Covering Tutorial for Beginning Builders
My good friends on this forum have convinced me that a basic tutorial on covering an electric plane could possibly take some of the terror out of the thought of tackling a kit.
I just finished building the superb flying Mountain Models Dandy GT.
Link to Mountain Models
During the covering phase of the building process I took a lot of photos. The covering techniques I favor are not the only way to cover a plane. I will attempt to demonstrate how to cover an electric "park flyer" with a low temperature iron-on film called So-Lite.
So-Lite is a strong and light-weight self-adhesive iron-on plastic film that is perfect for electric planes. I have used other types of iron-on film and the techniques are pretty much the same as So-Lite. Covering an electric plane is a bit easier than covering a glow plane. Glow planes have to be fuel proof so the covering process is a bit different for fuel planes.
So-Lite is also sold as NELSON LiteFILM, Coverite Microlite, and AeroLITE. The packaging and the instructions are the only difference between the different brands. The price ranges from $11 to $14 for a 6' roll.
All So-Lite is made in Great Britain. On one side of the So-Lite is a heat-activated adhesive. So-Lite has a clear plastic protective film on the adhesive side. This protective film is removed after you cut the So-Lite to shape and are ready to attach the So-Lite to the plane.
Iron-on film has two temperatures specifications:
(1) Bonding temperature, and
(2) Shrinking temperature.
Attached is my Iron-on Film Temperature guide. I have also attached an instruction guide I downloaded from the StevensAero site. StevensAero makes great kit planes.
Link to StevensAero
The kits from Mountain Models and StevensAero have precise laser cut parts and are extremely fun to build and fly! I hope that this thread will help those hobbyists interested in building but shudder at the thought of covering. So for Chuck "NoFly Zone", Spackles94, Controlled Fall, and anyone else intereseted in building, this thread is for you!
Next Topic: Getting Started - Tools and Bench Setup
Chapter 1: Getting Started - Tools and Bench Setup
To acquire the minimum set of tools for covering a plane a hobbyist need not spend a ton of money. Of course, if you feel compelled, by force of habit, to spend a lot of money you certainly can!
The minimum tools required are:
(1) Sealing Iron - $12 to $28
(2) Sharp Scissors - $10
(3) Single Edge Razor Blades - $4 for 10
(4) Hobby knife with lots of blades (I prefer an x-acto #1 knife w/ #11 blades.) - $5
(5) 36" Metal Straight Edge (I also have a 12" and 18" straight edge as well) - $10
(6) Cutting Surface (Cutting Mat or Glass) 24" x 36Ē - $25
(7) 1" Wide Blue Painters Masking tape - $3.50
The total for these tools is about $70. Chances are good you already have some of these items. If you already have a good cutting surface, knife and scissors your total investment is about $30.
In addition to the minimum tool set you can get a Heat Gun for $15 and a Trim Iron for $20. Just like everything in this hobby, any activity associated with RC cost money. However, the results that you obtain depend largely on having the right tools, and a good work area.
I have attached some photos of my tools and bench setup.
Next up - Iron-On Covering Primer
Chapter 2: Iron-On Covering Primer
Ok, letís say you have the bench ready. You have beat-up the credit card and purchased the required covering tools. You have just spent a few blissful evenings building a great laser cut kit. It is now time to take the big step and start covering the beautiful balsa structure. You now have get to have even more fun by selecting your color scheme. :D So-Lite comes in eight opaque colors and five transparent colors.
Link to Mountain Models So-Lite
Link to Tower Hobbies Coverite 21st Century Microlite Red (So-Lite)
Link to StevenAero AeroLite (So-Lite)
Link to Nelson Hobby - Nelson LiteFILM (So-Lite)
By far and away the easiest way to cover a plane is to use one color of iron-on film. Using a single color makes ragged edges less apparent. A single color is also easier to repair in the unlikely event of a hard "unplanned landing". :rolleyes: Once you are done covering the plane you can doll-up the plane with peel-and-stick trim sheets.
