1/4 Scale Cubs - Sig and Balsa USA, Rescue and Re-Build

[Joker 53150]

Sigh, looks like a complete rebuild of the Cub is in the future. I either lost aileron control or a strong wind gust sent it into the ground seconds after take-off. Not just a simple cartwheel, but a full-on nose-first death-dive. The wing has some damage where the two halves join together and will be a fairly easy fix. The fuselage... well, it's going to take some effort. It's broken completely in half, landing gear is bent, the cowl is cracked, and my new Xoar prop is broken. But it's fixable!

The two big questions I'm going to have to answer - do I rebuild the old fuselage or get a replacement fuselage kit and start fresh? Also, do I stick with gas or change to electric? A new fuselage kit would allow me to fix some additional "issues" I have with how the kit was made by the original builder. I can make it better and lighter than it was, but this comes with a higher cost. Although I like the sound and authenticity of a gas engine, it's kind of a pain in the butt to take all the extra stuff to the field with me. Plus, the 20cc I've been running is borderline too little power so I'd best upgrade it if I want to stay with gas. I'm strongly considering changing it over to electric which would also allow me to bring it to FTFF 17 (if I have the room for it).

Choices, choices. I'll post a pic or two of the carnage in the next day or two. It's not my best day at the field, but such is the hobby.

 

[Joker 53150]

So here's the fuselage in it's current sad state next to the 1/4 scale Pietenpole I'm building. After posting the previous thoughts, I looked at the Sig site and found a replacement fuselage kit is $50. New tail feathers are $10 (mine are still undamaged, but glued securely to the fuselage and would probably take damage trying to remove them). Standard landing gear wires are another $10. So for around $125 including new covering I could have a new fuselage and could lay it all out in a better manner, with better construction, and lighter weight. My mind isn't completely made up yet, but it's getting there.

 

[hackofalltrades]

Just read through your whole build. Your work is outstanding! It is hard to see all your hard earned work get all busted up like that. I know you will get her looking like new again.

 

[Joker 53150]

Following up on the crashed Cub... it's toast. I went through the fuselage and removed servos, engine, etc to better assess the condition and the forward 2/3 of the fuselage was just junk. The back 1/3 is fine, however. While the wings are fairly intact the spar is destroyed and there is a lot of loose/broken wood around the center of the wing. They would require full disassembly and re-building to go on a new fuselage.

Or I could go with "Plan B", which is to just replace the plane with another swap-meet find! Wings will have their organs harvested and the rest will be hung on my office wall as a decoration.

At the swap-meet I met a guy getting out of the hobby completely, and he was selling a nice Balsa USA 1/4 scale Cub. I've only had the Sig versions, so this will be a nice addition to my surviving Sig 1/4 scale Clipped Wing Cub. This one came with a G23 (at least that's what he claimed was inside, I haven't checked yet) and a semi-detailed interior complete with an ultra-creepy pilot. The guy who built it spent some time adding extra detail, like the pinking at the rib stitching. The covering only needs a little attention, which is nice. The landing gear is shot so I'll order replacement wire from Balsa USA. The carb on the engine probably needs a re-build, and other than that and checking out/updating the electronics it's almost ready to go!

And since I'm going to be asked, $100. I couldn't pass it up, and my hangar feels complete again!

 

[Joker 53150]

So I started digging into the new (old) Cub, to see what it's going to take to get it in the air. As mentioned in the previous post, the landing gear was shot. It appears to be a home-made suspension setup, but it'll be replaced with stock Cub gear from Balsa USA. A new spark plug and carb rebuild kit were also ordered - those carb kits are nice and cheap (around $7) and that often fixes most gas engine problems. The gas lines all needed to be replaced, and I have some 1/8" ID Tygon fuel line on-hand and a new bung for the tank, so that was all re-plumbed easily, including the line for the clunk. Both this Cub and the big Sopwith Pup I got a few weeks back had a fuel filler valve setup that I haven't seen before. Turns out it's made by DuBro and is fairly common. I ordered a rebuild kit for both planes, which includes a couple o-rings and a spring. There was also no fuel filter on the Cub, so I'm adding one from my stash once the carb is rebuilt.

