In flight CA hinge failure...
 

So, up until now I've sworn by CA hinges. Never had a problem, until yesterday. Granted the conditions where not the best with up to 20-25 mph gusting cross wind, but I've never expected this. Take a look at the pictures. This happened mid-air. The hinges look like someone took a #11 exacto knife and cut them off. Luckily I managed to land safely on the runway (not a pretty landing in the cross wind without a rudder:eek:)

What would have caused this?? Now I'm worried about the other hinges. I have already repaired the rudder by using Robart hinge points, but it would be a pain to do that to the rest of the plane.

The hinges were installed per instructions using a GP hinge electric hinge tool to cut the slots and I did drill a hole in the middle.

thanks,

tychoc

RE: In flight CA hinge failure...
 

Any flutter? How much and what type of CA did you use? You didn't double the hinges, did you?

Dr.1

RE: In flight CA hinge failure...
 

That's why I always fly with pinned hinges - never had a failure with them. Klett, DuBro, etc. I like the hinge points, and if installed properly never seen one fail. I seen a couple of planes have flutter with hinge points and they held tight (flutter was caused by to much slop in the linkage and excessive speed in a dive on one plane).

I lost an Astro Hog last year after it went into elevator flutter - one of the CA hinges looked like it failed causing the flutter and blowing one half of the stab off. The other side had a ripped CA hinge also. (I didn't build this hog - it was from an estate sale, that's why it had CA hinges) I'll only use a CA hinge for a slow flying plane like a park flyer or glider that won't get into the speed range to create flutter.

Hogflyer

RE: In flight CA hinge failure...
 

No flutter that I'm aware of, however this is only the 3rd time I'm flying this plane. No, I'm sure I haven't doubled the hinged. I used Zap CA and applied 5-6 drops of CA to each side as I belive the instructions said.

There's no slop in the linkages, but is it possible that a standard servo is not strong enough for this size rudder?

-tychoc

RE: In flight CA hinge failure...
 

The servo might be too small. Also, I only use 2-3 drops of thin CA per hinge side. Too much CA will stiffen the hinge and not allow proper flexing. Some people swear at them, some sweat by them. I've used CA hinges for over 20 years on everything from sport to trainers to pylon racers to giant scale. Never had an in-flight failure.

Dr.1

RE: In flight CA hinge failure...
 

It's possible you may have damaged one or more prior to flight and didn't notice it? I'm not a big fan of CA hinges either but they usually seem to do OK. I prefer the hinge points where I can fit them in. Keep an eye on the remaining hinges.

RE: In flight CA hinge failure...
 

I guess that's possible somehow. Not sure what I did wrong. So far CA hinges have worked great for me. I will also watch for flutter next time just to rule that out.

Yes, I will definetly keep an eye on the remaning hinges. I will try to "stress test" them at home to see if they appear brittle.

thanks,

tyychoc

RE: In flight CA hinge failure...
 

When I get a kit that has CA hinges, I toss them aside and use only the metel pin type. [8D]

RE: In flight CA hinge failure...
 

A friend brought me a fuselage the other day. He had jammed the rudder into someones back while carrying it. In doing so he managed to destroy 2 of the CA hinges. I know they were OK that morning because I had looked the plane over for him before he flew it. I cut the remaining 2 CA hinges (one partially torn) and installed pinned hinges for him.

RE: In flight CA hinge failure...
 

I will never use ca hinges,used them once did not like the way they flexed compared to dubro or klett pinned hinges.I have airplanes that are over 30 years old still flying with the original pinned hinges intalled and no failures or loose hinges.I do check them as part of pre flight each time to make sure,just as on full size aircraft

RE: In flight CA hinge failure...
 

You said you cut the slots with a Slot Machine - That's good

You said you drilled a wicking hole - also good...

The question that comes to my mind is: Did you have the rudder flexed MORE THAN IT WOULD TRAVEL IN FLIGHT before adding the CA?

I find that this type of failure is almost always caused by this. You can't just flex the surface a little (either in hopes of keeping a small gap or any other reason), it MUST be flexed farther than the servo will move it or this type of failure is almost sure to happen.

RE: In flight CA hinge failure...
 

sorry but what is a pinned hinge?

RE: In flight CA hinge failure...
 

A hinge with a metal hinge pivot pin in it?:D

http://www2.towerhobbies.com/cgi-bin...?&I=LXD940&P=7

RE: In flight CA hinge failure...
 

When you go to epoxy a pinned hinge, make sure you heat a bit a vasaline in a spoon, fold the hinge in half and dip the hinged portion in. You want the liquid vasaline to penetrate around the pin - this keeps exoxy out of it and keeps it from being a pain to free up. Also, make sure you don't mix up the protected (vasalined) hinges from the non-protected or you'll spend an evening with an X-Acto blade cutting out epoxy and flexing the hinges - and don't as how I know that :D.

