Episode 43 · Originally released November 14, 2020 · Hosts: Ron and Tom
Ron and Tom explain a systematic approach to trimming a new RC airplane so it flies predictably and efficiently.
In this episode
Episode Topics
Connect with RC Plane Lab
Chapters
00:38 — Shop updates and listener reminders
08:53 — What flight trimming accomplishes
17:46 — Ground checks before the first flight
26:38 — Establishing straight-and-level flight
35:31 — Adjusting controls, balance, and thrust
44:24 — A repeatable trimming routine
Episode Topics
Shop updates and listener reminders
What flight trimming accomplishes
Ground checks before the first flight
Establishing straight-and-level flight
Adjusting controls, balance, and thrust
A repeatable trimming routine
Key Takeaways
The episode combines practical RC airplane experience with firsthand workshop discussion.
The hosts explain not only what they did, but the reasoning and lessons behind it.
Listeners can use the chapter list to jump directly to the subjects that interest them.
Episode 43 Transcript
This transcript has been lightly edited for readability. Timestamps are retained.
Read the full transcript
[0:00] Hello and welcome to RC Plane Lab, a podcast for anyone interested in RC airplanes. 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,
[0:34] here are your hosts, Ron and Tom. Hello, everyone. Welcome to the RC Plane Lab podcast. I'm Ron. And I'm Tom. How was your weekend, Tom? well it was not long enough had to work oh yeah i forgot about that yeah yep i had to work make make money so i can spend it on airplanes so that's what 12 days in a row then you'll be working huh well with the veterans day coming up it's not it's not 12. i get a little break in there i get that oh yeah
[1:02] With the Veterans Day coming up, it's not 12. I get a little break in there. I get that Veterans Day off. Which will be Wednesday. Three days. Oh, Wednesday? Yeah, Veterans Day is Wednesday. I'm not sure because I'm taking Thursday off, and then I'll get Friday, Saturday, Sunday. So I'll have five days this coming weekend. Okay, so you're complaining that you had to work two days, but you have a five-day weekend coming up.
[1:24] Well, but I had to work two days after a five day work week already so by the time i get a day off i will have worked nine days in a row so yeah i'm complaining i do i do nine in a row to get five off yeah i guess it's not a not a bad deal but that's that's the exception that's not the norm usually the norm is 11 day work week and then I get a day or two off, and then another seven-day work week on top of that, and then so on and so forth. Yeah, that I wouldn't like.
[1:50] Yeah, I got a little bit. I guess this one I get lucky. At least you'll have enough time to do a bunch of work on your do list this weekend then, huh? Well, I'm hoping. But before we get into that, I wanted to hit the Patreon again. Just let our listeners know that, hey, we're out there on Patreon. You guys can support us, help us do what we do. Like we mentioned on the very first episode, we don't spend that money on airplanes. We spend it on the stuff that we're recording with right
[2:18] now, for example. Yep. Trying to make it better to make better things for you guys. Exactly. Yeah. And hey, speaking of making things better for you guys, help us help you. Fill out that listener survey, please. Oh, forgot about that, too. Yeah. Any chance you get, if you have anything you want to, any feedback you want to give us, anything like that, go fill out the survey, and that helps us out a lot, too. That's right.
[2:45] us out a lot too that's right it just kind of makes us or gives us the information on whether or not we're going the right way yeah or if we're going in a wrong direction or tell us what you want so we know where where to take this yeah it's good feedback for us tells us what just like you said tells us what you guys are most interested in listening to us babble about which i'm surprised so many of you like this. I am. Me too. That's awesome.
[3:06] Because I like talking about airplanes. I can talk about them all the time. And you do, actually. But believe it or not, eventually, I'll probably run out of things to say about airplanes. So that's where you guys come in. Let's hope we don't get there. You tell us what you want to hear. And we won't tell you what you want to hear, but we'll talk about maybe things you'd like to hear us talk about. There you go. How about that? Yeah.
[3:27] So I also wanted to bring up, you said you were going to post the pictures of the horizontal stabilizers that we both built. I did. I did, and I will get those posted on the forums this week. You can get to our forums how, Ron? Forums.rcplanelab.com. Thank you very much head on over there and you can see pictures of what Tom and I are working on he's he's posting those to make fun of me however I will say that that is
[3:55] not the one I'm gonna be using because apparently I like it apparently I like to do things over and over and over what you do? I didn't do anything actually wrong as much as I didn't like what it was going to look like. Oh. So I… maybe I should hold off building my fuselage because maybe you won't like your fuselage and then I won't have to build one. I'll just take yours. Is it bad that I did think about restarting on that one also? The fuselage? The fuselage. Oh, my gosh.
[4:27] So here's my reason. Okay. Five duelists later, Ron has a flying electric duelist. This is a $14,000 airplane by the time we get all the wood into it. No, okay. Most expensive duelist ever. ever. So last week we talked about, well, you talked about, and you chided me a little bit for liking to outdo you, apparently, which I didn't realize that was a thing. But I have to tell you. And now you do? Well, I do. I'm catching myself doing it now. So let me explain. I did get a little bit of
[5:02] work done on my do list. and it was not like to be ahead of you it was just because i finally got to the point where i had some time and was able to do it okay however this is when it caught me when i was like oh this is what he's talking about so i went ahead and i cut the what's the the wing tips that go on the end of the end of the wings right and i'm doing a little bit different than you are because i'm lazy and i don't know how to
[5:28] actually carve them 3d like so i'm just hard well it probably isn't but so what do you call the way i'm doing it because you you did it on your stick oh they're just basically plate mounted perpendicular to the rib, and then you put a few little gussets in there and cover it. Yeah, so I'll have pictures. I'll put them up on the website. Yeah, they don't look bad. Well, I don't think they look bad. No. I mean, I'm not saying that at all. No, okay.
