April 07, 2014

Flite Metal tutorial part 2

0. Introduction

This tutorial is following the one made by Joe Grice that you will find just below this article. This presents different techniques from the one used by Joe. The result achieved with my techniques will be slightly different. The panel lines will be more pronounced and the general aspect of the aircraft will be rougher.

1. Aircraft preparation

One nice thing with Flite metal is that it sticks better to mirror finished surfaces. So I usually just wipe the whole aircraft with an acetone dipped cloth to get rid of the demoulding wax. Then I fill the original rivets with a thin layer of 3M Acryl Green putty. This putty is very thin and very easy to sand. I make sure the rivets prints would still be visible after the covering process to punch them in again easily.

One wing in preparation.

The nose section being prepared.

I carefully vacuum clean the sanded areas with the brush adaptor and then wipe again the whole surface with acetone.

I then prepare the few areas that will be painted without Flite metal ( fin, nose and the area below the stabilizer ). Not covering the painted areas will save weighgt. However if you decide to make paint chipping s that reveal the underneath aluminium surface, then covering with Flite MEtal will be much nicer. Once again, I use acetone to remove the wax, then sand and prime. I use Warbirdcolors primer and sand it with medium grit 3M sanding pads.

2. Aircraft covering

The Flite Metal foils are not too difficult to put down but require a little bit of training. For the first timers, I'd recommend ordering 30% more material as you will find necessary to remove the patches a few times before you achieve a proper result.

Flite Metal web site is nicely documented and Ed usually ships the rolls with a set of covering instructions. If you stick to these instructions you’ll be on the right track to do a pretty nice job from the first shot. However I’d like to give a few recommendations.

Use the appropriate tools: I use exclusively 3M dry sanding pads and sponges and good quality drawing/ smudging pens ( burnishing tool ).

A selection of the used tools: Hole punchers, 3M sanding block and papers, steel wool pad, 3M medium and fine sanding pads, large and medium smudging pens, 3M green and grey sanding sponges.

Start with easy flat areas. If you mess up, do not wait too long to remove the film or the glue will set and removing the foil will get much more difficult.
Once the foil has stuck to the surface, do not try to re-fit it because you’ll stretch the material and get wrinkles. Therefore, the initial tacking is very important.
Prepare each patch carefully. You’ll have to cut them about 1” bigger. Once the patch is cut you will have to “work” it before applying it. This step is very important since it will make the aluminium much softer and less prone to wrinkling. Simply put it on a clean cutting mat and sand it with the provided 3M green sponge on both directions. The foil has to get flat dark grey. Note that this color will change when you will sand it again after the covering.

It seems that doing this softens both the aluminium and the backing paper. The foil will then be more flexible and easier to apply.

Here is how a prepared foil should look like: dull dark gray.

If you are getting some wrinkles, you can erase them by carefully “ironing” the aluminium surface down with a thin metallic ruler ( you’ll have to smooth out the ruler tip first with 400 grit sanding paper to get it less aggressive )
Cutting the patch: always use a sharp new blade. Dipping it into mineral spirit before the cut will lubricate it and avoid tearing the thin aluminium foil. It will also help separating the glue coat which is soluble in mineral spirit.

Here are a few additional tips and techniques depending on the area to be covered:

2.1. Flat areas

I like to start the flat areas from one edge of the aluminium patch. It is less tricky than starting from the middle since you won’t have to bend it dimensionally. I use the hinging method to place the foil. I place the sheet with its backing on the area and center it. I tape it on one side with low tack paper tape.

Step 1: I use low tack 3M masking tape to hinge the patch

I then lift it and remove the backing from the hinged side by about one inch. I then stick it back to the surface while working it with the burnishing tool. After ½ inch is done I remove the hinging tape, get rid of the possible bubbles and carry on the same way.

Step 2: removing the backing paper by about 1 inch.

The initial tacking of the aluminium is very critical for the rest of the operation, because you don’t want to introduce any foil warping at this stage.

Step 3: tack the aluminium gently.

I remove the backing paper gradually as the work progresses. This will help you a lot in holding the unstuck part of the foil. It will also support it if you need to apply some tension while working it out. Make sure you don’t lift the foil up by more than 30° when you hold it during the burnishing process, or you might get wrinkles.

