Great Planes Cherokee, Horse-Trading and Repairs

[Joker 53150]

A quick note about this new thread - it won't get in too deep as this plane doesn't need a ton of work. My thought behind a lot of these short threads is to show people new to balsa how they can get a used plane that needs a little TLC and get it back into the sky on-the-cheap. Balsa is not something to be feared, and with a little effort you can take a very cheap & rough plane and give it another decade of life. On with the show!

One of the nice things about having "too many planes" (according to my wife) and knowing other people in the same predicament is that there are sometimes trades to be made. In my hangar is an un-built Kadet Senior kit and in my buddy Mike's hangar is a used Great Planes Cherokee he recently acquired, complete with a Rimfire motor, ESC, and servos.

At face-value it's a lopsided trade in my favor, so to even it out I'm throwing in some parts needed to get his Sig 1/4 scale Cub airborne, plus the labor to mount the engine, gas tank, etc. He REALLY wants to build a Kadet Senior and I REALLY don't need a second one, so quoting John "Hannibal" Smith of the A-Team, "I love it when a plan comes together."

There are other projects ahead of it, but I needed to go through and check it out to get whatever parts are needed as this should (hopefully) be a quick project. The prop has already been removed to find out what size it is, as one blade is cracked. An omen, perhaps? A previous owner went a little overboard with decals for my taste, so I'll remove some to clean up the look a bit.




Other than a few small cracks in the plastic canopy the worst part is the tail. The covering has a lot of bubbles and the rudder has no throw to the right due to the way the hinges were installed. I think it's the original vertical stabilizer and rudder, but at one point they were re-hinged and re-covered.




Removing the vertical stab broke the nose on it. Not a huge issue, I'll cut new pieces and start fresh. There should be enough sheet material in my stash to do this all without buying anything. Hopefully the white covering I got for my big Cessna project is the same white for this plane!




As mentioned, the hinges for the rudder are an issue. Here's full deflection to the left, and notice how the rudder (to the right in the picture) doesn't line up with the vertical stabilizer? The hinge is way off center. I could probably just fix what is already here, but it's a bit rough and cutting the new pieces is fairly easy.




And here is the total throw to the right!




A little patching of the covering is also needed at the tail. Not sure if I'll just re-carve this entire block or not yet, but probably not. If the plane were in "new" condition I would, but this isn't going to be a show-piece.




Moving inside I'm test-fitting my 5 cell 5000mAh battery pack for my big electrics. It's snug, but fits! The instructions call for taking a 3S 3200 and a 2S 3200 and combining them to make a 5S 3200, but I'd rather not drop a bunch of money on battery sizes I have no other use for. The 5000mAh packs also work in my 1/4 scale Pietenpol, the Kadet Senior, and an Astro-Hog. When I checked the balance the nose was slightly down, perfect for a maiden! Then I noticed about 1-1/2 ounce of lead bolted to the tail, so maybe the previous owner used this same size pack?

 

[Joker 53150]

Ha! Turns out the rudder wan't going right because the previous owner applied the sticker over both the stabilizer and rudder and didn't cut it at the hinge line, so it was actually the sticker causing the problem! Either way, I'm re-building the pieces.

 

[PsyBorg]

So you mean its NOT a NASCAR Cherokee after all?..

Left turn..
Nother left turn...
Ohh look a LEFT turn!!

That sticker is probably why the prop is cracked. He tried to adjust for torque roll on take off and had nothin there to compensate with and bumped into something.

 

[Joker 53150]

Yeah, you think he'd have noticed the problem immediately after putting the sticker on...!

So it looks like all I need to buy is a prop for this one. It's got Deans connectors for the battery so I'll change that to match my 5 cell, plus a little time to build new vertical surfaces and this one should be ready for Spring to eventually get here. 4" of snow yesterday and 40-50* weather for the next few days, so the ground is going to be very soft for a while, so no flying.

 

[foamtest]

I can relate with the snow issue, it feels more like the 109th of January than the 19th of April.

 

[Joker 53150]

I pulled the covering off the vertical surfaces and am a bit surprised at what I found. Pics will follow tomorrow after I charge my phone. I'm not sure why I am still surprised by what I find when I dig into repairs. I guess it worked well enough for the guy who did it, but it doesn't take much more work to do it right. Or at least "more-right"... I usually aim for "right-enough".