[5:57] But they're just an easier way of doing it. Indeed. As opposed to making so much sawdust. But anyway, so the part where it really hit home what you were talking about, as I was designing them on the computer to cut on the laser, I designed it right per the plan, and then I was like, huh, I'm going to make each one of these a half inch bigger. That way I have more wingspan. That way my wingspan is bigger than Tom by an inch. So it measures 70 and a half inches across now. Mine measures 70.
[6:33] I haven't put my wingtips on yet. You could outdo me. And that's why I'm saying that now. Because what? I want to give you the chance. I'm not going to. Okay. I'm building mine as per the plan. So mine will be bigger. also be bigger yes so the reason by the way that i thought about starting my fuselage over so you can make it longer so i could make it longer saw it coming i was like what
[6:57] if i could just take each one of these formers and move them back a quarter inch yeah by the time yeah by the time you're done you've got a couple inches I've got a couple inches on you and that and then I thought what that is very childish funny though I almost did it still I wasn't saying childish is a bad thing but no so I really just don't want to go through all the cutting and doing that so what I did just to be sure it's a little bit longer is the tail that I
[7:22] made for it I did a different design on the tail nice okay it's a little bit longer is the tail that I made for it. I did a different design on the tail. Nice. So that's okay. It is about an inch longer. It's starting to click now. Why did you have a little bit different too with the elevators? Well, no, that didn't have anything to do with length. Like, I mean, that's not going to make it any longer. Okay. There's just something.
[7:41] I think it was probably because my first airplane was a Telemaster. I really hope yours comes out heavier than mine. It's not going to, but it would be awesome that way. You could outdo me on the weight. I don't want to do that because I want it to fly well. Right. And not Telemaster, I'm sorry. My first airplane was a Cavalier. And whoever built that Cavalier, the rear tail was not as to plan. It was more rounded and stuff. And I think that's
[8:06] one reason, like, I really like that airplane. And I think that's one reason that it kind of stuck with me. And I like that rounded tail look. So that is also going to be on this airplane. We'll see how that turns out. I don't know. I know you don't like it at all. Well, I'm not a fan of that shape on this airplane. And maybe I won't be either, but I won't know until i do it so we'll see so if you use number three you might have it all figured out
[8:33] no i won't go no this is number two or this is number one well i know number one now right number two for the redesign because you don't like the way number one looks after you get it all together and then number three because you don't like the way number two looks and you get it all together. And then number three, because you don't like the way number two looks, and it's not longer than mine. No, I'm sticking with number one. I'll just make a nose longer if I have to.
[8:51] All right, you heard it here. He's not going to build another fuselage. My plan is not to build another fuselage. I'm not saying that's not going to change, because we know how I do things. Right. So where are you at then? You've got the stab. Well, you're going to redo the stab the vertical you potentially might redo the vertical i don't think so the fuselage is kind of in the bones right now your wing looks really good thank you it's very close
[9:20] to being what i would say done glue the nacelles on and finish up the wing tips and run the wiring and stuff yeah so the only thing i have to do on the wing still is like you said the the finish up the wing tips and stuff i still have to sand the trailing edge yeah and then put the ailerons on after i mount the nacelles and then that's pretty much it yeah final sanding and stuff and it's almost ready for covering. So that should be, hopefully,
[9:45] before long. Nacelles are done. I just have to do a little bit of sanding on them. And then it's just on to the body, the fuselage. I don't think that's going to be all that difficult because I don't have a lot going into it, like we said before. No, yeah. I mean, you're not putting a nose gear in it or anything like that. So just a rudder servo and an elevator servo and that's and landing gear and maybe a switch because landing gear will be going on that too
[10:09] yeah oh yeah yeah well no your landing gear is gonna oh that's right you're gonna put a block in there for that that's right yeah it's gonna go on the fuselage as opposed to the wing but other than that yeah i mean it's i know it doesn't look like it but it's not that far away from being done. No, it really isn't. I might be able to be done by January 1st. Well, that was kind of what we indicated we would like to do in the last episode.
[10:39] I know, but we haven't done much since the last episode either. Yeah, but I'm, yeah, you're right. But we'll see. I mean, we've got a month, a little over. A little over. A month and a half, give or take. So that's what I've been up to on the do list. I know you haven't done anything because you've been working. Yeah, I got absolutely zero done. It's exactly in the same state that it was at on our last episode.
[11:09] I wish I could say that I had done more, but sadly, no. It happens. Well, I mean, I'll have some time this weekend to work on it, so that's my plan. Cool. At least a day, maybe two, hopefully. Yeah. Well, just… I have a lot of leaves I have to rake. I don't know about you. I just, I ran them over with a mower last week, and I think I'm done with it. See, we don't live in town, so I don't have to worry about having this nicely presentable lawn. Well, I mean, it's not so much that.
[11:35] It's just that in the spring, it makes such a mess whenever everything's muddy and soggy from all the rain, and I'm trying to get the grass to grow. So I have to clean it up in the fall when it's dry. We only have a couple oak trees that leave those huge, huge leaves yeah and those are the ones that i worry about but we don't do it often but when they get too bad we'll just kind of rake them up and burn them yeah see that's another thing you can you can burn them out
[11:56] here you should move out to the country yeah i know hey we've had this discussion and i'm not the one you need to convince i know i know so one day yep sadly i have no update on my dualist it's like i said it's still i did take a did i send you a picture of it with the nacelles sort of in place and the two engines kind of laying in front of it no okay maybe i didn't take a picture i'll take a picture of. Maybe I'll put that up there with the horizontal stand picks. Yeah, cool.
