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Hinges - how many ?

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DaveyP10/02/2018 18:45:47
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206 forum posts
47 photos

Hi all,

Again I'm picking your brains, the wing I'm currently building for my trainer is 60" with each wing having an aileron of around 24" .

So how many hinges should I have on each wing ? I am thinking either 3 or 4 which would be approx. 6 or 10 inch centres.

Is there a recommended distance or is it suck it and see....

Tia Davey.

Glyn4410/02/2018 18:49:13
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701 forum posts
92 photos

3 large Mylar should be sufficient I reckon.

Malcolm Fisher10/02/2018 20:13:51
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618 forum posts
7 photos

I tend to use either sewn hinges along the full length of the control surface or make a hinge with the covering material. The latter makes a hinge with no air gap which is more effective.

Malcolm

cymaz10/02/2018 20:35:32
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8666 forum posts
1177 photos

If it were mine...4 hinges. And don’t forget to pin them if you need extra protection.

Don Fry10/02/2018 20:51:17
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3946 forum posts
42 photos

Three.

Logic, if one fails, the two survivors gets you down, so you can repair the failure. Two hinges, and one failed, you crash. Four hinges, and one fails, why not wait, you still have margin for failure.

And, hinges have to be fitted square to each other, or else the surface becomes stiff. More hinges, a greater chance for the installer to get one wrong.

If the above logic is wrong, the answer is a hundred hinges. Think about it.

ChrisB10/02/2018 21:26:04
1220 forum posts
34 photos

All depends on the size, weight, performance and power train. If a small electric, or a low performance electric, then mylar will be fine.

If IC or high performance, I'd personally use robart or the kavan split pin plastic hinges, both glued using epoxy and pinned (other than robart of course).

Minimum of 3, as Don says, in theory, less chance of loss, or a full length film/tex hinge. Mylar is ok, but I have found it to be prone to failure due to engine vibration and given ts usually glued using cyano, which can cause the hinge to go brittle.

Piers Bowlan11/02/2018 06:34:44
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1871 forum posts
45 photos

For years I have used pin hinges and epoxy but I have not found a neat way of doing this. First, I put vasoline on the hinge part to stop it seizing up when the glue dries. If I put the glue on the flat part of the hinge it tends to get wiped off when I push the hinge into the slot in the wood, so doesn't seem very reliable? Alternatively I have trouble getting enough of the epoxy deep into the slot, if I do that before pushing in the hinge. Either way a messy operation. Using a syringe and hypodermic needle might put the epoxy where it is needed in the slot but you would get through a lot of syringes/needles when fitting all the control surfaces. Am I overthinking this or is there a simple solution? Recently I used superphatic and a thin spout to wick the glue into the slot. Took a time to dry, seems secure but I would rather use epoxy. Also, for pinning the hinges I usually use pieces of cocktail sticks cut flush when dry. Do people use pins instead?

I have been modelling for thirty years, you would think I would have it figured by now! crook

cymaz11/02/2018 07:03:46
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8666 forum posts
1177 photos

Piers...I recently used Kavan flat hinges on a refurb. Like you I use Vaseline over the hinge line but I use a hot glue gun or hairdryer to melt the Vaseline into the hinge. It’s a bit of trial and error to get just enough heat for the Vaseline to melt into the hinge without it running everywhere. I heat up the epoxy ( doesn’t take many seconds) and dribble into the slot using a cocktail stick and work it in with a scrap modelling blade. I find Cocktail sticks are easier to work with when pinning flat hinges.

Old Geezer11/02/2018 07:57:07
617 forum posts

There's a lot to be said (all good!) about Blenderm tape, and for smaller planes when you can get it, Diamond Tape. Properly applied your surfaces are free moving, and as there is no 'leakage' of air between aileron and wing, the ailerons are more efficient/effective. To any nay sayers, none of my taped hinges have ever let me down.

Ron Gray11/02/2018 08:13:26
1450 forum posts
363 photos

@Piers - I’ve started using Gorilla Glue for hinges as it expands and fills gaps. Any excesses can easily be cut off once semi dry but it is a case of trial and error to get the amount right without excessive ‘overflow’.

Piers Bowlan11/02/2018 09:24:33
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1871 forum posts
45 photos

Thank you Cymaz, I will heat the epoxy to make it runnier. yes Thanks Ron, I will try gorilla glue too.

I have used blenderm tape (and sewn hinges too) on smaller models to good effect, where the surfaces are too thin to slot.

 

Edited By Piers Bowlan on 11/02/2018 19:44:50

cymaz11/02/2018 09:31:47
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8666 forum posts
1177 photos

Use the heat sparingly ...a bit at a time.

Cuban811/02/2018 11:22:40
2725 forum posts
13 photos

I don't worry too much about getting glue on the hinge point of a pinned hinge. I apply a miniscule amount of oil to the pin area and then glue the hinge in place, one leaf at a time to the flying surface with room temp 30 minute epoxy. After about 15 minutes, clean any excess uncured epoxy away with a small piece of paper kitchen towel moistened with meths. Leave to fully set and repeat for the control surface. Sounds a bit of a faff to describe but dead easy to do in practice.  Never had one stiffen up or fail. Works just as well with Robart Hinge Points.

