Converting the 30in Rubber Powered Dumas Piper J-4 to Electric – Part 4

Converting the 30in Rubber Powered Dumas Piper J-4 to Electric – Part 4

Before we actually get around to putting some covering on this model airplane, we need to talk about the process and materials I’m using…stuff many of you reading this may only have heard of, but never seen. So…I’m going to put on my old teacher’s hat and give you “An Easy History of Tissue Covering”.

Tissue-and dope…what is it? Good question. For the purposes of this discussion it would be fair to say that it is the oldest practical method of covering and finishing model airplanes. “What is that?” is another good question, and we need to have good answers to both of them so we can be sure everyone knows what we are talking about. Tissue is pretty much the thinnest, lightest paper you are likely to come across. It ranges in quality from the cheap crinkly stuff you use to wrap gifts to the very finest hand-made material (like Japanese Esaki tissue, made from gampi fiber) that is considered an artist’s material and used for many other things beside model airplanes. Vintage nitrate aircraft dope is cellulose nitrate dissolved in a variety of solvents. It can be thick, for use as an adhesive, or thin for use as a sealer and coating, depending on how much solvent is involved. (Butyrate dope…cellulose acetate butyrate…is a more recent variation that became popular with aeromodelers during the ’50’s and ’60’s because it is “fuel proof”…it resists degradation by methyl alcohol-based based glow engine fuels. It is NOT the best choice for what we are going to do here. I’ll say more about that later)

Covering a model airplane means covering over and closing in of the “open structure”…those parts of an airplane that consist of framework like the leading and trailing edges and ribs of a wing where the surface/outer skin of the airplane is not part of the load bearing structure with tissue, fabric, or more recently, synthetic film. This leads us directly to finishing, which we can think of most simply as painting (although there is usually a lot more to it). In today’s world of model airplanes it’s easy to consider covering and finishing as a single job, using various iron-on heat-shrink materials that include their own finish. Before the appearance of the first of these products in the late 1960’s, choosing and applying a covering and then getting it sealed, surfaced and colored were separate and distinct jobs. As it turns out there are many things the separate-covering-and-finish approach can do that the iron-on products cannot, and to be a real model builder I believe that you need to know about both ways.

Let’s get specific. We are working on a 30″ span built-up balsa Piper J-4 designed according to the time honored stick-and-tissue tradition. There is, indeed, a supply of perfectly good TISSUE right there in the box, waiting for you to use it. Why would you do that? Why not use it instead of the various sophisticated iron-on coverings we are told will be lighter, stronger, quicker, easier, less messy and better looking? Tissue-and-dope, we are also told, is too hard, too smelly, too heavy, and too OLD…out of date and obsolete.  If that is so why do so many experienced, expert aeromodelers insist on continuing to use it? Why have I lost count of the times I have been asked about it? Why am I going through all this drill to cover my Dumas J-4 this way and then tell you all about it?

In my opinion…and I don’t think I’m alone in feeling as I do…tissue-and-dope covering and finishing for small, lightweight model airplanes is the Gold Standard by which finesse, quality of workmanship and professional appearance continue to be judged. Take my word for it, please. One step iron-on coverings can be quicker to use, easier to learn about, and admittedly less aromatic…BUT…in comparison to tissue-and-dope done right they may actually be heavier and/or more clumsy to handle. Puckers and wrinkled corners are almost inevitable, iron-on’s nearly always go slack and wrinkle overtime, and their seams can never be hidden, but what I consider to be worst of all is that no matter how hard you try, those plastic covering products ALWAYS look like shiny, crinkly food wrap instead of something that belongs on a miniature flying machine. Read on and I will demonstrate what I’m talking about.

Right here is where I need to add a big By-The-Way…this may turn out to be the longest single blog post you’ve seen coming from me. In short, in order to make it fit neatly with my “Master’s Workshop:” column in Fly RC Magazine I needed to include all this material on tissue covering in a single installment, and I  would not have felt right leaving any of it out.

