My first balsa build in 30 years

[kkelly]

After a long hiatus from aeromodeling I came back in the summer of 2018. I've been flying FT foam board planes since then. I always enjoyed the build as much as the flying, and I'm much more confident in my ability to not crash horribly now, so it's time to build with balsa again! As far as previous experience goes, I built a Gentle Lady kit sometime around 1989, followed by a scratch-built biplane in 1990/1991 that I never got around to flying. During that time I also built about a dozen peanut scale models. Now I'm starting anew with a Stevens Aeromodel 4Charlie.

Laser-cut parts are amazing. I'm used to either die-cut or hand-cut parts that more or less fit together, but not quite. The lack of finagling required feels a little weird. I was not prepared for how carefully I would have to handle the sheets of balsa. Just picking them up made several parts fall out. I dropped one sheet. It was chaos.

So far I've glued myself to the model three times, mostly because I was not prepared for how far through the wood thin CA travels (which makes me suspect I'm using too much glue).

I'm looking forward to working my way through this kit and (re)learning a ton about balsa building along the way. I'll probably be a nervous wreck the first time I fly it after putting so much effort into it.

 

[TooJung2Die]

Welcome back to our happy obsession. I can identify with everything you shared. I had a 40 year gap between balsa builds. The level of anxiety for the maiden flight of a balsa airplane you spent weeks building is on a whole 'nother level than a FT foamie you built in a couple of days. Foam is fun but balsa flies better!
Jon

 

[speedbirdted]

Balsa building is the only 100% unkickable addiction out there... but why would you want to? Do it once at any point in your life and you'll find yourself doing it again at some point, sooner or later

Stevens Aeromodel makes good kits. There was another 4Charlie build on here last year, that also being a first balsa kit experience; he succeeded in getting it flying in the end!

I don't build from kits much now; why give someone else money to cut out the parts for me when I could do it myself? My experiences with laser cut stuff is that those that are well-cut with good tolerances can almost be built without even looking at the plans while those that aren't are like trying to put together a Jenga tower with cooked spaghetti. However in any case the main pet peeve I find with them is the burned sections of wood cause black splotches to show through whatever covering film you're using. Sanding it off or painting over it is really the only way around that. That's really not a huge disadvantage comparatively, given that you should always be doing some kind of surface prep regardless of part cutting technique...

So far I've glued myself to the model three times, mostly because I was not prepared for how far through the wood thin CA travels (which makes me suspect I'm using too much glue).

Are you using fine-point applicators? They're very nice to have to prevent overapplication of glue. Many companies make them but these are the ones I like the most. They fit basically any bottle ever made, and are longer than most others, so they can get into recessed areas much better.

In any case, pictures would be appreciated...

 

[kkelly]

Welcome back to our happy obsession. I can identify with everything you shared. I had a 40 year gap between balsa builds. The level of anxiety for the maiden flight of a balsa airplane you spent weeks building is on a whole 'nother level than a FT foamie you built in a couple of days. Foam is fun but balsa flies better!
Jon

Obsession indeed.

To be honest, I was quite anxious during the first flights of most of my FT foamies, but that settled down once I reminded myself how easy they are to rebuild.

 

[kkelly]

Balsa building is the only 100% unkickable addiction out there... but why would you want to? Do it once at any point in your life and you'll find yourself doing it again at some point, sooner or later

Stevens Aeromodel makes good kits. There was another 4Charlie build on here last year, that also being a first balsa kit experience; he succeeded in getting it flying in the end!

I don't build from kits much now; why give someone else money to cut out the parts for me when I could do it myself? My experiences with laser cut stuff is that those that are well-cut with good tolerances can almost be built without even looking at the plans while those that aren't are like trying to put together a Jenga tower with cooked spaghetti. However in any case the main pet peeve I find with them is the burned sections of wood cause black splotches to show through whatever covering film you're using. Sanding it off or painting over it is really the only way around that. That's really not a huge disadvantage comparatively, given that you should always be doing some kind of surface prep regardless of part cutting technique...



Are you using fine-point applicators? They're very nice to have to prevent overapplication of glue. Many companies make them but these are the ones I like the most. They fit basically any bottle ever made, and are longer than most others, so they can get into recessed areas much better.

In any case, pictures would be appreciated...

