Announcer: Welcome to RC Plane Lab, a podcast for anyone interested in RC Airplane. We’ll share tips and tricks on how to build models and talk about successful flights, epic crashes, and everything in between. Visit us at rcplanelab.com to sign up for our email list and to ask us questions. You can also text us or leave us a voicemail at 818-351-9846. Please help us out by rating and reviewing us in your favorite podcast app. Thanks for spending time with us today. Now, here are your hosts, Ron and Tom.

Ron: Hello, everyone, and welcome to the RC Plane Lab podcast. I’m Ron.

Tom: And I’m Tom. Today, we’re going to talk about wing sheeting and how to build it.

Ron: Yeah, so this episode is going to be a little bit different than what we usually do. Tom’s going to kind of go through the process he uses to assemble these wing sheets. In order for this to make sense, you probably want to listen with our website pulled up in the background. I will have some pictures posted. And Tom will reference picture number one, number two, number three to kind of explain what he is talking about. So head on over now and visit us at rcplanelab.com slash wing dash sheeting. And that should bring it up. If you can’t find it that way, just go to the homepage, and there will be a link under the show notes for this one, too. You can actually play it in the browser. If you don’t want to listen to it through your podcast app, or you can listen to it however you want and just kind of follow along. Nice. As he discusses what to do. So, Tommy, you want to start?

Tom: Yeah. Yeah. So a lot of our airplanes today use balsa sheeting to cover the wings. You know, foam. A lot of the larger airplanes use foam cores, and then they’re sheeted with balsa. And you have to get those balsas and big, you know, balsa sheets and big sheets to cover these big wings. And this is one way to do it. There’s lots of different ways, but this is the way I’ve been doing it for years and years and years. And since I just recently did it on this Horton wing project, I thought, hey, why not put a little how-to together? So if you’ll look at photo number one, you’ll see how you start. You know, we start with these six-inch wide. These are 332-inch balsa sheets, or 16th-inch rather. And you basically want to make sure you start with straight edges. As you get these sheets out from the stores or the mail or wherever you buy your balsa sheets, they usually don’t come with nice, true edges. They’re mass-produced, you know, on machines. And, you know, machines produce a fine edge, but they’re never really perfect. And you really need almost—

Ron: Or they might get messed up in shipment even.

Tom: Exactly. Yeah, exactly. Or, you know, they’ll warp. You know, humidity does a number, especially on soft balsa. Right. So you have to true up all those edges before you can glue them together because you want a really, really, really nice, tight-fitting joint so that the glue we’re going to use, you know, has the best effect and provides the best bond. So in picture number one, you can see I’ve got this nice, long steel three-foot straight edge that I like to use to trim the edges of all the sheets that are going to be glued together. And so that’s what you can see in photo number one there. You can see I’ve—looks like I’ve trimmed the first sheet there or a few other sheets because you can see the little slivers there of what was left. And then the next picture, what I do is I’ll—once I’m satisfied with the fit of those sheets together, and it may sometimes even take a little bit, you know, a touch-up with a sanding block or whatever to make sure that you get a good fit. I’ll slide the sheets together, and I’ll initially just tape them together with, you know, short pieces of masking tape that you can see in the photo there to get them all nice and lined up and get those joints tight together. And once I’ve done that with all the sheets—in this case, I’m only gluing three sheets together, but it doesn’t matter how many sheets you’re gluing together—put them all together like this. And then I like to run a nice, solid line of tape because this is essentially going to be the backside. of the sheet. And having said that, I want to make a note that I assemble these sheets with the good side down. Usually when they run these sheets through the mills and things like that, there’s a good side and a bad side usually. And you can tell by looking at it or feeling it, the smoothest or the best-looking side I’ll put down. So in the photo number three there, you see I’ve got the three sheets—I’m sorry, four sheets, three seams taped together. And that is going to be the back of my finished sheet. So in the next photo, number four, I have taken the sheet and just flipped it over. And you can see it just so happens that the labels on these sheets were put on the good side, which is unfortunate in this case because those labels, when I peeled them off, they left residue behind that I then had to try to clean off. So anyway, once you’ve got to this point, then you’re going to be ready to have your glue. And I want to talk about that. I’m old school. I like to use wood glue or aliphatic resin is its technical name. Tight bond original formula is what I use. Sig bond is also a great glue that I also use whenever I can get it. Tight bond can be bought at most hardware stores, you know, Lowe’s, Menards, Ace Hardware. Sig, you have to get from usually a model supplier. I have seen it in Hobby Lobby before. So that’s also—and I want to make a note specifically here not to use CEA to glue your sheets together. And the reason for that is because CEA, when it wicks into the balsa, it creates a hard spot in the balsa. And when you go to sand that smooth, that spot where the CA is is then harder than the soft balsa around it. So the soft balsa around it will sand off before that CEA does, and it leaves you with, you know, divots or scallops or if you’re really getting aggressive with the sanding, it’ll let—you can actually, on this sheeting especially, you can run the risk of sanding through it and still having this ugly CA seam. CA has its use. It’s not here. So anyway, photo number five in this case, you can see I’ve got the sheets bent, almost like that tape is acting like a hinge on the backside. And what that does is it opens up the joint so that I can then, as in the next photo, fill that joint with the tight bond in this case. And just to—I mean, you can put as much glue in there as you want. Just know that any extra you’re going to be squeegeeing off in one of the next steps anyway. So I try not to overdo it. Tight bond is a wonderful glue, and so is Sig bond. They work really, really well. It doesn’t take a lot of glue to get a really good bond. So if you zoom in on that picture, you can kind of see the approximate amount that I like to lay in that joint. And then when you—