 

Dumas does not advertise the tissue included in their kits as the “real Esaki stuff”, but in my experience it is of better-than-average quality. This Piper J-4 kit contained two sheets of orange-dyed tissue which I like even though it may not be a “scale” Piper J-4 color. This is where we need to talk about an important characteristic of the classic tissue-and-dope process. Almost without exception tissue is supplied dyed to a particular color. Unlike plastic coverings, there’s no paint/color coating added to it. Hold colored/dyed tissue up to the light and you’ll see that it’s translucent…you can see light and sort-of make out detail through it. Once that tissue is attached to a model airplane structure, shrunk tight, and given one or more coats of clear dope, it becomes more nearly transparent and shiny. The dyed-in color that came with the tissue is where the color of the finished model comes from. Clear dope is WAY lighter than colored (pigmented) dope, and so you can build a specific model WAY lighter using clear doped dyed tissue than you could by adding colored dope to plain (or just “white”) tissue. That translucent colored “doped tissue” look is easy to get used to…it’s pretty much the iconic image of classic old time model airplanes AND the reason you see so many “see-through” plastic coverings. Those products are simply copying the appearance that set the standard fifty years and more ago. (…and yes, because I know you’re going to ask, “silk-and-dope” works the same way to produce a clear doped, dyed effect. Silk is heavier, stronger, and more expensive, and best suited to larger models.)

 

Tissue, like nearly all other fiber based coverings, has a grain…it’s a characteristic of the manufacturing process. Although you probably can’t see the difference the grain imparts to the tissue in one direction as opposed to another, you can bet it will show up in the way the material shrinks tight after being stuck to parts of a model airplane. You can be sure the grain direction will be parallel to one edge of whatever sheet of tissue you buy…the trick is to figure out which one. Here’s how you do it. Look at the two torn spots in the corner of one of the sheets from my Dumas kit…the horizontal tear on the left is pretty much straight, or controlled.. The tear at right angles to it is ragged and uneven. The grain always lies along the direction (parallel with) the smooth tear. Why this matters to us is that our tissue, when we water shrink it (and to a lesser degree when we use any kind of shrinking coating on it) the shrinkage along the grain is going to be noticeably greater than across it. For example, let’s assume that I cut a piece of this tissue to cover the top of a wing panel. The grain…the horizontal dimension in this case…should run spanwise (from root to tip) so that the greatest shrinking tension will be oriented in that direction. Why? Because we want to minimize the sag, or “scallop” effect of the tissue as it stretches across the spaces between successive ribs. Cover one wing “grain-long” (along the span) and another “grain-short (chordwise) and the difference will be impossible to ignore. The same relationship applies everywhere else…align the grain span-wise on the tail surfaces and nose-to-tail on the fuselage.

 

Now that I know which way the grain runs in the sheet of tissue from THIS KIT, I can lay out and cut appropriate pieces for each of the sections of structure to be covered. This is the bottom of the left horizontal stabilizer. I brushed a generous bead of tissue adhesive (paper glue from the craft store) along the balsa sheet stabilizer root and about an inch out onto the leading and trailing edges, then smoothed/pressed the tissue down into it. At this point the glue should just wet through to the outer surface of the tissue…if it’s TOO wet the tissue will appear soaked and be too susceptible to tearing.

 

The next step is to lift the as-yet unattached portion of the tissue away from the rest of the stabilizer structure and brush more glue all around the perimeter (outside edge). DO NOT put adhesive on the “ribs” or anything else “inside” the outline at this point. I’ll say more about this later.

 

Now lay the loose portion of the tissue smoothly out and across the open structure and press it gently but firmly down into the adhesive that’s waiting for it. If there’s not enough glue, the tissue will not stay in place. If that happened you would need to brush on a thicker bead and/or dilute the glue with water just enough to wet the tissue and “grab” it as I explained a moment ago.

