ramcharger

The last 2 times I have flown my TF (red box) P-51B Mustang, I noticed CA hinges were broken. Once, 2 of the 3 on the aileron and now 1 of 4 on the elevator. Luckly it has affected flight although I'm still mystified on the aileron. I have been using CA hinges for 9 yrs and no problem. Is some CA hinge material better than others????? Also, on this plane I made a extra efffort to minimize the gap and got thin CA on the portion of the hinge that bends. I'm sure I have done this before, anyway, is that a no-no ??????????????

AtomHeartMother

Yup, CA on the bending part of the hinge is a big no-no. Honestly, if you'd done this in the past, I'm surprised you hadn't lost an airplane.
The CA on the bending part of the hinge makes it stiff and brittle. It then quickly cracks right in half if deflected. Try it on a hinge before you install it as a test, you'll see what I mean.
A good trick is to mark the center of the hinge, then use Vaseline or even a wax crayon on the center of the hinge where it will bend. Install the hinge, then wick your glue in like normal. Once the glue has dried, clean off the wax or Vaseline and you're ready to go. Putting something like mentioned above on the bending portion of the hinge keeps the glue from soaking into it and making it brittle. If you think you've gotten glue on hinges of your other models..I'd take a good look at them and replace any suspect hinges. Sometimes, if you're quick the CA will pop off the hinge if you pick at it, leaving the hinge flexible.

TerrellFlyer

I USE BOTH METHODS AND SO FAR CAN'T TELL ANY DIFFERENCE,THINK MY OLDEST PLANE IS SEVEN YEARS

AndyF

My Feedback: (2)

AtomHeartMother,

I had never heard of this before. I just installed 5 hinges in in the ailerons of my Patty Wagstaff 300S that I now going to have to redo.

Thanks for the tip, you may have just save an airplane.

Andy

Joe B.

My Feedback: (1)

I've always soaked the entire hinge with thin CA. Never had a problem and although in theory it sounds plausible I think if any sort of experiment with valid imperical data were conducted you would find it next to impossible to NOT get CA on the bending portion of the hinge. Keep in mind, the hinge acts as a WIC and will draw the CA in all directions. I can not imagine a way to glue the hinge from the and not have it wic in all directions from the area where CA is applied to (directly adjacent to hingline where it touches balsa. If you're not putting enough CA to wic 1mm backwards you're definately not putting enough to wic 1/2" inwards into the wood. You HAVE to glue them from center outwards, it's by design.

Steve Guinn

NOT a no no. Install hinges in both surfaces and then put 5 or 6 drops of thin CA on each side. Makes no difference if you put vaseline in center. CA wicks through entire hinge through capillary action.


P.S. Seems to me the vaseline would interfere with the CA being absorbed by the hinge and you would end up with a weak bond.

vtsmx-DELETE

For what it's worth, here's my experience with CA hinges. I've had them on a GP 1.20-sized Super Sportster, the Midwest At-6 (84" WS), and the Midwest Extra (80" WS). All had over 100 flights. On all three I just inserted the hinge and applied CA to both sides. Didn't have any failures. I'm putting together the GP Wagstaff Extra and am using the CA hinges. This time I thought I would try putting a thin line using a white crayon at the center line of the hinge. After applying the CA it does seem that the hinge is left more flexible. Haven't flown the plane yet but I don't have any reason to belief the bond is any less secure because the area with the crayon is very narrow. Just my .02.

vtsmx

ramcharger

Normally I drill 3/16th inch diam hole down the middle of the slot and clear away the wood grain created by the turning drill and put the CA down the hole, on each side of the hinge. I didn't do that on my P-51B because of looks. I think its a good practice, although I must agree - a little ca wicks all over the hinge and I recall most of the time my CA drips from bottle before I get the nozzle near the hole and I get CA all over. I really don't want to go back to the plastic hinges. I tried all of them and they are not without problems either.

vtsmx-DELETE

On the Wagstaff Extra I'm putting together I'm using CA hinges from Sonic-Tronics. They have a slot cut in them which supposedly helps in the wicking action towards the rear of the hinge. I would think the slot eliminates the need for a drilled wicking hole. The instructions say to put the hinge in one surface, apply CA, and then add the other half of the surface, such as the aileron, and apply CA again. I thought it would be better to install the hinge in the trailing edge and then attach the aileron, etc. first and then apply 4 or 5 drops to both sides of the hinge.

When applying the CA to the hinge, are you using the really small applicator? It's small enough that you can get it right down to the hingle line and then count the drops as you apply pressure.

vtsmx

Joe B.