[12:30] Just to make a kind of a, here's what it might look like eventually. Here's one day. And I finally did make a decision. I guess I did do something. I made a decision. Oh, good for you. And I'm going to mount the engines on their sides and run the pipes under the wing. Oh, the exact opposite of what I said would be good. The exact opposite of what you wanted, yes. So mean it's yours you don't have to all right
[12:51] that was how my original tool is that's how they were they were mounted so well you crashed your original one too so well that's true i did maybe that was maybe that's the bad luck part to it is how they were no i think the bad luck part of it is me not doing a proper pre-flight. Ah. I think that's really the demise of that airplane. So maybe this time you'll do a proper pre-flight and be good. Yeah, I don't want to repeat history. Learn from your mistakes. Yeah.
[13:18] Learn from our mistakes. Yeah. Something else, by the way, I wanted to bring up because I wasn't doing it right. So, we have a page on the website on how to trim the balsa sheets and put them together. Yes. So that's awesome. But I will admit I have not actually successfully done that before. So I had you show me how to do it tonight. Wow. It's not hard. No, it's not hard by any means but i think
[13:46] i was trying to what's the word over over pressure it over doing whatever to where i was putting too much pressure on trying to cut it all in one swipe which doesn't work very well so what explain to all of us who really had not done it before okay how to do it and then also explain that it doesn't have to be perfect right because that was the other misconception i was under like i thought
[14:12] that the seams had to be just perfect in order for that glue to to hold very well like i almost actually took it out to my my joiner and ran it through there but i didn't know how the joiner would do on balsa and i know i didn't have a lot of 16th inch, so that's why I kind of stopped. Well, I have more. Oh. If you need more, I have more. Well, that's why I stopped where I was, because I thought, I'll let you show me how to do it, and we'll go from there. Okay.
[14:35] Well, I mean, the trick is, whatever it is you're using for a straight edge, for your straight line, you just want to make sure that that doesn't move. Because, you if it moves then you don't have a straight edge anymore because you've got one section of a cut worth the straight edge at one position and then if it moves even just slightly that it's gonna exaggerate the problem the farther you get away from it so yeah the key for me is to
[15:00] work in small sections which is not what I was doing. Right. You were trying to cut it all in one big slice. Trying to cut it in one long slice. So it's okay to break it up into small sections because you can have some degree of imperfection in that joint and the aliphatic resin or the carpenter's glue that we're using, it does soak into the wood and the wood does swell because it gets wet. Wood swells a little bit when it gets wet. Yeah. And it'll actually seal up those gaps.
[15:27] Like, sizable. Like, I mean, I'm not talking like a 16-inch gap. if you've got a gap that's, you could slide a couple sheets of paper through, that's fine. It's okay. Okay. It doesn't have to be, like, perfect. Because it would be nearly impossible with a, unless you used a, used a tool for the purpose. Because when you're holding the knife, you may hold it at 90 degrees when you've got your arm outstretched.
[15:51] But the closer you pull that knife towards you, you may tilt the knife out a little bit or in a little bit. So the angle of the cut is probably going to vary a little bit from the beginning to the end. So if you work in short sections, that does two things for you. You can keep a firm pressure on your straight edge so it doesn't move and then when you get to the you say cut six inches at a time get to that six inches and then you can move your hand with your knife still in
[16:16] the slot without moving your straight edge reposition your hand farther down the straight edge put some pressure on it and continue your. So use two hands to where you always have pressure on it at one time. Right. Yeah. So like, if you can imagine, you're leaned over your table, you got your, let's say your right hand, like me, you got your left hand down there pushing down on
[16:36] your straight edge, which is down there pushing your wood, on top of the wood. And you got your right hand extended out in your arm and you and you pull that knife towards you and when you stop it's okay to pull the knife out of the slot put your right hand on the straight edge so that you can then move your left hand on different to a different section of the straight edge so that it doesn't move you could also accomplish the same thing by clamping the
[16:57] straight edge to the to the table if you have room and clamps and things like that i didn't think of that yeah that would be a good idea anything you can do to prevent that straight edge from moving is gonna nearly guarantee you success actually if you if you clamp it that's actually a way better way to do because then you have two free hands and you can you can kind of use one hand to maybe hold it up against your
[17:20] other hand to maintain maintain the same angle of the blade and the other thing you did too that i was not doing is you did multiple passes whereas even with 16th you did like two or three passes to get all the way through it and i was trying to go through it all at once yeah i don't i don't try even softball so i don't try to get through it in the first pass i take a couple of different passes that way you can take your time and you're not putting a lot of pressure
[17:44] on the knife try and then the knife veers off or yeah or even worse tries to tuck under the straight edge and then you got then you got a gouge and that's what i ended up with i had just several of those so yeah so yeah they just take your time and multiple passes and you can do it in short sections if you're using just your hands but if you're clamping the straight edge you can do it you can make them long passes but make a couple different passes
[18:08] don't try to cut it all at once and so how thick of of wood do you do that with like obviously 16th and eighth but do you go any thicker than that for trying to do an edge well if i'm gonna if i'm gonna say let's say we're talking a quarter inch If I'm going to cut that, I'll use a balsa stripper. what I mean? But I'm talking about if you're trying to make sheets. Yeah. Yeah, I'll use the same technique, but then I'll come back with a sanding block.
