Finishing Those Foam ARF RC Scale Airplanes … Scaling-Out the Atomik RC/Sonic Modell EPO ARF B-17

Finishing Those Foam ARF RC Scale Airplanes … Scaling-Out the Atomik RC/Sonic Modell EPO ARF B-17

Recently I devoted several weeks of workshop time to determine just how far I could go with fiberglass-and-paint resurfacing and refinishing of a typical large foam/ARF electric powered RC scale warbird … in this case the 61” wingspan J-Power P-51-D available from Atomik RC. My intent was to go all-out to fill and/or cover those exaggerated molded-in surface details that are typical of most models in this class, provide a new fiberglass-based skin to improve the durability of the standard-issue molded EPO foam finish, and then add a traditional detailed, airbrushed paint finish to see how close I could come to creating the appearance of a built-up (non-foam) airplane without adding so much weight that the flyability of the model would be compromised. I did it, it worked, and I learned a lot. Check out http://www.rcmodel.com/2014/07/finishing-those-foam-arf-rc-scale-airplanes/for all the details.

While I was busy tempting myself by checking out Atomik RC’s entire line of foam ARF warbirds (and had already committed myself to the big P-51-D) I couldn’t help wondering what cool things I might be able to do with one of their Sonic Modell 74” span B-17’s. (Check out http://www.atomikrc.com/collections/almost-ready-to-fly/products/b-17-flying-fortress-74in-pnp-rc-airplane) For a whole lot of good reasons I decided to stash the (very big) B-17 box under one of the workbenches in my shop and concentrate on learning everything I could about improving foam ARF’s by working on the P-51. I never quite managed to let myself forget that a six-foot B-17 was waiting in its box in the shadows under the table … but … I kept my promise to myself and left it there until the P-51 was finished, flown, evaluated and written up as the report I’ve already referred to.

If you have already checked out that P-51 feature, you know that I invested a LOT of time and a LOT of work on that conversion project. What should I do with this B-17? My wife, Teryl, who has been at my side supporting and encouraging my model airplane thing for a long time suggested that “That P-51 is a mind-blower…most modelers would never know it’s an ARF unless you told them. But, most modelers might be scared off by all the work you put into it. They’re going to be pleased that you showed that it can be done, and how … but isn’t there as simpler way to get the same sort of results?”

You already know my answer had to be, “No … but almost, yeah, you could come pretty close.” And that’s when I decided to use this B-17 to show how far you can go with scaling out/improving a foam ARF without getting into the whole resurfacing-fiberglassing-painting deal. Here’s how I did it.

 

As it comes out of a very big box there is a whole lot of pre-assembly done on this model airplane. Here you can see the bottom surfaces of both wings – the right panel is in the foreground – with just about everything already put together. Not only are the engine nacelles pre-molded in as part of the wing panels , all the servos with extension cables attached and in place as well as the motors and ESC’s are in place. As this model is fitted with (four) brushless motors, it’s necessary that there be a dedicated ECS for each of them. See those black panels (with big air passage openings) near the leading edge just inboard of each nacelle? The ESC’s are slip-fitted into cutouts in the EPO foam wing right under them. We’ll decide in a bit what, if anything, I ought to do about them. I’m sure you also noticed that the retractable main landing gear units are already assembly/mounted in place. You could bind your receiver, plug ‘em all in and they would work RIGHT NOW. If I were planning to do an all-out resurface-and-refinish job on this model as I did on the P-51, my main concern right away would be to pull everything you see here apart so I could start filling, priming and sanding…but…we’ve already accepted the idea the factory fresh foam finish is here to stay, so the question becomes, “What else can we change to improve the appearance, and what’s the best way to do it?”

 

Here’s a closer look at the bottom/right wing panel. Once we accept the decision to keep the molded-in detail (and work on disguising it with an artful paint job)we can focus on whatever other details we want to improve. Those open channels/grooves where the servo, light, throttle and RLG cables are recessed into the foam surface don’t need to stay like that, nor do the servos themselves. The ailerons servos came pre-installed with real mechanical hinges and they look OK , so I’ll leave them that way.
The flaps, on the other hand, are mounted/hinged with a strip of tape. My first thought was, “That has to go…” but in fact they work the way they need to and won’t look out of place on what’s going to be a really busy wing under surface.

