Balsa Build Along 2017/18 - Hobbico 300S, Thinning the Herd

[Joker 53150]

Here's a simple trick for anybody using the Gold-n-Rod style pushrods. The most difficult part is normally getting the threaded rod into the pushrod far enough to be secure. The pushrod is fairly small and the farther you screw it in, the harder it gets.




What I do is wrap one end with a couple wraps of painter's tape to protect the threads, and then insert the taped end into my cordless drill.




Once in the drill, simply run the drill to screw the threaded rod right into the pushrod. It's super quick and easy!




And the end can then be installed and turned in/out as needed to adjust your final pushrod length.




Here's what I was aiming for with my pushrod locations - I wanted them to be as straight as possible for easy operation. In this case both pushrods ended up aiming pretty darn near exactly where I was aiming for. Final tweaking can be done by adding some slight bends to the threaded rod, although not ideal. In my case I'll have to do that as I miscalculated the servo arm locations and figured them sitting lower than they are, so I'll add a small Z-bend to both threaded rods to lift the clevis up a bit.

 

[PsyBorg]

Cant just shim up the Servo's instead of creating a weak spot in the metal parts of the push rods? Threaded rod will be hard as heck to bend I would think.

 

[Joker 53150]

It actually bends fairly easy. I could change how the pushrods are mounted, but this doesn’t worry me as I’ve seen it on much larger planes. In hindsight I should have connected the pushrods and then created the structure to hold them. Other times I’ve done this I’ve been more accurate.

 

[Joker 53150]

Just to clarify a bit, I'm not putting a harsh Z bend in the threaded rod. It's just two light bends that leave plenty of room for the clevis to get threaded on. Is it ideal? Not really, but it is still plenty strong for the application.

 

[rockyboy]

I did the same height miss-match thing on a smaller plane (I forget which one) and installed a linkage stopper upside down so it extended down from the bottom of the servo arm. Since you're going the clevis direction I don't think that would help here, but it's another option for anyone who finds themselves in a similar situation.

 

[Joker 53150]

I did the same height miss-match thing on a smaller plane (I forget which one) and installed a linkage stopper upside down so it extended down from the bottom of the servo arm. Since you're going the clevis direction I don't think that would help here, but it's another option for anyone who finds themselves in a similar situation.

I've done that accidentally and on purpose in the past! The first time was an accident, and then I realized how much lower it kept the pushrod so I was able to use it to my advantage. It worked great on a couple guiders I built a few years ago.

For this build, it actually COULD work as I do have the stoppers big enough handle that thick of pushrods at the servo arm. The more I work with the clevises the more I like 'em. They're a bit bulky to use on smaller planes, but for this size and bigger they're fantastic, and give me plenty of adjustability.

 

[Joker 53150]

It doesn't show up in the picture as well as it does in person, but the stabilizers are fiberglassed and have two coatings of Zpoxy applied, and they're nice & glossy, especially compared to the bare fuselage. The finish brings out the grain nicely, although it does also show a bit of the balsa filler as well. The finish isn't as smooth as I'd like as a little weave is visible. It's still glossy, just not glass-smooth. I'm thinking about getting a can of clear gloss spray to see if that helps, but I'm not expecting much difference. Normally I'd spray it with filler-primer, sand it, and prime again to fill that last bit of unevenness. Overall, I like where this is going!

 

[Joker 53150]

Pics to follow, but fiberglassing the fuselage is a chore! I was able to do it with one piece of 'glass, but a few times as needed to conform to the shape of the fuse. The rear bottom ended up with a few wrinkles and bubbles, but I think it'll all work out in the end.

 

[Joker 53150]

The clear finish is taking time, lots and lots of time. I can work on an area, but then have to let it sit and cure, during which time I need to avoid creating dust that would get stuck to the epoxy. So I do some work, then find something else to do for a while, do more work on it, rinse & repeat.

As it sits right now most of the fuselage is done, although the tail needs a little work as does the area under the cowl. Once the stabilizers are glued in place I'm planning to add a small layer of balsa filler to smooth it all out, and then epoxy over that as well.




Overall I really like how the balsa looks with this finish, and how it's giving it a "wet" look. The filler is visible, but that's bothering me less and less as I move along.

 

[rockyboy]

It's looking gorgeous!

