Doculam: What I have been learning

[payne9999]

So, I have been building a lot in the last months and have learned more about applying and finishing Doculam. I have some significant hours on planes finished this way so I can say if you fly a lot you will chip the paint. If it is a warbird or some utilitarian type of plane it can add to the appeal by making it looked weathered and chipped (as Pat Tritle points out in his tips). I fly before work, sometimes at lunchtime and sometimes even after work so I can pile the hours on and make an airplane look worn quite fast. I guess what I am trying to say is the durability of Doculam will depend on how much you fly and how much you knock you planes around.

I don't want to go on a rant about commercial pre-finished films but they are just too expensive for me and I always seem to run out just before I have finished or need an extra roll for repairs.

There are tons of places to buy Doculam on the net and for 40-50 bucks you can have a 1000 feet of it (enough for a lifetime as well as sharing with friends at the flying field).

Application and shrinking:

First off nothing shrinks like Doculam so for odd shaped open frame areas or difficult areas around a the tail, wing tips or fairings I found I can really abuse it with the heat gun on high. I think people who state that it doesn't shrink as much as other coverings haven't blasted it with the heat gun yet. I believe if you had a helper you could pull the material around a complex shape (like a rounded wingtip) with both hands and have your helper apply the heat with a hot air gun and successfully stretch the material around some pretty difficult shapes. It seems to take the heat indefinitely on high if you don't get closer than about 1 inch. Lately I have found that I was under-shrinking the material by just using my iron. Now I blast the entire area that has been covered with the gun after I apply it. You have to be sure to seal the edges good or it will pull away but the magic is that Doculam has an incredible capacity to shrink without undo force on the airframe. I have shrunk very light balsa tail structures with very little warp issues. It seems I can shrink out the ugliest wrinkles with the gun.

On really light structures like the vertical stab, horizontal stab, ailerons and flaps I found it sometimes helps to make small pinholes on the back side of the surface in the corners of each framed area to let some hot air out. Otherwise when shrinking it with the heat gun it puffs up with hot air and then when it cools it sags. Making tiny pinholes will solve this issue.

Also, when sealing around the edges and onto frames I found I could crank the iron up and not have any serious melting. If I do this I find the seal holds permanently. I think it is really annoying when covering starts to lift especially when finishing with paint because it is hard to re-tack without damaging the paint.

Sealing the edges one final time before cleaning and finishing will insure there are no loose edges later after painting.

Painting:

The nice thing about painting is you can select from any color and it can be matte (like for warbirds) or any gloss level you like. It makes free form camo pretty easy with a cheap airbrush.

I have seen many opinions about acrylic paint or house paint sticking to Doculam really well. I have NEVER experienced this. So far almost any paint I have tried has adhesion issues. It is a flexible substrate and as such the paint has to be very flexible. House paint, model enamels and artist acrylics don't seem to be very flexible. However, I have found some techniques that help. Maybe some flex agents could be added to paint that will be applied with an airbrush but I am still looking for something to test.

I use Scotch-Brite pads to dull the Doculam before painting. If I try to abrade the surface after it is on the plane it wears away faster on the stringers, ribs, longerons etc and can cut through. So, I layout the raw material on a very flat clean surface and scrub it with the Scotch Brite first. This way I don't get any cut through. Norton also makes these pads and I think either Home Depot or Lowes has them in various grits.

As far as paints go to me the art acrylics, house paints, plastic model enamels, and various rattle can paints all work about the same. However, I found one style of paint that sticks a lot better. It is the fake aluminum types such as Model Master metalizer flat aluminum or Krylon short cuts "chrome" which looks and goes on just like the Tetsor's flat aluminum. So, I use this as the "primer" coat. Any color that you paint over the aluminum seems to be truer anyway because of the neutral effect of the silver paint. Also, the aluminum covers the Doculam with just a whisper of a coat and weighs practically nothing.

Lately I have been priming with the aluminum paint and then using whatever I want over it. One warning: Krylon paints have changed in recent years and if you re-coat after 24 hours it will wrinkle the original coat badly. Apply all coats in the first 24 hours. So, if a second color is going on you need to wait about 1 week for full cure.

Masking:

My favorite method is to separate two colors by a pin stripe to hide any problems with the masking pulling up paint. Painted Doculam is really sensitive to any tape. So, what I do is make a mask out of newspaper and only apply the tape to a very narrow 1/8" area all along the edge. This limits the area of the first coat that sees the tape adhesive. Also, I try to take the adhesive down a notch by, (I know this sound funny) sticking it to my forehead or to the surface of my jeans to reduce the tack quite a bit.

