the 1" wood, 2" squares on the 2" wood. Then use the miter box and razor saw to cut out a supply of 45 degree right triangles. Now all you have to do is pin 2 triangles on each side of the rib or former to hold the part at a perfect 90 degree angle till the glue dries. Please note because of the dihedral on some models it is necessary to glue the wing root ribs at an angle. In these cases simply calculate the proper angle, and use a protractor to transfer it to the triangles used to hold that rib in place.

When building a model, there is always the extra glue that has hardened around a joint and has to be removed. This can be minimized by using flat toothpicks as glue sticks. Instead of squeezing large gobs of glue onto the parts, apply the glue to the end of a flat toothpick and then transfer it to the parts. Not only does this permit you to apply the glue where it is needed and no where else, it also saves the cost of all the wasted glue, and the time and trouble of removing the excess later. - Allan P. Weisman

Make your own Glue Clamps (click for details)