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monokote hinges

Old 04-05-2005, 08:43 AM
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majortom-RCU
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Default monokote hinges

I used to be a fan of monokote hinges. I've done several models with one piece of covering going all the way from Leading Edge, through the hinge gap, then back to trailing edge of control surface. I would leave a gap such that I would get monokote on top stuck to monokote on the bottom for at least 1/32" or 1/16" along the full length of the hinge, believing that the two would never come apart. And so far that's how it has turned out.

The problem is with my latest instance of this technique, in which I used an old roll of monokote. I find after about thirty flights the hinge gap in my ailerons is coming apart, the monokote cracking right down the hinge line. So far only a couple inches, but I don't like the way this is going.

The tail is hinged with ultracote, of more recent vintage, and that is holding up very well. I notice the old monokote is a bit more brittle. When I start a cut in it, it slices very easily with a sharp blade. The ultracote, on the other hand, seems tougher and more fibrous; when I cut it with a sharp blade, I get a more ragged cut, as though I were cutting across a grain of some kind.

One more thing: I had a deadstick landing in which the plane came down off the edge of the field, where the ground slopes down. I was able to see and control the plane all except for the last few feet, when it went out of sight. The plane landed maybe a bit hard, but still on its feet with no damage, except for one bay of the stick-built ailerons, where the monokote split across the one bay, diagonally across opposite corners. There was nothing the aileron could have hit, since the inboard end was protected by the fuselage and the outboard end was protected by a further 3" of fixed wingtip. I expected the monokote to be tougher than that.

So I am still sold on the idea of film hinges, but I think I will use ultracote from now on instead of monokote for this purpose.
Old 04-05-2005, 12:08 PM
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britbrat
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Default RE: monokote hinges

Thanks, that's a usefull heads-up. I use film (monocote) hinges & haven't experienced that problem yet, but I will be extra vigillant now.
Old 04-05-2005, 02:05 PM
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Default RE: monokote hinges

Monokote seems to have gone downhill quite a bit in the past couple of years. The adhesive on it and the shrinking qualities have definitely gotten worse. I also feel that the plastic they are using for the film has gotten a lot more brittle - it is more like EconoKote/Towerkote now.
Old 04-05-2005, 05:55 PM
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martyg
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Default RE: monokote hinges

As a further data point, I agree with majortom.

I have used "covering" hinges on my last 5 40-60 size planes. (Over the last 24 months)
2 were done with Monokote, 3 with Ultracote, using the same assembly technique.

The Monokote hinges started failing only after a few outings.
The Ultracote hinges are still going strong after hundreds of flights, and a few minor crashes.
Old 04-05-2005, 08:08 PM
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mirwin
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Default RE: monokote hinges

This is all very interesting, fellas. I've also used monokote hinges in the past, but I think I'll switch over to ultracote.

The question now is: how well will the ultracote hinges adhere to the monokote covering? I've not heard good things about that.
Old 04-05-2005, 08:11 PM
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mirwin
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Default RE: monokote hinges

Marty, I grew up in the Dallas area, but I live in Virginia now. I go to Wylie often to visit my daughter and grandchildren, and I've thought about flying while down there to get my grandson interested in RC. Where do you fly? I know the old abandoned airfield just off of LBJ used to be popular but that was years ago.

Old 04-06-2005, 09:37 AM
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majortom-RCU
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Default RE: monokote hinges

The ultracote is not an unmixed blessing either. I can't comment as to how well ultrcote adheres to monokote, but I can say that ultracote needs to be wrapped around an edge before you put the heat gun on it to shrink out wrinkles, otherwise it will creep at the edges, enough to be a real problem. Monokote in my experience, once stuck down, resists creeping better than ultracote. So if you wanted to lay strips of ultracote on top of a monokote covered model in order to make the hinges, I don't think I'd recommend it. The only way I would do an ulltracote hinge would be to use a single piece running all the way across the chord, and turned over both leading and trailing edges.
Old 04-06-2005, 01:41 PM
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Default RE: monokote hinges

ORIGINAL: majortom-RCU
The problem is with my latest instance of this technique, in which I used an old roll of monokote...

So I am still sold on the idea of film hinges, but I think I will use ultracote from now on instead of monokote for this purpose.
I just love this kind of reasoning. You've got an old roll of something, and compare its performance to a new roll of something else. The most humorous part is people completely missed this and said things like " Monokote seems to have gone downhill". Some folks are so quick to hop on the "Monokote is bad" bandwagon...

How old was that Monokote? Have you stored it carefully, or has it been subject to extreme temperature and humidity variations? Much to everyone's surprise, adhesives and plastics do not last forever. Their life span is greatly influenced by the conditions in which they are kept. When they get old, they get brittle.

I've recently used some old (more than 15 years) and new Monokote. I found they both worked exactly the same as they did 20+ years ago when I first used Monokote. I'm not disputing other people's experiences, or preferences of people who have tried both, I just have not experienced the problems some people are so vocal about.
Old 04-06-2005, 03:23 PM
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Default RE: monokote hinges

I can't say how old it is. It's off a 100' roll I bought used. I've had it four years, and used it with no issues on a couple other planes. Storage under my ownership has been at stable temp & humidity.

If any covering gets brittle as it gets old, then that should be worth knowing if you're thinking of flexing them thousands of times in the same exact spot.