 

When I brushed that first bead of glue onto the bottom surface of the horizontal stabilizer I put it only on the “flat” surfaces where the tissue would naturally contact it when laid in place. As soon as that glue has begun to dry and grabbed the tissue so that I can pull against it gently without having it slip, I can move on to wrapping the overhanging/extra tissue around the structural edge. The first step in that process is to brush more glue along each of the edges of tissue that I want to wrap. (This happens to be the left half of the elevator that I’m working on, but that’s OK) It will take some practice for you to get a feel for adding just enough glue…too little (too dry) and the tissue won’t let you wrap it around and stick where you want it to,, too much glue (too wet) and you’ll get a messy job and make the tissue much more likely to tear or even just fall apart.

 

This is what the job of “wrapping the edges” looks like as seen from the opposite side.

 

I use the technique of sliding the palm of my hand gently down-an-around the edge to help the just-sort-of-wet portion of the tissue follow whatever curvature is there and stay in place when I let go of it.

 

When that happens and the adhesive is still slightly wet, the covered surface should look like this.

 

In real life, paper glue-type tissue adhesives are going to take perhaps half an hour to become dry enough for trimming. (REALLY DRY means overnight) I worked on another part of the airplane until could come back to this elevator section and trim the excess overhang of tissue neatly using a piece of 320- or maybe 220-grit sandpaper.

 

If you tried to sand/trim the tissue too soon it would have balled up and torn instead of separating from the structure. The leftover bits of tissue should come loose easily, like this. If you waited too long, the glue would have dried enough that you would have to pick/scrape/sand the excess tissue from the balsa.

 

OK…the first side is covered and trimmed. Now I can cover the other side of the structure with another piece of tissue using exactly the same technique. When I’m finished, my second edge-trim job will have become a narrow overlap to add a bit of extra dent resistance to the structural edge.

 

Off camera I finished covering all the control surfaces (rudder, elevator and ailerons) along with the fixed horizontal tail. (I’m leaving the fixed vertical tail for later…you’ll see why) Now it’s time to move on to the wing, where my electric RC conversion has added some structural surfaces that require special attention. This is the inset portion of the trailing edge that forms the front of the aileron well (or cut-out). On this model, as with many scale jobs, this surface is concave and I’m dealing with it separately rather than get caught in a really FUSSY edge-wrapping operation when I cover the main wing surfaces. Here I have brushed the usual wet bead of glue onto the curved surface of the cutout and I’m using a calibrated fingertip to convince the tissue to settle nearly into that curvature and stay there.

 

See how the tissue nestles happily down into the “trough” created by the concave aileron well surface? Left to its own devices, it wouldn’t do that. WATER makes all the difference. Too much (too wet) and even the best tissue will want to fall apart; too dry and that crinkly stiffness won’t relax and the tissue won’t stay where you place it. BY THE WAY, this is where one of the important differences between using water based glue and the more traditional clear nitrate dope shows up. The dope dries quite a bit faster, with the result that you can trim edges and cover the opposites sides of surfaces sooner. BUT dope does nothing to relax the “crinklies”.You have to press and pet and fuss with those calibrated fingertips until it dries enough to grab.

 

When the water based adhesive IS dry, it’s easy to use the sandpaper technique to get a clean trim along those sharp structural edges.

 

All cleaned up and ready for the main covering it should look like this.

 

Same as with the tail surfaces we already worked on, I’m starting the wing panel covering on the bottom surface with a sheet of tissue cut to fit the working area (in the case the entire bottom surface) with an overhang of at least one inch to provide enough material to grab, adjust and pull on as necessary.

 

The sequence of covering a simple wing panel like this one is just like what I did on the tail surfaces. Here I have brushed a bead of glue all along the root rib (the inner end of the panel) and out an inch or so along the leading and trailing edges. Here I have pressed the tissue into the wet adhesive and then folded back the remainder of the sheet in preparation for sticking it to the outer edges of the rest of the panel.

 

At this point the glue has grabbed the covering along the wing root and I’m able to pull “out” gently at the tip to ensure that the tissue lies flat and smooth over the entire panel.

 

Same as before I’m adding a fresh bead of glue along the opposite side prior to folding/pressing the tissue overhang around the edge.

 

Along a clearly defined edge like this aileron well/trailing edge I can also use a SHARP blade to slice the tissue overhang off neatly. In places like this do not try to economize by attempting to get “just one more cut” from a worn blade. Doing that invites cuts that tear and pull at the tissue.