[18:37] Because on quarter inch, like if you're going to, let's say you're going to build a horizontal stabilizer out of quarter inch sheets, and you're going to edge glue them together. Yeah, which is what I just did. Yeah. In that case, I'll use the same technique. I'll lay my straight edge down and cut that over the course of several passes. And then I'll come back with a sanding block and true up that edge and make them as square as possible before I glue them together.
[19:01] The other thing I noticed when I was doing it, I think eight inch sections were the longest I actually had to worry about. So I wasn't doing a three foot long piece of balsa. So it was a lot easier to sand that true when it's shorter than your block that you're sanding with. What do you think of, like if you ever need to do a long piece though, do you think like a joiner would work better or? I've never used a joiner
[19:25] like ever never mind i don't know it'd be worth a shot a joint so i use joiners quite a bit for like oak and and that kind of stuff that's okay that's a a heavier duty wood right right it's harder harder thank you but like i wouldn't want to do it on something as thin as like 16th of an inch. Yeah. But quarter inch would probably be just okay. Yeah, I bet quarter inch would. I bet it would work perfect. Especially with sharp blades, I would think.
[19:53] But not everybody has a planer or a joiner or whatever. Well, maybe they need to get one. Everybody needs a fully stocked shop, right? I don't disagree. So, there you go. I'll tell you what. Remember quite a few episodes ago, I picked up all those woodworking tools fully stocked shop, right? I don't disagree. So there you go. I tell you what, remember, quite a few episodes ago, I picked up all those woodworking tools that have been,
[20:10] I find that I use those all the time. Oh, yeah. Like, even just for simple stuff, it's amazing how easy it makes even the simplest jobs. It makes them that much simpler. Yeah, the right tool. Does that make sense? It makes sense. The right tool for the job makes things a lot easier. So that's why everybody needs to have a fully stocked shop. Fully stocked workshop. Don't you agree? Yeah, I do. I mean, I don't disagree. I said that once already. So anyway. So what else you got?
[20:43] Well, I thought maybe this episode, I've been wanting to talk about it for a while, how to, and I think we even got a question or two on the surveys. I'd like to talk about flight trimming an airplane. That's a good one. Yeah, I think we had a couple of people ask about that, and I don't know anything about it. So, just tell me. I mean, I'm not going to do, like, the deep, the deep dive into it.
[21:04] So, yeah, I mean, I mean, I'm not going to do like the deep, the deep dive into it. But basically, there's some there's a few steps you can take once you've got an airplane finished and flying. There's a few steps that you can take to make that the best flying airplane that it can be. OK, so the first thing, obviously, is, getting the CG right.
[21:28] Luckily for for us, most of the time that is done for us, or at least they're giving us a range. If you look at the plans, there's usually a range where they tell you that you should balance the airplane. And the instruction manuals and ARFs, same thing, they usually kind of tell you where to measure back from the leading edge or what have you. And those are great starting points.
[21:50] So let's say that you have an airplane, though. You might have bought one used or something like that. You're not sure what it is. What's a good rule of thumb on where to start? So the rule of thumb that I use is 25 to 33 percent MAC. And what that means is MAC is short for mean aerodynamic chord. And so it's an average, right? So there's a cord length at the root and there's a cord length at the tip. And to keep things simple, let's say they're both the same.
[22:19] And let's say that it's a straight wing. There's no sweep or anything like that. Now, I'm going to caveat all this. There's all kinds of calculators on the internet on how to figure mac i don't have the formulas memorized for tapered wings and wings that get narrower at the tip and any of that but yeah basically it's a mean number or an average if you will of the cord at the root compared to the cord at the tip. And you're going to measure at the root 25% to 33%.
[22:50] And you'll find that most ranges, that's where they're calculated, even on plans, on ARF kits, that's usually where their range is located. So if you can find what the mean aerodynamic chord is, and again, back to my example, a straight wing with no taper, no sweep, or anything like that, it would be basically 25% to 33% back from the leading edge of the wing at the root. Or what I was going for is it's usually at the main support that goes across the main spar
[23:25] is usually right around that general area. Yes. And if you have an airplane that uses panels, the plug-in panels, usually wherever the tube goes into the wing, that's usually a pretty good spot to put the CQs. Yeah. And that's a good point. Most of the ones I've've seen that's where you'll find them but there are there are odd exceptions out there swept wings sometimes i've seen them way back there because of the weird shape of the way and the taper or whatever but
[23:55] it's a general rule though for like what we would be flying or what we would buy if we're not sure about it just a trainer or something like that usually right on the main spar it's usually right on the main spot yeah yep right on the main spar, yeah. Yep. So, but getting back to what I was talking about, that's a range. That's a recommended range. And everybody likes their airplanes to fly a little bit differently. Like, you can take an old Great Plains trainer 40
[24:16] and ask 10 different pilots how they want it to fly. You'll get 10 different answers. And you can change the characteristics of where an airplane flies by by moving that center of gravity forward or back moving it too far back obviously is bad but moving it back a little bit makes the airplane a little more lively does aerobatics a little bit better it stalls at a higher speed
[24:42] yeah but a pilot who knows what he's doing can probably do more with an airplane that has the CG farther back than a pilot can do with it moving forward. So get the CG on your airplane set where you like it. Get the airplane so that it doesn't tip stall on you when you're coming into land because you have it so tail heavy.
[25:06] But that's the first thing you're going to do is get the CG in the range at the very least, wherever it says on the plans or 25 to 33 percent Mach, whatever that happens to be. And so then after you have your CG figured out, like how do if a plane is too tail heavy or too nose heavy? What characteristics do you have in flight that's going to make you say, hey, I need to move the CG back or I need
[25:32] to move it forward? Right. So usually a tail heavy plane will porpoise. And what that means is, okay, here's a good test for your CG. Fly along straight and level. Get the airplane trimmed as best you can to fly along at a straight and level at a pretty good clip. Say, let's just say wide open. Okay. And then pull the throttle back and then wait a few seconds.
