AirCore 40 Trainer Revival Project
 

I recently picked up this plane along with three others. It has been sitting for at least a decade and of course the engine was locked up. I managed to get the engine to free by flooding it with fuel and letting it soak overnight. However, the carb barrel is still frozen. I would normally just remove the engine from the plane but this plane is built so that getting to anything is nearly impossible. If I could unscrew the front wheel horn I could slide out the tray that the engine and fuel tank sit in. However,I don't see how since there is no access. Any ideas here

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2 possible ways to loosen up the carb. If you have a heat gun you can heat up the carb to loosen it. Or, very carefully use a hand torch.

I should have mentioned that I can not get access to the two screws that hold the carb in place due to the front fuselage ends being in the way.

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These planes were built using an unusual cardboard-like material and the whole thing is basically glued together. In typical balsa trainers there are front canopy covers that are removable and allow easy access to things. The concept behind these AirCore models was having the engine, fuel tank, and servos in a slide-out tray on rails that you could transfer between models. The problem is that without unscrewing the front wheel control horn I can not slide out the tray. I can not unscrew the wheel hrom because there is no access without destroying the windshield part of the aircraft. What a pain. To even get the receiver battery out of the plane I had to pry open the bottom fold under the fuselage as it was nested between the bottom and the aforementioned tray.

You won't like this answer, but this plane is hardly worth putting effort into to save, especially if it's just preserving the cosmetics. Poke some holes if you have to. You can put colored tape over them afterward if it bothers you.

I think that's what I will probably have to do. First time I've come across an unserviceable plane, LOL. It would be like building a car with no hood. I bought it because I have not flown in two years and need to brush up on my skills. If I wreck this I won't care. I just need the flight time. That's if I even manage to get it running.

BTW, the landing gear is supposed to be glued to the fuselage. ***? I have the construction manual and nowhere in it is the CG for this model. A goofball of a plane, that's for sure.

You might free up the carb with penetrating oil (like Liquid Wrench) or WD-40.

I've refurbished a lot of gummed up engines. Get it out of the plane, the take off the carb, glow plug, and backplate. Soak it in fuel for a few hours, and see what has freed up. Turn everything that will a few times to loosen up the varnish, then soak for the rest of the day.
After that, you'll be able to evaluate the bearings. If the crank spins freely and there isn't any roughness or notchy spots, your bearings are fine. If there is, soak in another day while spinning the crank every few hours to see if it improves.
Use a thinned toothpick to clean out the fuel inlet and spraybar.
Put all new O rings and gaskets wherever they are needed. I've used regular copy paper to make backplate gaskets before. I've never had one fail. Gasket maker works too. Don't skimp on the O rings though.
You can often save the glow plug by soaking it and swishing it around then applying glow driver heat to burn off the contaminants and soaking again. You might as well do it while you're doing the engine. It's $7 you don't have to spend if it works.

The durability of the Aicore's was from the Coroplast material it was made from And tthey were quite durable surviving horrendous crashes, This however was at a price and that was weight, The performance loss compared to common trainers of the time was reduced somewhat by using a higher aspect ratio wing (wingspan divided by wing chord).

The airplane was not an arf but instead a kit, Just a box of flat preprinted sheets that you folded at the lines and glued with plastic solvent.

The engine, fuel tank, battery, receiver and three fuselage servo's were all mounted to a giant chunk of plywood that would slide out in plastic channels as you noted. To remove the tray rudder and elevator clevis' were removedas well as the nosewheel that you mentioned. There was a small screw on each side just at or beside the engne that secured to ply tray to the plastic rails. Now it was not unknown for some folks to simply glue the ply permanently to the rails. If that's the case you are SOL and to gain access you will have to fabricate various access panels.

The airplane is a nice flyer and I did train a few with them but it will use more runway than others and it will snap roll off the ground if forced off too soon. Do not be tempted to use an oversized engine (anything over .46) as it will turn into a flying monstrosity, very unpleasant.

Balance it no further aft than quarter chord or the results will agine be very unpleasant. .

John:cool:

The carb is currently getting a WD-40 soaking. John, the construction manual says to use contact cement to adhere the Coroplast. Can I use epoxy as that is what I have.

Between this model and the Duraplane which one do you think was more durable?

Sure you can try to use the model epoxys and may get some service out of it,. Adhesion has always been the downfall of "Corroplast". The one epoxy that I do know of that would work is BVM Aeropoxy but of course the astronomical price tag for this product rules it out in this case.

A direct comparison between the Aircore and the Duraplane's durability is impossible. However the aircore is a far better flyer than the Duraplane or similar coroplast combat planes.

John

I made some progress. This is how I freed up the carb and the WD-40 definitely helped too.


https://cimg6.ibsrv.net/gimg/www.rcu...f4528a79ac.jpg

Now on to the radio dilemma. The plane came with an old Airtronics Vanguard system which I don't know if it is in working order. I don't think I should spend thirty dollars worth of new batteries to find out it doesn't.

https://cimg0.ibsrv.net/gimg/www.rcu...f703041843.jpg
https://cimg5.ibsrv.net/gimg/www.rcu...0ca08fb80e.jpg

Not the kind of RC system I would care to invest any money in, a not particularly high quality "one airplane/one transmitter" system of 35 years ago. Even though yes it may still be legal Its time you invest in a system you can grow with. Something you cannot do with one like this. or a whole bunch like this.