The other method is to use wet newspaper. I have a hard time getting a sharp edge with this but recently I used this method for touching up. So I applied my second color but had some finish issues on the first. I used wet newspaper to cover the second color and sprayed from an angle kind of across the paper which shielded the second color from the touch up spraying I was doing. This works really well.

Yet another method:

If you have wing stripes or other decorations that don't cover large areas then I recommend using decal material. I just paing a sheet of decal material and then cut out stripes and other markings and apply them using them as if they were printed water-slide decals. Water-slide decal paper for ink jet printers are available all over the net but I like decals.com. By the way water-slide decals made on a inkjet printers work really well on painted Doculam. I print mine on a $50 Brothe printer and they look as good as commercial decals. Of course you have to seal them after they are printed before you get them wet to apply them. They also have to be clear coated lightly after the are on the plane.

All of these ides were generated just because masking painted Doculam is really hard!

Windows:

You can make a variety of side and top windows by just covering the whole part of the plane (window areas and all) and then mask the window areas before painting. Because Doculam turns very clear when fully heated it makes windows that look quite real and in a way appear like scale Lexan (plastic (Polycarbonate)) windows. Any flat window can be made this way. Think about a Piper L-4 with all the observation windows. It saves you the difficult task of gluing all that clear acetate in place and the frustration of smearing the glue on the clear areas.

Also, if you are into finishing a plane in a clear this is the stuff. I have seen people install LED lighting inside the aircraft frames to allow for night flying.

I am still learning so if anyone out there has any other suggestions for how to successfully use Doculam then please reply.

Dave

[RUSH]

Thanks for the very detailed information on Doculam! I'm going to be using it on one of my current projects, and this will help a lot.

[slipstick]

Are you actually using "Doculam" material (which I'm told hasn't been manufactured for years) or do you mean some other type of laminating film ? If so what type are you using ? Gloss or matt ? What thickness ?

Steve

[mararra]

I have stayed away from doculam because of the painting issues. Sounds like you've got it figured out. I might just give it a shot. Thanks for the helpful write up

M

[Al_M]

You can also lightly dust the adhesive side with spray paint and it will light up in the sun.

[payne9999]

Originally Posted by slipstick

Are you actually using "Doculam" material (which I'm told hasn't been manufactured for years) or do you mean some other type of laminating film ? If so what type are you using ? Gloss or matt ? What thickness ?

Steve

Steve,

I understand the original Doculam is not in production but I don't really know the exact formulation of the original. The current material that is used in place of it is PET or polyester film. I have not tried the matte material but I am wondering if it would be more paintable. Currently I am using the more common gloss (1.5 mil, .0015") and dulling it down with the scotch-brite.

Dave

[payne9999]

Originally Posted by mararra

I have stayed away from doculam because of the painting issues. Sounds like you've got it figured out. I might just give it a shot. Thanks for the helpful write up

M

I wouldn't say I have it completely figured out but I still prefer it over the Monokote types of products. The painting situation isn't perfect but acceptable for me for the time being. I just wish someone would introduce a really easy to paint product. I like warbirds and military versions of civilian planes (like cubs/L-4 and Cessnas/T-41 etc.) and to get the finish similar to the full size plane paint is much better.

I guarantee if anyone who hasn't used Doculam before tries it, there will be a learning period and some frustration. However, with it you can acheive some effects that are not possible with Monokote type films.

Dave

[slipstick]

That 1.5 mil gloss is the stuff I tried a while ago. As you say it goes on and shrinks well but I've never managed to get any paint to adhere all that well. The best I tried were the old Humbrol enamel paints but they're smelly and rather expensive.

I keep hoping someone else will try the matt to see if it's any better but, at least over here, it's very difficult to find in the lighter weights...75micron (3 mil) is available but that's too heavy for most of what I want to do.

Steve

[payne9999]

Originally Posted by slipstick

That 1.5 mil gloss is the stuff I tried a while ago. As you say it goes on and shrinks well but I've never managed to get any paint to adhere all that well. The best I tried were the old Humbrol enamel paints but they're smelly and rather expensive.

I keep hoping someone else will try the matt to see if it's any better but, at least over here, it's very difficult to find in the lighter weights...75micron (3 mil) is available but that's too heavy for most of what I want to do.

Steve

I am considering buying a roll of the matte just to see if there is a difference. My latest experiment with the Scotch Brite, Krylon aluminum as a primer and top coat of Krylon Fusion is looking pretty positive.

I am also looking at adding some flex additives to various types of paint and spraying them on with my airbrush. I think regardless of the adhesion the flex issue would still cause the paint to crack if the paint is not flexible enough.

