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Hinge problem

Old 02-06-2010, 07:20 PM
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Jetdesign
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Default Hinge problem

I would like your advice:

I was just walking past my plane on the build stand and wiggled the rudder, and a hinge broke. I cut all the hinges and am up for suggestions on re-hinging the rudder, and whether or not I should do the rest of the plane. Truthfully I am not happy with the motion of the other surfaces. I'm sure there are people who prefer CA hinges but I never liked the way they come out.

One thing I noticed is that the bevels on the rudder are not cut symmetrical, so the point is not really centered on the rudder. The hinges were cut on the point so the rudder was installed slightly off-set, and thus motion was disturbed by the glued-in tail wheel. I noticed this right away and changed out the tail wheel for one with a spring, though I don't understand how this could have been a problem since the rudder has just been hanging loose on the build table with no servo installed yet.

So, what should I use on the rudder, should I re-do the rest of the plane, and do I really need to reshape the leading edge of the rudder?

Thanks.
Old 02-06-2010, 07:39 PM
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NJRCFLYER2
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Default RE: Hinge problem

Joe, just slice off the CA hinges flush with the wood, then use the small Robart hinges with 30 minute epoxy to bond them in place.
Old 02-08-2010, 07:59 AM
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mtcarey
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Default RE: Hinge problem

I use this to get the hinge on center
http://www.centralhobbies.com/Tools/...ent.html#Taper

I use to have problems with CA hinges breaking. I then used a small hypodermic needle to inject the thin CA glue between the wood and the hing
keeping the glue off the area were the hinge flexes. So far 3 years of pattern competition and no failures.
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Old 02-08-2010, 12:10 PM
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Ryan Smith
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Default RE: Hinge problem

I've never cared for CA hinges on a pattern plane much anyway, especially on the rudder. You'd probably feel better using pinned hinges or hinge points.
Old 02-08-2010, 12:26 PM
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Jetdesign
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Default RE: Hinge problem


ORIGINAL: Ryan Smith

I've never cared for CA hinges on a pattern plane much anyway, especially on the rudder. You'd probably feel better using pinned hinges or hinge points.
I started cutting the rest of the hinges the other day, and it felt great! I ordered a few sets of the 1/8" Robart hinge pionts along with the drilling guide; hope to have the plane fixed up and balanced by the end of next week.
Old 02-08-2010, 05:40 PM
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matt13
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Default RE: Hinge problem

As always nothing is simple. I have seen Robert hinges fail by pulling straight out, I think that the problem comes from having too tight a fit which pushes off most of the glue when fitting the hinge. I have used pinned hinges in the past, but have seen a lot of CA hinges in pattern over the last few years with out too many problems. But I have always found that once you have the cut off and replace a CA hinge, the new one is much harder to fit.
Old 02-08-2010, 08:54 PM
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NJRCFLYER2
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Default RE: Hinge problem

I have seen Robert hinges fail by pulling straight out
I've seen wheels fall off! They weren't mounted correctly either.

Use a decent 30 minute epoxy, butter up the hinge hole and the hinge, wipe off excess as it is fit into the opening.
Old 02-08-2010, 09:15 PM
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Jetdesign
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Default RE: Hinge problem

so 4 on each aileron, 3 on each elevator half, and 3 on the rudder sound right? It's a 110 size plane.
Old 02-08-2010, 09:18 PM
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Default RE: Hinge problem

3 on the rudder sound right?
I would probably use 4 on the rudder.
Old 02-08-2010, 09:19 PM
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Jetdesign
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Default RE: Hinge problem

will do, thanks for the help Ed.

May is getting closer and closer...
Old 02-09-2010, 04:03 PM
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Jason Arnold
 
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Default RE: Hinge problem

Pacer Hinge Glue works a treat on both Robart and pinned hinges. I don't use epoxy at all for hinges now.

Try some on a piece of scrap balsa with an old hinge. You won't break the glue joint thats for sure.

Cheers
Jason.
Old 02-09-2010, 05:13 PM
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Default RE: Hinge problem

Looks like Hinge Glue is discontinued. I have 'canopy glue' but not sure if that's the right thing to use. Supposedly the Zap glues will etch the surface of the hinge for a better bond, while epoxy doesn't necessarily bond to the plastic?

Robart says a few different glues will work, and they list epoxy, so that's probably what it will get.
Old 02-09-2010, 05:32 PM
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Default RE: Hinge problem

Just called Robart. They said to use Epoxy.
Old 02-09-2010, 09:00 PM
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Rendegade
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Default RE: Hinge problem

I recently completed a GP cap 232 27% unsing the supplied robart style hinges. They're good but I've seen a fair few fail on planes I've seen and/or bought, so in an effort to make sure that didn't happened, I made extra sure there was enough epoxy in each hole and all over the barbs of the hinges.