 

With the glue dry I can use the sandpaper technique to get a neat trim around the laminated wingtip bow.

 

Properly trimmed, the wingtip looks like this from the other side.

 

Now it’s time for the opposite (upper) surface. I’ve added a “wing root gap cover” of styrene sheet to match the outline shown on my scale reference drawing. I chose to attach this to the upper 1/32″ balsa sheet surface before covering in order to get a better structural bond. Now I’m marking the end of the top surface covering to match the subtle curvature of the cover strip.

 

Same place. moments later. I added the usual adhesive bead to the balsa sheet right up to the edge of the plastic cover and pressed the tissue into place.

 

Just as with the bottom surface, I’m pulling some tension into the tissue from the tip (against the inboard seam I just glued) to get it to lie smooth.

 

I’m using 320 grit sandpaper to trim the tissue on the upper surface of the right wing along the front part of the leading edge radius.

 

I’m peeling away the trimmed-off tissue overhang from the left wingtip. If you look carefully you should be able to see where the upper and lower sheets of tissue form a narrow overlap. I didn’t mind the line of slightly darker color this creates….I’d rather have the extra thickness of the doubled covering for dent resistance.

 

Let’s work on the wing struts. I sanded these to shape and glued them together using the pattern on the plan, but for greater durability I substituted basswood strip of the same dimensions as the balsa supplied in the kit. Changes like this will always be a judgment call of weight-vs.-strength. I expect to fly my airplanes a lot under real world conditions, so I opted for tougher struts. I could have painted them to match the color of the rest of the model, but using tissue adds strength, saves some weight and looks more consistent at the expense of some extra work. Here I’m using the brushed bead of glue to attach suitably wide strips of tissue to one side of each strut.

 

For this job I put on a more generous line of glue that allowed me to press-and-squeeze the overhanging edges of each strip around to the opposite side of each strut. (We’re setting up for another overlap here)>

 

With a tissue strip added to the opposite side of each strut and given the finger-pressure treatment, the basic wing strut assembly looks like this.

 

I’m dealing with those balsa sheet landing gear strut/fairings the same way. Tissue wetted with paper glue is going to stick readily to the face of the strut and wrap neatly around those narrow, thin edges.

 

It goes on smooth and easy, like this. Off camera, I brushed glue along the strut edges underneath the tissue and did another fold, press and trim job on it.

 

Same deal on the carved/sanded balsa engine cowl. I’m going to have a go at wet-forming a single piece of tissue around the entire nose bowl (the front face of the cowl).

 

I’m giving the entire working surface a wet coat of glue. This is not going to be an easy bit of covering to get right, and I wouldn’t blame you for passing on it.

 

It wasn’t perfect, but I got away with it. Now I’m trimming the excess tissue right at the parting line between the nose bowl and the single curvature sheet cowl sides.(Check out the subsequent images of the cowl to see if you can spot the “fudge-factor fixes I had to make).

 

All smoothed out and trimmed it looks like this. I intentionally created an overlap at the rear edge of the noses bowl and along the lower edges of the top portion of the cowl to represent the sheet metal joints on the full scale airplane. I’ll leave the openings covered until after the first coat of clear nitrate dope has sealed the tissue tight to the balsa surface.

 

Let’s get started on the fuselage! Right away I have to make another judgment call. I was able to cover most of the flying surfaces (remember what that means? I’ve used the term before) including the upper surface of the wing with a single piece of tissue on each side. That works because those parts are either flat or single curvature, so I don’t have to try to make the tissue STRETCH around compound curves. Remember the effort I just put in on the front of the cowl? Dry tissue will not accept a compound curve without wrinkling badly, and wet tissue, for our purposes, becomes too fragile to work with. There’s an exception to the “rule” that you may already have noticed. Al those folded over-and-around edges like the wingtips are classic compound curves…but…those curves are defined by (and supported by) solid structure, so that when I take advantage of the water in that paper glue to relax the tissue at those locations, the tissue is SUPPORTED wherever it gets wet and if I can pet and tease it gently enough I can get it to follow the curve without tearing.

