|Jul 16, 2007, 07:34 AM|
Your work looks excellent! My next purchase is going to be an EVA Bipe. The "heat-and-pull" technique can be used any place that the So-Lite must wrap around a curve. Sometimes, in very tight places, the only "pull" that can be applied is the friction of the iron against the surface. You probably noted that as you pulled and heated the wrinkled So-Lite there was a point when the So-Lite relaxed, stretched and the wrinkle disappeared. The So-Lite shrinks as it cools making the results both smooth and drum tight.
|Jul 16, 2007, 04:06 PM|
Chapter 11: Multi-Color Structure-to-Structure Wing Covering
Let's recap the subjects addressed from the Introduction through Chapter 10.
The Introduction addressed basic concepts such as bonding temperature and shrinking temperature. Attachments included covering instructions from StevensAero, and my temperature guide for Iron-On Film.
Chapter 1 addressed required tools and bench setup.
Chapter 2 outlined covering and trim materials and sources. I included pictures of some of my planes. I didn't mention that this tutorial was going to give you the knowledge to make you planes look as good, or even better. When I wrote chapter 2, I was just not that sure of my ability to convey enough information about covering.
Chapter 3 showed the time-tested method of covering a balsa block for practice. There is a lot of information in this post including cutting and sizing the covering, removing the backing to expose the adhesive, attaching covering with a sealing iron, and trimming excess covering.
Chapter 4 dealt with the "So-Lite Bane". Given half a chance So-Lite will fold over and stick to itself on the adhesive side like iron. I tried to show how to get it unstuck without hurting the So-Lite.
Chapter 5 was about the care and feeding of covering irons.
Chapter 6 showed how to work So-Lite around compound curves.
Chapter 7 presented a few tricks for covering open structure elements.
Chapter 8 demonstrated how to get a perfect clean cut in stretchy and squirmy So-Lite using a wet piece of glass.
Chapter 9 showed how to cover a wing surface with one color of So-Lite.
Chapter 10 looked at patching small holes in the So-Lite so the patch was barely noticeable.
Chapters 1 through 10 present the basic knowledge you need to cover a plane in one color of So-Lite. These first chapters are fundamental to covering a plane, just as dribbling is fundamental to basketball. One of the advantages of building a plane from a kit is that you get to choose a unique color scheme that appeals to you! Now that you have mastered the fundamentals, I will show you how to make a plane pretty!
This chapter 11 will present ways to take advantage of structural elements to achieve a multi-color wing. These multi-color "wing" covering techniques can also be used on fuselages, stabilizers, hatches and control surfaces. However, the wing presents a special challenge since the wing's structural elements tend to be relatively small and widely spaced.
You may have noticed that in chapter 7 I did sneak in instructions regarding a two color aileron. The two color aileron demonstrates the structure-to-structure covering method. The seams between the red bottom and yellow top are over solid balsa structure. Multi-color Structure-to-structure covering uses solid structure to support the color seams. Wing structure includes leading edges, trailing edges, sheeting, ribs, tips and spars. To use this structure-to-structure covering technique, you must plan out your color scheme to take into account the position, size and geometry of structural elements. Using structural elements to support seams is not all that limiting.
Example 1: You want the wing tip to be red, but you want the rest of the wing to be white. You simply find the rib that is closest to where you want the seam between the red and white. You cover the inside part of the wing with white. You use the same tacking and stretching sequence for this part of the wing as you do for the entire wing. You trim the excess from the leading and trailing edges. You may also need to trim the wing root depending on the wing configuration. You trim the So-Lite at the rib, where you want the seam, leaving at least 1/4" of over-hanging excess. You roll the excess over the edge of the rib, which firmly bonds the So-Lite to the side of the rib. Lay the red So-Lite over the wing tip. This red So-Lite should over-lap the white So-Lite by 1/4".
It just so happens you learned yow to do this in chapter 9. In chapter 9 we covered a wing using two pieces of So-Lite. The first piece was attached to a center section and a rib. We could have used a completely different color for the second piece.
Example 2: Now you want a leading edge that is red with the rest of the wing being white. Most planes have a wing spar. We cover the back of the wing white up to the spar. If the spar is single vertical structure, with no cap, we roll-over 1/4" of So-Lite onto the spar.