Ron: Yeah, and a little goes a long way with that, too. I mean— It does. You know, the balsa is not very strong to begin with. So you’re not looking for a joint that’s going to, you know, hold a brick or anything. You just want it to be as strong as the rest of the balsa. Exactly. And really, even with just a little bit of glue in there, if you bend that and break it, that glue joint is going to hold. The balsa is going to break.

Tom: That’s exactly right. That’s exactly right. And like I said, you run the—I mean, this glue will soak into the wood a very, very small amount, not like CA does. But like you said, this joint will be stronger than the balsa around it. So if you, you know, were to—when this thing is cured, you were to bend the sheet right there along that seam, the balsa around it’s going to crack and break before that seam is. So, yeah, that’s about the amount of glue I use. And then when you flatten those sheets out, it squeezes out the excess glue to the good side of the sheet because you’ve got the tape now on the backside. No, you can’t—you’re not going to get much squeeze out back there. So then in the next photo, you can see I’ve flattened the sheets out. It’s—you can see how much glue has then kind of oozed out of that joint. And what I do is I come back and I scrape that off with either, you know, a small sheet of balsa or, you know, an old credit card or even if you just want to use a paper towel, you know, moistened with a little bit of water. Wipe that off and that’s the next picture. I’ve come back and done that. And then what I do is once I’ve done that, I’ll apply a piece of tape to that seam as well. In that photo number eight, you can see that I’ve squeegeed the glue off and then there’s tape on the other seams. So now I’ve got these joints taped on both the front and the back, right? And then once you’ve got all those together and you’ve got them all taped up, you let it sit. I like to let it sit for 24 hours because the type on, you know, if you go to sand it too early, it gets kind of gummy and then kind of balls up on the sandpaper and that’s no fun. It can leave divots, you know, in the ball. So I let it sit, in this case, overnight, 24 hours, 12, 24 hours, whatever it was, peeled all the tape off and that’s what I ended up with in photo number nine. And then you hit that with some, you know, 220 and you got a really, really, really smooth sheet now ready for applying to your wing. And that’s really all there is to it.

Ron: Do you notice any difference when you go to do like a compound type curve or even when you’re trying to curve with the grain, do you notice any difference in how it bends?

Tom: Sure.

Ron: Okay, so you do notice a difference where it bends, like where you have the glue?

Tom: It does, yeah. But usually, you know, some tricks, you know, there are tricks out there that you can use to assist. In the case of this Horton wing that I’ve been working on that I actually built this skin for, it has a lot of compound curve and the actual, the underside of the wing has a reflex, actually. So it has almost an undercamber portion. So it was really difficult to get the sheeting to conform to the wing. And here’s where, you know, the little, you know, tips of the trade or tricks or whatever is. I like to use Windex, the full-on ammonia version. And what that does is, you know, you spray it on the surface and that makes the wood a little more pliable. Ammonia actually breaks down to some degree the fibers in the balsas. So I actually recommend not straight ammonia. I mix mine 50-50 with water just because I don’t want to break down all the fiber of the wood. But breaking down those fibers makes that wood more pliable so that it can then conform and then, you know, to the, to the substrate. And then, so…

Ron: So you use, you use ammonia mixed or do you use Windex?

Tom: I use Windex that’s thinned with water. So I’ll use Windex 50-50 with water.

Ron: Oh, okay.

Tom: Yeah.

Ron: Okay, I got you.

Tom: I don’t, yeah, I don’t go full strength with it just because, like I said, the ammonia does break down. I believe it’s the cellulose that’s in some of the, some of the wood.

Ron: And that would be permanent then. That’s nothing that’ll come back.