My Feedback: (1)

I use a very small applicator. Severl of our LHS's sell small plastic tubing (less than 1mm OD) that you stick in the end of your bottle. It comes in seceral foot sections and you can cut off however much you need. I use 3 or 4 inches so I have enough to put the end of the tube (very small) in the hinge, then tilt the bottle and can actually see the CA move up the small tube and get just the right amount. This tubing is smaller at the tip than the small applicator supplied with ZAP brand CA.

ssmith

I came real close to losing a plane because of CA hinges. 2 out of 4 elevator hinges ripped in half and the plane barely pulled out of a dive. Last time I'll ever use CA hinges.

AndyF

My Feedback: (2)

After having lost a bunch of CA hinges on the elevator of my trainer over the course of a flying season, several years ago, I went to wider hinges and the problem seem to go away. Because of that, I am in the habit of checking all of my hinge surfaces before I fly. Its the old ounce of prevention worth a pound of cure thing.

Andy
CORCS - Central Oklahoma Radio Control Society

rajul

My Feedback: (58)

Not all CA hinges are created equal. I did an evaluation with gp and sig hinges a while ago. Slotted scrap balsa and drilled the centers of the slots. Inserted the hinges and dropped thin CA on both sides of hinges. Left them to fully cure before pulling them out with a pair of pliers. Result : the sig hinges came out without any balsa on it. The fiber cloth stayed inside the slot and only the middle plastic film came out clean. The gp hinges pulled out the balsa with them and no separation between the fiber/plastic film was seen. FWIW..............

AtomHeartMother

That's a good point rajul.
I got to thinking about it and noticed that there seems to be different types of CA hinges. I honestly thought they were all the same. The hinges I've seen fail came in a card and you cut them out yourself. These did seem a little thicker than hinges I've used on other models.
I guess it depends on what kind of material it is. Only way to know is to test it. I found an old modeltech construction manual laying around, and in that manual it did recommend using Vaseline or something on the bending portion of the hinge to insulate it from the glue. It also suggested epoxy as the preferred glue, not CA. The hinges looked like any other CA hinges I've seen...very odd. I haven't seen those instructions in any other kit manuals. Either way, as stated above and thorough pre-flight check is the best solution.

MinnFlyer

My Feedback: (4)

I'm with the majority here. I don't use wax or vasaline, or anything, I drill a wick hole (unless the hinge is slotted), and I have 10 year old planes still flying with no hinge issues

One thing that ramcharger said however, has caught my attention:

When you install CA hinges, deflect the surface MORE than it will move in flight. This will result in a larger gap because the more you deflect the surface, the more hinge will pull out of the wood. You can (and should regardless of it's size) always seal the gap later. Without deflecting the surface, you may end up with a smaller gap, but at what price? Now, every time you move the control surface, the hinge is trying to pull out but can't, resulting in stress on the hinge, the wood, and the servo.

ramcharger

Minn Flyer - You recommendation seems to fall right in line with what happened to my Mustang. I have never had any problems with CA hinges with or without CA on the bending surface. On my P-51B I pressed the control surface straight into the wing, fin, and stabilizer in an effort to eliminate any gap. This put the hinge in tension when deflected. Normally I do what you suggested - deflect the surface to some slightly exaggerated amount and insert the CA in the hole. You then get a gap and you can deal with that later. I never had a CA hinge break in 15 to 20 previous planes and now I break 2 on the right aileron and 2 on the elevator. I did the test of soaking a few different brands of CA hinges, CA'd them between balsa (made sure I got CA all over each hinge) and mounted them to my drill press plate that deflected them each at a couple 100 rpm (in both directions) and none broke. Not sure of the brands, some I cut from a sheet and some where from kits. They represent the ones I would use since I have a small drawer full of the them. The flyers at our field have very mixed opinions on CA hinges. Our 2 best builders say they won't use them any more because of failures. No hinge is failsafe, I have now had failures with all of them.

OUTCAST

This may be an obvious point, but CA hinges don't handle high frequency vibrations very well. I know for a fact an out of balance prop, espically on a high RPM 2-stroke can cause a failure. We proved it on a trainer that broke 2 elevator hinges in a row, the prop was changed and the problem went away, the student broke the new prop and put the old one back on and it broke a third hinge. Since then the prop has been replaced and with 30-40 more flights there have been no problems. Just check the balance before you condem the hinges or airframe.

Crash_N_Burn

Forgive me if some one already posted this, I looked and didn't see anything so here's my theory about CA hinge failures....

IMHO, It's not the actual properly saturated CA hinge that causes the hinge to fail at the flex line, but an excess of CA that puddles at the hinge line and hardens into little sharp crystals and actually cuts the hinge.

I examined a number of mine that failed last year under a strong magnifying glass and you can clearly see the crystal deposit and can tell that the hinge had been cut, not a normal mechanical wear failure.

To cure this I started drilling a hole in the center of the hinge slot as MINN said and reduced the CA to 3 drops a side. Additionally, to ensure no CA builds up on the hinge line, I mark it with a crayon. Use only GP cut-to-size hinges and cut to 1" x 1-1/4" for 60 size applications, a little oversize, but, hey.

No problems whatsoever.