The vertical stabilizer was made from two pieces of wood, one side was balsa and the other a thin layer of ply. I'm not sure if the ply was added for strength or to widen the structure up a bit. Either way, it's warped and getting replaced. The warp may have been from not laying it flat when laminating the pieces together, from the covering being too tight on one side, moisture, etc. It won't be visible in the pictures, but it's right along with the grain of the wood, the easiest direction for it to warp. My plan is to cut a few pieces of 1/4" sheet stock to run the grain in three directions. This will not only help keep it from warping, but will also let me run the grain straight along the exposed edges which makes it easier to sand smooth compared to trying to sand end-grain. I don't plan on using any light ply in the tail, so this should shave a few grams off the final weight as well.

The rudder was cut from fairly soft balsa so it was easy to flex/bend it along the grain. The control horn was also crushing the balsa which became a weak spot in the wood, and no doubt it would eventually fail. I'll use a different technique to make sure it's strong. Hinge pins were also starting to break through which would be visible through the covering (if the covering weren't all wrinkled and loose).

 

[Joker 53150]

Picture time! After removing the covering on the original pieces here's what I found. Note the grain direction on the vertical stab is almost all going the same direction which isn't ideal.

The other side has light ply laminated to it.

The original was marked up with my plan for building a replacement. The arrows indicate the grain direction I want to use. Note that doing it this way is more work, but will help avoid warping plus it's easier to get a good even rounded edge when sanding WITH the grain instead of AGAINST it. The original design had a ton of end-grain.

Last is my version waiting for glue to dry. The worst part of this will be sanding the rudder's taper towards the trailing edge as I went with a fairly hard balsa sheet. The goal is to prevent flex along the length and to make it sturdy for the control horn installation. Note that most of the sanding I'll need to do to round the stabilizer edges will be with the grain of the sheet. Warping should not be an issue with this design.

 

[rockyboy]

I know this project has been a lot of work on your end, but I'm learning a ton!

 

[Joker 53150]

This one has been pretty quick & easy compared to other projects, just a rebuild on the vertical stab and rudder is about it.

 

[Joker 53150]

The structure is now complete and only needs a quick final sanding before covering is applied. For the hinges I'm using a style I normally avoid (because I generally don't like them) - CA hinges. In this case they'll match what is currently used on the rest of the plane and I guess I should try and embrace them a bit since they're really not a bad product. Once the props I ordered for the Cherokee arrive all it'll need is a receiver programmed for it and it should be ready to go. Oh, and I guess I should also re-cover the block of balsa at the TE of the vertical stabilizer since the original red is peeling off...!

 

[Userofmuchtape&glue]

Nice! looks like a great plane.

What do you reckon about this large scale electric stuff? Got a friends 40. trainer in storage with a seized up motor and I was gonna just buy another glowie for $60 but thinking maybe electric is the way to go now. Thoughts?

Abe

 

[Joker 53150]

There are big advantages and disadvantages to each, although as you get into the .60 or .90 or larger sizes I feel that gas or glow are better options. I can take my 1/4 scale Cub out and fly for easily a couple hours on a single LiPo receiver battery charge and maybe 1/3 gallon of gas/oil mix - figure an hour to charge the battery and $2 worth of fuel mix, which is a great value in my opinion. That same plane would require 10 (maybe 12?) cell battery packs and would get roughly 10 minutes per flight, plus each battery pack is probably in the $100 range and would require a bigger charge system than I currently have meaning even more expense. The gasser has more noise, it's not as maintenance-free as electric, it can be a pain to get running right, is a bit dirty (glow being more dirty than gas), etc. But when a big plane cruises by and you hear the engine firing away it's all worth the effort! You also obviously need a place to fly gas/nitro that won't lead to clashes with the neighbors, such as an actual flying field.

In the .40-.46 range it's a bit of a toss-up. Since I've already got 3 other electrics in this size I've also got the 5 cell batteries which work well, so keeping this one electric was an easy choice. If I didn't have that gear I'd probably have picked up a glow engine for the Cherokee. Then again, I'm pretty happy with wet fuel recently and have all the gear to use it. It appears far more people are going electric in the .40 range than any other power system for good reasons.

For your seized engine, if it's a good brand and not damaged you can probably save it. I've cleaned up a few that were gummed up solid by soaking them in hot antifreeze overnight, followed by soap & water, lots of after-run oil, and reassembly.

 

[Userofmuchtape&glue]

Yep oaky Joker, my motor is a Enya 40. I freed up the crankshaft and cylinder after soaking them in various stuff for a few months but the carb is hopeless I am afraid. It has started to corrode it seems, so I may buy a new carbie but really it would be easer to get a new engine.

Might keep it glow but will ask him what he wants.