Here’s where all that is going: A fuselage whose shape is defined by stringers…like this one…can be covered smoothly using tissue only if we break it down into a series of long, narrow single -surface curves (sometimes called “gores”, as in parachute nomenclature), and cover each one separately, carefully trimming the tissue overlaps at each successive stringer. Think of how you would do a Spitfire fuselage. On this model it happens that some of those compound curves are really shallow, with the result that I can get away with pushing the limits of the tissue just a bit and cover structural surfaces like half of the belly (fuselage bottom) with a single piece of tissue. What I’m doing is taking advantage of the water based glue where the tissue wraps around the longerons (just like those wing tips) AND the ability of the tissue to shrink nicely when sprayed with water AFTER it’s fixed in place.

Watch…I’m going to cover the bottom/left surface of the fuselage (as defined by the lower longeron, the bottom center stringer, and the back edge of the boot cowl) with this sheet of tissue. There’s an auxiliary stringer on each side of the central one that stops short of the tail and so does not form a closed surface, so we can’t use it to define a “gore”. Unfortunately it sort of sticks up in the middle and forces a compound curvature onus. Here’s what we do about that.

 

Here I have used the usual brushed-glue-bead technique to stick the tissue panel along the longeron and the central stringer. I’m using my thumb to wrap the covering up and around the side of the longeron and I have left a generous overhang along the stringer.

 

I have lots of room to work with here, so I can use a blade to slice off that overhang along the outer edge of the stringer.

 

Same deal along the upper edge of the longeron. I have also glued and trimmed the tissue along the rear edge of the cowl to form an enclosed surface, which happens to include that compound curvature we just talked about. When I pressed down those edges the tissue insisted on starting to wrinkle. I used the “wet glue” effect to chase those wrinkles away from the edges out into the center of the panel where they became waves and slack spots. THOSE I can count on the water-shrinking of the finished covering job to shrink out and eliminate.

 

The first half of the belly is covered and trimmed. I have cut one edge of the tissue panel for the other side into an accurate straight line that will follow the center stringer to create a neat overlap with the first sheet of covering. Here I have attached the sheet at the front (the cowl edge)…you can see it folded out of the way just above my fingers. I’m applying the bead of adhesive CAREFULLY along the center stringer where I want to create that overlap without having to do any further trimming there.

 

The front and rear legs of the landing gear strut get in the way when I try to attach the tissue edge along the longeron. What I’m doing here is making two shallow slits in the covering just deep enough to permit the tissue to lie smoothly around/past the metal legs…there it will wrap neatly around the longeron, ready for trimming. (I already did this step on the other side).

 

I’m going to use the same ‘push-the-envelope” technique with the tissue to cover each of the fuselage sides with a single sheet. All this is going to set up the scene for my method of creating one of those “fabric fairing” jobs on the vertical tail. I’m starting by cutting a sheet of tissue that will cover from the lower to the upper longeron, all the way from the rear/side of the boot cowl to the tailpost. To make that work I have cut a 1/8″ wide slot in the covering long enough to fit down over the fixed horizontal tail with some overhang.

 

As with earlier parts of the covering job I have brushed adhesive onto the structure around the stabilizer base and along both longerons up to the stabilizer leading edge, to enable me to anchor one end of the working sheet of tissue…to give me something to ‘pull against”…for the rest of the panel.

 

The next step is to add adhesive along the upper and lower longerons. Now it’s easy to pull the tissue down smoothly over them.

 

We happen to be looking at the opposite side here, but it’s all the same. I cut a slot to allow the tissue to fit neatly around that protruding wing joiner stub spar and continue sticking the edges down all the way to the cowl.

 

This is the upper left longeron just behind the wing…I’ve used some 320 grit sandpaper to make a delicate,, accurate trim of the tissue along the longeron. Here I’m lifting the cut-off material away.