Link to Tower Hobbies Trim Sheets
These graphics are pressure sensitive. The trim sheets can be cut into different shapes to (1) make the plane prettier, and (2) more importantly, make the plane easier to see in the air.
In addition to trim sheets, another way to decorate your plane is to use trim tape stripes.
Link to Tower Hobbies Trim Tape
(Note: Trim Sheets and Trim Tape are available elsewhere. Tower Hobbies just has the best descriptions and pretty pictures.)
I have attached photos of the various ways I have used So-Lite, Trim Sheets and Trim Tape to cover and decorate some of my models.
Next Chapter: Getting Down To Business
Make sure you get double strength glass. A large sheet of single strenth glass will crack under its own weight.
Be cautious when you first use the Woodpecker. The Woodpecker comes with 4 removable cutting blades. I recommend you only use three blades spaced very closely together. My Woodpecker was very oily when I got it, which made the blades stick in place. I used rubbing alcohol to clean the oil off. Be very careful handling the blades as they are really sharp. :eek:
The Woodpecker is a tool designed to keep air bubbles from forming beneath
film covering (such as MonoKote, Ultracote, etc). It prevent air pockets from
forming between covering and wood or from between two layers of film.
The tool has four wheels with VERY sharp tines that make small, short slices
in wood and/or covering to release the trapped air that causes bubbles in film
covering. The wheels are removable to make the work area of the tool narrower
(for corners, etc).
Constructed entirely of stainless steel and the handle is rubber covered for
comfort and grip.
Chapter 3: Getting Down To Business
Is it time to start covering the plane? :confused: Well, yes sort of! First, I need to address some basics in handling, cutting, attaching and trimming So-Lite.
I am going to walk you through covering a block of balsa! Exciting stuff I know! Many experts recommend covering a block of balsa as practice prior to attacking covering a plane. I actually didn't heed this advice, and jumped right into covering my first plane. In retrospect it would have been better if I would have covered a block of balsa for practice first!
The process for covering a balsa block is also used to cover square or rectangular parts, such as a battery hatch. I used a very similar technique to cover the Dandy GT ailerons. After you look at the attached photos, you may scratch your head and say, "Is that all there is to it?" The answer is "Yup!"
Here are some interesting points:
(1) Achieving a tight, bubble-free and wrinkle-free covering over solid structure is actually more difficult than getting a tight covering job over open structure.
(2) "Solid Structure" is any part of the plane where the covering is mostly in contact with balsa (sheeted fuselages, wing centers, battery hatches)
(3) "Open Structure" is any part of the plane where the covering film is mostly suspended. (wings)
Iron-on film, such as So-Lite, will shrink more when suspended over open structure than when attached to solid structure. This means that you can more easily shrink your "mistakes" away on a wing than on a fuselage.
Next Chapter: The So-Lite Bane
Chapter 4: The So-Lite Bane
So-Lite is great stuff! So-Lite is thin but tough making it the first choice for electric planes. However, So-Lite is not perfect. The bane of So-Lite is it tends to fold over on the adhesive side and stick to itself. So-Lite carries a static charge. Sometimes as I remove the clear protective covering to expose the adhesive, I can hear the tell-tale crackle of a static electricity.
One way to minimize this static charge is to put a towel over your work area that has been dried in a dryer with a "Cling-Free" sheet. I don't particularly like this method since the towel usually ends up in my lap! Another way to combat So-Lite's tendency to fold over is to keep the excess around a part to a minimum. However, as we shall see later, sometime you need quite a bit of So-Lite sticking out over an edge. I just prefer to fight the So-Lite on its own terms!
Attached is a series of photos that shows how to unfold So-Lite. If you are unfortunately enough to apply heat to the folded-over So-Lite the stuff will be bonded together forever!