The Dandy GT has the seam on the wing top over open structure. This open structure seam is done by bonding the yellow and red So-Lite together before attaching the So-Lite to the wing. To demonstrate the structure-to-structure technique I will use photos I took while building my MiniFlash.
|Jul 17, 2007, 12:18 AM|
Chapter 12: Multi-Color Covering over Open Structure
For my Dandy GT, I decided I wanted a "V" pattern on the top of the wing. This "V" pattern mans that the majority of the seam between the Red and Yellow So-Lite is over open structure. Therefore, the yellow and red So-Lite has to be bonded together, and attached to the wing as one piece.
The attached photos show the pre-bonding process. Here are a couple of key points:
(1) You are going to use soapy water on glass to hold the So-Lite in place during the heat bonding. The glass and water acts as a heat sink. You will have to crank the temperature up on your iron to at least 250 degrees F.
(2) You have to get the seam to the 200 degree bonding temperature; you will have to go over the seam many times with your hot irons. Move the iron slowly and let the heat build up. Feel the seam to make sure it is getting hot.
(3) Remove the clear protective backing from the So-Lite prior to putting the So-Lite down on the clean wet glass.
(4) An overlap of at least a 1/4" is required.
(5) LET THE SO-LITE COOL COMPLETELY before attempting to lift the bonded So-Lite. 20 minutes should do it.
(6) Always lift the So-Lite off the glass in a way that the lighter color supports the darker color.
(7) If the bond falls apart as you peel the So-Lite off the glass, re-wet the glass and start the bonding process again, and use more heat this time.
(8) The tacking sequence is different then that of a single color.
(9) The process for covering the wing is the same as shown previously.
This wet glass pre-bonding of the So-Lite covering can be used in a lot of ways to achieve numerous decorating effects.
|Jul 18, 2007, 10:29 AM|
Side Bar - Bevel on Taped Hinges
You are most welcome! I know you had some questions about the taped hinges on your MudBug. Here are some pictures of the hinges on my MudBug.
|Jul 18, 2007, 09:01 PM|
Chapter 13: Iron and Covering Temperature
Ok, here is a bit of a review on iron-on film temperature specifications.
Iron-on plastic covering has a heat activated adhesive on one side. When this adhesive reaches "bonding temperature" the plastic covering will attach to your plane. Once the covering is attached to your plane, applying more heat will shrink the covering and, hopefully, remove most of the wrinkles. The temperature when the film reaches maximum shrinkage is called the "shrinking temperature". For So-Lite, the bonding temperature is 175 to 195 degrees F, and the shrinking temperature is 230 to 250 degrees F.
If you forget to remove the clear protective backing film to expose the adhesive, the covering will sit there inert when you apply heat and maybe curl up a bit. If you remember to remove the clear protective backing, but mistakenly put your covering on your plane with the adhesive side up, you are going to spend some time cleaning goop off your iron!
Ok, that is that! Just set your iron to the correct temperature for what you are doing, be it tacking, sealing or shrinking, and all is well, right? Well, uh, not exactly! Here is my version of Murphy's Law as it applies to RC planes:
1st Law of RC planes: If it sounds simple, it is not!
2nd Law of RC planes: If it looks easy, it is not!
3rd Law of RC planes: If sounds complicated and/or looks complicated, it is far more complicated than it sounds and/or looks!
What complicates getting the correct iron temperature is as follows:
(1) Iron temperature is not what matters. What matters is the temperature of the covering!
(2) Iron-on plastic film has three layers that react to heat differently. These layers include adhesive, color, and plastic film.
(3) There are times when you want to tack and seal without shrinkage, other times you may want a bit of shrinkage while tacking and sealing.
(4) The temperature of the covering is related to iron setting, how fast you move the iron, how much pressure you exert, and what is under the covering.
What we are doing is transferring heat from the heat source, iron or heat gun, to the covering. How hot the covering gets depends on how much heat we apply, AND how fast the covering transfers heat away! In chapter 12, while bonding two pieces of covering over wet glass, I needed to set the iron pretty high and move the iron very slowly to reach bonding temperature. The wet glass transfers a lot of heat away from the covering. Attaching covering to a thin structure, such as a rib, may take more heat than attaching to a thick structure such as a solid balsa cowl. When attempting to shrink covering, the covering will get hotter over a balsa sheeted fuselage than over the open structure of a wing.
While working on this chapter, I consulted with two very experienced builders on the subject of iron temperature. I contacted Brian Eberwein, who owns and operates Mountain Models/Lazer Arts, and Jerry Thompson, owner of Thompson's Hobbies and Crafts. Not surprisingly, both of these accomplished builders said exactly the same thing when I asked how they set iron temperature. The answer: "When if feels right." I interpret this to mean they look at how the covering is responding to the heat, and gauge if they need to turn the iron up or down, speed the iron up or slow the iron down, use less pressure or more pressure.