Abe

 

[Joker 53150]

The price of used glow engines is so low these days it's probably cheaper to get an entire replacement engine compared to buying parts to fix one! I don't know if a carb from a different brand engine would work or not, it may be another option if the rest of the engine is good. When swap meet season comes again late this year I'm thinking about focusing on picking up some good old glow engines for my stash-of-stuff. Right now they're cheap and reasonably available, no idea what will happen over the next decade with them...!

 

[Joker 53150]

What better way to unwind after a long stressful day of work than covering balsa? Total work time was about 2 hours and it turned out nicely. The white covering isn't exactly the same white as the rest of the plane, but since there is space and another color separating them it's not noticeable. The red I planned to use for the block around the tail is too far from the original red, but I'll probably still use it as it's closer than not having any covering at all. The original rudder design had a little artwork on it, so I may try and duplicate it on mine.

Assuming the new props arrive in the next few days it'll be ready for a maiden this coming weekend!

 

[Joker 53150]

Oh, and for what it's worth, the original rudder and vertical stabilizer are still available from Great Planes since this is still a currently produced plane. New pieces would have set me back a whopping $20 plus shipping. The rebuild was done using all parts I already had, and I've got maybe 4 hours into the tail rebuild. If you figure a few dollars for shipping my work cost me about $5/hour. I got more than $5/hr worth of satisfaction in having done it myself so I came out ahead on this one!

 

[PsyBorg]

Beautiful work Joker. This will look great in the air with some blue skies and green grass decorating the rest of the screen around it.

 

[Joker 53150]

Thanks, I'm looking forward to getting it in the air!

A bit of work tonight and the punch-list is almost finished. Hopefully my new props arrive before then, but I had one that was good enough for now. The Deans style plug was removed and an XT-60 soldered on. I pulled a 6 channel receiver from my Kadet Senior which only needs a 4 channel and programmed my Taranis.

Then things got a little confusing..... On the right side of the plane is a nice big power plug that kills power directly from the battery by disconnecting the positive cable, a nice safety feature. What I didn't notice is on the left side toward the middle of the plane is a power switch, presumably to kill power to the receiver, and I figured it was there as this plane can use a glow engine.

So I skipped that switch for now and ran the servo wire from the speed control directly to the receiver like most planes would have and plugged the battery in.

No joy, no power at the receiver and no mystical beeping of the motor. A little research and I find this speed control has no BEC built in, which solves that mystery.

It's been a while since I did anything with a bigger power system like this and I'm trying to remember how it all works! Should I get a separate voltage regulator that plugs in to the 5 cell battery to step the voltage down for the receiver and servos, or should I simply put a receiver battery in place?

For some reason I am thinking two different batteries connected to the receiver (Channel 1 for the throttle to the ESC and then Channel 6 for battery voltage from the receiver battery) would be an issue, but I may be wrong on that?

 

[Joker 53150]

I'll answer my own question here, as this one was weird. Most times when a separate voltage regulator or BEC is used you'd have to disconnect the red wire on the servo lead from the ESC, but in this case that doesn't work. Some digging online and I found the manual for this ESC which basically says to just plug it in and use a separate battery pack (or BEC) to power the RX & servos. So that's what I did, but now I only got one beep until I went full-throttle to actually arm the ESC, and then everything was puppies and rainbows. A 4 or 5 cell NiMh receiver pack easily fits inside the fuselage, and there was even a Velcro strap for one already installed, so that must be what the previous owner was doing as well.

Strange, and still a good learning experience! So I guess it's ready to fly now.

 

[Joker 53150]

Maiden Flight Report!

Today was a perfect day to take some planes out for maiden flights. Sunny, 60*, low winds, only me and one other guy at the field. First up was the Cherokee. Great Planes touts this as a great second plane after the "trainer" is mastered and I'll agree with them. Even though I was carrying a 5000mAh 5 cell instead of the recommended 3200mAh 5 cell (which then required about 3/4 ounce of lead at the tail) it handled the weight well and took off on grass with ease. I can only assume that a lighter battery and no tail weight would be that much better.

I put three flights on it, each around 6-7 minutes but didn't have a battery checker to see if I could have gone longer. The flaps really helped slow my landing speeds so the weight penalty I'm flying with didn't really matter. Later in the day the winds picked up and it sliced the air barely noticing the gusts.

Now that I know it's a "keeper" I'll do some work to tidy it up such as removing the extra decals. The tail also needs a little color so the plan is to re-create the design on the OEM piece. With less weight on it this could really be a sporty plane that leads into warbirds. My only issue with it is that it has an electric motor.