I read that thread you referenced before ordering the kit. It helped me decide that the 4Charlie would be a good plane to start with.

I'm finding the tolerances on the parts to be excellent. So far I've been able to hide all the burn marks by facing those sides inwards. I'll likely go back to scratch building eventually, but I didn't want to jump right back into it with my first build.

I forgot to order fine point applicators with the kit. I went to a couple local hobby shops. The one I like to shop at didn't have any. The one I don't like to shop at had some, but it looked like they would only fit one brand of bottle. I'll order a bunch of the ones you recommended if I can't find anything local. In the meantime I'm using the fine-ish detachable tip that came with the bottle. I'm getting better at controlling the amount of glue it dispenses.

I'll post some pictures soon. I'm building very methodically (but still managed to make a mistake), so I'm not all that far along yet.

 

[speedbirdted]

If you can't find anything local that works you can try a trick some old codger taught me which is to take plastic drinking straws, heat it near the middle with a lighter, and then pull it so it thins out and then cut it right where it closes up. It takes some practice to get it right but the end result is cheap applicators, much cheaper than anything commercially available.

 

[Tench745]

If you can't find anything local that works you can try a trick some old codger taught me which is to take plastic drinking straws, heat it near the middle with a lighter, and then pull it so it thins out and then cut it right where it closes up. It takes some practice to get it right but the end result is cheap applicators, much cheaper than anything commercially available.

I've heard of doing the same with plastic q-tips.

 

[kkelly]

If you can't find anything local that works you can try a trick some old codger taught me which is to take plastic drinking straws, heat it near the middle with a lighter, and then pull it so it thins out and then cut it right where it closes up. It takes some practice to get it right but the end result is cheap applicators, much cheaper than anything commercially available.

That's how we used to make very thin glass tubes in the chemistry lab when I was in college. I hadn't thought of it as a way to make glue tips. I'll have to try that one if I can't find anything ready-made.

 

[TooJung2Die]

I've heard of doing the same with plastic q-tips.

That's what I use. Get the cheap hollow plastic handle q-tips like the ones from the dollar store. I find using a heat gun works best because it creates a wide even heat. I always mess up the first one so once I get it right I make a bunch of them. You get two tips from each q-tip.

 

[kkelly]

It's been a bit of a busy week, and I took time to improve my building board, so I've not made as much progress as I had hoped. Still, what I have so far vaguely resembles an aircraft:

I'll probably finish the fuselage this weekend and possibly get started on the tail surfaces.

I checked again with the hobby store I do like to shop at and realized they do carry glue tips. They just hide them behind a counter in the back that isn't always staffed. Once I use those up I'll definitely try the straw or Q-Tip method.

I'm mostly resisting the urge to modify the plane's design, but there are a couple changes I'm considering. From what I've seen in videos the 4Charlie doesn't handle well on the ground and benefits from a steerable tail wheel. How much grief would I cause myself if I tried to add one?

I'm also unsure about the control surface hinges. The plans call for tape hinges. I've never used them before. Are they reliable or would it be worth using something else? I used CA hinges on a build decades ago, so they're not completely new to me, but I also recall having trouble aligning them properly.

 

[Born2bwire]

I built the Squirt 400 which calls for tape hinges, I think that's just a characteristic of the Stevens kits. Never had any trouble with them but I don't see any reason why you couldn't use CA hinges or an equivalent either.

 

[speedbirdted]

A steerable tailwheel will work wonders for the ground handling but they can add problems with tail weight and servo strain. Mounting the tail wheel directly to the rudder is incredibly dumb; people do it and then wonder why they keep breaking tail hinges or have servos suffer premature deaths. It doesn't look like you could do it here anyway based on the design of the rudder. What I would do is use a tailwheel mounted to a separate bracket and steered off the rudder with some way of soft mounting it to the rudder; a rubber band or springs are good for this.

Here is an example of the type of thing I'm talking about on one of my planes. The weight is supported by the bracket, while shock from the wheel that would normally go straight to the servo is instead absorbed by the rubber band.

Finding a bracket small enough not to introduce excessive tail weight might be a bit of an issue though, so what you can do is find a plastic tube that fits snugly over whatever wire you use for the tailwheel, glue said tube into the fuselage, then secure it with a collar. Not as strong as a bracket, but if you grease the landings it will hold up just fine.