Tom: Exactly. Yeah, yeah. Okay. In this case, it’s probably not a big deal because I’m going to be fiberglassing this wing anyway. But, yeah, I didn’t want, you know, I don’t want to lose all the strength of the wood. I’d like to retain some of it. So, and you just don’t need it. I mean, this wing was pretty, pretty complex in all the curves that are on it. And, and the, the mix that I use was fine. I was able to get the, the balsa to conform. But getting back to the glue joints, they are a little more challenging because they’re not as flexible because they are, you know. I mean, you bonded two sheets together with this really, really great glue and it’s made a really, really strong joint that is now not quite as flexible as the wood around it. So, that’s something that you’ll want to think about when you’re, you know, maybe planning your, your wing skin sheet construction. Sometimes you can, you can strategically place those joints in areas that aren’t quite so curvilicious, you know, for lack of a better word. Like leading edges. You know, when you’re trying to conform a sheet of balsa to a leading edge, you may not want a glue joint in that area if you can avoid it.

Ron: So, you might want that sit a couple inches back on the top and bottom then.

Tom: Right. And there’s lots of strategies too for, you know, for, for avoiding that too. Like, you know, sometimes I didn’t do that in this case, but I’ve done it before where I’ve, you know, I’ve constructed a sheet, you know, for a wing and I’ll cut back the leading edge. And then I’ll, I’ll trim another sheet of balsa, let’s say two inches from the leading edge so that that grain will then run parallel to the leading edge. Whereas, you know, the overall sheet may be perpendicular to the, to the root of the wing. And if it’s a tapered wing, well then that, you know, that grain’s not going to be parallel exactly to the leading edge. So, then may not be as pliable. So, what I’ll do is I’ll, I’ll trim two inches back off the leading edge of my sheet, parallel to the leading edge of the, of the wing, if that makes sense. And then I’ll come back and I’ll glue a straight sheet with the grain running parallel. It’s hard to describe. It’s easier to draw a picture of it. But anyway, that’s how you build a sheet and you can strategically place those joints should you need to. And then what I, go ahead.

Ron: I said perfect. And then one question I do want to ask though, um, that’s obviously edge gluing. What about like end gluing pieces to make them longer? Is that something you can do too? Or do you really want to stay away from that?

Tom: You want to stay away from that. Uh, end grain balsa is not particularly strong. Um, you can’t, it’s hard to get a really good bond end grain. It can be done. Um, but it’s not something that, that, that you, you, you like to do. And there are ways to, to get around that too. You can, you know, you can cut a bias on the end of a sheet and then cut a matching bias on another sheet. So you have more, more glue area or more bond area. Um, but generally speaking, yeah, you want to, if at all possible, try to, uh, avoid gluing ends together to make longer pieces. And that doesn’t just go for balsa sheets that goes for sticks as well. Like if you’re building, let’s say, uh, uh, you know, uh, uh, a J3 Cub, let’s say has really, really long longer-ons in the fuselage and you don’t have sticks long enough to do it. There are strategies you can do, you know, cutting, cutting angles and to maximize the glue joints, but you want to avoid that if at all possible, whenever you can. But yeah. And then, uh, once you got your sheet built and then, you know, you glue it to the airframe. And I like to use wood glue for that too. And, and lots and lots of weight.

Ron: Oh, so that’s all you use on it. You don’t pin it or anything?

Tom: Pins, weights, whatever, whatever it takes. I liked, I’ve, I’ve, uh, I’ve made these little shot bags out of BBs, um, that, uh, are nice because they actually will come form. You know, you can kind of roll them around and they’ll, they’ll take the shape of whatever’s underneath them.

Ron: Um, that’s a good idea.

Tom: Yeah. You have to be careful. I mean, too much weight in between, let’s say on a wing in between a wing rib will cause that area to. You know, bow, if you will, down between the ribs. So you want to be careful. You want to be straight. Exactly. You want to be, you know, careful where you place your weight. But, um, yeah, I like to, I like to use these little bags I’ve made and, uh, T pins. Sure. Uh, especially around the leading edges to keep it pinned down to leading edge. And, uh, and my, my ammonia mix, uh, does a pretty good job. But that’s how you build a wing skin.

Ron: All right. Thanks everybody. Uh, until next time, I’m Ron. I’m Tom.

Announcer: We hope you enjoyed this episode of the RC Plane Lab podcast. For topic suggestions, to ask questions, or to give any feedback, connect with us at rcplanelab.com or email us direct at either ron at rcplanelab.com or tom at rcplanelab.com. You can also text us or leave us a voicemail at 818-351-9846. Please subscribe, rate, and review us on your favorite podcast app. Until next time, may your landings be gentle.