 

Let’s start “fixing” with those servo cable channels. I cut some ½” strips from adhesive backed aluminum tape from the hardware store and trimmed them to fit the various cable openings I want to disguise. The edges I created are not in any “scale location” , but when all the tapes are in place and painted, they will look as if they are supposed to be there.

 

We have got to do something about those exposed aileron and flap servos. At least they’re recessed flush with the wing surface so I don’t have to make decisions about cutting into the wing to keep them from looking like mechanical warts sticking out of the airplane. As it turns out all I have to do is draw out a pattern for a cover plate with an opening/slot for the servo output arm and make four of them from lithoplate (or aluminum roofer’s flashing). Deluxe Materials Foam 2 Foam is my adhesive of choice here… it’s guaranteed “foam friendly” and provides a firm, slightly flexible bond between the foam structure and the metal cover plates.

 

Foam 2 Foam is also my choice for keeping those ventilated ESC covers in place. I wasn’t entirely comfortable that the original adhesive would “stay stuck” in flight. I got ahead of the camera a bit here…that blue masking tape is holding the covers firmly in place while the adhesive sets.

 

Back on top. Some of that over-enthusiastic surface detail is easy to deal with. There are five fuel tank access covers (gas caps) on the upper surface of each wing of a B-17-F. The crude, oversized molded-in rings that represent them on this ARF are just too chunky to ignore, so I sliced them all off flush with the wing surface with a sharp/new razor blade. Wait and see what I’ll do with them next.

 

In place of a more involved fiberglass-skin-based surface treatment on this airplane, I’m keeping it simple by using Deluxe Materials Foam Armour one-step surface reinforcement and finish base formulated for foam ARF models just like this one. Here I am beginning the job of brushing a generous (wet) coat of Foam Armour over the entire airplane. (You may occasionally find that Foam Armour has thickened just enough in the container that it becomes difficult to brush out smoothly. That’s easy to fix. On ANY Foam Armour application you can thin the material as necessary with plain old water to get a brushing consistency you’re comfortable with.)

 

I let my coat of Foam Armour run right over and onto the narrow seams at the edges of all those sort-of-transparent window insets. Since there’s no detail inside to worry about hiding, the slightly clouded finished appearance I’ll get on the windows hurts nothing and actually enhances the camouflaged “working airplane” look I’m trying to achieve. Right now you are looking at the entire airplane with that single coat brushed on (for good coverage) as wet as I can get it without risking runs or sags. That milky look over the color finish will go away…

 

…and the Foam Armour surface will look like this after a few hours of drying time. Can you see how the material has self-leveled and created a smooth surface that does a good job of beginning to hide that “spotted-foam finish”? It also does a fine job of blending in the replacement “gas caps” I made from more of that adhesive backed aluminum tape I used on the bottom of the wing.

 

One of the obvious details that got left out on this particular ARF rendition of a B-17-F is the characteristic light gray paint job on the bottom of the airplane. The model will fly OK if you leave it all olive drab the way it comes out of the box, but this step will make it look WAY better. Although this B-17 is made of EPO (expanded poly olefin) which will accept just about any type of paint finish you might want to use, not all foam ARF’s are so fortunate. To show how easy it is I chose to use ordinary craft store acrylic paint (in those little plastic bottles). Everybody names their colors differently. Since we’re not going to be concerned with scale judging for color accuracy, just pick a color that looks close to you. I started with the bottom of the right wing…

 

…and went on to the fuselage. I’m using my Badger double-action artist’s airbrush to get the control I need to “free hand” the camo color separation along the sides of the fuselage. BTW: Denatured alcohol is the best way to thin craft store acrylic so you can airbrush it…don’t be afraid to thin it A LOT if you have to. Keep thinning until it sprays properly.