Next Chapter: Taking Care of Your Irons
Chapter 5: Care and Feeding of Covering Irons
Your irons must be clean and smooth to obtain the best results. A rough and/or dirty iron can scratch the covering. When using a multiple color scheme, you can get streaks of the darker color on the lighter color if your irons get contaminated. I guarantee that you will make a boo-boo and get melted adhesive on your irons. You may also over-heat some covering and get it stuck to your irons. My favorite way to screw-up my irons is to lay down my hot iron on some of the clear protective backing film that I carelessly left on my bench.
What do you do when you have a gooey mess all over your iron? You have to turn off the iron and let it cool down. Attempting to clean a blazing hot iron is a good way to burn yourself! :eek: Don't ask me how I know this! I clean my irons with a combination of sanding blocks, fine #000 steel wool and rubbing alcohol.
I recommend when you get your brand new irons that you sand the irons smooth. On my 21st Century irons this means I sanded off some of the Teflon coating. I rough sanded both my trim and sealing irons with a 400 grit wet or dry sandpaper block. I finished with a 600 grit wet or dry block. I then polished the irons with #000 steel wool. I removed the entire residue with rubbing alcohol. Do not use the sanding blocks that you use on your irons on your plane. You will get black residue imbedded in the balsa. Don't ask me how I know this! :o
To clean your irons you may just need to use rubbing alcohol. If you have a real mess you may need to use the steel wool, then the alcohol. If your irons are a total gooey nightmare, you may have to repeat the entire sanding, steel wool and alcohol process.
Chapter 6: Covering Compound Curves - Dandy GT Stabilizer
I am now going to demonstrate how to get a nice wrinkle free finish on a compound curved surface. So-Lite comes off the roll flat. However, most planes have curved surfaces. When Iron-on plastic covering is heated while under tension it will stretch. When heated while relaxed covering will shrink.
To make the covering conform to curved surfaces, I use either my trim iron set at about 240 degrees F or my heat gun. I simply pull the covering around the curve and heat until the covering stretches and becomes smooth. This "heat-pull" technique is considered pretty advanced. However, the heat-pull technique is easy to learn and makes a huge difference in the quality of the final covering job. :)
The heat-pull technique can be used on wing tips, round fuselage elements or any place the covering tends to bunch-up.
Chapter 7: Open Structure
In Chapter 6 we looked at covering the Dandy GT stabilizer. The Dandy GT has solid balsa vertical and horizontal stabilizers. Many kit planes have built-up open structure stabilizers, rudders, elevators and/or ailerons. I have just started building a Mountain Models Switchback Sport, which has open structure stabilizers and control surfaces. My LittleBirdz LoLo also has open structure stabilizers and control surfaces. The LoLo has nicely curved lines, which meant I had to use the heat-pull technique to make the So-Lite conform to the compound curved edges.
The Dandy GT has open structure ailerons that I will use to demonstrate how to cover flat open structure elements. The basic technique I used on the Dandy GT ailerons is applicable to open structure stabilizers and control surfaces.
My Dandy GT color scheme uses red on the bottom of the ailerons and yellow on the top. I attached the yellow So-Lite first. I the trimmed the yellow So-Lite with a straight edge on the trailing edge to 1/8" and 1/4" on the inside and outside edge. I cut out the corners out of the So-Lite just like covering the block in Chapter 3. I rolled the covering over the edges with a 200 degree F sealing iron. I sealed and smooth the edges with a 240 degree F trim iron. The leading beveled edge I rolled-over with my 195 degree sealing iron and trimmed the excess.
The "fold-over" of the yellow provides a good sticking surface for the red So-Lite. This means a flat piece of red So-Lite can be attached to the bottom of the Aileron without extending around the trailing, inside and outside edges. The red So-Lite folds over the leading beveled edge and was trimmed flush with the top edge. This produces a red bottom surface with no visible yellow, and a yellow top surface with no visible red. The line between the red and the yellow is sharp and well defined.
