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RC Guys Cessna 188 AGwagon ARF, Rescue

Joker 53150

Mmmmmmm, balsa.
Mentor
#1
Well, I *was* going to work on a P-47 now, but a small series of events has changed my plans. A few weeks ago I ran across a guy who was selling a couple Zenoah gas engines, a 20cc with electronic ignition and a 38cc with a magneto ignition, both of which are now mine (I can't pass up a great deal). Then yesterday I ran across an RC Guys Cessna 188 "AGwagon" (agricultural wagon, AKA: cropduster) on FaceBook Marketplace, which is designed for up to a 40cc gasser. It was meant to be! :p The seller wanted less than half the price of the new ARF, and it came with most servos and a smoke system. No engine, a little hangar rash, needing some electronics. The plane is actually still available new, although in this case I don't really need any parts from them. If I like the plane after it's done and flying I may go ahead and re-cover the wings as they're a little rough.

These first pics are of a finished 188 I found online, not my plane.

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Here's mine, shortly after getting it home and putting it up on the stand for inspection. Both wings have their servos, there is a servo for each elevator installed at the rear, and there is a servo in the nose, possibly for the throttle. It's missing the rudder servo for the pull-pull rigging. The smoke system is controlled by the receiver and programming, no servo needed. The original ARF included plastic covering for the control surfaces which mimicked the corrugated material the original used. It appears this plane originally had that installed as all control surfaces show signs of re-covering and repair. Wings are both solid and I didn't find any broken balsa there or in the fuselage (yet), kind of a first for my projects! :D

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Here's the Zenoah G-38 I picked up. It's been fighting my attempt at getting it running, but I think I'll win. A previous owner did a lot of "creative" work on it that I'm attempting to un-do. First, a home-made carb mounting block was made for it to turn the carb and make hooking up the throttle pushrod easier. If you saw my build thread for the big blue "Nothin' Extra" you may remember the bellcrank and linkage needed to make the throttle work. The carb mounting block this engine had does away with that and gives you a straight shot from the servo to the carb. The downside? In this case it also required another fuel line to get the "pulse" from the engine to the carb to pump fuel. A semi-flexible fuel line isn't going to give me a good solid and reliable pulse like the original setup, so I'm getting rid of the home-made stuff and going with a stock-type setup. Actually, I also ordered another carb block that may work better than stock, I'll compare the two and go with the better option.

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The carb has been disassembled, and again I'm un-doing previous alterations. First, I had to remove an elbow mounted into the back plate of the carb. This is where the pulse line from the mounting block attached. When the parts are cleaned I'll plug the hole as it won't be needed. I also removed some type of Bondo-ish material used to block the pulse inlet port on the carb, as I want to use the port again. The pieces are all disassembled and ready for a soak in Denatured Alcohol for a few days. Before this pic was taken I spent some time cleaning the major dust & dirt off the carb so I could more easily disassemble it.

The stock muffler in the bottom right of the pic is being replaced by a B&B smoke muffler designed for the G-38. I've never had a smoke system, and this one has a Sullivan Sky Writer pump installed.

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As with my other G-38 engine, I'm replacing some pieces that are probably still OK with new ones, especially if the new parts are cheap! The plug wire and plug cap are about $3 for the set, and since the pieces that came with the engine were getting crusty it was an easy decision to swap 'em out. Until I tried removing the old parts... :mad: Somebody put some epoxy or other fairly aggressive adhesive in the coil to hold the plug wire, and it was a beast to remove. It took about 20 minutes of picking at it with the Harbor Freight picks shown below, but I finally got the old stuff out and reinstalled the mag back on the engine.

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A new plug will go along with the new plug wire and cap, a new exhaust gasket goes with the new muffler, new carb mounting gaskets with the new carb mounting block, the carb is getting a full re-build, a 3-1/2" spinner, and maybe a few other tweaks, and it should then be ready to mount in the plane. Hopefully the engine mount that's shown doesn't require any work to get proper prop/spinner placement at the cowl, I haven't checked that yet.....
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#2
Well, I took some measurements to see if the mount currently on the engine would work or not, and it appears that it'll be far too long. It would end up leaving about 3/4" between the cowl and spinner which would look a bit silly. B&B has a mount that is about 1/2" shorter that might work. A 1/4" gap wouldn't be too bad, but I want to get the nose of the plane apart first to see what kind of fun awaits me on the firewall before I order an engine mount. It also looks like someone has bolted a thick piece of plywood to the front of the firewall - hopefully it's easy to remove so I can start from scratch. I could end up building my own mounting plate for the engine like I did on the Rascal 110 project.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#3
The carb repairs went well, other than waiting for a new elbow that goes in where the GREEN arrow points. The original piece is a brass base with a plastic 90 attached. The brass was fine, but the plastic was brittle and cracked so I pulled the old pieces out and am waiting for the new piece to replace it.