I hold the foil and pull the backing paper with one hand. This gives just enough tension while burnishing it. Note the low foil angle.

Burnishing the aluminium: proceed with gradual passes. Changing the burnishing motion will help getting rid of the wrinkles before tacking them down to the surface.

We can see here the aluminium foil being worked around some access panels.

2.2. Curved areas

Curved areas shall be started from the middle. Since you are going to work the foil dimensionally to get rid of the wrinkles, you don’t want to exceed the material deformation capability and tear it. Working the patch from the middle will minimize this risk

Large curved areas can be very tricky to handle. In some cases it could be interesting to remove the foil backing on only one half and proceed with one half after the other.

Curved areas need practice. Each patch will be different and will require a different burnishing motion and strategy. You have to study the area first and decide how you are going to work it out. Do not hesitate to remove the patch if the covering goes wrong. It took me one day of trial and error to achieve proper results.

The key point to avoid wrinkles in a curved area is to put a bit of tension on the foil while tacking it down. You’ll have to “massage” the aluminium just before it sticks to the surface. Too much tension will almost certainly tear the foil apart. This is why the paper fiber smudging tool is so much useful here since the tip it is soft and flexible. Note that a used buffed tip will work better.

The canopy frame is usually a difficult area for applying Flite Metal.

3. Rivets

I used a steel hole puncher to mark the rivet heads into the soft aluminium covering. It is a very easy and quick process. Since I didn’t completely seal the rivets holes during the preparation I was still able to locate and punch them in quickly.

I used several different puncher sizes to match the different rivets sizes of the real plane. I also made a special tool with a modified Philips screwdriver tip and a brass tube to engrave the panel screws.

When using the punching tool you should have a light hand otherwise the soft aluminium will make a ridge outside of the rivet print due to a possible excessive pressure.

4. Weathering technique

Flite metal weathering is a bit more time consuming than paint weathering. It requires different steps as explained below in the proper order.

4.1. Pre covering

The process starts before covering the plane as a first sanding of the aluminium patch is required, as explained before.

4.2. Creating the metal appearance

Working the aluminum will remove the initial dark dull gray color and make it shine. It will also create the typical bear aluminium wear appearance.

After having tacked the patch to the surface, I proceed with the following sanding operation: I use different 3M sanding pads and sponge grades or steel wool grades. The idea is to use a different grade for each panel. This will make every panel look slightly different from the other one. You will have to work the aluminium by crossing each pass. The last pass should be parallel to the air flow to achieve a realistic wear pattern.

4.3. Weathering the plane

After the later operation and the painting is done I start the weathering process. I use black and dark brown artist oil paint. I mix them with a bit of linen oil to obtain the required thickness. I apply the mixture only along the panel and rivets lines. I work perpendicular to the lines to put a maximum of paint in them. I then let it cure for a while ( from a few hours to a few days depending on the temperature, type of paint and required thickness ). I wipe it off with fabric tissues and a bit of mineral spirit. The stain will stay in the rivets, panel lines and along the raised panels ridges if you don’t use too much mineral spirit.

The artist oil medium applied to the panel and rivets lines.

4.4. Diversifying the metal shades.

The F-84G is made of different qualities of aluminium, especially on the wings and front fuselage. This gives a remarkable look which has to be reproduced.

I use the following technique:

I prepare different artist oil mixtures with the following colors: black, dark blue and brown. I dilute the colors with only mineral spirits so that it has the consistency of milk.

I then apply a different color to each panel with a cotton tissue according to the pictures of the real plane I have. The coat shall be very light and transparent. I let it dry completely ( about one hour ) and then sand it off with a 3M green sanding sponge. The required effect will be done by varying the sanding intensity and pattern.

The wing after weathering and dirtying.

4.5. Making airflow streak marks

Long airflow marks are done with aquarelle paint and a lot of water. I simply put some paint on the wing leading edge or surface front and wipe it with a wet cloth along the airflow motion.

Diffused panel marks are done with artist dry chalks. I place a tape on the front panel line side a apply the chalk with the same paper fiber pen that I use for Flite Metal.

I did this step after painting and applying the nomenclature and other dry transfer marking.

If you want to seal everything, you’ll have to apply a thin clear coat as a last operation.