The battery pack was removed and is being replaced with a new LiFe pack and voltage regulator. All servos appear to work very well, so nothing will be changed there. I'll probably change the on/off switch setup for the receiver to make it less likely it's accidentally shut off. Currently it's just a wire that sticks through the side of the fuselage.

Most of the real work needed on this plane revolves a re-build on the door & side window. They both open, but the window only opens about 1/3 of the way due to the way it was hinged. The door only opens part way as well, making it difficult to reach big hands inside to attach the wings. Both pieces will be removed, modified, and re-installed along with some magnets (maybe) to keep the pieces either open or closed.

So it may sound like a lot of work is needed, but it's all fairly quick and easy stuff. The biggest project will be assembling and soldering up the new landing gear once the wires get here. The carb rebuild is maybe a 15 minute project, and most of the new gas lines are already done. This one should be ready to fly shortly after the parts arrive.

 

[PsyBorg]

Creepy aint the word for that pilot. He looks like a mix of George Bush's head on Cotton's (Hank Hills dad) short legged body. Its like the Chucky doll of the RC world. You could probably stick pins in that and make someone twitch or feel pain somewhere on the planet.

The plane on the other hand does not look so creepy. You lucked out on your recent finds it seems. I guess since you are fairly motivated on this one we get to see video soon?

 

[Joker 53150]

I really didn't think I was going home with this plane, much less at a crazy-low price. After getting home I noticed it was also advertised on Craigslist for the past month with a bunch of other planes. The seller was only listing it as a package deal with a bunch of other planes and evidently got no interest, so he took the planes to the swap meet.

There is a lot of motivation to get it finished soon... Spring is coming and none of my other gassers are ready to fly. The non-flying planes are piling up and eventually my wife is going to notice the dust collecting on them. The Cub takes up all of my workbench and if it's finished and ready to fly I can move it out to the garage so it's ready to take to the field on a moment's notice. Assuming it flies, I'll get some pics and video for sure!

 

[Joker 53150]

Balsa USA came through with quick shipping, and my replacement landing gear wires arrived today. I haven't soldered gear wire for a while, but it looks like it worked well. As the original suspension gear was removed it was very obvious it was beyond repair. It was probably home-made and let the Cub sit too low, to the point where the prop could more easily hit the ground, and this should fix that problem.

The carb rebuild kit has shipped and will hopefully arrive tomorrow so I can rebuild the carb over the weekend. If all goes well I may be able to test the engine.

 

[Joker 53150]

New gas lines are installed, the carb is re-built, linkages are adjusted, the filler valve has all new internals, replacement landing gear wire is secure, and the new LiFe battery pack is on the charger.

Tomorrow morning I'll get some fresh gas to mix with oil, check the electronics with the new battery, and mount the wheels on the landing gear. It should then be ready to fire up for the first time in years.

Assuming that goes well I can then re-build the door and side window so they open properly and are secure in flight.

 

[Joker 53150]

The landing gear is done and I've got fresh gas/oil mix. So far, only a few sparks of life but no love yet. My electric starter doesn't seem to have the power to turn this engine over, hopefully it's just a low battery. After a lot of flipping I know the carb is pulling gas, and I know there is spark. I didn't touch the needles during the re-build, hoping the previous owner had it set well, but that's the next item I'll look at.

 

[Joker 53150]

I adjusted the carb back to factory default start settings to see if that would help it start. Who knows where the previous owner had it, and since it wasn't starting for me I had nothing to lose. I tried hand-proping it for a while but just couldn't get it to go, and finally the electric starter *barely* had enough power to turn it over. A couple seconds of turning with the starter and it popped to life. She LIVES!

