CyA Hinges Failing?

YES!!

CA hinges fail just that way when they are aged and exposed to sunlight (UV radiation). That is why I dislike them.

UV exposure and age would certainly make sense, if the hinges had been in use for 3 or 4 seasons. These hinges were on a plane finished just last fall and which had fewer than 30 flights. It hasn't been sitting in the sun much. I never found any oil residue in the hinge gap, so I don't see any type of chemical erosion causing this.

I carefully checked all the other hinges on the plane ( made from the same batch of hinge material ) and fortunately no others are cracking.

Very weird.

Thanks for the input,

Mark

The most common reason for premature hinge line failure is too much CA used during installation. This causes a buildup on the hinge line of cured CA.

One good way to avoid this is to wick the excess CA off the hinge with newspaper. After applying the CA, use strips of newspaper in the gap to soak ou any excess. I have had several planes last many season in the Arizona sun without any hinge failures.

I do the same, except I use small squares of paper towel to soak up the excess. I also like to use a fresh bottle of thin CA when doing the hinges.

Alan Harriman

The writer failed to mention the brand of hinges -- I've been using Radio South, SonicTronics, and Sig for YEARS and never had a failure.

To avoid build up and subsequent stiffening, I draw a thin line across the center with a kid's crayon before installing.

I have had the same problem but I think the cause might be that I folded and creased at the center line for positioning..

Yes Mark, In this area of the US we have had several failures as you described. Some with very costly crashes when the elevator pulled out. Another failure mode is that the fuzzy surface that is suppose to be bonded to the hinging material de-laminates and the hinge pulls out. I suspect that these hinges are made off shore and are made of an inferior plastic and not nylon or mylar and not bonded properly. I no longer use this type of hinge and have replaced every hinge in my two ARFs with pinned hinges. Pinning them in place, of course, with tooth picks or straight pins. Good Luck Gene

As others have already responded, I use only Sig easy hinges and use newspaper to wick away excess CA while installing them. I have never had one fail yet. Perhaps the way you sealed your gaps put some strain on the hinges.

John VB

Personally, I think the UV-failure reasoning is bogus. I've used CA hinges for almost 15 years, and have only seen two failures. One was during catastrophic flutter when the whole wing half disentegrated. One was when the builder doubled the hinges and used thick CA to install them. The warnings you've seen to not crease the hinge are valid.

Properly installed, I think they are just (if not more) reliable than most other types. Here's my procedure for installation:

There are several rules to follow for an easy, correct CA hinge installation. These rules are good for hinges from different manufacturers, including Great Planes and Radio South. I?ve used them on many planes from pylon racers to Unlimited class Fun Fly planes to even a giant scale Stinger (the 1/4 scale size hinges). I have never seen an in-flight failure using this procedure.

I have seen only two in-flight hinge failures. One failure was from catastrophic flutter, which also destroyed the wing panel. The other was due to doubled hinges and the use of thick CA.

Here we go:

Use a #11 blade to cut the slots. Cut only once per side/per hinge. Use only thin CA. Do not double the hinges. Do not use ?kicker?. Install after covering.

1. Slot the wood pieces, install the hinges, and mount the control surface. Gently push the pieces together.
2. Flex the control surface both ways for the maximum amount of travel you expect to use. This will automatically create the proper hinge line gap.
3. Slowly drop 2-3 drops of CA on each hinge at the hinge line on one side only. If any CA puddles in the hinge line, blot it with a paper towel.
4. When that is dry, apply 2-3 drops of CA to the other side of each hinge.
5. When both sides are dry, flex the control surface both ways.

That?s it! The wood will pull out before the hinge will let go. The surface will tend to stay centered and will not flop around. Both will help prevent flutter. Dr.1 Driver "There's a Hun in the sun!"

I predict you'll get a bunch of comments from people who have had the same thing happen to them. And yet, lot's of people continue to use them. Go figure.

MJC

On 8/12/2004 9:45 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

One thing I would like to add. For MAXIMUM penetration of the CA, I drill a 3/32" hole in the center of the hinge slot. This allows the CA to penetrate into the center of the hinge where it may not normally get to without using excessive CA.

The hinges were cut from the Great Planes bulk sheet.

Hinge slots were cut with the GP electric hinge slotter ( w/ jig ), and a

CyA was carefully applied using a fine gauge insulin syringe.

The only thing I can think of is that I had a bad batch of hinge material.

Mark D. Fain

I've only had one failure, and that was because of my own ineptness. I thought I could use medium CA to glue 'em in and had the elevator part company with a Stick 40. Someone here suggested making a stripe across the hinge with an ordinary child's crayon at the hinge line to keep CA from penetrating the hinge at the actual hinge line, and stick a pin through the center of the hinge to make sure equal amounts of hinge go in on each side. That may help.

Morris

Well, I think you will be surprised. If there was a generic problem with them, people would NOT be using them and all the major kit manufacturers would not supply them.

Properly installed ("properly" being the operative word) they are as reliable and durable as any other type I have seen. The methods to properly install them are also much easier and more repeatable than any other type..

The crayon idea is a good one. keep the flex line from being hardened by the ca..

I like that, I might try it. Dr.1 Driver "There's a Hun in the sun!"

DR1's tutorial is right on, I just pulled out a quickie racer that has been in moth balls for 12 years stuck a .46 on it for breakin and went out and flew just fine. I use Radio south Hinges they are blue and I think the only one that is that color. The only time I have pinned them is with ARF's were the slots are too big and the bond is questionable.

Radio South hindges will not break if properly installed.

Sparky

I have used SonicTronic and Great Planes hinges for many years with no failures.