 

Same game on the top of the airplane. Those new gas tank covers are among the various places on the model that are going to need some touch-up of the original olive drab base color. Another BTW: It’s going to be difficult to get an exact match to the pre-existing color on the model . This would be the case on any ARF you might work on. In this case “close enough: is OK…I’ll say more about that later.

 

See what I mean about the less-than-exact color match (and this was the best match of five different shades I tested). Don’t get all worried about precise color matching here…not only are we not concerned with scale judging, we also need to remember that this is a model of a COMBAT airplane. It got fixed and patched and fussed into “one more mission” so often that there might have been very little factory-standard paint left on a given full scale subject.

 

Same game on the tail group. Assembling the horizontal and vertical tail parts per the instructions left noticeable gaps along the joining edges. I filled them all with a careful “fingertip-smooth” application of Deluxe Materials Roket Gel and used the airbrush to begin camouflaging the repair job.

 

Now it’s time to get “down and dirty”. I mixed up a special batch of “dirt” color…sort of a grimy gray-brown…to represent exhaust, oil stains and mud. With single batch of color I can control how dirty/oily any particular part of theairplane gets by airbrushing on just a little for a light smudge or a lot for an oil leak or exhaust stain.

 

More of the same. If you have ever had a good look at a big airplane with multiple engines (especially radials) out on the wings, you’ll already know that the entire nacelle and ALL of the lower wing surface behind each engine gets DIRTY. After a couple of missions a B-17 is going to appear almost black there. Don’t try to put all the staining on in one shot, though…sneak up on it as I’m doing here and replicate the look of a sequential, layered buildup. A general rule for airbrushing exhaust/dirt/weathering is that less is almost always better.

 

The main LG wheels are going to get just as grimy as everything else behind the engines. Don’t worry about overspraying onto the tire…it’s gonna’ be dirty too. Notice the other main wheel/tire in the background. That clean-out-of-the-box plastic really sticks out, right?

 

The B-17 had an exhaust-driven turbo-supercharger mounted in the nacelles behind each engine. The moldmaker for this particular ARF did an OK job of representing them, but we need to make each one look as if it’s mounted within an opening in the sheet metal cowl, made of various grades of steel that discolor from heat in operation, and often show a touch of oxidation (rust) as well. So far this one is still the overall belly-gray you saw me add in steps 10 and 11.

 

Here I want to represent the sharply cut-off appearance of the dark inside of the cowl as defined by the sheet metal edge on the full scale B-17. I’m brushing dark gray into the turbocharger cutout using the molded edge of the simulated cutout to define the paint line. I’ll add more detail here later.

 

The top of the airplane gets dirty, too. I’m using more of the same bottle of “dirt” paint to fill in every place where the airflow would naturally concentrate any stray exhaust or oil spray against the outer surface of the airplane.

 

The cabin/cockpit enclosure is a separate, removable feature on this model that provides access to the LiPo packs as well as the receiver. I don’t want to get any dirt/matte overspray on these windows because they are one of the few parts of an operational B-17 that would be aggressively kept clean. I masked off these clear panels to protect them and later “dirtied up” the green (sheet metal) portions. (Yes, I missed giving you a masked-off shot, but you’ll get to see the final results later.)

 

The four engine cowls are all the same/interchangeable on this model. Each includes an acceptable molded plastic representation of a vintage radial engine with sufficient clearance for the working motor and cooling air entry area. Their appearance is OK, but there are two features on each cowl that cry out “toy airplane” and we need to deal with that. That flat flange of yellow plastic that extends inward beyond the curved/turned under lip at the front has to go. On the full scale B-17 that portion of the cowl was a precisely formed/rolled aerodynamic shape that influenced airflow into the cowl and over the engine. I decided that on this model, grinding away the flat portion of each cowl lip with a rotary sanding drum would work OK to get rid of the offending extra material.

 

While I’ve got the sanding drum on the tool, I can cut away the molded-in “webs” that connect each of the simulated cowl flaps to its neighbors. Each cowl flap is supposed to be a separate, rectangular piece of aluminum that is curved to match the contour of the rest of the cowl. While they are operated simultaneously, each moves independently. We need to make them LOOK like individual structural components.

