Cyanoacrylate - or CA for short - glues are becoming more and more important in today's DLG assembly process.
There was a time when you had to use epoxy when you are assembling your new glider, and many had their own reasons. The main reason being, cores used in bagged wings and early solid core molded wings were made from a foam material called expanded polystyrene - XPS for short - which is not compatible with regular CA and many solvents.
Although there still are a few planes made with XPS foam, the majority of commercially available DLG's on the market are now either hollow molded with 1 mm Rohacell sandwich material, or solid molded with a Rohacell or equivalent milled core. These new materials are not reactive to CA, and forms the basis of modern DLG assembly with CA.
Now, there are several big advantages to using CA on a DLG compared to epoxy:
- Short curing times, which can be further accelerated with kicker/accelerator,
- Low preparation time, just open the bottle and use,
- Strong bonds, especially with fibrous materials,
- Ease to find and buy good quality CA in most hobby shops, and even hardware shops,
- Ability to use instantaneous on-field repairs,
- More accurate construction by decreasing cure time,
- And, all the above boils down to less time in the shop, and more time in the air.
Of course, there are also downsides to CA glue compared to epoxy:
- Joints are relatively more brittle,
- Opened glues have shorter shelf-life,
- Filling applications are heavier,
- And, not compatible with all material types (such as XPS).
We have used CA to assemble our own gliders for quite a while now, and have found some ways to make life even easier when using it:
- As with all adhesives, first you must prepare the surfaces by lightly sanding it and thoroughly cleaning the surfaces,
- For servo trays, tack in place with medium CA, spray kicker, remove servos, and apply thin CA along the joint. Allow it to cure, and reapply, continue until a fillet forms,
- Use needle applicators on the bottle to ensure accurate application,
- Running the needle over an open flame from a lighter will usually unclog potential clogs,
- Ensure tight fit for all joints, avoid open gaps as much as possible,
- Blades must be installed with an epoxy hardpoint pre-embedded into the wing (CA is not suitable for T-blades where the tongue goes inside the wing),
- Keep your CA in the fridge for long term storage,
- For repairs, clean up the cracks as much as possible and realign, wick in thin CA to bind the fibers back together before sanding smooth and applying fabric outside,
- If there is any slop between servo horn/control horn and pushrod, wick in a drop of thin CA and let it cure. Move the servo afterwards to break the bond on the pushrod, for a perfect CA bearing and no free play,
- After installing the springs in the tails, stick the applicator needle into the foam right alongside the spring and apply some CA right into the area, applying little by little as you pull the needle out,
If you have any additional tips, or suggestions, please feel free to drop us a message and we will include it onto the list!