I am glad you are enjoying building your Switchback. I just remembered you asked me about sanding grit. For rounding and shaping I use 220 to 240 grit. For finish sanding I use 360 to 400 grit. When you are sanding a flat open-structure part, such as a stabilizer, you need to be very careful not to catch a rib with the sanding block and snap the fragile balsa. You also don't want to deform the frame of the part while sanding. Smooth light strokes with the sanding block are the best. I sometimes do very fine finish sanding with 600 grit. I mostly use wet or dry sanding paper.
Chapter 8: Precision Cutting So-Lite
Even my old eyes can tell if a line is straight, or not. Cutting a straight line in So-Lite is deceptively challenging. So-Lite stretches and squirms under a blade. If the blade is even a little bit dull, the So-Lite will tear. So-Lite comes off the roll with a curvature from being on the roll, and will not lay flat.
There are two alternatives to get a precise cut in So-Lite:
(1) Tape method -Tape a piece of So-Lite to your cutting surface. You want to be sure the So-Lite is flat and wrinkle-free. Put pressure on your straight edge during the cut to keep the So-Lite from stretching and squirming.
(2) Wet Glass Method - Wet a piece of smooth clean glass with a mild water- detergent mix. Lay the So-Lite with the protective film side down. (Adhesive side down-but you still have the protective film in place.) Use a credit card squeegee to work the air bubbles from under the So-Lite. Tape a straight edge to the glass. Or if you are making a curved or complex shape put your template in place. Using a new x-acto knife blade, or single edge razor blade, smoothly slice the So-Lite in one continuous cut.
The water-detergent mix is made by adding a few drops of old-school dishwashing liquid to a quart of water. The exact mixture is not that precise. The detergent breaks the surface tension of the water and allows a better bond between the glass and the So-Lite.
Chapter 9: Covering Structure-to-Structure on Wing Bottom
When covering over open structure, So-Lite must be tacked down and sealed over adjoining solid structure. Solid wing structure includes ribs, leading edge, trailing edge, spar, wing tips and center section. Not all wings have spars or solid center sections. Sometimes is easier to cover half the wing at a time. Most often, but not always, it is most convenient to cover the bottom of the wing first, then the top.
This chapter 9 will show how to cover a wing using two pieces of So-Lite and covering half the wing at a time. Most electric plane wings can be covered using one piece of So-Lite extending across the entire wing span.
In Chapter 6, Covering Compound Curves, showed a heat-pull technique for making So-Lite conform to surfaces with curved edges. Guess what? Wing Tips are typically a veritable symphony of compound curves. The heat-pull technique can be used to make a nice smooth wing tip.
The steps in covering a wing are as follows:
(1) Cut the So-Lite to shape leaving 1" to 2" of excess on the leading and trailing edges, and 3" to 4" of excess at the wing tip. The large amount of excess at the wing tip is necessary so you can get a good grip on the So-Lite while heating and pulling the So-Lite around the curved wing tip. On the Dandy I needed about an 1" of excess at the wing root. The amount of excess you need at the wing root will vary depending on the wing configuration. It is better to have too much excess that you can trim, than to have too little.
(2) Tack the So-Lite in place using a 195 to 200 degree F sealing iron. There is a general order that you want to tack the So-Lite down. You also want to stretch the So-Lite as you are taking it in place. Tack the inner edge first. Stretch the So-Lite toward the outer edge and tack. There will be wrinkles in the So-Lite running between the two tacks. Tack at the leading edge, then pull tight and tack at the trailing edge. The tacks at the leading and trailing edge will pull some of the wrinkles out that were between the first two tacks. You continue this process pulling the covering tight between tacks. You may have to heat a tack you have already done and pull it tight as you progress. The goal is to get a fairly smooth and wrinkle-free covering job prior to applying the shrinking heat. Do NOT Shrink the covering until both sides of the wing are covered!
(3) After completing the tacking of the wing covering, you are going to use the heat-pull technique to make the So-Lite conform to the wing tip. Use your heat gun or your blazing hot 240 degree trim iron to heat the So-Lite at the wing tip. As you pull on the hot So-Lite the So-Lite will around the wing tip. AS you work the hot So-Lite will adhere to the wing tip edge. When you are done the wing tip covering will be evenly distributed around the wing tip curvature. However, the So-Lite will have some wrinkles at the wing tip as the wing tip deflects toward the tension from the covering. When you cover the top wing tip, most of the wrinkles on the bottom wing tip will disappear.