 

The power tool is the best way to remove the bulk of the extra plastic here, but we need to switch over to the relaxed pace and precision of a hand-powered custom sanding tool to get the fine details right.

 

Same game when I go back to clean up the rolled lip at the front of each cowl. In this case my “calibrated finger” (behind the rolled –up 150-grit production paper) is the key to reproducing the aerodynamic curve of the full scale cowl opening.

 

More “dirt”. On a more fastidiously “scale” model I’d be doing intricate, specific dummy engine details, but for this one a pass with the airbrush will do the job.

 

I chose not to mask of the portion of the cowl that would unavoidably get hit with overspray. Instead, knowing that some denatured alcohol would clean every trace of the still-wet craft store acrylic paint off the original yellow plastic finish, I took the easy route.

 

There’s a lot going on here. Remember when I brushed a dark gray background color onto the supercharger assemblies? Off-camera I went back to them and airbrushed some rust color (heat-oxidized steel) over most of the actual supercharger housing(s). I also let some overspray escape to either side of the opening to provide a little more gratuitous dirt. I also used another pass with the airbrush to differentiate the cowl flaps from the portion of the cowl ahead of them. The cowl flaps are subject to oil and grime blowing back from the engine over/through the gaps at their leading edges; the metal surface ahead of them is not. I used a strip of masking tape just like what you see here to protect the “front” cowl while I dirtied up the cowl flaps, then removed it once the paint started to dry. The next step was to mask off the front (the yellow identification band) of each cowl…that’s what you see here…for the next step.

 

Remember that the rest of the airplane’s undersurface had to be airbrushed light gray? The bottom of each cowl…behind the yellow bands…gets the same treatment. Notice that I did not re-mask the “dirty” area on the cowl flaps. On the underside of the cowls on an active service B-17 it would be really difficult to distinguish light gray camo from general dirt.

 

When all the masking and base-color painting and airbrushed detailing was done, I gave the entire airplane a single coat of matte clear overspray. The trick here was to get just enough clearcoat onto all of the various surfaces to flow out wet, but to minimize excess weight, not a bit more. For this job I’m using an ordinary hardware store spray can product (Valspar, in this case). I wanted to demonstrate that with solvent-resistant EPO foam and those craft store acrylic paints just about anything you can get will work OK if you spray carefully and LET IT DRY before trying to handle it.

 

With all that done … and a safe overnight drying time…the tops of the cowls I was just working on look like this. See how it all blends together to give the impression of a weathered, dirty, working combat airplane?

 

Same deal on the other side of the airplane, as seen from behind. Can you see how those modified gas tank caps blend in and look real?

 

Let’s go wide…here’s the entire airplane from the same angle. Once you get a few feet away the changes I’ve been making on the model begin to “work” at creating a convincing scale appearance.

 

Same thing from the front quarter. It’s not difficult to let yourself start to forget all about the model’s ARF origins.

 

Mission-ready. This might be about as close as we get as aeromodelers to how it felt to fly one of these things off into a real British sky full of brooding grey clouds.

 

It flies great! In the end the few ounces of weight I added to the box-stock ARF from Atomik RC make no noticeable difference in the way this B-17 flies. I made one change to deal with the weight gain in the tail…I substituted two Venom 3S 20C 3200 mAh LiPo packs for the 2100 mAh packs suggested in the instruction manual and the balance/flight trim came out “right on” with no addition of “dead weight” ballast necessary. Right now the model is cruising level at about 50% power…and it’s super-stable and flying at a believable representation of scale speed.

 

More of the same, but banking away with somewhere to go. If creating the impression of what it might be like to see a full scale B-17-F in flight is what interests you, you’d NEVER have to go to full throttle with this Sonic Modell/Atomik RC B-17 as I have modified it. Full power on takeoff makes it jump off the ground in fifty feet or so…WAY too quick. If you are working at being one of those “good scale pilots” who has learned to make good use of the often-overlooked throttle, getting one of these B-17’s and modifying it the way I have here would be a fine way to polish (and show off) your skills.