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Hinging up!

Hinging up!

Andy Green looks at methods for hinging control surfaces - 27/3/12

gazzazh31/10/2011 18:05:35
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Almost lost my plane today due to ca hinges. I wanted to know what makes ca hinges brittle. Is it the type of ca used or the type of hinges . Is it the fuel .. What exactly. I am planning to put together a funtana 125 and it came with ca hinges so before I proceed .. Need some advice please.

In my sparrowhwak that I almost lost , I replace all ca hinges to robart . It was a nightmare cause there was not enough wood for robart. Had to remove covering , add more wood and so on..

Please can anyone advice.

Thanks a million

Cheers
Peter Miller31/10/2011 18:24:16
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I use CA hinges a lot. I use those made by Kavan. I used to use Sig ones when I could get them.
 
Never had one break.
 
I wonder if yours are some strange plastic used on ARTFs.
andy watson31/10/2011 18:37:37
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I never use the CA hinges, I always replace them with other types- like Robarts.
 
Having said that I have no idea why- as yours is the first time I have ever heard of someone who has experienced a problem with them.
Alan Cantwell31/10/2011 21:06:00
3039 forum posts
possibly toooo much cyno, try this, first, draw a line up the middle of the hinge, place through this a single pin, if the hinge has a slot in, dont use it, use solid hinges, dry assemble the joint, have a good look at it, are the hinge slots all in the same line up? many arnt, re-cut if needed, drill down the middle of the slot, a 3mm hole, this is for whicking in the cyno, place the hinge in, up to the pin, whick the cyno down the hole, not a lot is needed, leave to dry, mount the control surface, bend back, and again, whick cyno in the hole, it just may be that there is too much glue, making the hinge brittle, i was going to mention the lack of meat for the robart, which i had now, on the seagull models mew gull, i too had to add some block to get the hinges into, me thinks ALL artf kits suffer from this, whith cyno hinges, its no problem, they just glue to whatever structure there is there, robarts need quite a bit of balsa to glue into, i use kavan leaf and pin hinges, they arnt as fussy,
gazzazh01/11/2011 03:08:40
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Posted by Alan 4 on 31/10/2011 21:06:00:
possibly toooo much cyno, try this, first, draw a line up the middle of the hinge, place through this a single pin, if the hinge has a slot in, dont use it, use solid hinges, dry assemble the joint, have a good look at it, are the hinge slots all in the same line up? many arnt, re-cut if needed, drill down the middle of the slot, a 3mm hole, this is for whicking in the cyno, place the hinge in, up to the pin, whick the cyno down the hole, not a lot is needed, leave to dry, mount the control surface, bend back, and again, whick cyno in the hole, it just may be that there is too much glue, making the hinge brittle, i was going to mention the lack of meat for the robart, which i had now, on the seagull models mew gull, i too had to add some block to get the hinges into, me thinks ALL artf kits suffer from this, whith cyno hinges, its no problem, they just glue to whatever structure there is there, robarts need quite a bit of balsa to glue into, i use kavan leaf and pin hinges, they arnt as fussy,

so maybe i had too much CA and that is why it went brittle.. I heard some people say that it depends on the manufacture of CA and that some manufactures are better that others.. dont know if this is any true.. But i guess i will go with Ca with the Funtana and hope for the best..How many drops are needed.. and after you glue them, do you add more CA.. this is frustrating.. and the funtana also does not have enough wood for robart and it will bring tears to my eyes to remove the covering ..

Thank you all for the help..

Cheers
 
 
 

Wingman01/11/2011 07:20:50
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4 or 5 drops will do the job (depending on the size of the drops) but it must be thin CA. You cannot add anymore CA after the first lot has stopped wicking as it will just pile up on the hinge line and make the control movement stiff. Personally I've never had a CA hinge break on me even in my larger petrol powered planes nor have I had any pull out and I don't pin them.
Peter Miller01/11/2011 08:10:07
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I like the tip of drilling a hole down to help the CA wick in better.
 
I never pin mine either.
Wingman01/11/2011 08:23:28
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Yeah I've always done the hole thing it definately makes a difference but not 3mm I usually do 1.5mm and make sure the hole is clean of wood fibres. One thing I forgot to mention is that I pare away the covering from around the slot with a new scalpel blade so that the CA can only wick into the wood and not under the loose edge of the covering, where it's just pierced for the slot, or run down the hinge line along the wing.
Myron Beaumont01/11/2011 08:52:47
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When the covering is on ,then I find where the slot is behind it and using a little pointed tool with a pencil shaped end,I rub along the surface causing an "V" shaped indentation .Then using a new blade ,I cut the centre of the slot only (easily seen now),Then using the tip of my covering iron I go over the indentation again,,This slightly opens up the recess and re- glues the covering to its new shape for the hinge entrance & allows you to try out several trial fits before the final assembly without dragging the covering backwards and forwards,
I drill a small hole too as mentioned & have never used pins ,You can tell when enough thin CA has gone in as the shallow recess / hinge interface will show a meniscus which usually all but disapears within a few seconds .
Myron YO13 invisible hinge dept
Martin Harris01/11/2011 09:16:58
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Somewhere in the dim and distant past, I read some advice that you should always assemble the joint and wick the cyano into both sides at the same time to avoid hinge failure.
 
