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Frustrated with Covering

Old 08-23-2006, 09:39 PM
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fstevenj
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Default Frustrated with Covering

I have one monocoat airplane and one ultracoat. Although I thought covering was easier with ultracoat, the covering has a problem that really bothers me. I have my plane in the car all day while at work and by the time I get off and out to the plane the covering has wrinkled. I re-shrink the covering and it continues to happen. I have tried to cover the aircraft while it is in the car, but apparently the sun exposure isn't the problem, I guess it is the heat which is strange because the covering shrinks when you heat it. The monocoat covered aircraft had the same problem, but I do not remember it being as bad. I am about to cover a third aircraft, and want to minimize this problem. Do others think that monocoat is better for this application, and does anyone have any suggestions to improve the wrinkling problem. I live in St. Louis so all summer the car gets really hot, and my parking lot has no shade. Thanks.
Old 08-23-2006, 09:42 PM
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Cyclic Hardover
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Default RE: Frustrated with Covering

Don't leave it in the car all day.
Old 08-23-2006, 09:56 PM
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RaceCity
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Default RE: Frustrated with Covering

Coverings of any brand do tend to wrinkle when exposed to temperature extremes. Hot or cold.

This can be minimized to a great extent by your covering technique. It's a learned thing...I can't teach you here BUT...

Sheeted surfaces must be absolutely clean before covering. Vacuum, tack rag, then vacuum again. Keep your hands spotlessly clean while you work.

Do not "shrink" covering on sheeted surfaces. Use only enough heat to get the material to adhere, and no more. Work from the center of the surface outward. If you use the "meat wrap" technique to do your airplanes....wrinkles will be a permanent part of your life.

Open bay structures also must be spotlessly clean. Make every attempt to get the covering as wrinkle free as possible BEFORE heating/shrinking. Carefully smooth the material without bunching, and tack securely around the periphery of the open structure, before you try and shrink the material. Keep in mind that the more "shrink" you put in...the more that can come back out later.

It takes time, patience and a fair amount of practice to do great covering job that will actually STAY great.

Keep at it.
Old 08-24-2006, 07:28 AM
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bruce88123
 
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Default RE: Frustrated with Covering

Too many people "depend" upon the shrinking qualities of the material when installing. It is important to pull the material taut before tacking it down and then you don't have to shrink it as far. I live here in Memphis which is just as hot as you and leave my planes in the car for weeks at a time and never get a wrinkle. I use Monokote and admit to never using another brand as I have no problems with it.
Have you seen MinnFlyers videos? You're probably past that point but there may be something to learn.
Old 08-24-2006, 07:56 AM
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RCKen
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Default RE: Frustrated with Covering

I totally agree with Bruce here. If the covering is completely shrunk before you start adhering it to the structure it will help keep the covering tight in hot weather. But there is another HUGE cause of loose covering that most people completely miss (including those factory workers assembling ARF's), and that is open bay structures. I'm talking about open bays in wings, open areas in stick built tail sections, or any other open area that will be covered up by covering. The problem here these bays are completely sealed and air trapped inside the structure has no where to go. So when you place the covering over the bay you completely seal that area in. As you heat the covering to shrink it the air inside structure expands which pushes out against the covering. The covering will shrink around the bubble of heated air. When the heat is removed the air inside contracts back down and now the covering has slack in it. This slack allows wrinkles to form later on. So how to you avoid this?? Simple, ensure that a structure has a path for air to escape from it. It's as simple as just sticking a pin through the side walls of that area. Keep doing this so until there is a route for air to pass from the outside of the structure to all internal areas. If you look at the attached pictures you will see how I prepared the wing on this LT-40 for covering. I used T-pins to create air vents in all of the internal areas of the wings. I made sure that there was a path for air to vent into all of the internal areas of the wing.

I use monokote on all of my planes and I have never had any problems with wrinkles forming in hot weather. My planes are stored in my garage and here in Southwest Oklahoma it regularly hits 120°-130° in my garage during the summer. I have also left planes in my truck during the day and have never had any problems with wrinkles. As I said above, the trick is to get the covering completely shrunk before pressing it down on the structure.

I hope this helps

Ken
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Old 08-24-2006, 09:31 AM
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MinnFlyer
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Default RE: Frustrated with Covering

Well, here's my take on this...

I have noticed many times that before the covering shrinks, it expands - This is completely normal when you think about it. If you heat anything up, it expands. Right?

So for example, let's say I have the covering tacked down on all sides of a wing and there are no wrinkles - Now I start to put the heat gun to it. The first thing that happens is the covering wrinkles up, and THEN starts to shrink. The wrinkling is due to the heat expanding the plastic film.

Of course, once a certain temp is reached, the covering begins to shrink.

Now... Put that covered plane inside a hot car (Or leave it in the sun on a hot day, etc) and there is enough heat to make the film expand - but not enough to shrink it.

SO....

The best way to avoid this is to make sure that (as others have said) the wood is VERY clean and DUST FREE before covering - AND that after all of the shrinking is done, you go over all of the contact areas with an iron and make sure that it is stuck to the wood.

I know that I have a problem following my own advise there - Once the covering is shrunk I rarely go back over the WHOLE thing with an iron, but when I do, I rarely get wrinkles.
Old 08-24-2006, 08:50 PM
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fstevenj
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Default RE: Frustrated with Covering

Thank you all for the advice. I will try these techniques and I think I will use monokote. Does everyone agree that you shouldn't shrink covering on sheeted surfaces? I have a four star forty that has solid vertical and horizontal tails and the covering wrinkles on these surfaces also. I also use coverite balsarite, could this contribute?
Old 08-25-2006, 07:11 AM
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bruce88123
 
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Default RE: Frustrated with Covering


ORIGINAL: fstevenj

Thank you all for the advice. I will try these techniques and I think I will use monokote. Does everyone agree that you shouldn't shrink covering on sheeted surfaces? I have a four star forty that has solid vertical and horizontal tails and the covering wrinkles on these surfaces also. I also use coverite balsarite, could this contribute?
On solid surfaces I tack down the perimeter after pulling the material taut and as wrinkle free as I can. Then I do a minimum shrink with a heat gun followed by ironing it down.
I have never found a need for balsarite as yet but if your wood has become contaminated with fuel or such it would help, I believe.

I ask a second time, have you seen MinnFlyers videos on installing covering? Very helpful to a beginner. Can provide links if needed.
Old 08-25-2006, 07:56 AM
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Campy
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Default RE: Frustrated with Covering

The cause of the MAJORITY of wrinkles is trapped air.

1st. As several others have stated, make sure the surfaces are free from any dust, dirt, etc.

2nd. When doing sheeted surfaces, start from the middle and work your way out to the edges WHILE PULLING ON THE COVERING (keep a CONSTANT tension on the covering while ironing it down.

3rd. (IMHO, the most important) On open bay areas AND built up parts, make sure air can circulate between the bays (holes through the ribs insure this) AND, if the part is completely sealed (ailerons, flaps, rudders, elevators, etc), AFTER the part is completely covered drill a 1/16" - 3/32" hole in an inconspicuous spot (normally along the hinge edge ) all the way through to the bay area to allow any build up of air to escape.

This will take care of 99.5% of the wrinkling problems.
Old 08-25-2006, 09:35 PM
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fstevenj
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Default RE: Frustrated with Covering

I have seen the videos and thanks again for all the suggestions.

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