[26:08] gradually, but doesn't really gain a lot of airspeed, your CG is a touch on the nose-heavy side, but pretty close to being ideal, actually. If, however, the airplane just sort of slows down and then eventually wants to climb, and maybe even to the point where it points straight up and then stalls and flops over, then you're definitely on the tail heavy side okay if your airplane when you when you cut the throttle back if it sort of maintains that altitude and climbs
[26:32] a little bit slows down and then kind of noses over and then picks up speed climbs a little bit slows down noses that's called porpoising and you're a touch on the tail heavy side at that point so somewhere between that point and the point at which the airplane kind of noses over and gains airspeed you're right in the range okay and from there it's just fine tuning what you like the airplane to do
[26:56] like me personally i fly mine generally speaking a little on the tail heavy side because usually a nose heavy airplane tends to be bouncy, if that's a word, on landing. And the reason is because you lose control authority of the elevator because you're trying to overcome all that weight on the nose and your landings tend to bounce. And I don't like bounced landings. Nobody does. So I fly mine a little on the tail heavy side. And the sacrifice to that is it floats a little bit.
[27:28] Maybe the flare is a little bit longer than it would be if it was slightly more nose heavy. But it's a tradeoff for a smooth landing. And it flies better that way too, right? And it's more sprightly. Yeah. So more of a handful if you can handle it. Exactly. Yeah. Experienced pilot, no problem whatsoever, especially if it's an airplane that you're very familiar with, an airplane you've been flying a long time. It's fun actually sometimes to experiment
[27:55] with CG within, within the range. Right. You don't want to put it too far back. And then it porpoises when you're just trying to fly. And it's hard to get down. Like, for instance, my old Contender. When I built that thing many, many years ago, I put the CG right in range. Many, many, many, many years ago? Yes, it's been a few years. But when I put the CG in the range where, on the plan for that airplane, it flew great.
[28:20] And I flew it like that for years and years and years. A few years. And then, once I was really, really comfortable with the airplane and I could, I mean, it was my go-to for many years.
[28:42] not very good at spinning. Like, it doesn't snap very well. Like, it doesn't do very good snap rolls unless you get that CG back there on the very, kind of at the very limit on the trailing edge of where it should be. Yeah, exactly. And once I got the CG back there, now, of course, I had to add weight or whatever, but I could actually get it to spin because, it was tail heavy, essentially. But anyway, if you're comfortable with an airplane, try playing with the CG.
[29:11] And I think most pilots like them a little on the tail heavy side. So it makes them more aerobatic. So next, once you've got the CG where you like it, well, the next thing I do is I try to check my thrust angles.
[29:40] So most airplanes, I don't want to say most, but a lot of airplanes will have thrust built into the firewall, right? Like sometimes it'll be some right thrust or maybe it'll be some down thrust or what have you. A lot of airplanes, you build the airplane with the thrust line not in alignment with the center line of the airplane. Does that make sense? Mm-hmm. Yeah. There's a lot of reasons for that, aerodynamic reasons, and I don't want to get into that.
[30:01] We talked about that quite a bit, actually, in the propellers episode. In the propellers episode, yeah. So if you haven't listened to that one, go back and listen to that one. You'll kind of understand what we're talking about. Which is funny because there is a lot of good information in that episode about selecting the right propeller. And that's really important for trimming your airplane too. Because a different propeller, without getting too deep into it,
[30:21] a different propeller will produce different P-factor type results, or they'll produce a different shape slipstream, and all of those variables will go into the trim of the airplane. So once you have the propeller selected that you're going to use with that airplane, that's another thing towards properly flight trimming an airplane. But that's a decision you want to make and stick with throughout the process because it'll probably change if you select a different propeller.
[30:49] So don't change it out if you break one? Just kind of stick with what you fly with, right? No, I mean going to a different size or whatever. I mean used with the same one that you break. Right, yes. Not the actual same propeller. Exactly. But the same pitch and diameter. Yep. Yeah. So one of the tests that I do to test thrust angles, so it's kind of similar to the CG test, sort of.
[31:12] So for, let's say, for the vertical thrust angle, up or down thrust, what I do is same thing, straighten level flight, get everything kind of trimmed so it's flying, wings level, hands off, and then pull the throttle back. And what the airplane does right away is going to tell you what, where the, what the condition of the thrust is. So, for example, let's say you're flying long, straight level, wide open, and you cut the
[31:42] throttle. And let's say the airplane immediately pitches up, right? So if you think about it, at straight and level, the thrust, you've got it trimmed for straight and level. And if the airplane pitches up when you cut the throttle, what that means is at straight and level flight, your airplane has been compensating with down thrust to basically pull the airplane down because its natural tendency is to want to go up right so how do the difference between
[32:13] that and cg then because you're you're watching what the airplane does immediately like with a cg you don't you don't really watch that right With CG, you kind of watch what happens once the airplane is starting to slow down. So when you chop the throttle and the airplane pitches up, then kind of counterintuitive, you have to actually add some upthrust. I know it sounds weird. If you think about it, though, it makes sense because you're losing the pull down. Exactly. Yeah.