 

I trimmed the belly and the side sheets of tissue off at the rear edge of the boot cowl, with about 1/8″ left attached to the sheet balsa structure. Here I’m using a separate sheet of tissue cut to fit around the boot cowl. I overlapped it with that 1/8″ of tissue from the belly and sides, let the excess hang out over the front former/firewall, and trimmed that flush when it dried.

 

Now we get to the good part! I’m going to cover each side of the vertical fin AND the corresponding half of the fuselage top al the way to the front (at the top edge of the windshield) with one piece of tissue. This isn’t so hard with stretchy fabric, but to make it work with tissue I had to make a paper pattern that would permit me to cut a hockey-stick shaped sheet that would lie flat across the middle of that surface formed by the fin leading edge, the center stringer and the top longeron and then fall into place more or less flat along the fin and fuselage top. With that piece of tissue ready, I’m brushing adhesive along the outer edges for just an inch or so where those surfaces intersect.

 

Here’s that odd shaped sheet of tissue stuck down into that short stretch of glue but still resting loose over the fin and fuselage top.

 

Working back and forth along the fuselage, I’m pressing and teasing and GENTLY stretching the tissue to lie flat along all those structural edges with minimal wrinkles/slackness in between. You have to JUST DO this job to get it figured out…don’t be shy about wasting some tissue (and starting over) on your first try until you get it figured out.

 

Here’s how it should look from the opposite side when the first panel of tissue is stuck in place. I have not yet trimmed the overhang on the fin leading and trailing edges.

 

Time for more glue along the center stringer…note that this is a good place to keep the glue brush under control so you don’t slop excess adhesive out across the tissue that’s already in place.

 

I’m starting with the other half (the left side) by lining up the working sheet of tissue,which has been cut to fit STRAIGHT along the center stringer and more or less “flop” loosely into place across the fin. I’m using the windshield top and the center stringer as positioning references.

 

When it was all dry I used more 320 grit sandpaper precisely along the outer radius of the longeron to trim the new (top) tissue without cutting the piece that was already in place beneath it.

 

This is how the overlapped tissue seam along the left upper longeron should look when it’s trimmed and cleaned up. If you look carefully you’ll see that there are slack places or waves in the area where the tissue bridges open space, but that there is no bunching, puckering or wrinkling along any of the edges. Water shrinking the tissue, which is coming soon, will tighten those slack areas but it will not get rid of actual creases along the edges.

 

Here’s another look at the tail assembly at the same stage of the covering job. What it’s about is that none of those wrinkles “out in the middle” are trapped at the glue line.

 

This is the entire fuselage side, still before I have done any water shrinking. I have glued all the outer tissue edges around the cabin window area, but not any of the “inside” framing. After the tissue is shrunk tight I’ll depend the first coat of dope to attach it firmly to all those window edges.

 

This is the top of the left wing, again before shrinking the tissue.

 

Given a gentle spray of water…just enough to wet it thoroughly without having water run off the surface…it should look like this. Water spray the entire airplane all at once. If you let one side of a structure get wet and then shrink before the other side, you’ll risk severe warps.

 

Now go away and leave the airplane to do its own thing. It will take several hours AT LEAST in an ordinary warm, dry room for all the moisture to evaporate. As that happens the tissue will shrink and draw itself tight. When that has happened it is supposed to look like this.This happens to be the rudder, not the wing we just looked at, but it all works the same.

 

The next step is to give every part of the airplane a single, wet coat of thinned clear nitrate dope. Going on it should look like this., but after it dries some of the shine will go away. The more coats of clear dope you put on, the more of that deep, translucent sheen will remain…BUT…more than two or three coats will risk warping the structure uncontrollably and WILL add more weight than you want.

 

This is the fuselage after the first dope coat has dried. I’m sanding the edge gently to get rid of the last few “fuzzies” that never seem to give up. I used shrinking nitrate clear for this first coat to pull the covering up to the maximum tautness I felt the airframe could handle without distorting (warping). Any subsequent coats ought to be non-tautening nitrate dope or another non-shrinking clear lacquer product. On this model I added a second and a third clear coat using Stits PolyTone Clear, the same non- tautening full scale aircraft finish I use on my larger models.