(4) Seal the rest of the wing by rolling the So-Lite around the leading and trailing edge with your 195 to 200 degree sealing iron. I like to reseal and smooth edges with my blazing hot 240 degree trim iron.
(5) Trim the trailing edge excess So-Lite even with the top of the leading edged. Trim the So-Lite off the leading edge leaving as much So-Lite as possible in contact with the leading edge. Trim the excess So-Lite from the wing tip leaving about an 1/8" of excess So-Lite that you will roll-over and seal onto the top of the wing tip structure.
(6) Trim the So-Lite on the center section. Roll the So-Lite over the edge of a rib or other structure if necessary to secure the So-Lite. Use the 105 to 200 degree sealing iron to roll the edges over the structure than reseal and smooth with the blazing hot trim iron.
(7) Take a break and come back and cover the top of the wing. Shrink the So-Lite on the top and bottom of the wing after both sides are covered.
(8) Eye-ball the wing to determining there is any unwanted twist in the wing. You take the twist out by manually twisting the wing the opposite direction. You will notice that the once tight covering will wrinkle. While still holding the wing twisted. Use your big sealing iron set at 240 degrees, or your heat gun, to shrink these wrinkles out. Hold the wing until the surface cools. When you let go of the wing the wing will spring back a bit against your twist. Recheck to see if the wing is still twisted, or you twisted it too far. Repeat the process until the wing is straight. Wash out is a twist in the outer 1/3 of the wing where the wing is purposely twisted so the leading edge points a bit down. Washout is put into the wing by the process described above.
I don't have any photos of this twist-heat shrink-cool process as the Dandy wings were not twisted. The Dandy GT also has symmetrical wing that are not supposed to have any wash out.
If any control surface or stabilizer gets warped or twisted you use the same process as above. However, I recommend you only use a hot big sealing iron to shrink the covering. A heat gun is liable to burn your fingers when holding these smaller parts.
Chapter 10: Small Patches
Hanger Rash: Any non-flight related damage during storage or transportation.
I went flying this morning. I took my LoLo and Dandy GT. While driving back from the field, somehow the tail skid of the LoLo poked a hole in the wing tip of the Dandy GT! :censored: This minor disaster has provided me with the opportunity to show you how to patch small holes. Serious damage requires a different approach.
Patching a Small Hole:
(1) Cut a small oval or round "patch" from a piece of So-Lite. The round shape will stay on the plane better. A square patch will lift at the corners.
(2) Peel the protective backing off the patch.
(3) Wet the patch with a mild water and detergent mix.
(4) Place the patch over the hole and smooth with your fingers.
(5) Use a 195 to 200 degree F sealing iron to attach the patch. Use this iron very briefly.
(6) This is the cool part! Use your trim iron set at 240 degrees F to work the bubbles from under the patch. Start in the center and work outwards using the tip of the iron as a "squeegee". The soapy water under the patch will allow you to chase any bubbles from under the patch. Once the water is gone the patch is sealed in place and nearly invisible. This "hot iron squeegee" eliminates the trapped air bubbles typically seen in covering-over-covering patches. :cool:
Techniques applied over weekend
Bruce, here's some more feedback that your "students" are putting your hard work to use. I did my first covering job with Solite about 10 days ago and found it frustrating. This weekend, I just left my browser on this thread all day so I could quick reference it.
The cowl I dreaded? Piece of cake. I pretended it was a wingtip and used lots of heat and lots of pulling with some creative knifework.
And here's a wing from my EVA bipe. For once I was quite pleased with my quality! Thanks again for the detailed pictures and descriptions. They are truly worth a 1000 words!
P.S. Sorry the EVA shot is a bit blurry...just inspected the camera, and our 2 year old must have found it judging by the fingerprints....
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