The RED arrow is where another 90 was installed. Normally there is no hole here (or to the left of it - that's just a recess in the casting. A previous owner attached a pulse line from the carb mounting block here. Normally the pulse from the engine enters the carb at the hole with the YELLOW arrow. This hole was plugged as part of the modification that was done, and I've un-done it all so the YELLOW hole is again the pulse line for the carb and RED is blocked with JB Weld.

The carb is still a little dirty in spots, but is MUCH better than before. The denatured alcohol I soaked the carb in was yellow from the dirt this morning!

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I'm not sure why, but I keep most of the misc. pieces that come with my engines. To the left is the home-made carb mounting block that came with this G-38, and you can see the nipple for the pulse line that was run to the back side of the carb. To the upper right is a fancier home-made metal block that was on the other G-38 I did recently. The metal one was pretty interesting and took some real work to do, and even required some machining of the cooling fins on the cylinder head for it to fit. It also appears that the carb mounting holes were drilled wrong and then re-drilled for proper orientation? It also doesn't isolate the carb from the heat of the engine like the other blocks do. The bottom piece is the most home-made of the bunch, although I don't recall which engine it was made for.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#4
Round 2, the fight with the engine continues...

As mentioned previously, the engine stand that came with this engine is about 3/4" too long for this plane, so it has to be removed. From the factory, Zenoah uses a simple plate bolted to the back of the engine with four Phillips head screws. When this long mount was installed, it was done with the original screws plus some Loctite. Now, years later comes the task of trying to remove them..... :eek:

One screw had a slot cut in the top so a standard straight blade screwdriver would fit, and that's the only 1 of 4 screws that didn't fight me. The other three screws, not so much. One had a good head (not chewed up) and some light use of an impact screw remover did the trick, so I was down to two screws left. Both had heads that came to me partially stripped so I had to get creative in getting those screws out.

First I tried a screwdriver, but the screwed up heads wouldn't let me get any grip. Next I tried the impact screw remover again, but again no luck. I wanted to add a little heat but there is an oil seal close by that I didn't want to mess up. The next step was going to HAVE to work or I'd be facing surgery with the engine case. I could either drill the head and use an Easy-Out or I could cut a slot in the head to try a straight blade screwdriver. I've got Easy-Outs, but not a small one, so time to cut a slot! First, to even get at the screw head with the Dremel tool and a cutting disc I had to cut a hole in the side of the mounting base and feed the cutting disc in from the side. I tried one first to see if it would work before cutting the other screw head, and lucky for me it came out fairly easily with a straight blade! Success followed on the last screw as well, and the aftermarket mount was finally removed.

All four of those screws were thrown away and replaced by allen head bolts. I may simply use the original flat mounting plate Zenoah ships with their engines (it came with the other G38 I recently got running) with some stand-offs on this project if the stand from B&B Specialties doesn't work.

So I think the worst with this engine is behind me now as all old parts are gone and it's getting reassembled with new pieces. It has plenty of compression, the cylinder walls and piston look to be in good shape, it's got good spark, and the carb should be good to go as well. This may be a good time for me to make an engine stand that attaches to the work bench I recently made, which would allow me to test and tune the engine before installing it in a plane...
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#5
With a parts delivery today the G-38 is pretty much done other than soldering on the wire for the kill switch. The new plug wire & cap are on, new exhaust (I'm going to swap this one with the one on my other G-38 as that's a smoke muffler and this one isn't), and the carb rebuild done. I put the old engine mount back on temporarily as that'll be the easiest way to get it mounted to a test-stand. I don't have a spinner for it yet and will borrow the one off my other G-38.

Next to it is another engineI got at a swap meet about 4 years ago for $20. I'm 98% sure it's a conversion engine, probably a Ryobi, and my guess is somewhere around 31cc. Give or take a few cc's... :) The rumor is that these conversion engines are heavy for their displacement and that they don't spin up as quick as modern purpose-built RC engines, but that doesn't matter much to me, I just want to make it run!

It's just been sitting on a shelf collecting dust so I put an electric starter on the cone to spin it to see if it even has spark, which it does. It's also got good compression, so while I had all my carb rebuild supplies out I cleaned out this carb and put all new gaskets inside. Other than the old gaskets being stiff, the carb was very clean and easy to work on. I need to get a few nuts & bolts to secure the engines to the test stand and would like to try starting them both this weekend. *IF* it runs well it could be a good candidate for a SPAD type of plane - old school design with an old school engine. Or maybe an old Robinhood 80 (or bigger)...

