Glue deterioration and other concerns

NC74392

NC74392

New member
These wings on 392 are 64 years old. What happens to Resorcinol Glue over all this time? Does it crack leaving the wing skin seperated from the ribs/ spars, etc?
I have a crack in the leading edge of the right wing where previous owners decided they would exit the wing from the front instead of off the T/E. I screwed up and installed a flat piece of mahogany plywood behing the crack. It flattened out the area. Now I have to figure out a way to get that piece off without screwing up the formed leading edge (sigh).

I was covering my left-hand elevator when I noticed the sound of particles sliding inside. Only thing I can think of is rust flakes sliding around. I walnut-blasted the piece and inspected it minutely using a punch to probe for weakness. Didn't find a thing, so I drilled a small hole and filled it with a rust conversion coating found here:

http://www.aircraftspruce.com/catalog/cspages/convcoat.php

I poured the excess out and let it dry, then gas-welded the hole shut. Nothing slides around in there any more and the elevator seems to be quite strong. Question is- am I deluding myself?

Trying to run new nav light wiring through the wings along side of the old. The old is stapled down throughout its length, so I don't plan on opening the wing to get it out. Trouble is, I can't seem to find a good way to thread the new in without pulling the staples and using the old stuff to pull in the new. I don't eve know if I should do this from the wingtip or the wingroot.
Advice solicited :?
 
Dave, I put wing tip strobes on my 14-13 and I wasn't able to use the same "track" that the old wire was in. It has been a couple of years so I don't remember exactly how I did it but it wasn't a big deal. I believe the new wires run through the area just behind the leading edge.
Gary
 
The best way to remove the glued-on piece is to use a wood chisel and carefully break the piece away from the wing skin. I hope you used Resorcinol or equivalent as epoxy adhesives are not approved and epoxy can become much harder to break than Resorcinol.
Once you have it removed you will have to clean off the area and make it as smooth as possible. Since mahogany is a hardwood sanding is permissable and probably will be necessary. Many folks will tell you that sanding is not allowed but that is only true for softwoods such as the spruce structural members.
Once the area is clean and smooth take a piece of mahogany plywood and cut a reinforcement doubler of sufficient size making sure that the grain is oriented in the same direction as the grain of the skin. Soak the doubler in hot water until it becomes sufficiently pliable to form into the required curve. This can take a couple of hours or more so be patient. Once it is flexible enough block it into the general shape you need it to be and let it dry overnight. I used some sections of 2X4s and a 40 lb. barbell weight.
While the doubler is drying cut some spruce or 1/4" plywood and shape to fit around the edges of the doubler. These will be used as nailing strips when you install the doubler. You can find the dimensions for these in AC 43.13-1B Change 1 Ch. 1.
Now mix the Resorcinol (or Cascophen) and coat both the doubler and the repair area and install the doubler using 1/4" nails driven through the skin and the doubler and into the nailing strips. You could also use very small wood screws to hold the repair in place. The fasteners are used to provide clamping pressure to the joint while the glue dries. After the repair is secure clean off the excess Resorcinol with a wet rag before the glue dries. After the glue dries the nails or screws can be removed if desired. A thin bond joint is critical when using Resorcinol.
As far as I know Resorcinol is very durable. It can crack in fillet areas with age and this might allow moisture to contact the wood which can led to wood deterioration under the joint, resulting in joint failure. The glue in the bondline itself doesn't fail but the wood underneath it can if moisture gets in. The only time I've ever seen this type of failure is in areas where moisture has been allowed to come in contact with older structure. Coating the older bond lines with a good epoxy varnish (this is approved) will seal any cracks in the glue fillet surface and inhibit wood deterioration under the joint. I've had to make a number of repairs to NC74233's wings during the course of my project and I've found most of the bond lines to be very secure. The joints in the fuselage superstructure were another story entirely. They were all loose.
I've found it best to use par-al-ketone, line oil, or boiled linseed oil to coat the insides of tubular metal structures. Phosphoric acid conversion coatings are hard to control where you can't see them and may actually contribute to corrosion over time.
 
Thanks RHunter.
I'm using Resorcinol throughout. Will get started on the new LE doubler ASAP.
I have a line on a set of elevators. I believe that would be the safe route. I wonder if the hinges will align with the original stabilizer?
Any suggestions for unwarping the pilot window wood? It's warped outward at the bottom making a perfect rain-catcher. I believe the previous covering job did this when they iron-tightened the Ceconite (I'm using Poly-Fibre).
 
Dave,
I don't know how much your wings have been disassembled, and I'm not familiar with the 14-13. But when I threaded nav light wires and cables for wingtip strobes on my 14-19, I used the same course used for the original wires(that is behind the forward spar.) The fuel tanks were removed, and the wings were off. Using 1/2" PVC pipe helped guide the wires into and through the ribs, where the original holes were. Even with this, there was still much cursing. As to the condition of the glue in your wings, unless yours were really abused, you're probably fine. I had Randy Scott( he used to run the wing plant at Bellanca) go through my 1950 wings, and he gave them a thumbs up. He put a couple of small surface patches on the underside, replaced some of the wing walk area, and applied sealer to the spar butts. Tom Robinson
 
The window facing wood is very difficult to straighten out once it is warped and it's usually warped. Mine was real bad. At least 2" of distortion from moisture and the old taughtening dope that was used on the cotton fabric that NC74233 still sported when I trucked her down to Texas from Indiana in a U-Haul. I could write a book about that...
I covered the window facing with a thick, wet towel and then heated the towel and the underlying wood with a heat gun. I had to keep this up for at least an hour before the wood became somewhat pliable. I then used some 2X4 blocks and C-clamps to try and block the facing back into shape. It isn't perfect and still sticks out some but it's a lot better than it was and it sure beat trying to fabricate a new piece, which would have been my only recourse had I not been able to straighten this one. Rain got into that gap even when the airplane was new so I wasn't worried about trying to make a weather-tight seal there. It ain't gonna happen. It's impossible with this design. I just don't ever plan to park '233 in the rain. My project is not a restoration, anyway. I just want to fix what's broken, cover it, paint it, and go flying.
 
I replaced the wood on the pilot's window on my 14-13 and it wasn't a big deal. I removed the old broken wood and fabricated new for both sides. It wasn't a big deal but I knnow more about wood working than restoring airplanes. :(
Gary
P.S. Randy Scott still runs the wing shop at Alexandria Aircraft.
 
Dave-
I'm sorry but I just realized that I forgot to answer your question about the stabilizers! All elevators and stabilizers will interchange with each other as long as they are of the same model. All 14-13 elevators will fit all other 14-13s and all 14-13-2 and -3 elevators will fit all other 14-13-2s and -3s. The 14-13 stabilizers and elevators are shorter than 14-13-2 or -3 tail feathers so you can't use an elevator from a 14-13 on a 14-13-2 and vice-versa. Lots of 14-13s have been converted to 14-13-2 configuration by installing the -2 tail feathers and these are considered to be 14-13-2s.

Rogers
 
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