Kavan hinges.......not cheap butyes

Invest in a proper hinge slot cutter as well, no more nasty modelling knife slots for pinned hinges.

 

 

 

 

 

Edited By Cuban8 on 11/02/2018 11:35:23

Ron Gray11/02/2018 11:29:21
1450 forum posts
363 photos

Whilst slightly off ‘piste’ (the OP was questioning the number of hinges) I think the concern about fixing hinges is more to do with getting enough glue in place to ensure a good fix rather than the glue getting into the hinge mechanism. But C8, you are spot on, any form of oil, Vaseline etc on the hinge mechanism should prevent gumming up.

As to the OP question about pins, IMO if the model is too small for cocktail sticks, as long as sufficient glue is on the hinge then I don’t bother with pins.

Geoff Sleath11/02/2018 12:07:27
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3368 forum posts
272 photos

Funnily enough I've just been doing the aileron hinges for my DB Cirrus Moth winter build. Rather than using the Mylar hinge material provided I've opted for using SLEC pinned flat hinges. I use 5 minute epoxy to secure them and add cocktail stick pins cyanoed in after the glue has gone off. A touch of Vaseline on the hinges protects the hinge from becoming unhinged by epoxy. If it does stick a bit I find working the hinge soon frees it off.

wing build 4.jpg

I cut the slots initially with a scalpel and then use these home made tool to make the slot big enough to take the hinge which is a tight fit even before glueing (applying glue to the end of the hinge only, means it gets wiped back as it's pushed in, thus glueing the whole surface.) I always glue and pin the aileron (or rudder/elevator) very early in the build, then cover it. I cover most of the wing before attaching the aileron so I can hide the pins. 3 hinges are plenty. It's hard enough getting 3 exactly in line - more would be a nightmare.

The home made tools are simply 2 halves of a Junior hacksaw blade set into bits of dowel I had handy. They are made to cut in opposite directions but I find cutting as I pull the tool out of the slot is easiest. Not my idea but one of one of our club's very best builders, Jim Harrison. He's that rare combination of superb builder of own design scale models and equally skilled flyer.

Geoff

 

Edited By Geoff Sleath on 11/02/2018 12:12:28

Cuban811/02/2018 12:45:47
2725 forum posts
13 photos

Not too sure about the wisdom of using 5 minute epoxy to secure pinned hinges. I like time to really work the glue into the hinge slot either with a spare hinge leaf, or thin bit of metal strip - I'd worry that with the quick set stuff going off so rapidly, very little opportunity is given for the glue to really soak into the surrounding wood and flow nicely into the hinge keys.

5 minute epoxy does seem to be quite brittle when fully cured and might not give such a good bond as the slower varieties, and being quick to harden makes getting alignment correct and clean up, all the more crucial - just make sure they're in the right position as well before going for a breaklaugh.

I never bother to pin, pinned hinges with 30 min epoxy as the fixative, and have tested a hinge to destruction on a test piece, with the plastic failing before any sign of the glue to wood joint breaking.

As always, horses for courses......................

Edited By Cuban8 on 11/02/2018 12:51:13

Nigel R12/02/2018 15:05:14
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3066 forum posts
475 photos

Big standard polyprop hinges, 3 of them, glued with alliphatic. Rough up the hinges with some 200 grit.

Canopy glue, or RC modellers glue seem also to work well. My suspicion is that both of those are a PVA or alliphatic base with some kind of added plastic etching agent.

All these type glues clean up easily. I've never had a problem with hinges pulling out - YMMV.

Epoxy certainly sticks hinges like messy stuff to a blanket but it is itself, at least it seems to me, rather messy to apply.

John Stainforth12/02/2018 19:15:55
310 forum posts
38 photos

I never use 5 minute epoxy, because it becomes unworkable too quickly for the speed at which I work!.

Martin McIntosh12/02/2018 21:09:11
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2933 forum posts
1073 photos

I now only use the furry c.a. hinges, as recommended for the original Capiche 140. Dead easy to do since a scalpel blade slot suffices and as long as super thin c.a. is used there is no way that they will ever pull out. A little Vaseline on the flying and control surfaces helps. I have found that the large Kavan hinges have a lot of slop in the pin so no longer use them since it defeats the object of having accurate servos.

Cut them to width to suit small models. 6" spacing sounds about fine, say two or three per elevator half, three per outboard aileron and four for strip ailerons.

PatMc12/02/2018 22:32:00
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4200 forum posts
521 photos

Neat way to fix furry hinges - drill a 1/16" [or 2mm] hole on the centre of each hinge slot position, cut the slot with scalpel, fit the hinges then a drop or two of thin cyano in the hole each side of the slot. The cyano wicks over the full length of the hinge surface. Same method works with most leaf hinges which then don't need to be pinned.

OTOH if the trainer of the OP is going to be film covered my choice would be to use the film as a hinge.

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