Also, some people will drill and put a tooth pick through the plastic flat to secure it in place after they epoxy them in place just for added security so they won't pull out.

Hogflyer.

RE: In flight CA hinge failure...
 

If you use hinge glue
http://www2.towerhobbies.com/cgi-bin...&I=LXCX67&P=ML
the extra care will not be needed. Or at least that is what darock has promised me. I haven't tried it yet myself. :D I'm willing to trust him though.

RE: In flight CA hinge failure...
 

Bruce,

Next time I do hinges I'll try that hinge glue. If it does bind them up I'll expect you to head west a bit and take care of flexing them for the evening until they free up - don't worry, it's only about a 9 hour drive over mostly 2 laners. :D

Hogflyer

RE: In flight CA hinge failure...
 

Not me, call Darock! [:@]:D

RE: In flight CA hinge failure...
 

Or you can call some friends of mine in Gridley,Ks.

RE: In flight CA hinge failure...
 

At this point I don't know if I did flex it appropriately. This certainly is a possible reason for the failure. Due to the strong cross wind, I had the rudder on high rates while taxing on the runway and several times I had to give full rudder to turn the darn thing around.

I certainly will remember to check for this in the future:D

-tychoc

RE: In flight CA hinge failure...
 

I accidently dropped some thin CA on my pants a while back; when I flexed the spot where the CA was the cloth BROKE like a piece of glass!! What does this tell you?

RE: In flight CA hinge failure...
 

Cheap pants that shouldn't be used as hinge material? :D

RE: In flight CA hinge failure...
 

This tells you that you should:

1. Not use your jeans for hinge material.
2.. Not wear the PLASTIC hinge material as clothing.
3. Wear an apron in the shop.
4. Be less clumsy.

Dr.1

RE: In flight CA hinge failure...
 

It's really interesting that the hinges failed after only three flights. Never seen any that failed that quickly.

It appears that at least some of the CA hinges that fail were not installed in slots that were straight along the hinge line. If the slot isn't cut in line with the surface the hinge can't easily flex along just a simple fold. It'll stress from each side. I've seen a number of prehinged "you get what you pay for" models that had hinge failure and two things were common in each case. There was at least one hinge that wasn't in line, and the hinge material was the naked or slick plastic. They weren't the layered CA hinges that have wicking material on both sides.

I would hazard a guess that either one of the outboard hinges was not in line or had been nicked. Some plastics will tear easily if given a starting place for the tear.

I also wonder if some of the plastic used might not be weaker in one direction and more likely to tear across than lengthwise (or vice versa).

RE: In flight CA hinge failure...
 

I almost always use flat "pinned" hinges instead of CA ones, but it's mostly because.... awwww, forget this long winded spin off..... back to the topic:

I do use CA hinges sometimes, and have started flexing them before using them. I flex in both directions to see which way, if any, they bend easier. And I've run into a couple that seemed odd feeling and trashed them. And seen a couple that had ragged edges, although the "ragged" wasn't along the edges that'd be flexing.

When I started out checking them, I thought that they all seemed pretty stiff to be good hinges. I was "brought up" in modeling to understand that any binding or resistance was detrimental. That's not nearly a problem today in RC. But I recently started assembling a SkyBolt and was taken by the obviously greater quality of the hinges in that ARF. They were obviously better than all that I'd seen before.

So it's clear that there is a fairly wide range of quality in CA hinges.

I guess we're just going to have to develop some experience with them that includes learning to spot the ones that are going to fail. Now, if we just knew what to look for.

RE: In flight CA hinge failure...
 

I CAN'T STAND IT!!! I GOTTA SPIN OFF!!!!!

I have found that for me, it's as quick to use Dubro flat pinned hinges as it is to use CA hinges. I use hinge glue and it's dead easy and quick. And I've yet to assemble a pre-sliced ARF that didn't have a couple of skewed slices or slices that were above or below the hinge line and was going to need correction.

I discovered through autopsies, that CA hinges that're simply slipped into the slices through Monokote don't always wick CA into them. And drilling the wicking holes takes time that isn't needed with flats and hinge glue, so that balances out. So if I do use CA hinges, I spend time slicing away covering, and drilling wicking holes. If I use flats, I spend less time with a piece of hacksaw opening the slits. And can easily correct skewed slices or off line slices, and the covering "closures" are actually a positive. The glue gets into the slots because it's mechanically put there and the covering closing back simply helps fuelproof the area.

OK..... sorry...... had to spin............

RE: In flight CA hinge failure...
 

I've become the "coroner" at our field. I do autopsies. Truth is, I've been doing them on model airplanes since my first one and that was back...... sorry...... starting to blabber......