You can also heat your wire and then wrap it a few times around some non-burnable object to create a spring which will further help save whatever mounting setup you use.

I wouldn't use tape hinges. Do they want this airplane to fly once? CA hinges would work fine. My technique for them is to cut the slots and then drill a hole from the top down through whatever surface is having a hinge glued into it; this then allows you to glue the hinge with zero gap and not risk accidentally gluing the wing and aileron or whatever together. You can then stick a toothpick into that hole and sand it smooth for an extra measure of safety. Speaking of cutting the slots, putting masking tape wherever you want the hinges and then drawing the lines where you want to cut will work wonders helping you cut out straight and aligned hinges. I do not even cut with a straightedge or slotting tool; just an X-acto knife, and I get smoothly running centered surfaces every time.

 

[kkelly]

A steerable tailwheel will work wonders for the ground handling but they can add problems with tail weight and servo strain. Mounting the tail wheel directly to the rudder is incredibly dumb; people do it and then wonder why they keep breaking tail hinges or have servos suffer premature deaths. It doesn't look like you could do it here anyway based on the design of the rudder. What I would do is use a tailwheel mounted to a separate bracket and steered off the rudder with some way of soft mounting it to the rudder; a rubber band or springs are good for this.

Here is an example of the type of thing I'm talking about on one of my planes. The weight is supported by the bracket, while shock from the wheel that would normally go straight to the servo is instead absorbed by the rubber band.

View attachment 196783

Finding a bracket small enough not to introduce excessive tail weight might be a bit of an issue though, so what you can do is find a plastic tube that fits snugly over whatever wire you use for the tailwheel, glue said tube into the fuselage, then secure it with a collar. Not as strong as a bracket, but if you grease the landings it will hold up just fine.

You can also heat your wire and then wrap it a few times around some non-burnable object to create a spring which will further help save whatever mounting setup you use.

I wouldn't use tape hinges. Do they want this airplane to fly once? CA hinges would work fine. My technique for them is to cut the slots and then drill a hole from the top down through whatever surface is having a hinge glued into it; this then allows you to glue the hinge with zero gap and not risk accidentally gluing the wing and aileron or whatever together. You can then stick a toothpick into that hole and sand it smooth for an extra measure of safety. Speaking of cutting the slots, putting masking tape wherever you want the hinges and then drawing the lines where you want to cut will work wonders helping you cut out straight and aligned hinges. I do not even cut with a straightedge or slotting tool; just an X-acto knife, and I get smoothly running centered surfaces every time.

I may forego the tail wheel for this build, but I'm still considering it. Thank you for the description of how to do it without killing some other part of the plane.

Sounds like CA hinges are the way to go. At a minimum they'll give me peace of mind, and I might as well hone my skills for installing them.

Here's where I am after another few days of sporadic building:

The tail surfaces went together in about 1/10 the time I expected. They lie in place almost perfectly aligned without any adjusting, so I won't have to deal with my typical misalignment of them when I glue them on. I'm putting off shaping the nose block because I'm a bit of a perfectionist and don't want to subject myself to that just yet. I ran into a few small alignment issues, but nothing that couldn't be fixed with a little sanding or the addition of a very thin slice of balsa to fill a gap.

This is my first time working with laser-cut parts. How important is it to remove the burn marks from surfaces that will be up against the covering film? A light sanding is removing about 80% of the burns, but I'm concerned about removing too much wood and affecting the fit. Do I need to get those surfaces back to pristine balsa or just lighten them up?

 

[speedbirdted]

It depends on the covering film. Some are very opaque, while others have a degree of translucency. As a general rule of thumb, darker covering materials will hide burned sections very nicely, while lighter colors will not. It's worth a test with whatever covering you plan to use, as there are lots of them available and they all behave a little differently in this regard.

It's also worth noting that if pressure is not applied, often a burned section will not show through, regardless of the translucency of the covering. This is useful as when covering a wing, you can adhere it with the iron only around the edges, and then use a heat gun to tighten it up elsewhere, and regardless of the amount of burned crap on the wing ribs, very often the burning will not show through.

Another way around the problem is to use a transparent film. The burned sections will show through, but everything else also will, and it'll end up looking fine.