It's still a bit cold out so I'll hold off on the final tuning of the engine before the maiden. Hopefully a new plug and a little more break-in will get it to start more easily. Either way, I'm probably going to need a bigger electric starter in the near future!

 

[Joker 53150]

The servo tester to control the throttle servo is hanging out the door, and the main kill switch for the magneto ignition system is hanging down on the left side near the muffler.

 

[Joker 53150]

Mentioned above, my electric starter *barely* had the umph to turn this Zenoah 23cc gasser over, although it handles the 20cc Zenoah from the crashed Cub with no problem. It also had some difficulty with the XYZ 26cc in my Clipped Wing Cub, although it spins that one better than the 23cc. The starter was probably made for smaller nitro motors. Hand-flipping is always an option, but I'm right handed and my right shoulder is in bad shape from years of rock climbing, so flipping the prop is a last resort since it leaves me with pain for days.

I was looking for a more powerful battery powered starter, and the bigger ones are normally well over $100. There is also a model I've seen on eBay and other sites that is in the $80 range that is supposed to be good for up to 80cc engines. I've looked at it a few times, but decided to hold off. Today I got an e-mail that it's on sale for $62.99 including shipping, so I pulled the trigger and ordered it. It kind of looks like a small car engine starter motor with a handle. As long as it works, the looks won't matter. Ideally it will start the 58cc for my 27% L-19, which is currently the biggest gasser I've got. That bigger starter may need a bigger battery than the one I've got, so a larger battery may also be in my future. Lucky for me, the company I work for does maintenance/repair work on heavy-duty vehicles and we're constantly replacing batteries. A battery that isn't good for starting a big diesel engine (we normally use 2 or 3 per vehicle) may be perfectly good for a season's worth of flying. Time to go check out the inventory!

 

[Joker 53150]

One day after ordering and I got confirmation that the new starter has shipped, so it's safe to say it's not being sold by GearBest! Delivery is listed as just under 2 weeks - fingers are crossed.

 

[wilmracer]

Sounds really nice! When is maiden scheduled for?

 

[Joker 53150]

Hopefully sometime in April the weather will be good enough. I'll maiden it at the field near my dad's house, which is a 3 hour drive. It's a small club and we probably won't have any company watching that way. At this time, it will get the following before the maiden:

• Door and window need to be re-hinged.
• Final tuning on the gas engine.
• Prop will be re-balanced.
• Landing gear cleaned and painted.
• Electronics (RX and battery) installed.
• TX programmed with failsafe.

Less than a day's work, but since it won't fly for a while I've been working on other planes.

 

[RCMAN]

That looks great and sounds sweet. Hopefully you will have a maiden vid.

 

[Joker 53150]

The Sig Kadet Senior has been put on the back-burner for a while, since I don't have the plans (yet) to re-build the parts I cut out, and the Cub is back on the bench. I spent the last 90 minutes or so trying to find the dang receiver from the crashed Cub, but to no avail. I'll find it sometime after my replacement is delivered... For now I'll just drop in a temporary receiver so I can start programming the transmitter. The door and window will also finally be worked on.

 

[Joker 53150]

.....and when I go to fire up my Taranis to start programming I find out that the "C" switch on the front is broken. No idea how that happened as it's been sitting in the case for months, but a replacement switch has been ordered as well. I'll have to program around that switch for now.

 

[Joker 53150]

The past few weeks have been an absolute train-wreck around here, but working on planes is far cheaper than therapy. I've re-installed some of the interior on the cub, although it really needs to be re-built as the balsa flooring is starting to split and the seats are kinda fugly. The receiver battery and RX are under the floor, and only the aileron servo cables and battery charge leads will be visible.




Here are the original door & window, both of which are going to be re-built from scratch with better hinge placement. The plan was to do this today, but the engine in my wife's car failed in a spectacular manner on the freeway after work, and that took up much of my otherwise free-time.