After looking at the three pictures of the failure, I've noticed something. Everyone would certainly agree that from the 1st picture it's clear that the hinges failed from the top one down. Now, if you look at the 2nd picture, look at the top hinge.

Where did that sucker let go? Down inside the slot, right. You can see that the hinge material that really should be in the slot is gone.

I'd hazard a guess that it wasn't a flex failure that defeated that hinge. The sucker shouldn't have been able to flex down inside the wood. And it wouldn't have wanted to anyway. No doubt the model checkout for the maiden and next two flights included working the rudder and the model certainly was taxiied some. So the hinge must have been flexing ok along the hinge line. Yet the failure is obviously away from that line.

My coroner's report would suggest the quality of materials of the hinge material in the top hinge gave under load due to a weakness in the material near the hinge line. We've all seen plastic stuff with bad streaks in them, right.

......... ok, time to quit running my mouth

RE: In flight CA hinge failure...
 

As has been said about CA hinges - some people swear by them, some people swear at them. But any hinge that you have to know so many "secrets" to install correctly have too much wrong with them.

CA hinges are the only hinges ever made that have this high of a failure rate. Every other hinge system is better including monokote hinges and sewn hinges. I guess if you know all the secrets then there's nothing wrong with using them.

Add me to the group that only uses "real" hinges. I always trash CA hinges when they come in a kit.

RE: In flight CA hinge failure...
 

Now I'm disapointed - I was just getting ready to hear some stories of Langley and his Aerodrome....... :D:D

Sorry, but I just could resist that open door....... ;)

Hogflyer

RE: In flight CA hinge failure...
 

Thankx for the info on the hinge glue. I have a bottle of it but haven't used it because as mentioned before, it ljust looks like wood glue. I won't be so leary to use it now. I always pin my hinges after any way with the round tooth picks and wood glue. Then I dremel the outside edges flat and seal them with a drop of CA. [8D]

RE: In flight CA hinge failure...
 

hogflyer,
That whippersnapper Langley? JohnnyComeLatelys ain't worth talking about. Heck, he didn't even build his own motor, did he.

Now Leonardo was a modeler you can get me to talk about. He was over to my hut one day, wantin' ta borry some balsa wood 'cause I'd just discovered it and........

;)

RE: In flight CA hinge failure...
 

While I've never had a CA hinge fail, I can say that I don't use them unless I have to. Robart hinge points are soooooo much easier to use. They are bullet proof, easy to align, easy to glue in with poly, inexpensive, strong, I could go on and on.

Once you go Robart, you'll never go back. :)

RE: In flight CA hinge failure...
 

I think I will be joining the "throw away CA hinges" camp after this....:)

Just the thought that the model could have crashed on it's third "day" out after hours and hours of building the kit is enough. No chain is stronger than the weakest link etc.

Consider me converted, well actually, when I was a kid and built kits (70s and 80s) there were no CA hinges and I used the regular pinned ones, so I guess I'm going back to what I used to do. :D

-tychoc

RE: In flight CA hinge failure...
 

Fastsky,
Make up a quick and easy test. Cut a slot for a Dubro flat pinned hinge in a couple of pieces of balsa. Drill the holes for robarts too. Use the hinge glue and take only the minimum effort. After the drying time suggested. Try to pull each apart. Then go ahead and cut what's left up to see how well both are glued to the wood.

I think you'll find that both types were very, very solidly glued to the wood. I wound up trying to hold the balsa in a vice without crushing it so I could pull harder. And autopsys of crashed airplanes will have pulled hinges, but the flats are still solidly glued completely to the shredded balsa that was pulled out with the flat.

Robarts are excellent and easier with hinge glue.
Dubros are excellent and easier with hing glue.

I wish I owned the company.

RE: In flight CA hinge failure...
 

Well, like Deadeye, I too have never had a CA hinge fail. However, with the exception of a few large-scale planes, I have used CA hinges exclusively since the late 80's - that's almost 20 years.

I have even used them on some large-scale gassers.

Two of the planes that I used them in back in the 80's are still flying.

Also keep in mind that I do product reviews for RCU. That means that while most guys build one or two planes a year, I build about one per month - and I have NEVER had a failure.

Are there a lot of "Secrets" to getting them right? No.

I wrote a "How To" about putting in CA hinges that many of you may have read where I say to "Remove the covering around the hinge slot, and drill a wicking hole" - The truth is, I don't even do THAT! I put them in, bend the control surface MORE THAN IT WILL MOVE IN FLIGHT, and add 4 - 5 drops of CA (to each side)

I have used every type of hinge on the market (And some that AREN'T on the market) and NOTHING is easier.