I am not partial to either monokote or ultracote. They each have advantages and disadvantages, and I will continue to use them both until something better comes along. But for film hinges I think I'll stick to ultracote.
Old 04-07-2005, 08:22 PM
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Flyboy Dave
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Default RE: monokote hinges

I have been sealing my hinge-lines with clear Mono-cote. It has been holding
up just fine....I use it with CA hinges to seal the gap a swell as provide extra
strength....usually a 3/4 or 1" strip does the trick.

I bought some white Mono-cote last season....I could not iron it down and
it would not shrink. []

FBD.
Old 04-07-2005, 10:27 PM
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Default RE: monokote hinges


Ha Ha

I think I would age the monokote another four years and test it again on a hand launch glider
to see if its value increases with vintage . If that doesn't work, maybe crack open an older bottle of wine and think about another day of flying.

cassat
Old 04-10-2005, 04:50 PM
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CafeenMan
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Default RE: monokote hinges

I have always hated Monokote and probably always will. It is by far the most difficult of the films to apply. What it has that no other covering has is very vivid colors. Oracover (UltraCote) looks dull next to Monokote.

I've had no problems with Monokote being brittle with the exception of some old transparent stuff that was in non-climate controlled storage for about 10 years and was already about 5 years old before that. When I got it out of storage it crumbled in my hand into pretty little flakes.
Old 04-10-2005, 07:44 PM
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SST
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Default RE: monokote hinges

Fabric hinges, such as the old Granite State hinges, are stronger, more flexible, and will last longer. I wouldn't hinge with any mylar film on a bet...
Old 04-11-2005, 12:09 AM
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CafeenMan
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Default RE: monokote hinges


ORIGINAL: mirwin

This is all very interesting, fellas. I've also used monokote hinges in the past, but I think I'll switch over to ultracote.

The question now is: how well will the ultracote hinges adhere to the monokote covering? I've not heard good things about that.
I often use more than one type of covering one the same airplane for a variety of reasons - what I have on hand, how much strength the covering needs to provide for any given component, color choices, etc.

I've had no problems getting any iron on film to adhere to any other iron on film.

My favorite film by far is Oracover Lite. I bought some when I was in Germany and it is the easiest to apply, doesn't sag in the Florida sun and it stays down. It's much more pliable than Monokote or Oracover/UltraCote and can go around compound curves with no wrinkles.

I would be leary about using it on anything larger than a .60 size ship though. I have used it on some wings that were very flexible before they were covered and even though it's more pliable than other coverings it still stiffened the wing adequately.

The only place that I know carries Oracover Lite is Hobby Lobby. Beware of the transparent yellow. I bought a roll on two separate occasions and both rolls were defective. The first roll was mottled as if the adhesive/color had large fish-eyes. The second roll had streaks running the length of the roll.

As far as adhesion goes, you have to make sure the surface is clean. Just because you may not have touched it and then wiped it off doesn't mean it's clean. There can be skin oils on the covering or mold release and who knows what else. Before you iron the hinge down be sure to wipe down the covering with alcohol or acetone.

[link=http://airfieldmodels.com/information_source/how_to_articles_for_model_builders/construction/film_hinges/index.htm]This is how I apply film hinges[/link]
Old 04-11-2005, 11:59 AM
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mirwin
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Default RE: monokote hinges

I like the way you apply your hinges, CafeenMan. It's a nice, neat appearance. I guy in my RC club taught me a variation to your procedure. I included the photo which I prepared on my (rudimentary CAD system) to illustrate what I'll try to describe here.

I apply as many 3/4" - 1" wide hinges to each control surface as will fit. The 1st hinge is ironed onto the top of the wing / stab and on the underside of the control surface. The next hinge is applied on the underside of the wing / stab and on the top of the control surface.

To accomplish this, I make up each hinge with half of the adhesive side face-up and the other half face-down. I overlap the adhesive parts where they join in the middle, the overlap being the approximate thickness of the wing / stab. For example, I want a hinge that is 2" long and the stab is 5/32" thick. I cut one piece of monokote to 1" length, and another to 1 5/32" length. I place the 1" length on the work surface with the adhesive side up, and I place the 1 5/32" length piece adhesive side down, overlapping the 1" piece by 5/32". I then iron the overlapping part together. And I have one hinge.

I also round the corners of each hinge, of course, to help prevent a corner from coming loose.

Placing each hinges side-by-side onto the plane as close as practical to the adjoining hinge fills that gap between the wing/stab and the control surface.

Having many hinges provides redundancy in the even that one hinge fails. If I have 10 aeleron hinges and one fails, I won't suffer a catastrophic failure while aloft.

In most cases, when I'm concerned about hinge material matching the color of the aircraft (MonoKote is bad about consistent colors), I use the clear MonoKote.

Mike



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Old 04-11-2005, 03:09 PM
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Rodney
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Default RE: monokote hinges

I do it like Mirwin with the following additions. Before ironing on the hinges (made up like he did) I iron a strip of covering over the entire length of the area to be hinged on both the moveable and fixed surfaces. Then iron on the hinges. Do all this before covering any portion of the surface. Now, when you put on the covering after the hinges are ironed on, the final covering goes over the top of all the hinges which helps prevent them from ever comming loose. The strip you ironed on prior to placing the hinges prevents any bare wood from being exposed.

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