Seems good, but after all that I feel they're heavy, and I still don't trust them that much. Time will tell I guess.

for the record, I've used CA hinges on pattern ships and haven't had a problem, but I do like the klett/ fu-bro style hinge, where i can run a single wire through all the hinges, and remove the control surface if need be. I don't know why but I feel safer with this setup than anything else.
Old 02-09-2010, 09:47 PM
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Jetdesign
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Default RE: Hinge problem

I'm sure the CA hinge failing was my fault do to imperfect gluing techniques. I like the Robart because it seems that there is a little more of a mechanical hold versus the 'du-bro' plastic pin-hinges. Even on the CA hinges I have that have held up fine, I never was satisfied with the range or restriction of motion of the control surface.
Old 02-09-2010, 11:04 PM
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Jason Arnold
 
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Default RE: Hinge problem

It's still on the Zap site but Tower doesn't seem to list it anymore...

http://www.zapglue.com/Hinge.html
Old 02-09-2010, 11:18 PM
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Default RE: Hinge problem

Most people that carry it seem to list it as discontinued, and Robart confirmed this when I talked to them today. I was advised that epoxy would result in a stronger hinge joint compared to canopy glue.
Old 02-10-2010, 07:06 AM
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lodomjr
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Default RE: Hinge problem

gaRCfield,

Somewhere I watched a video of a guy using hinge point from Robart and he glued them in with polyurethane glue. With the swelling action of this glue you will have a hinge that will never fail. The trick to this method is how to handle the glue because of the swelling action. As normal you have to oil the hinge elbow and do all at once for the surface you are working on. One thing this video showed is that the guy had to baby sit the whole thing because the glue foaming action would push the control surface out. I was not going to do that so I took a little Vaseline and put a thin film on the control surface and wing hinge line, I even let the vaseline go on top a little. This is to keep the glue foam from sticking to your finish on your wing. Now the fun part, take a small q-tip and wet each hinge hole with water, then put a small amount of glue in the hole and a small amount of glue on the hinge tips. Make sure you use a small amount of glue, it goes a long way. Put the hinges in, then the control surface on, move the control surface up and down, this will align the hinges in the hinge line. Now get masking tape and tape the control surface to the wing so the glue can not push it out. Come back about 30 to 45 minutes and you should see the foam blob at the hinge point. Don't freak out, take a small exacto chisel blade and carefully pull the foam out. If the glue is still wet and can smear wait a little longer. It should be soft but not leave a residue and the foam blob should just break out clean.

I put these hinges on a patten plane once and I know they are heavier that Radio South CA hinges, but I promise you this, your glue job will not fail. I also had no gap in my hinge line and the control surface moved with such ease. If you took the servo loose the surface would fall full travel down. Just remember to use a small amount of glue. Ask me how I know, I got that crap on everything in my shop.
This sounds like a long drawn out method, but once you do it the first time it's really easy and fast. You may come up with a better method than mine. Good luck I hope I was some help.

Larry
Old 02-10-2010, 08:05 AM
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Default RE: Hinge problem

David Johnson wrote this short article on installing Robart hinge points with polyurethane glue, there is an attached video which I haven't watched:
http://www.rcuniverse.com/magazine/a...article_id=269


Similar to lodomjr's approach but David's article suggests revisiting the just-glued assembly every 5 minutes or so, untaping, flexing and retaping.
Old 02-10-2010, 09:37 AM
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Default RE: Hinge problem

Just to make sure, was I supposed to get the 1/8" size or the 1/2A size?
Old 02-10-2010, 12:12 PM
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Default RE: Hinge problem

I think that's where is saw the video on gluing in the hinges. Basically I just modified his way of doing it. As far as the hinge size I used the 1/8th inch size. I notched the control surface at the hinge elbow to allow clearance for the elbow to work and keep the hinge line tight. If your surfaces are covered in monokote and you get some glue where you don't want it, acetone will dissolve the dried glue. If your plane is painted, well just don't get the glue where you don't want it to be. Just make sure that you put the vaseline on everywhere around the hinge hole including the entire trailing edge of the wing and leading edge of the control surface. My rudder and elevators on my pattern plane were both done using my method and they were both painted. It looked good and the hinge line was tight. Just my 2 cents.

Larry
Old 02-10-2010, 12:25 PM
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lodomjr
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Default RE: Hinge problem

I just watched the video and that's the one. Great info and the only difference is I put the vaseline around the holes and everywhere else I think the glue might get and let the glue do it's thing for about 45 min. After you get the foamed up glue off the hinge area use a little windex to get the vaseline off. Like the gentleman said on the video you will have a hinge that will never fail.

Larry
Old 07-11-2010, 01:21 AM
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Default RE: Hinge problem

i have always used yellow carpenters glue on my robart hinge points both the 1/8 and 3/16 and never had one pull out
you have to put the glue into the hole and a little on the hinge point
no way would i use polyurethane on them due to the foaming action
and epoxy is way to messy
as far as c/a hinges go i built a giant scale aeromaster in 2000 the kit came with c/a hinges
they began to break at the hinge point within a dozen flights
i no longer use them on giant scale but would on .60 or smaller airframes
Old 07-11-2010, 09:01 AM
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Default RE: Hinge problem

I think the primary reason for CA hinges breaking is using too much CA. People have a tendency to glue the hinge, then go back and glue it again just to make sure it is 'good'. That second/third covering of CA bridges over the hinge pivot area and makes the hinge brittle at that point. Continued flexing of that stiffer joint causes the hinge to break. I am only referring to the hinge breaking, if the hinge pulls out, that is a different problem.

The process I go thru is to assemble the pieces with the hinges in place, flex the control surface one way and wick thin CA into the slot on each side of each hinge. Turn the piece over and flex the surface the other way and repeat the wicking process. Let everything kick (do not hit with accelerator) and flex the surface back and forth a couple times. Do not, I repeat, do not apply more CA across the hinge line. After a mentor taught me this approach, I have not had a CA hinge break.

Woodie

Old 07-11-2010, 09:17 AM
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Default RE: Hinge problem

I use Dubro pinned hinges for my 2m and smaller planes. They are light, strong and allow absolutely free movement of the control surfaces.

I heard good stories on CA hinges but never tried myself. Seems the correct installation is hard to achieve.

For 50cc or larger planes, Robart hinges are the way to go. The stems should be sanded lightly though to allow good grip by the glue.

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