[32:47] No, I can understand that. And vice versa. If you're buzzing along and wide open and you cut the throttle and the airplane immediately pitches down, you need to add a little bit of down thrust. And we're talking one degree max at a time. Yeah. And so you do that and you repeat that step over and over until you get it to where, it doesn't do anything immediately after you cut the throttle. Right? Make sense? That way it just continues on. And that sort of plays well into my hands
[33:15] because I like to tinker and experiment and things like that. So, plan on, to do it right, plan on a full day at the field with lots of fuel or gas or batteries. lots of fuel or gas. Or batteries. I said or batteries. I know. I had to wait for it. That was the last thing you said. It was the last thing on my mind. So anyway, once you have the up and down thrust sorted out, it's a good idea to recheck the CG. Because with all that up and down,
[33:45] maybe you didn't catch it right away or whatever, and maybe you're waiting a little bit too long. Recheck that, do that CG test again after you've got your up and down thrust. Just to make sure you've got it right where you want it. And then the next thing I do is to check the left and right. So I don't want any right thrust or left thrust depending on the airplane yeah a cub obviously i'm probably gonna have as much right yeah or as much right
[34:10] thrust as the plans tell me to put in it but so the test for that one and what sorry off topic what makes the cub so so special i guess when it comes to that. Because anybody that's flown a Cub knows how finicky they can be, take off flying and all that. But it's not quite the same on any other airplane that's even remotely like that. I think I'm using Cub as a generalization, honestly. Because Taylor Crafts do it. Even the Cessna 150, I think they call it the texas
[34:47] twister they actually a cessna produced the 150 as a tail dragger for a while even those experience the same issues that a cub experience i think probably the reason we always go to cub is because it's it's very popular so there's a lot of them out there, and people probably have the most experience with those because that's the airplane they built. what I mean? I've had tail draggers though that don't react nearly as badly as cubs do.
[35:15] Like I've flown cubs and I've flown other tail draggers, and the cubs are the ones that really just, I mean, you have to fly those on the ground. Probably because they're slower and bigger so like i've flown a lot of tail draggers and mo and i'm gonna get on my soapbox i i promise i'm gonna get back to flight trimming i promise so today and not just today but it's been going on for years we seriously overpower our airplanes. We really do. It's fun, and I'm not going to stop doing it.
[35:50] But because of that, like a side effect is we tend to tolerate poor aerodynamic performance, especially during takeoff. Because what do you see guys do with the field they get their airplane they fire it up they tune they run it up to full throttle and off they go in 10 feet yeah i mean when have you gone to an airport and seen a full-size airplane do that so we get through those those nasty aerodynamic tendencies like a cub sometimes with the adding right rudder
[36:25] and things like that, we just sort of skim through it because the takeoff is so abbreviated. what I'm saying? Yeah. So on a Cub, because they're kind of big and kind of lumbering and even if you overpower a Cub, it's a big, slow, draggy airplane and it's only gonna go so fast fast so you don't you don't get that free pass you can't just kind of skate right past the bad tendencies straight
[36:51] into flying so maybe that's why so all of them like all airplanes probably have the cub tendencies but because you go past it so fast exactly that's what i'm that's what my thing maybe okay that's what so you you guys at home and girls pilots at home do an experiment try try on your next takeoff on your high performance tail dragger try your next takeoff at quarter throttle and try it
[37:16] at scale levels yeah see what happens maybe maybe you find that you're gonna have to add some right rudder where you didn't have to before maybe yeah so anyway okay i'm off my soapbox like i said i'm not gonna stop overpowering airplanes but it's fun and it's easy to do it gives us a free pass on some of these other things that we should be learning how to do like coordinating turns which i'm going to talk about in another
[37:38] episode yeah i don't know how to coordinate turns i admit admit it. It's lazy. So anyway. Wow. All right. So next we're going to do left and right thrust. And here's my test for that. It's very similar to the up and down thrust, except we're going to do it in a vertical plane. So again, straight and level, wide open, or fast cruise, whatever you want to do. Pull the throttle back and pull up, right?
[38:04] So that your air point is pointing straight up. Almost like you're going to pull back and do a loop, but we're not going to do, pull the throttle back and pull up, right? So that your air point is pointing straight up. Almost like you're going to pull back and do a loop, but we're not going to do a loop. We're just going to pull up and let the airplane just keep going straight up. And I take that back.
[38:15] You're going to leave the throttle in it when you do that. Leave the throttle in it, pull up so that it's going vertical, and then cut the throttle. Now what you're doing is you're isolating that thrust component. And when you pull back on the throttle, you are sort of mitigating those aerodynamic forces like P-factor and gyroscopic pre-session, a lot of stuff by throttling back. So now you've got a true indication. The airplane's going straight up with a little bit of power and
[38:44] you've cut the power. And whatever the airplane does now, left or right, is what you're going to correct with thrust. So, for example, let's say we pull up, cut the throttle on the airplane immediately. Immediately, that's the key word, turns left. Same idea, only this time, if the plane turns left, it's because you already have too much right thrust. Does that make sense? Yeah. It's the opposite. It's the opposite. Right. Exactly. So same sort of test as up and down thrust,
[39:15] only we're doing it in a vertical plane and it's sort of backwards. Okay. In my head, it makes sense. And hopefully I've explained that so that, like I said, if you're straight level, level wide open you pull up and once you've past that vertical you pull the power back and if the plane veers a little bit left it means you've got a little bit too much right thrust because the right thrust was compensating now you pull that away right so now yeah exactly
[39:41] okay i understand that yep okay i hope everybody else does but i get it and that also will sort of at straight and level flight obviously you're going to have the ailerons trimmed a certain way or maybe maybe you've built them great and your aileron trim is neutral which is awesome but at straight and level flight and so at wide open, the same trim is not going to do the same thing at different airspeeds, right?