 

All the “tissue-over-balsa” surfaces like this landing gear strut will tolerate somewhat more aggressive sanding in the interest of a smoother final finish…but…don’t sand through the tissue.

 

With that first dope coat dry I can cut out the window openings. The tension imparted to the tissue by the drying dope makes the cut-free edges curl up. However, the areas of tissue that we want to keep are stuck tight to the window frames and so on and will stay there.

 

Same game for the prop and air intake openings in the cowl. This is the time to use a light touch with the sandpaper to clean up any persistent ragged edges.

 

The standard paint scheme on the J-4 was an overall base color with a trim stripe and registration numbers in a contrasting color. On this model the base color-orange-is provided by the orange-dyed tissue covering. The kit includes a sheet of adhesive-backed black vinyl stripes and numbers. These are intended to be cut out by the builder and stuck in place on the finished covering. That would work, but in my opinion the stick-on markings would look out-of-place on the clear doped orange tissue, and would probably require enough pressure to try to attach evenly to risk damaging the covering.

“Tissue trimming” is the classic method of putting markings like these on clear doped dyed tissue coverings. It’s been standard practice for the model builder to cut out his own markings from the appropriate color of tissue using a pattern of one sort or another, or perhaps even freehand. In this case the existing vinyl markings sheet provides a perfect pattern. To transfer them to tissue I start by spreading two sheets of black tissue on a smooth cutting surface and taping them securely in place so they can’t slip under the pressure of cutting. Here I have the side stripe patterns separated from the numbers. I’m going to tape this piece of material securely over the tissue and use a sharp No. 11 blade to “trace” the outlines through the vinyl and the underlying tissue. There are two stripes on the pattern sheet, but I’ll need to cut only once because I used a double layer of tissue.

 

With the vinyl pattern material removed, the cut-out black tissue stripes lift away like this.

 

I repeated the process with another double layer of black tissue and the vinyl registration numbers serving as the pattern. Doing the cutting requires nothing more than a careful touch. Use a straightedge wherever you feel it might be necessary along those straight lines. Be sure to press hard enough to cut all the way through all the layers of material.

 

Separated, the “N” numbers for the bottom of the left wing look like this arranged loosely in place. I have aligned the “N” exactly and brushed thinned clear dope through it to bond it to the doped tissue underneath. I’ll align and attach the remaining characters in the same way.

 

This is the upper surface of the right wing with all the registration marking characters doped into place.

 

The kit includes a paper pattern for the windshield and cabin side windows and a sheet of clear plastic to cut them from. I’m leaving off the side windows for cooling air exit and for access to the servos, etc., inside the cabin, as the top wing center section isn’t removable on this model. I cut out the windshield pattern and trimmed it for an exact fit to the actual airplane.

 

I used the pattern to cut an accurate windshield from the clear plastic, then used masking tape to get it secured in exactly the position I wanted.

 

With that done I removed all the tape except at the top center so the sides/ rear edges could fold free of the front cabin doorposts where they will be attached. Then I brushed a bead of RC “canopy glue” along each of the frames.

 

The next step was to tape both side/rear edges firmly in place and then go away to let the canopy glue dry completely.

 

Next I glued the top/rear edge of the windshield and taped it in place. When it was dry I pulled the tape and brushed the entire windshield edge with a wet bead of glue that flowed into place along the joint to mate the windshield neatly with the doped tissue surface of the cowl. Wait to see what that looked like when it dried!

 

All done (almost) and ready for those final RC system and airframe adjustments that have to be done before I can trust her to the air. I’ll be preparing a separate Flight Report for you when al that has been done.

NEXT…something different from the same era. All I’ll tell you now is that it has multiple propellers and, as the old time pilots like to say, the small wheel on the correct end of the airplane.

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Converting the 30in Rubber Powered Dumas Piper J-4 to Electric – Part 1
Converting the 30in Rubber Powered Dumas Piper J-4 to Electric – Part 2
Converting the 30in Rubber Powered Dumas Piper J-4 to Electric – Part 3
Converting the 30in Rubber Powered Dumas Piper J-4 to Electric – Part 4