I know this is probably not very satisfying. There is no real tidy answer. I have attached some photos to help you recognize "When feels right.". I have also included some instructions from the Coverite Microlite web site that also discusses iron temperature, among other useful things.
Here is a point of clarification. When I tack and/or seal the covering, I want to be able to lift and reposition the covering so I can make adjustments. I tack and seal with the iron set at 195 to 200 degrees F. After I am satisfied with the position and alignment of the covering, I crank the iron setting to 250 degrees F and shrink the covering. Once the covering has been heated to shrinking temperature it becomes very firmly bonded to the plane and is difficult to remove. Of course, this is exactly what I want!
If you tack and seal at too high a temperature you may cause wrinkles and creases to form, and you cannot reposition the covering without damaging the covering. I use a sealing iron at 195 to 200 degrees F to tack and seal, but I have my trim iron set at 240 degrees F. As I am covering, I may want to tack, seal, and shrink in a small area. Then tack, seal, and shrink someplace else. I do not tack everything, then seal everything, then shrink everything. For example, I may use my sealing iron, then my hot trim iron, sealing iron, hot trim iron, heat gun, hot trim iron, sealing iron, sealing iron, hot trim iron, sealing iron, heat gun, and so on.
Parting shot: Effective manipulation of covering temperature is the number one difference between an adequate covering job, and an outstanding covering job.
|Jul 18, 2007, 09:35 PM|
Not long. Just long enough for your iron to heat up.
|Jul 19, 2007, 07:46 AM|
First covering job photos — and how bad is my horizontal stabilizer?
OK, here are some pics from my MudBug — enjoy! As always, feel free to give me raw, relatively uncensored criticism. I'm here to learn how to build and cover better, not to receive pats on my ego.
|Jul 26, 2007, 01:33 AM|
Joined Jul 2006
So far, so good
This is the progress so far on my first ever balsa kit, the Mountain Models SwitchBack Sport. I'm probably spending more time on it than usual, because every step is a 'first' for me, but it is actually going surprisingly well!
So far, everything is dead straight and true... and I haven't broken anything yet.
I'm using an old 23" x 31" drafting board I had that is covered with a sheet of double strength glass. Just to the right of it is my glass kitchen cutting board I was using at first. The wife is still looking all over for it, but I pretty much have her convinced that she must have thrown it out in the trash.
|Jul 27, 2007, 09:02 PM|
Chapter 14: Sheeted Fuselage - Part 1 (Prep)
The Dandy has a fully sheeted fuselage typical of quite a few kit planes. An equal number of kit planes have a partially sheeted fuselage with some open structure, such as the StevensAero Re-Groove 480. Occasionally you run into a plane that has a completely open fuselage structure, such as the Dumas Wedell-Williams Gilmore Red Lion Racer.
Fuselages come is a wide variety of shapes. Therefore, covering a fuselage takes a bit of creativity. The general sequence for covering a fuselage is as follows:
Step 1: Cover the bottom
Step 2: Cover the sides overlapping with the covering on the bottom and wrapping about a 1/8" to 1/4" over the top.
Step 3: Cover the top
However, you can throw this sequence away depending on fuselage configuration and your color scheme. All you need to do is make sure you have the 1/8" to 1/4" overlap at the seams so the So-Lite will seal properly.
The attached photos show the preparation of the fuselage for covering. The first things I do are radius the edges and shape the cowling. I also rounded the tail-end of the Dandy fuselage. However, some planes need a beveled edge on the back of the fuselage since the rudder may mate to the back of the fuselage.
I sand the fuselage smooth with the appropriate grit sand paper. The best sandpaper grit depends on the grain and hardness of the balsa. The coarsest sandpaper I use is 220 grit. The finest grit sandpaper I use is 600 grit for finish sanding. I fill holes, dents and other surface irregularities with a balsa filler. Once the balsa filler is dry, the filler is sanded using a medium grit sanding block (320 to 400 grit). 600 grit can be used for finishing and smoothing the filler. Once the fuselage is smooth and filled, I gently run the TopFlite Woodpecker over the flat surfaces. Too much pressure on the Woodpecker will tear-up the sheeting. The resulting shallow holes will give small trapped air bubbles someplace to go. Gently re-sand the fuselage with a medium or fine sanding block to knock down some of the raised balsa around the Woodpecker holes. Remove the sanding residue with a tack cloth.