John

You're throwing good money and effort after bad, my friend. If you really want a coroplast plane, yank the engine and refurbish it right, then go to the SPAD forum and get planes for the Debonair. You will likely be able to use the wing from your Aircore. It's probably take you 2 hours to make a new fuselage that will be lighter than the one you have now.

I have a JR X6102 transmitter that I like a lot. Here's the problem:

1) The spare R700 RX I have decided to stop working.

2) Even if I get it to work or get another R700 I will have to replace the servos in the plane because, of course, the connectors don't fit into the newer JR receiver. Thankfully, I have Futaba servos that work with my R700.

3) Saving this old radio is not a bad idea because I can sell the complete plane down the road. Some guys look for complete running trainers to get into the hobby. I know, as I have sold them before. If I replace the servos and RX with the JR equipment it will be a tougher sell. For a beginner these old 72mhz radios are fine. The one in the original trainer was even more simple than this. It was a basic 4 channel, this one at least has 6 channels.

4) I have no way to test the Airtronics TX or RX because they have different connectors than the batteries in my JR stuff.

I don't care about the Coroplast construction. Rather, I just needed a trainer and bought this in a bundle deal. I should have kept looking for a traditional balsa trainer but it's too late now. I have get this rig up and running somehow.

I`m with you on working with what you`ve got in order to get up and flying asap, as long as you`re not putting yourself or anyone else at risk, or spending too much on it. You might try to find one of those plastic holders that you can load with regular alkalines just to see if that old radio system will work.

https://cimg4.ibsrv.net/gimg/www.rcu...f3474bc1fa.jpg
I made a lot of progress today. I ended up replacing the servos and receiver to make it work with my JR transmitter. All the control surfaces work as they should. I also filled the tank partially with fuel and tried to start the engine and to my surprise it rumbled to life immediately. It seems to run well but as soon as I remove the glow plug driver it dies. Here is the glow plug that came in the engine. It looks fouled probably from the WD-40 bath the engine received. I am guessing it's the original one. What is the story on these types of plugs with the bar through them. I also have a number 6 plug and was wondering if it is okay to use in this O.S FP Max engine? What is the ideal mixture setting, 1 and 3/4 turns?

The ideal plug for any FP's is in fact the OS #6 (formerly A3).

The Idle bar glow plug is from the dim past when virtually all model engines used some form of loop scavenging. The piston top dam tended to shoot fresh charge directly into the plug coils, tending to dampen the ignition resulting in poor idle and or throttle response.

Most all modern engines use a number of porting senario's with no piston top dams. Therefore the idle bar plug is somewhat redundant.

John

I made some more progress today. Ran the engine with the number 6 plug and it idles without the glow driver. Now I have to secure the RX battery in place, epoxy the bottom coroplast folds, epoxy the land gear to that, and finally balance the plane. Perhaps there is another way to secure the landing other than using an adhesive? This is in case I have to gain access to the battery in the future.

Yup, secure the mains with two bolts and large fender washers inside and outside. Plugs from wooden hole saws work well in situations like this.

John

I got the landing gear attached and the plane is ready to fly. I went to run the engine today and was wondering how you can tell it is running max RPM's without a tach? Maybe I am just not used to this engine but at WOT it doesn't seem to scream all the way, for lack of a better description. The idle is smooth and steady and the transition is likewise smooth without hesitation. Anyone know the ideal mixture setting on this engine?

I use the "pinch" test for my 2-stroke engines..

With the plane level and open full throttle: Quickly pinch (just long enough to stop fuel flow - less than half a second) the fuel line somewhere between the tank and the carb. If the RPM increases, you are not too lean yet. Lean the needle valve by a couple of clicks.

[for those with Remote Needle valve; you pinch between the tank and the needle valve]

After 10-15 seconds for the engine to "settle" then pinch the line again. When it "sags" or tries to die immediately, you are now at or past the max RPM (Too lean to fly) and need to back it out the needle valve a couple clicks.

Then, let it run a bit, test the transition from idle to full. If it no longer transitions well, you may need to re-set the idle mixture.

Then do 'nose in the air tests'.

Starting level, go to full throttle and then hold the plane pointed straight up at full throttle for at least 10 seconds, it should not sag or try to quit. Then bring the plane back to level.

Reduce the throttle to idle for at least 30 seconds - then tilt the plane nose up about 30 degrees for about 30 seconds. It may increase in RPM a little, but should not go to lean or try to quit (this is kinda simulating your landing approach).

It should keep running reliably in all of those orientations..

That's just my "generic" way of tuning a two-stroke if you don't have the manual..

Do NOT use this on a 4-stroke; gotta have a tach for them..

Thanks, TEBerg. I will do that.

Update. I got the engine and radio system working fine and went to fly the plane today and on Saturday. It's as if it lacks power or something and just won't climb. Flying brick is the best way to describe it. I think I should just salvage the engine and my radio system and move on. I tried at least. Good news is that the park flyer Cessna I purchased as part of the three plane deal flies fine. Anyone need an Aircore carcass for free?

So a k&b .61 would not work?