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Joker 53150

Mmmmmmm, balsa.
Mentor
#7
Here's the first look with the cowl removed. Although the top is hacked up (there should be a series of vent holes) it's at least solid. It'll require a bit of scrubbing, but so far so good.

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Flipping it over and again the structure is in good shape. The covering is ugly, and most of the white covering in this pic has been replaced at some point in the past. There is quite a bit of room for the fuel and smoke tanks in the nose. My plan is to just clean this up and use it as-is for a season and NOT re-cover it now, which would just slow the project down.

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Although they're both marked as "Smoke", the smaller tank (bottom one) was actually for gas. I hadn't thought about it before, but this does appear to make sense as the pump drains the smoke tank much more quickly than the engine uses fuel. I'll probably re-cover the pump cover since that covering is very wrinkled and ugly, and will likely replace the other hatch (the one on the right). It's not the original, it's cracked around the screw holes, and is an easy fix.

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From the tail looking forward, there is a lot of open space. Elevator servos are at the rear and only the pull-pull cables and servo extensions are found in the center of the fuselage. We'll see how that changes as I add batteries, receiver, etc.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#8
I took a few minutes with the heat gun to shrink the covering a bit. Some spots were a little loose, but overall the covering is usable as-is on the fuselage. Except for the forward 2/3 on the bottom where it was recovered in the past, this area needed to be stripped, which will be finished when the landing gear comes off.

I am going to re-use the rear hatch in the pic below, although I might patch the switch hole first. I think a previous owner used it for a power switch on the smoke pump. Speaking of the smoke pump, I powered it up and confirmed it works well. At 6volts it pumps a LOT of fluid quickly, so hopefully the heat of the muffler can keep up and make plenty of smoke for me. :)

The forward hatch is a new piece that I cut from 3/16" ply, replacing the original that was about 1/16" thick. Since it was only a cover and nothing was secured to it the lighter material was marginally OK, but my plan is to attach some electronics to the hatch (probably the receiver) so I want it a little stronger.

A rudder servo was installed to test the linkages and everything works properly without any need for adjustments. A heavier-duty servo will be installed soon and this lighter-duty one will be re-purposed as a throttle servo.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#9
Just as I was about to fall asleep last night I realized something - there is no easy access for batteries on this plane. The only hatches are on the bottom, and to remove the canopy requires removing 8 screws.

The previous owner had a pretty simple setup with a single NiMh battery strapped to the bottom of the engine mounting block, but I'm going with dual LiPo's and the Dualsky VR Pro Duo (the same setup as some of my other giant planes). This will mean I need easy-ish access to the batteries so I can pull them when the plane isn't in use.

My initial thought is making the forward hatch either easily removable, or maybe hinging it instead of having it screw-on. Maybe mount the batteries to the cover and have the entire cover held in place with some bigger nylon bolts. Plenty of options, and lots of time to figure it all out while I wait for parts.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#10
IT'S ALIVE! We were about half done with tuning when I took this video, and the engine kept running better and better as we went along. Honestly, I wasn't sure what to expect with this engine after all the headaches I had getting this far. It primed and pulled gas very well, and after getting the needles set well enough for it to run a bit we let it run to get some heat into it for the first time in who knows how long.

I mentioned it on my previous work with the Zenoah G-38 - the needle settings are very strange with the original/stock carb. Mike was tuning again for me and he started at 1-1/2 turns out on high, which is usually good enough to get other engines running. It was running extremely rich and he kept dialing it in a little at a time, and found it kept getting better and better. Eventually the high needle was all the way in and it ran great (along with tweaking the low needle a bit). I told him before we started that many people find 0 to 1/2 turns out on the high works great, but somehow he "forgot" and turned the needle to 1-1/2 turns before we started the tuning session. :LOL:

After tuning I swapped mufflers with my Nothin' Extra's G-38, which came with a smoke muffler. Before removing the engine from the stand I'm going to try running some smoke oil through it. After testing the pump last night I know it works, but I want to get a feel for how much smoke oil it needs. My pump's output is variable so I can tie it to my throttle channel - more throttle = higher smoke fluid volume. That'll be a fun project! :cool:

 

Joker 53150

Mmmmmmm, balsa.
Mentor
#11
Time for a smoke break! Since the G-38 was still mounted to the test stand and I had all the hardware (and smoke oil) to test the smoke system I figured today was the day. I ran a second tank for the smoke oil, mounted the pump with Velcro to the stand, and tested the system to make sure it worked. Normally this smoke pump would be tied to the throttle channel and would send more oil through the system at high throttle than low, but we controlled it all manually today.