 

[Joker 53150]

First tests with clear gloss spray are done, and the results are encouraging. I took some before & after pics, but it's hard to get a really decent picture that shows the difference. After spraying with gloss clear the entire finish is simply "more evenly glossy". It doesn't fill in the weave at all, but that wasn't expected. It is basically just evening out the finish, so from a few feet away you won't notice some areas have more epoxy built up than others. Good enough for me!

 

[TexMechsRobot]

What clear spray did you use?

 

[Joker 53150]

I'm trying regular Rustoleum clear enamel since that's what I already had. So far I haven't found any info on it being compatible or not, or if it'll just peel off eventually. So far it sticks nicely, doesn't lift or orange-peel, etc.

 

[Joker 53150]

Getting back to working on the Extra finally... The stabilizers are installed, but without any of the original covering there is nothing to hide the gaps between the fuselage and stabilizers. From a distance it's not that noticeable, but I'd rather have a small fillet to smooth the transition. My first thought was to use the balsa filler and then clear-coat or epoxy over it, but I decided to go with epoxy and microbaloons instead to make the fillet stronger.




Going this route made the seam much more visible, but I can live with it. Other spots on the plane will be "non-balsa" as well, and some paint may be used to hide some of the spots like this. Function over form, I guess.

 

[nhk750]

The wood grain Looks nice, I wonder if adding some color to the fillets by hand painting would help? I'm no artist so I'm just flapping my gums here.

 

[Joker 53150]

I'm planning on adding some paint to the finished airframe just to give it some color, so this area could easily be painted if I want. I'm also considering just leaving it all as-is, so the cowl and belly pan would be their natural colors as well. Kind of a "peek behind the curtain", I guess.

 

[Joker 53150]

The only pieces left to 'glass and epoxy are the ailerons. I took care of the wing over the past few days, and really like how it's turning out. The surface isn't as smooth as glass, so to speak, but it's close enough for me. Soon I'm going to have to start trying to figure out how to make a canopy...!




The gap along the wing saddle is nice and even, and some stick-on foam tape will be applied to fill the gap and give me a soft cushion between the fuselage and wing.

 

[nhk750]

Looking sweet.

 

[Joker 53150]

The punch-list on the wing is getting shorter, and all it really needs now is ailerons. They haven't been 'glassed yet as I've gotten a little burned out on the process. They're actually the last parts that need any 'glass work in general, so I'll have to get off my butt and just get 'em done. With the wing mounted and some fresh snow on the ground it was time to take the plane out for some decent-ish pictures. Overall I'm very pleased with how the balsa looks. The finish isn't perfect, but it's glossy and really shows off the wood grain.




The belly pan is now epoxied into place as well. The white plastic will probably be used to my advantage in the final color scheme for orientation. In this picture you can also see some darker & lighter areas on the balsa. Lightest areas are from the balsa filler, and some of the darkest areas are from wood staining due to age and possibly moisture in the past. This picture exaggerates the light areas, as they really aren't normally quite that visible. Either way, I'd choose the light spots from the filler over low spots in the finish. Due to age and quite a bit of hangar rash there are a lot of filler spots. Sometimes sanding the balsa revealed a lighter finish which helped the filler blend in.




The aileron servo is also installed in it's pocket on top of the wing. The design was well thought out, as the builder could use one servo or two to handle the ailerons. Going with two servos would allow for some more flexibility as you could use the ailerons as flapperons or spoilerons as desired. In my case there was already a lot of extra weight added so only one servo was used to save a little.

 

[Joker 53150]

The more I work with gas and nitro engines the more I appreciate external hardware. The silver dot is a fuel filling port. In many glow installations you use two fuel lines and pull the fuel line from the engine and fill through that, but with a full cowl that isn't easy to do. The fuel dot will be a third line that I can fill or drain the tank from without touching the line to the carb.

The switch is an upgraded version of a regular switch often used on glow engines. Normally the switch simply cuts power from the battery to the electronics, but this switch also has an LED to let me know power is on and it also includes a charging port for the battery. This will allow for fast and easy charging at the field without removing the wing to access the battery. One additional item that'll be added to the exterior of the plane as I move forward is a battery monitor that is designed to warn me as the battery charge is getting low. If it works as it should I'll be adding them to most of my gas & nitro planes.