As far as CA cracking the material of your pants, yep, I've got several articles of clothing with one of those dredded CA cracks, but this is FABRIC that the CA wicks into and hardens. CA does not wick into the plastic which stays flexible (AS LONG AS YOU HAVE GIVEN IT ROOM TO FLEX)

THE single most critical thing about installing CA hinges is to hold the control surface in a deflected postion (Once again, more than it will move in flight) as you are applying the glue. If you do that, you should never have a problem.

RE: In flight CA hinge failure...
 

I love the CA hinges........I have never had them fail.......Darock...good coroners report, but I need to be devils advocate here...I agree the top hinge was the first to go....But under normal circumstances the others should have held tight....I feel flutter must have torn the hinges for all of them to go like that...My 2 cents...

Also I never drill wick holes or open up the slots anymore than to slip the CA hinges in....I would say one of the most important things that is commonly overlooked is to use Super Thin CA........very important...I think alot of people use the regular CA they got laying around.....Doesnt wick very well at all.....

RE: In flight CA hinge failure...
 

One thing I didn't see in any replies (may have missed it) but double applications of CA can and will cause failure. The failure in the picture looks like the CA hinge 'tore' away from the joint, not pulled out from the balsa that it was set into. Double applications of CA can result if you put one side of the hinge in ( let's say you put it in the vertical stab ) and let it set. Then apply CA then attach the other side of the control surface, in this case, the Rudder and let that set too.

This is a double application of CA and is probably going to fail. I saw this myself with my Tiger 60 aileron a while back.

I was not aware of this double application of CA and, for simplicity sake, and because I didn't know better, I put the hinge in the wing TE and applied glue then mounted the ailerons and applied glue again. Not good. After several flights, I noticed that the ailerons were beginning to get 'loose' or flex when pressure was applied. My flight instructor asked me a few questions and it came out that I had applied CA twice to the hinges. We took the ailerons apart, and re-hinged it, this time correctly. The old hinges were loose in their slots and were ready to pull out. One actually broke or tore like the picture above.

That does not mean that this was the cause of the failure, it appears that flutter may have taken it's toll by tearing as mentioned above. But dual glue applications can and will make the hinges brittle and prone to failure.

DS

RE: In flight CA hinge failure...
 

Wow! It seems that even though there are lots of flyers that swear by the CA hinges, there are lots of rules that have to be followed or the hinge will fail!! From following this post I have concluded that I will stick will my metel pinned hinges and I will try the hinge glue that I have a full bottle of. [8D]

RE: In flight CA hinge failure...
 

For pinned hinges, I've always had an issue with the glue being wiped off the hinge as you insert it into the slot. It always made me leary of the amount of glue that is actually in the slot.
My friend came up with (or at least suggests) using a small syringe (he uses one that came with a tooth whitening kit) filled with glue and flattened on the end to fill the slot with glue.

By the way, he submitted his idea to Tower Hobbies and they gave him a $20 credit for his next order. Something to keep in mind.

RE: In flight CA hinge failure...
 

Back when I built a PT-40, I used Dubro hinges. Manual suggested using a soda straw with the end flattened to do this. Scoop up some epoxy with the flattened straw, insert it into the hinge slot, blow. Worked pretty well

RE: In flight CA hinge failure...
 

The flat Dubro hinges have holes through the flats. Those holes are the trick.

The hinge glue solves the problem as well. It's simple to place the tip against the hinge slot and squeeze. You can see that glue gets into the slot. Now, take some time to smear glue on the flat of the hinge that's to go into the slot. That time gives the glue in the slot time to start soaking into the balsa. And the slot isn't going to be smooth on the insides anyway. The gouges and cracks in that slot are going to soak some of the hinge glue into themselves. It's also very easy to use the hinge glue bottle tip to spread a thin layer of glue on the hinge flats. The glue coming out of the bottle almost automatically fills each of the holes in the hinge flat.

The hinge glue starts to get tacky almost right away. By the time you've gotten the hinge flat lightly coated with it's holes filled (something that was dead easy to do and actually didn't take any time at all) the glue on the flat is tacky and the glue in the slot has worked into the balsa. When you push the hinge into the slot you'll feel the tackiness. But you'll also see some excess push back out of the slot.

Once the flat is in the slot, the glue that rode into the slot in the holes in the flats will then start to bridge from the balsa on one side of the slot to the other. You'll have glue "pins" from balsa to balsa in 6 places on each flat.

How do I know all this "inside" stuff? I've done some test hinging and torn the test pieces apart. And I've had the opportunity to autopsy some crashed airplanes that had Dubro flat hinges glued in with hinge glue. Do that yourself and you'll find out for yourself just how well the hinge glue holds to flat, pinned hinges. But be prepared for an effort. You WILL have some trouble getting down to the hinge flats themselves. They will be solidly "coated" with balsa that isn't coming loose without a struggle.