This process takes longer to read about than it actually takes to do!
Next Chapter: Sheeted Fuselage - Part 2 (Covering the Upper Sides)
|Jul 27, 2007, 11:49 PM|
Chapter 14: Sheeted Fuselage - Part 2 (Covering the Upper Sides)
My Dandy GT has seven separate pieces of covering, these are:
Two yellow pieces for the upper sides
Two yellow pieces for the top (one for the front and one for the back)
Two red pieces for the lower sides, and
One red piece for the bottom.
This chapter will address the covering of the upper sides in yellow So-Lite. I cut the yellow So-Lite to the proper size using the wet precision cutting method shown in Chapter 8. Using a 195 to 200 degree F sealing iron, I tacked the So-Lite to front and back of the fuselage. Starting at the front of the fuselage, and working toward the back, I attached the So-Lite using the 195 to 200 degree F sealing iron. As I progressed along the fuselage with the iron, I popped the rear tack loose, and stretched the So-Lite.
If you get wrinkles or bubbles as you attach the So-Lite, just pull the So-Lite loose from the surface and re-iron the So-Lite down while stretching the So-Lite to eliminate the wrinkles and bubbles.
After the side pieces are attached, I used the hot 240 degree F trim iron to heat and pull the covering around the cowling and tail. On the top of the fuselage, I trimmed the So-Lite so that there was about 1/4" of excess. I rolled the 1/4" of excess over the top edge with the sealing iron. I used a hot 240 degree trim iron to seal the top edge of the So-Lite. This hot trim iron will smooth out any wrinkles on the upper edge. I trimmed the So-Lite around the cowl flush with the opening. Sometimes it is best to leave a bit of excess (1/8") at the cowl and roll this excess into the opening with the hot trim iron. The attached photos illustrate this process.
|Jul 28, 2007, 07:15 AM|
Chapter 14: Sheeted Fuselage - Part 3 (Underside)
If I were doing a fuselage in a single color I would likely cover the bottom of the fuselage first. The side covering is rolled over the lower fuselage edge on top of the bottom covering, thus "hiding" the seam on the bottom. The method for covering the bottom is similar to the method for covering the upper sides shown in Chapter 14, part 2. However, I trim the bottom covering to be flush with the side. I used the heat-pull method around the edges of the covering to make the covering conform to the compound curves on the sides, cowl and tail. I use the heat-pull method quite often. The photos show the sequence I used to cover the fuselage bottom.
|Jul 28, 2007, 10:31 AM|
Chapter 14: Sheeted Fuselage - Part 4 (Lower Sides)
Since I decided I wanted a two color fuselage, I covered each side of the fuselage in two stages, upper and lower. If you imagine the yellow and red So-Lite on the side of the fuselage is one piece you will get an idea of what the covering the side fuselage in one color will look like. For your first covering job I recomend that you make the fuselage all one color. Preferably you want the fuselage to be a dark color so you can more easily see the fuselage outline aganst the the light sky. I find the fuselage more challenging to cover than the wings. Using two or more colors on the wings will give you a nice color scheme. The wings are larger and more eye-catching than the fuselage. I have attached a photo of a nicely done Mountain Models Switchback, which was done with a single color fuselage and mutli-colored wings.
For those of you interested in fun planes that are pretty easy to build, check out the Mountain Models site. The Dandy is a bit easier to build than the Switchback but neither plane is hard to build.
Link to Mountain Models Switchback
For a contrast with the "easy" building planes take a look at the Aero-Labs Pitts Special. There are a some things that I want you to notice about this kit. First this is a magnificent kit! However, this kit has some challenges that make it less-than-ideal for a first build:
(1) The Pitts is a "short" kit, meaning you supply the hardware, wheels, stringers and every item but the basic structure.
(2) The Pitts is a biplane, which increases the level of difficulty about 3 times.
(3) The Pitts has a wonderfully styled fuselage that, unfortunately, is a symphony of complex compound curves, which would cause a beginning builder (and even me) no end of frustration.
(4) The fuselage has the dreaded "open structure" which tends to increase difficulty.
Link to Aero-Labs Pitts Special Short Kit at Zeke's Park Scale Models
Link to Aero-Labs Pitts Description
Even though this Pitts is a "builders" kit, I want one! I have included a photo of an Aero-Lab Pitts Special that is expertly built and covered. The multiple color scheme on the Pitts is just not easy to do. The reason I am comparing and contrasting the Switchback with the Pitts Special is to encourage you, as a begining builder, to make life easier on yourself and get an easy-to-build kit, and start-off using a very simple color scheme.