There are some flex additives for the auto painting industry that are used on plastic parts that are not rigid. Some of these additives are compatible with several types of paint. If I can ever crack the code, I would like to develop a paint that really works well with polyester film. Some of the research I have been doing indicates that epoxy based paint would work best but I don't know of any epoxy paints that are left on the market for hobby use.


Dave

[offtom]

Using some for the first time recently and so far have been enjoying working with it. Like you said, it can take the heat better than the other stuff and is real easy to pull around corners with the heat gun.

The one big down side is not finding your errors (missed wrinkles) until the paints on. Like someone wrote in another thread on the stuff, you really have to look at it from different angles and light sources to catch some of them.

Overall I really like the stuff.

[whitecrest]

I've had good luck with it as well. Painting seemed to go much better after scuffing the surface with 000 steel wool. It shrinks well and doesn't sag over time. Some acrylics appear to bond to it more efficiently than others. In my experience, the paint is holding up very well.

[payne9999]

Originally Posted by whitecrest

I've had good luck with it as well. Painting seemed to go much better after scuffing the surface with 000 steel wool. It shrinks well and doesn't sag over time. Some acrylics appear to bond to it more efficiently than others. In my experience, the paint is holding up very well.

What brand and type of paint have you had the best results with?

Dave

[whitecrest]

Originally Posted by payne9999

What brand and type of paint have you had the best results with?

Dave

I've been using artist's acrylics in tubes. They're easy to mix and thin with water. One brand is Amsterdam and the other is generic in unmarked tubes. The generic brand adhered readily to the film while the Amsterdam tended to scrape off after application. By mixing the two, I was able to get good adhesion.

The artist's acrylic colors are vivid and have not faded after many flight hours. I'm going to try other acrylics and see how they fare. The finish looks a lot like the old dope and tissue. It's nice to do a covering job without opening all the windows.

[Davethebluessinger]

Have to admit I'm not a builder but read your thread with interest.
In the UK there's a brand of spray paint called Plastikote. They make all kinds of paint for different projects, one of whichis for painting plastic garden furniture. Maybe that would have the degree of flex you're looking for?

[Tenderfoot]

I have been following the various methods and uses of Doculam and can add one that may not have been tried yet. I was looking to get the weight down on a full flying glider stab, but didn't want either transparent or the added weight of the paint. I tried food coloring on the balsa frame and the covering stuck and at least there is some color in the tail. Don't know if this is of general interest, but for me -- it works.

[payne9999]

Originally Posted by Tenderfoot

I have been following the various methods and uses of Doculam and can add one that may not have been tried yet. I was looking to get the weight down on a full flying glider stab, but didn't want either transparent or the added weight of the paint. I tried food coloring on the balsa frame and the covering stuck and at least there is some color in the tail. Don't know if this is of general interest, but for me -- it works.

Nice idea!

Also, I am convinced now that the paint issues are not just adhesion but more of a flexibility problem. I have decided to try a specialty water based acrylic paint designed to remain flexible (for painting fabric).

Dave

[pd1]

Maybe someone else has tried this and can tell me what to expect.

In an effort to save dope and work in applying a silk finish, I covered a plane with doculam first. I then covered the rudder with silk and the silk went on surprisingly well. Butyrate clear sticks well to scuffed up doculam.
Two coats of clear and the weave of the silk is filled. I think the end result is the finish will be lighter than a traditional silk finish.

I've only done the rudder so far because the weather here has been great for flying. In another week or two I plan on covering and painting the rest of the plane.

Anyone else tried this?

[gyrocptr]

Originally Posted by pd1

Maybe someone else has tried this and can tell me what to expect.

In an effort to save dope and work in applying a silk finish, I covered a plane with doculam first. I then covered the rudder with silk ....
Two coats of clear and the weave of the silk is filled. I think the end result is the finish will be lighter than a traditional silk finish.
....
Anyone else tried this?

Similar to a technique used in the old days with balsa framework. Back then the poly covering was Saran Wrap. Then the silk or nylon was applied over the film. The poly film reduced the amount of dope needed to fill the weave, and prevented the dope from dripping through the fabric and forming "stalactites".

[Bill G]

Originally Posted by payne9999

.... I always seem to run out just before I have finished or need an extra roll for repairs.
Dave

I can specifically remember at least 5 times, where I was literally 1 inch shy of having enough covering to complete a plane (see: Murphy's Law of Iron-on Covering) and had to buy another roll. In one instance, I had to use up ever scrap of covering, to repair the wing on a Dumas Peashooter micro conversion. Now how does someone run out of covering, needed for a repair on a plane that is itself so small that you can barely see it with the naked eye? I honestly have no idea, but it just seems to work out that way. Making matters worse, I eventually bought another roll of that covering/color for another project, and have to stare at the "patch of triangles" repair on the Peashooter wing.