I've almost finished with my first airplane and could use a little advice. I built r/c cars and boats in the 80's, but this is my first plane. I went with the arf kadet lt-40 and was very impressed with the ease of assembly and the overall quality of build. My engine choice was an os 46ax. Here lies question number 1. Is it a terrible thing to use a fill line as well as vent and feed on my fuel tank? The 46ax has the needle valve on the back of the motor so my fuel line is about an inch long. This is a pain to take off to fill the tank. Can I fill the tank through the line between the carb and valve? (doubtful. but it never hurts to ask..)
My next question is the location of my rx antenna. Is it best to run under the plane like the book says or on top from behind the wings up to the tail?
Any help would be greatly appreciated. I hope to break-in engine thursday night. With good weather, my buddy (cert. instructor) & I can fly this thing on Saturday...

The 46AX is a great engine for this plane and you will be at 1/2 throttle a large part of the time.

Yes, you can use a 3-line fuel system. Connect a line to the third tube coming out of the tank for filling. You'll need to plug the line while running the engine.
Inside the tank you will want another line with a second "clunk" on it. This is needed to defuel the plane.
You don't want to fill between the needle valve and the tank or between the carb and needle valve. Either point would result in a flooded engine unless you clamp off the line to the carb or needle valve.
I prefer to have the antenna come out the top as it will not snag on things so easily(grass, branches, etc).

1.25 ton,
Instead of hooking up a 3rd line to fill the tank with, try this. Hook the fuel line on the inlet of the needle valve. then use a piece of brass tubing to "splice" it together with the line going into the tank. When it's time to fill the tank just separate the fill line where it's connected with the brass tubing.

On the receiver wire, you can route it either way that you want to. I prefer to have the antenna running along the bottom of the fuselage. But that is just a personal preference, either way will work just fine.

Hope this helps.

Ken

Edited to correct mistake.

Ken are you saying to fill the tank THROUGH the remote needle valve? You seem to be addressing a non-remote needle installation.

Hey, that 46AX is a HORSE!!! Good choice.

And it runs great on a 3-line tank. It really is going to be happier if one line runs from the tank to the muffler pressure connection that's already on the muffler. And that actually works great as the overflow line into the tank. If the inside of that line goes to the very top of the tank, when fuel fills the tank, it'll immediately flow out the muffler and you'll know the tank is full.

The second line would be from the clunk in the tank, out to the needle on the engine. And that line and it's little brother that goes from the needle fixture to the carb can be hooked up when you assemble the plane and you won't have to touch them again. because.....

The third line can come from the tank and go anywhere. It's tube into the tank can go anywhere in the tank you wish but just through the stopper works excellent. But the line from outside the stopper can go anywhere that's readily accessable. What you do is plug the end of it. There are things called "fuel dots" or you can go cheaper (and better) and just use a plug. If you want something that's made up already, there are some small black plastic ones sold by Tower and every hobby shop I've been in the last year. They're a buck or so and 4 to a pack. Or make your own. whatever..........

To fuel the plane, you grab the end of that third fuel line and pull the plug. Stick in your fueling line and crank away. I use a hand cranked fuel pump and slow down when I know the tank's about full and...... when fuel drips from the muffler, I stop cranking. Stick the plug back into that fuel line and you're good to go.

It's dead simple to rig.
It's dead simple to use.
It costs almost nothing.

Sorry, mistyped there. No, the line coming off of the back of the needle valve. thanks for the cover.

Ken

bruce88123,
edit........ oops I typed this while RCKen was typing his response. He don't need me to answer for him, and I really wasn't working to do that, only to fill in the idea of the disconnect being outside the cowl.

A lot of people route the line for a disconnect so that it comes out of the cowl to the disconnect and then back in. To do that takes a bit of extra fuel line. And you wind up with it hanging out. Needless to say, if the plane doesn't have a cowl....

Running a 2-line system appeals to some people. Truth is, 3-line systems work as well, so there really isn't any winning argument which is better at running the engine when you're flying the sucker. Plumbing either one isn't really much different either. So do what appeals to ya' 'cause both work great.

Thanks for the info- I think the three line setup will be the easiest option. The plug on my tank has the third hole in the metal caps so I'm halfway there.
-Any tips on break-in or tuning 46ax? The last engine I built was a 454 chevy, so this will be a little different...

I do what Ken suggests on my Avistar and WM T-34, both with os 46 fx`s . It`s easy and simple.

1.25ton,

We just did the same build(ARF) about a month ago.

We turned the needle to the horizontal position and left about a extra inch of fuel line so as to make it a gentle turn. No problem getting the fuel line off and on with the needle in the horizontal position.

We had major radio problems putting the antenna through the bottom as directed. It would flutter at 10 paces on the initial radio check. We think it was due to the antenna crossing the landing gear. We ended up running the antenna out the left side and to the top of the vertical stabilizer. Radio test went to 35 paces and we stopped... still no flutter.

Great plane and a great power plant... we are extremely happy with this set up.

Cheers,
Steve

Hey Steve, with the recommended setup was your plane nose heavy??
Thanks, Bill

No, ours was dead on... it could depend on your battery, receiver, etc.

Well, we survived Saturday's 18 mph winds and had six good flights. And one kinda bad one..... A gusty landing approach ended up with a couple of sheared wing bolts and a broken prop. The kadet is a very tough plane. Today I got another six flights and was able to takeoff, fly our est. tankfull and aproach before my buddy took over. After running r/c cars and buggys for fifteen years, this is a welcome challenge. I'd strongly reccomend lt40 arf and the 46ax (with a good instructor) to anyone looking into this hobby.

Sounds like you're well on your way to a great start. There's no turning back now, you're offiacially infected!