The covering job on my Red and Yellow Dandy GT fuselage took me about 3 times longer than if I had done the fusealge in one color. I had four time-consuming precision cuts to make. I had to be sure to position each side piece correct, making sure the seam between the yellow and red was straight, and the left and right side were exaclty same. Of course, a two color fuselage is not hard to do. However, the two color fuselage just takes time and there is more opportunity for mistakes. I used a straight seam between the colors. A curved seam takes even more time.
The attached photos show how I attached and trimmed the red So-Lite to the lower side.
|Jul 28, 2007, 12:58 PM|
Chapter 14: Sheeted Fuselage - Part 5 (Top)
Ok, we are almost done covering the Dandy GT. We still need to cover the top of the fuselage. I actually covered the upper sides in yellow So-Lite first. Then I covered the top. I did the bottom of the fuselage in red So-Lite. I then did the lower fuselage in red. The actual sequence doesn't matter much. Using the heal-pull method to make the So-Lite conform to the fuselage curves also makes seams disappear.
Now you may ask, "Master, why have you not done any shrinking of the So-Lite on the fuselage?” I would answer, "Grasshopper, by using the heat-pull method to make the So-Lite conform to compound curves you ARE shrinking the So-Lite". Now, of course, it you feel compelled to shrink the covering over a solid structure, such as a sheeted fuselage, the best way is to crank up your sealing iron to about 240 to 250 degrees F and lightly go over the covering. You can use a heat gun to shrink the So-Lite on the sheeted fuselage. However, the 450 degree F heat gun can burn a hole in the covering very quickly if you are not careful.
To cover the top of the Dandy fuselage, I cut some yellow So-Lite to give me about 2" to 3" of excess. This excess gives me plenty of room to pull when I do the heat-pull method. I attached the top covering with a 195 to 200 degree F sealing iron. I use the 240 degree trim iron to heat the perimeter of the So-Lite and pull the covering around the edge. I trim the excess flush with the side and seal the seam with the hot trim iron. As always, keep the dull edge of the razor blade as flat against the side as you can to keep from nicking the side covering. This covering process should start sounding familiar.
We are done with the basic covering!
|Jul 28, 2007, 06:05 PM|
Chapter 15: Cutting Rectangular Holes for Servos and Battery Compartments
After the plane is covered, there are a few things left to do prior to final assembly. We need to cut a few holes in the covering for battery compartment and the aileron servo. Both these holes are rectangular. We could simply take a sharp knife and chop a few holes in the covering. However, the covering around the holes would loosen and could possibly rip.
I am going to show you what I can the "picture frame" method for cutting rectangular holes. You cut a hole in the covering somewhat smaller than the size of the final hole. You slice angle cuts at the corners. You then simply fold the excess covering into the hole and attach using a 195 to 200 degree sealing or trim iron. This results in a solid covering around the hole that will not lift or tear.
|Jul 28, 2007, 08:33 PM|
Chapter 15: Assembly Tips (Stabilizers)
The horizontal and vertical stabilizers must be glued in place with a wood-on-wood joint. I am not real big on "must do" instructions. However, this is one assembly step that cannot be bypassed, modified, ignored or skipped.
To expose the wood on a mating surface you carefully cut the covering with a sharp x-acto knife. I use a straight edge to make sure I get a straight and even cut. Try not to cut too deeply into the balsa. However, you must cut completely through the covering. Peel off the covering to expose the wood. On the Dandy I cut a thin covering strip off the fuselage on where the rudder would mount. I did not cover the mating surface on the rudder but I did need to expose the sides of the rudder mounting tabs. I cut a "V" in the both sides of horizontal stabilizer corresponding to the shape of the fuselage.
I use 5-minute epoxy to attach the stabilizers. Thick CA sets too fast for me for get the stabilizers lined up properly. Thin CA tends to wick under the covering and leave dark spots. I use painters tape to hold the stabilizers in place until the epoxy dries. I find it is easier to attach the horizontal stabilizer first and let the epoxy set. Then I attach the vertical stabilizer. Do not assume that the slot or surface for attaching the horizontal stabilizer is square. You may have to do a bit of filling and/or sanding to square up the mating surface.
For those of you that have put together balsa ARFs this assemble process is likely familiar to you. Getting the stabilizers aligned properly is critical to getting the plane to perform up to its potential.
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