[40:09] So that's another reason I do that test heading vertically with low airspeed is to sort of neutralize whatever the ailerons might be doing trim-wise. Okay. If that makes sense. Yeah. Are the ailerons going to do a lot, though, for, like, which way it starts to go? So, you remember, ailerons can cause drag, right? That's why a lot of airplanes, we have differential aileron throw, like more up than down, for example. I got you.
[40:39] So, yeah, if your trim is, if for some reason the ailerons are, you've got a lot of right aileron trim to overcome a warped wing or whatever the case may be, maybe a heavy left wing panel, who knows. At a low airspeed, that effect of those ailerons is going to be lower. So you'll be able to really see the indication of left and right thrust as opposed to trying to trim that at wide open throttle. And I've seen a lot of guys try to trim their thrust, left and right thrust,
[41:08] by doing kind of the same test, pull it up vertical, and then they jam the throttle and watch what the airplane does. That's not a really accurate way to adjust your left and right thrust because you're adding a whole lot of percentage of torque and P factor and all this other stuff. So it's best, like I said, you pull up, cut the throttle, and watch what the airplane does. And I guess I should have said this too. When you pull up, let it bleed off a little bit of airspeed if it can.
[41:40] Like I said, we overpower most of our airplanes. So a lot of our airplanes will climb, vertically at full throttle. Yeah, unlimited vertical. Maybe if your airplane is one of those high-performance kinds that does that, maybe perform this test at half throttle. Gotcha. Or, you want to eliminate a fair amount of airspeed if you can while still maintaining some power so that when you cut the power, you can see what the airplane does.
[42:05] I got you. Hopefully that airplane does. I got you. Hopefully that makes sense. I think so. Yeah. So that's the left and right thrust and the up and down thrust. And then really after that, once you've got the thrust figured out, and I like to build my airplanes so that I'm 0-0. I like my engines pointing straight ahead. I like my thrust line in line with the airplane center line. And then adjust from there.
[42:33] Now, obviously, if an ARF comes with two degrees of right thrust and a degree of down thrust built in, obviously, I'm going to go ahead and build the airplane like they say in the instructions. Because they've tested it. exactly yeah exactly but an airplane like the dualist like even dave platt on these plans says hey mount the engine zero zero zero degrees right thrust or left thrust and zero degrees of up or down straight ahead and that's how i like to build anyway because
[43:02] zero degrees is easy to get with a square yes very much so you're not worried about any odd angles and stuff on the nacelles or on the front of the airplane so on the firewall and then just to just to touch on the on the aileron trim i would say how i trim mine is a straight level flight at half throttle or half cruising speed or whatever airspeed you're going to fly that airplane probably the most. That's where I trim my ailerons. Because I'll
[43:32] be honest, when I build an airplane, I may not be the world's greatest builder. I may have built a little bit of warp into my wing, or maybe one wing panel is, longer than the other, or maybe one is heavier than the other, and I didn't balance it, laterally. So I'll trim the airplane, at least with the ailerons, about where I figure I fly it the most, at whatever speed range. That's when I'll trim the ailerons. And
[44:03] then if I need to compensate, usually Iilerons and then if i need to compensate usually i don't but if i need to compensate on high speed maneuvers or landing i'll just do that with the stick but now that you have your adjusto jig it should be a lot easier to build well it will be from now on yes well because i didn't build my wing with my well that's why i said now that you
[44:22] have one from now on yeah right it'll be easier yeah for your next build yep and then the only thing left to to trim at this point is is your your throttle and elevator and a little bit of rudder rudder is a good is an easy test because you can do that one that's sort of the same when you do the the the left and right thrust test but just leave the power in it that's how i adjust mine oh yeah okay i can see that then because then you'll
[44:51] see if it's tracking straight or if it's exactly yeah because you have airspeed to help you overcome the torque and p factor and all that stuff yeah all that stuff is usually behind the airplane envelope at that speed so but yeah anything anyway after after that it's elevator and throttle throttle is pretty simple get a good idle and then make sure you can shut the thing off and make sure you get wide open if if you want full power
[45:14] and then the elevator is trimmed to taste yeah because that is going to change a bunch on speed yeah so kind of the same thing as your ailerons so i probably set those all at the same spot you think yeah that way if most of the time you're flying half throttle you're going to be set that's exactly for everything that's that's a like i'll usually trim my ailerons and elevator simultaneously and that's usually like i said at a speed where i
[45:38] figure i'm going to fly the airplane the most and so what's it take like time wise i know you said or have a full afternoon setup but just if you're not wanting to get into the whole like because one degree two degrees of of thrust offset is not going to make that much of a difference when you're flying you'd be surprised really yeah yep well forget what i said then well i mean maybe one degree two degrees no but even like when you get out to three degrees,
[46:05] imagine three degrees over the course of a hundred foot, let's say a hundred foot line. Three degrees is quite a significant distance. And if the airplane is trying to fly that distance and you're trying to trim against that, it can be quite the battle between trim and aerodynamics. I guess it adds drag and all kinds of other bad things to your and the airplane's going to do weird things like for instance at the top of a loop where the air
[46:30] speed is slowest and you're you're anti-lift at this point airplane may do something weird like fall out of the loop and start spinning and if you do it low enough you may not have enough time to recover yeah so you want to make sure that, get it, get it right. So spend the time to make sure it lasts you for years and years and years.
