Friday, October 5, 2012

How to Install CA Hinges

By Troy Newman
With CA hinges I'm very picky about CA. Get a fresh bottle of glue. This can make a huge difference. I like the small capillary tips for hinges they make a huge difference in applying the CA in the right spot with just the right sized drops. It’s very important to have fresh glue. As it ages it will start to thicken and will take longer to soak into the hinges. So a fresh bottle of glue is important. I actually buy a fresh small bottle just to hinge with. I tried the new INSTA-Flex CA and its great for CA hinging. This glue was specially formulated for CA hinges as it is rubber toughened to keep from getting brittle.

A couple of tricks will make the hinge installation process go smoothly. Using a 1/16” drill bit drill a small hole in the hinge slot right in the middle of the hinge location. This hole is parallel to the hinge and only needs to go in as far as the hinge will go. This will allow the glue to flow easier deep into the wood and the hinge surface. I do this for all the hinge slots on the wing, stab and fin, as well as the control surfaces themselves.

Next trick is to use a small straight pin or “T” pin in the middle of the hinge. This insures the hinge material is not getting pushed too deep into the surface and not getting good bite on the other side. These pins are only used while aligning everything and inserting the hinges. Remove these pins before gluing as they will not allow you to get the gaps tight. Below is a photo of the pins I used. Once the surface is up tight against the pins then remove them and push the surface tight together. 

CA hinges offer the benefit of getting very tight hinge gaps. The larger this gap the more effect the gap will have on way the model performs. Large gaps can cause nightmares with control linkages, surface effectiveness and even flutter that can cause you to crash the model. 

For glue application take one hinge at a time. Put a drop using the fine capillary tip on the glue bottle. Place one drop at a time on one side of the hinge and watch for it to soak into the fiber hinge. Too Much glue will run down the hinge line and make a mess only a small drop right on the fiber of the CA hinge. This drop will soak in, and then add another drop. Continue this process until the drops don’t soak in as fast. Then flip it over and drop by drop the same process on the other side of the same hinge. Never use Accelerator this will make the hinges brittle. 

Once the hinge can’t take anymore CA move to the next hinge. Again drop by drop until it will not soak up anymore… Be sure to apply some to both sides of the hinge in the drop by drop manner. The reason to do one hinge at a time is if the CA kicks off before the hinge gets saturated it will not let anymore glue in and will not have enough for the bond. The idea is to keep it wet and absorbing until it can’t absorb anymore. Then it has enough….So watch the drop soak in then apply another immediately until it is saturated. Once you have all the hinges on a surface glued set it aside. Don’t go messing around with the moving the hinge just let it cure.

After about 10-15mins the hinges will be glued in place. The surface will be a stiff…Move it back and forth and the glue will break free right in the middle and the surface will move freely. It may crunch or making a cracking noise at first but this is normal. This is not the hinge breaking it’s the glue on the surface popping loose.

Your surfaces are now hinged!
Troy Newman