La 46 breaking to hard.

[Ron Hess Sr]

I have a os la 46 and the break is to strong,it comes on @8 and stays on until level again? suggestions on how to 4/cycle more. Thank you. Ron.     here is the setup.
11.5x4 apc -T.bolt plug.
10/22 powermaster 1/2-1/2.
.282 venturi and ST.nva and 1-head gasket.
scott dinger muffler with no pressure.
B.line air filter with green screen.
6.oz uniflo tank.

[Gene O'Keefe]

One or two head shims / try 5% nitro / try 12.25 X 3.75 APC prop .. and read "What is your set up for LA 46"
in engine section.

[Ron Hess Sr]

One or two head shims / try 5% nitro / try 12.25 X 3.75 APC prop .. and read "What is your set up for LA 46"
in engine section.

Thanks will repost there. 

[Bruce Perry]

I like the 5% suggestion too.  I would try an 11 x 5 and richer.  We use stock 46's here with that prop and it's a near perfect stunt run.  We're using Sig 5% champion fuel.  Allana has had her best success with this combo.  To be fair we did try other props but they need the RPM's too high (lean) to get acceptable lap times.  This lean setting caused issues exactly like you're describing.  It would come on and stay on, sometimes allowing a severe whip up in consecutive loops.  Things like the hourglass were awful since it would break on the downward leg. 

The 11x5 fixed all that.  Richer, more hold back, no runaway, good lap times, strong tension. 

Try it.

B

[Brian Massey]

I'm running an OS LA 46 on a 52 oz Trophy Trainer. Tried the APC 12.25 x3.75 and got crap for results. Then tried an APC 11x4, better, but still not "ideal". Finally I quite trying to make a (cursed) uniflow tank work and went back to a "standard" clunk tank with muffler pressure. Fiddled a bit and wound up with an Xoar 11x5. I now launch at 9750 and have very sweet, very consistant runs. Oh yea, all this on PowerMaster 10/22.

Brian

PS: Did you know that fuel will quickly ruin the rubber bands that hold your tank in place . . . ask me how I know.

[andrew stokey]

Brian, try making rubber bands out of different side bicycle inner tubes.  Last a long time.

[Brian Massey]

Brian, try making rubber bands out of different side bicycle inner tubes.  Last a long time.

Sounds like a good idea; thanks.

Brian

[Bill Heher]

Find a real hardware (not Home Depot or Lowes) store with a good selection of O-rings. Buna-n and Viton type are fuel proof. They last and don't stretch out and lose tension.

[Mike Haverly]

"Finally I quite trying to make a (cursed) uniflow tank work and went back to a "standard" clunk tank with muffler pressure."

You know, there is nothing wrong with muffler pressure *with* the uniflow tank.  In fact, it is preferred by many people, including me.  My LA 46's run best set up this way with a .272 venturi and the APC 12.25 x 3.375.  Don't need head shims.

Mike

[Doug Moon]

Clunk tank with muffler pressure is a good start. 

I have found more nitro yields more 4 stroke throughout the pattern. 

If you go down in nitro you may get more break but it will be softer which is ideal. 

You will just have to try props until you get the closest off and on power delivery.

[Dave Hull]

Ron,
I ran thru all of those combinations with a .46LA on a Cardinal except for the low nitro options. I got a very good run with the stock muffler, but I wanted to lighten up the nose, so I tried a Dinger muffler that I had. That change forced me to retrim the plane and also add about 3 feet to the lines because it put out more power and broke a lot harder. After I got it trimmed, I liked it better that way and left it. But of all the factors, I found the muffler was the biggest one. With the Dinger muffler, I didn't find the supposed magic of the APC prop, and am running an 11x5 woodie that the pro-stunt guys here kid me about....  ("Looks a lot like a prop kit to me. When you going to put an airfoil on that lumber?")

Dave "McSlow" Hull

[Phil Coopy]

On my LA46's, Carl SHoup turned me on to the idea of removing some of the head material in the combustion chamber to lower the compression. According to what I have read on 2 srtokes, adding shims moves the squish band away from the top of the pistion which will create inconsistant flame front, which translates to uneven rotation, which makes accurate needle settings difficult and sensative.

Below are pictures of how the problem of runaway was solved on both 40's and 46's. Top is stock, bottom is modified.  Solved my runaway problems in hot Florida.

Phil

[Clayton Berry]

I liked the APC 12.25 x 3.375 on my Cardinal.  It didn't work at all on a 38 Special lookalike I built. I liked the 12/5 Rev Up for it (it didn't have enough forward speed with the APC).  5-10% with 22% blended oil.  Don't know what the venturi diameter is.  ST NVA - in the venturi.  Tongue muffler.  Tank as close to the cylinder as I could put it. 

How long does it run on 6 ounces?  I use a 4 1/2 oz uniflow.  A closer fuel pick up would likely soften the break as well (by using a shorter tank length).  These things like to rev.  But the one I have runs great.  I even used it on a slightly stretched Twister lookalike.  With the APC 12.25 x 3.375, again.

That's my story, and I'm sticking to it.