Bob Pastorello
Posts: 6277
Score: 126 Joined: 2/23/2002 Last Login: 6/20/2013 From: El Reno, OK, USA Status: offline
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Personally, I have used, and will use good CA hinges since they came out. There are a lot of reasons these hinges fail. Most, I think fail due to too much glue, too loose slot, or combination of those. I use the following technique, it has been very reliable on lots of aerobatic airplanes. First, I try to make sure that CA is going to penetrate WOOD. That means that I carefully cut away any covering around the hinge slots BEFORE gluing. Usually, that's about 1/16" either side of the slot. Second, before fitting the hinges, I use a soft graphite pencil, drawing a center line on both sides of the hinges at the middle. This becomes the "flex point", and CA will not penetrate/stick to the graphite. Next, I always install the hinge to the movable surface. After inserting the hinge up to the pencil line, I insert a straight pin parallel to the hinge, sticking several holes in the wood adjacent to the hinge, right up against the hinge surface. This makes small glue paths to force the CA to wick to the full depth of the hinge. I prepare the NON-movable surface the same way, using a spare hinge in the slots to permit the straight pin to do it's thing. Then - on the movable part, I put a VERY, very small droplet of CA at the edge of the slot where the hinge is making contact. This doesn't wick, but simply stops the hinge from shifting. Finally - I insert the movable surface into the lifting surface slots, making sure that the hinge goes all the way to the pencil line. This method permits VERY close gaps, usually less than 1/16". At this point, holding the wing/stab/fin horizontal, I apply several drops to the hinge, usually about 6 or so. Top or bottom first, but after letting that first side glue "set", immediately flip it over, apply the glue on the OTHER side. Leave everything alone for 15 - 20 minutes..... You will NOT pull that hinge apart without destruction of the wood. Try this on a test piece. Put vise grips on the hinge, pull with scale attached; Write back what your test reveals is the "pull apart" load. You will be happily surprised, because what you will really learn is the WOOD pull out strength of grain. Sorry for the length of this post, but MY Ultimate just arrived, and I'll be doing CA hinges on her, so thought I'd share the technique I've had success with. Of course, YMMV, and this may not work for someone who doesn't want it to. But for everyone else, it will provide a VERY durable, and amazingly strong hinge.
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It really shouldn''t be this hard....
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