[46:56] Exactly. And get it flying right from the beginning. Yeah. Yep. So, okay. So that's just my, that's my take on flight trimming. I mean, certainly we could get deeper into it and maybe I will eventually like maybe flight trimming for different modes like I kind of hit on that here a while back about setting up my dual rates and expos on a switch so that I could go crazy mode or regular mode or beginner mode or
[47:15] whatever there's different trim techniques for each one of those modes too that I maybe I could break that down one of these days okay Okay. Might be fun. Maybe. So that's really all I got for flight trimming. If you guys have questions, hit us up. There's lots of ways to contact us. The forums, the phone number, the text. The website. The email. The email. Lots of ways to get a hold of us. If you've got a question. Don't be shy. Don't be shy. Yep.
[47:49] Tom will answer them. Hey, speaking of questions. Yeah. I've got one here i'd like to read on the on the oh okay show if that's okay sure it's from our friend liam i'm i think you're familiar with liam yeah we hear from him from time to time he had a question and i'm gonna go ahead and read it he says hi ron hi tom he said ron first of course he did so we all we know it goes in order of importance right well i mean you do the most work just ask you i am a umx aircraft owner
[48:13] umx is ultra micro that's for e-flight for those who don't know very fun airplanes we've talked about those before yeah yeah most of them have the AS3X, which we love. I am a UMX aircraft owner in Flyer and asked about a Nitro engine a while back. I thought my engine was a SuperTigre. It's really a GP. So he has actually a Thunder Tiger GP7. What plane would be good for this engine? He answers his own question right here. He says, a mini stick.
[48:45] He says, also, would you all recommend floats for the sport cub ss from horizon so liam thunder tiger gp7 would be a perfect engine for a mini stick and a mini stick would be a perfect airplane for your first scratch build because they're really super easy to build they're very simple box type construction the hardest part about that build is probably getting the wing saddle just right did you say scratch build I did say
[49:09] scratch but what I meant to say was plans build thank you for correcting me see don't do that cuz you're gonna confuse me and then I'm gonna know you're right yes I said I said scratch boom what I meant was a plan build okay build yourself a mini stick from plans and I find it funny that you look at me when you said what the motor was like i would know what engine that is and i'm sort of
[49:29] like oh i know what you're talking about now yeah if i said it was an e-flight bl 550 you'd probably know exactly whatever that would tell me more than what you said on previously so anyway liam yeah mini stick would be perfect for that engine I think anyway and we're a big stick fan well I am I like sticks they fly great what I think I think next spring when we get out I'll probably fly yours yeah especially because somebody bought it from
[49:56] you and then gave it back to you so if I crashed like a free airplane at this point right yeah yeah so anyway as far as what he says next would would you all recommend floats for the sport cub ss from horizon i would say that if horizon offers floats for that cub i have not done the research yeah i'm not i imagine they probably do i don't know that but if they do i would absolutely recommend them i love flying off of water, like with floats.
[50:26] what else is fun flying off of? Snow with skis. Yeah, yeah. I have that for my car. You can fly off of snow with floats, too. I've done it. Really? Yep. If the snow is kind of like not that frozen hard stuff on top, but the light, fluffy, fresh. Oh, yeah. Floats do wonderful on snow. Really? Yeah. So the little rudder thing that goes in them doesn't well that you you kick it up okay and make sure you
[50:49] know you have a kind of a straight area to take off and land because the rudder is not very authoritative in the snow but yeah they will work really well in the snow but the skis are fun too yeah skis are awesome i've never actually flown with the skis really yeah dubrow makes them in a couple other places. It's weird because it actually changes the lift characteristics. When you take off and those skis are pointed down or up, pointed up, I guess. Yeah, okay.
[51:15] Because I think somehow they're spring-loaded, right? They are. Yeah, to keep them from, because you don't want them to go down to where the front of them digs into the snow. Yeah, then it's like an air brake. Right. Well, no, not only that, but like when you're actually landing, you don't want that front part down to where the front of them digs in then it's like an air brake right well no not only that but like when you're actually landing you don't want that part to dig
[51:27] out of the snow and then just kind of be shoveling it out yeah yeah so they have little springs on them to keep them at the right angle and that does provide just a little bit more lift cool and it flies a little differently especially with it was a little foamy i was flying so yeah yeah but yeah could you imagine how much fun a stick would be in the wintertime off snow i was thinking to do lists i guess you can't do it but i could no i would because you'll have the
[51:49] tricycle gear but yeah this might be fun on on skis it's going to be about that time if we get we can make skis pretty easy yeah so anyway liam thanks for thanks for contacting us he contacted us through the survey so once again if if guys would, go out there and hit that survey and fill it out for us. Yeah. Maybe your question, we'll make it on a show. Or send us a voicemail. Forgot about that, too. Yeah, that's right. I forgot about that. That's another option. Leave us a voicemail.
[52:20] We'll play it on the air. There you go. Do we have any questions? We don't. Oh. Nobody likes us enough to do that, I guess. Okay. okay well we did play a couple for the halloween episode so that was we did it was fun yeah so all right all right anything else you want to talk about so no ron that's all i got all right cool well thanks for listening everybody until next time i'm
[52:39] ron hit us up on patreon oh there you go if like i said at the beginning if you guys want to help us out by becoming a patron on patreon that would that would be great because we're thinking about doing some other stuff with maybe some video we are so that stuff is expensive so anything anything you guys could do to help us out would be great but we're gonna keep on doing what we're doing so either way we. We're going to keep on keeping on. Yes, exactly. So yeah.
[53:07] Anyway, sorry. Just wanted to get that out there. That's all I got. All right. Are you sure? I'm positive this time. All right. So until next time, I'm Ron. I'm Tom. Good night. Good night. 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.
[53:37] Please subscribe, rate, and review us on your favorite podcast app. Until next time, may your landings be gentle.