To remove the burned sections you can go over the airframe with high grit paper (600+ is usually what I use) until the burned sections are gone to your liking. This will help eliminate excessive removal of material, as the process is slow. It also prepares the airframe for covering better, by making it smoother.

 

[kkelly]

Another few days of here-and-there building and I suddenly realized the airframe is assembled. No pictures at the moment, but I'll post some more after I finish shaping the wing leading edge and the nose. I was planning to go with the same color scheme as on their website (red with white trim), but I saw a nice darker metallic blue at the hobby shop that I might use in place of the red. I currently fly at a park where the grass can be a bit rough on planes. What's a covering film that strikes a good balance between weight and durability? I'm looking into joining a flying club since flying at that park is one giant compromise, but for now it's my only option (model flying is very restricted here).

I was so into the build process that I didn't think about electronics until now. Stevens suggests a motor that comes with no warranty beyond "it will work when it gets to you", so I'm looking for something else. Their recommended setup is a 2212 1400Kv motor with an 8x4.7 prop on a 30A speed controller and a 2S 1350mAh battery, maxing out at 150W. I know what all those numbers mean, but I'm still learning how performance varies as the numbers change, in particular the motor's physical dimensions. I have a couple of B-pack setups already (one FT Radial and one old style) with 3S 1300mAh batteries, but I'm not sure if they would work in this situation. The FT motor matches the physical dimensions required to fit in the plane's nose, but it's only 1050Kv. The 3S battery would seem to make up for the lost RPMs, but it also weighs twice as much as the 2S. Suggestions?

 

[TooJung2Die]

I think the 2212 series motor was the original FT 'B' pack motor. I like them a lot and have used them on several airplanes about the same size as your 4Charlie. It's a workhorse motor. It's also one of the cheapest motors you can buy, five or six bucks from China. They make them from 930KV to 2700KV. I think 8x4 to 8x6 is a good range to try on the 1400KV with a 25A or 30A ESC. The 930 to 1000KV motors can swing a bigger 9 or 10 inch prop. I always check the Amp draw if I want more thrust and switch to a bigger prop or battery so I don't let out the magic smoke.

 

[kkelly]

I think the 2212 series motor was the original FT 'B' pack motor. I like them a lot and have used them on several airplanes about the same size as your 4Charlie. It's a workhorse motor. It's also one of the cheapest motors you can buy, five or six bucks from China. They make them from 930KV to 2700KV. I think 8x4 to 8x6 is a good range to try on the 1400KV with a 25A or 30A ESC. The 930 to 1000KV motors can swing a bigger 9 or 10 inch prop. I always check the Amp draw if I want more thrust and switch to a bigger prop or battery so I don't let out the magic smoke.

Mine is an Emaxx 2213-935. It's been through me relearning how to fly and several nose-in crashes and still works. Would that or the FT Radial motor (2212-1050) work well in a 4Charlie on 3S? I'm guessing both will have plenty of power for it, but the 3S batteries weigh about twice as much as the recommended 2S do, so I'm worried about weight.

 

[TooJung2Die]

Would that or the FT Radial motor (2212-1050) work well in a 4Charlie on 3S?

Yes, it'll work on 3S. It's all about the Amp draw and not frying your electronics. You can use the motor charts if you have them as reference but checking with an actual Amp meter is best. With the lower 1050KV motor you can use a bigger prop with 2S batteries to get the thrust you want. In my experience having the exact motor size is not critical. You are well within the kit manufacturers recommendation. You can play around with prop size/pitch and 2S or 3S batteries to find the combination you like best.

 

[kkelly]

Yes, it'll work on 3S. It's all about the Amp draw and not frying your electronics. You can use the motor charts if you have them as reference but checking with an actual Amp meter is best. With the lower 1050KV motor you can use a bigger prop with 2S batteries to get the thrust you want. In my experience having the exact motor size is not critical. You are well within the kit manufacturers recommendation. You can play around with prop size/pitch and 2S or 3S batteries to find the combination you like best.

Okay, then I'll start with what I already have on hand. The foamie the radial is in right now is on its last legs anyway, so I'll be looking for a new home for its electronics.

 

[FlyingTyger]

I flew my 4charlie on 3S. It was a great setup and the little bit of extra weight helped with any wind. I was running a Rimfire 400 and a 3S 1500mah mounted in the cockpit.