As expected, the Zenoah G-38 fired up and ran well (we'll do the final adjustments when we can see how it works in flight). We ran it for 5 minutes to get some heat into the muffler, and then to mid-throttle while I gave it a small stream of smoke oil into the muffler. Immediately we were getting plenty of smoke! Only a few ounces of smoke oil was run through the system as it was leaving a very oily mess. I'm not sure if that is normal or if it's un-burned oil? Either way we're claiming a victory, and I can proceed with work on getting the engine mounted on the airframe.

 

Joker 53150

Mmmmmmm, balsa.
Mentor
#12
I was looking at the AGWagon again last night and took some measurements from the firewall to where the base of the spinner will be to clear the cowl, which will tell me how long the engine mounting standoffs need to be. Looks like 7/8" should be a pretty good number, so I looked at my usual source and placed an order for some nice metal pieces. Today I got an email to let me know they're discontinued and not available... :(

After giving it about 30 seconds thought I realized that the standoffs are so short I should just make them myself and save some money! This will be a fairly easy project and will involve simply taking 1/4" layers of plywood and laminating them together to give me a 1" starting point. From there I'll mount the engine and re-check the spinner-to-cowl spacing, followed by sanding the standoffs as needed for proper fit. I'm not sure why I didn't think of this yesterday, but I guess it's a good reason to sit and think about a problem/solution before just jumping in.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#13
The engine spacers turned out pretty well. They're made from 3/8" hardwood sandwiched between two pieces of 1/4" ply for a total 7/8" thickness. From what I can tell so far, that's the minimum thickness I need, and it *might* put the spinner right up against the cowl. If so, I can simply space the engine out with washers between the backplate and the ply. Next up is trying to determine the centerpoint on the firewall so I can drill holes in the proper locations.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#14
Some planes are designed to make installing & centering the engine easy. This isn't one of them...

To center the engine in the cowl I need to hold the plane vertically, set the engine in place, and fit the cowl. Super easy to do if you've got 8 arms, so I had to get creative. This step ladder turned out to be the perfect size, and the paint tray is a great rest for the landing gear to sit on. The strap just keeps it all in place, "just in case".

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My home-brew motor mount worked well, although I would have been better off going with 3 layers of 1/4" ply as my mount turned out about 1/8" too long, so it'll need a little trimming. I also need to get a spinner on the engine to make sure it's really in the best spot vertically and horizontally before I mark the holes for drilling.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#15
I guess I found a new way to kill a bandsaw blade... To shave 1/8" off the engine mounting blocks I ran them through the bandsaw. Between the epoxy and the thick 1-1/4" piece of ply I was sawing through (the block was turned up on it's side), it effectively destroyed my blade quickly. The blade had some miles on it to begin with, but I'm really impressed with how dull the blade is now! :eek: It's a "safety blade".

A replacement has been ordered, and on the good side, the engine appears to be sitting almost perfectly now in the cowl opening. A spinner will be placed on the engine to make sure it's all lined up nicely and then I can get to work mounting the blocks to the firewall.
 

rockyboy

Skill Collector
Mentor
#16
Ouch! Usually those blades don't mind a little epoxy, but if it gets heated up cutting a thick piece it can start to lose it's tempered hardness and dull down a lot more quickly. Sort of an accelerated destruction process :D
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#17
I'm finally getting around to mounting the engine now that the mounting blocks are installed on the firewall. I'll have to make a small amount of room for the muffler as it's currently just barely touching an edge of the firewall. I was also hoping to have a new spinner for the plane, but shipping from China is taking longer than normal so I'll have to do some checks with a spinner from a different engine. Hopefully the engine is still centered as planned - it looks a little low in this pic but that may just be the camera angle.

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I had to cut some clearance for the muffler pipes and spark plug. Most of this was already cut-out and I'm just tweaking it a little bit. There should be plenty of room for hot air to get out. I'll also add some exhaust extensions to get the exhaust residue and the smoke oil away from the fuselage. The smoke oil creates a BIG mess and I'd rather not have a massive cleanup each time I fly. A couple extra inches should work well.

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#18
You’ll love this plane. I had one I did as an electric for an article and it flew beautifully on an electric 50cc motor and 12S lipo power. Very easy flyer and looks great in the air. I kinda regret selling mine.