Iron-on coverings with decals?

[Tim McTigue]

Just wondering: can waterslide decals be used on iron-on coverings such as UltraCote?

[fox4ever]

Tim you must have ESPN. I was just wondering the same thing. I make my own decals and always give them a couple of light coats of Sig spray can clear and let dry before aplying. Hope it works on the iron ons. I guess if it don't stick, no big deal, can do no damage. Maybe someone will let us know.
Lee TGD

[Tim McTigue]

I imagine so, since I remember from my youth using water-slide decals on plastic models with no problems. They weren't homemade, but I think they were essentially the same sort of thing...

[RetNavySuppo]

The following applies to all plastic iron-on coverings (MonoKote, Ultracote, etc.).

First and foremost, the surface must be absolutely clean. These plastic iron-ons come from the factory with some sort of chemical on the surface left over from the manufacturing process. I clean the surface with acetone (keep acetone away from covering seams) and then with denatured alcohol (the real stuff, not rubbing alcohol).

Water slide decals:

They usually tell you to soak the decal in warm water until it can slide off the paper backing. Substitute a warm 10% solution of water/liquid dishwashing detergent for the plain water. Wet the area of the covering where you want the decal to go with this same solution and then slide decal into place. The solution on the covering under the decal will allow you to slide the decal around somewhat to get it positioned just right. Then take a piece of soft balsa with a straight edge and squeegee the excess water and air bubbles out from under the decal. Gently squeegee until all the air bubbles are gone and the decal looks dry. Then go have a cigar and leave it alone for 24 hours. Come back and with a damp (not sopping wet) paper towel, wipe off the dried soap solution on and around the decal.

The fats in the liquid dishwashing detergent act as a glue which adds to the holding power of the decal adhesive. Also, it makes it slippery enough to move the decal around during final positioning.

What about fuelproofing the decal? Well, some decals say they are already fuelproof. Yeah, right. You can run a thin coat of clear nail polish or clear BUTYRATE dope around the edges of the decal to seal it down. However, a couple precautions here. Some decals will be dissolved by the dope or the acetone in the clear nail polish. Test a sample decal first. Also, some clear dopes yellow badly over time (especially over a white decal) with exposure to light. Aerogloss clear dope is really bad in this respect. I use a commercial grade of dope and the clearest one I have found is Certified Coatings Clear Butyrate (Non-Tautening). I can give you a source if you want it.

You could also use a clear polyurethane but few polyurethanes are really "crystal clear". They usually have a pronounced amber tint which will show up over light colors. They also vary in resistence to fuel. Based on my experiments (using up to 15% nitro fuel), the water based polyurethanes are absolutely useless. The only other polyurethane that is fairly fuelproof is Minnwax Helmsman Spar Urethane (green cans). But again, you have the pronounced amber hue. It's alright over some colors, but be careful over the light colors, especially white. Professional modelers use automotive polyurethanes that are indeed crystal clear, but they are so dangerous to use, I stay away from them.

So what do I use if all else fails? I use several heavy coats of automotive wax to seal the surface and edges of the decal. This has to be renewed periodically which means you have to clean your model once in a while. By the way, I also wax the whole model with car wax BEFORE a single drop of fuel gets near the airplane. Plastic coverings are easy to clean. They are even easier to clean if the dirt and grime are sitting on top of a good wax job. The coats of wax also protect the covering seams, so use the wax generously on the seams (again, BEFORE your model is touched with fuel).

Pressure sensitive decals:

Same precautions. Mostly same methods. When I peel the decal off the backing, I dip it into the soap solution and then place it on the surface that has been wetted with the soap solution.

General:

As much as possible, don't have sharp corners on your decals. Round them off as much as possible. Sharp corners have a tendency to lift up over time much easier than rounded corners.

Most decals, of whatever type, don't like going over compound curves. On a built-up wing, the shrunken Monokote will not be a flat surface. It will be flat over spars and concave over rib bays. Often, the same decal will have to go over both ribs and spars. This is where the squeegeeing with the piece of balsa comes in handy. Removing the water under the decal combined with the extra stickiness of the detergent will make the decal stick down harder and give you a chance to coax the decal to stick to the variations in suface topography. Usually, with a lot of cigar smoke, Navy cursing and the kicking of one of my Rottweilers who is usually sleeping on my feet while I work, I can do a pretty good job of getting the decal to stick down on most of these difficult surfaces using the squeegee.