While it could well be twaddle, I could envisage that 2 opposing flows (I'm assuming "hairy" hinges, not the smooth ones which I wouldn't touch with a bargepole) could cause a hard line at their junction when the second application meets the original dried glue leading to cracking sometime in the future.
 
Might be worth bearing in mind if you suffer from hinge failures and have glued your hinges in 2 operations?

Edited By Martin Harris on 01/11/2011 09:18:11

Steve Hargreaves - Moderator01/11/2011 09:21:38
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Like the other posters I use furry hinges a lot & have never had a problem with them going brittle & breaking......as has been said I suspect a bit too much CA has been used.
 
One trick I have heard about (& used once or twice although I couldn't tell if it made any difference...) is to run a wax crayon along the centre line of the hinge on both sides before installation. The wax from the crayon is supposed to stop the CA penetrating this part of the hinge....
Wingman01/11/2011 09:30:50
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If you type - How to do CA hinges - into google there's loads of stuff including youtube tutorials - there's even one where they neither cut away covering nor drill holes and two large guys can't pull the joint apart!
Wingman01/11/2011 09:36:00
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I've tried drawing a centre line with a chinagraph (waxy) pencil but I can't say I noticed any improvment in flexibility so I don't bother any more.
Myron Beaumont01/11/2011 17:18:08
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If you use plain non-furry hinges which the majority of my old (still flying-pre furry models have, I must say that I rubbed the first 2/3 of the hinge from each end I rubbed with coarse glass paper . Never let me down .By the way ,the slot should be a good sliding fit, not too tight ,
Lee Smalley01/11/2011 17:33:21
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I have neve had a cyno hinge break until I flew my black horse Ryan sta with 30cc moki in and on second flight the right elevator came off on further inspection some on the ailerons had split and most on the flaps had gone as well.
I dug them all out and replaced with great planes furry hinges and have had no further problems, I think the plastic used in the original ones was too thin and of poor quality they did not feel like the gp. Ones did!
gazzazh01/11/2011 17:51:12
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187 forum posts
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Thanks all.. You have all be a great help.. I am not happy with ca hinges.. this is was only the 4th flight and my hinges were done correct.. I read that sometimes a certain type of CA glue will brittle certain hinges.. dont know i this is true... and how would someone know which thin ca glue is good for which hinge manufacturer.. anyway.. i will install robart hinges so i would not have to worry.. I also heard of a ca glue called flex something that dose not brittle the hinges... not sure of the brand thu.. i hate these hinges.. you feel your never safe..I mean i understand a pilot error that makes u crash.. but crashing because of ca hinges is just tooo much ..
 
Thanks a million
 
cheers
 
gazzazh01/11/2011 17:56:43
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187 forum posts
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Also the problem is not with how to glue ... but is why did the hinges come brittle after 4 flights.. and broke in 1/2 in the middle as if they were cut by a knife...
 
Cheers
 
Martin Harris02/11/2011 00:00:09
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I usually, but not exclusively, use ZAP thin but have never had a problem. I only use them on smaller models (up to .60 size) but on occasions where I've subjected them to extreme functional testing (you might know this as crashing!) they have remained intact with slivers of wood still attached...
 
What type of CA hinges were you using? Furry, fibre, shiny plastic?
Biggles' Elder Brother - Moderator02/11/2011 00:15:32
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I have seen this once before - not on a model of mine but that of a clubmate. Again it was fairly new model with only half a dozen flights on it or so. He was practicing some aeros for a scale comp and I was calling for him. Suddenly we noticed something hanging off the wing - the aileron!
 
After landing (no damage fortunately) we took a look, the hinges had simply snapped along the "flex-line". They were still perfectly glued in the wing and the control surface but all three and broken with a completely clean snap.
 
I use CA hinges a lot - and I've never had a problem nor seen this before or since until you have described now. Worrying.
 
The modeller concerned was very experienced and I sure he's fitted hundreds of CA hinges in his modelling career and I don't think he's ever seen this before or since either. But there would seem to be either some type of hinge, or some combination of hinge material and CA that produces this effect.
 
BEB
Martin Harris02/11/2011 00:27:47
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It might be interesting to know whether the hinges were glued one side at a time (see my previous but one post) in any cases of failure...

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