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Engine basics => Engine set up tips => Topic started by: Dwayne on April 06, 2008, 04:33:40 PM

Title: LA .40 rpm
Post by: Dwayne on April 06, 2008, 04:33:40 PM

Hi all
I know this has probably been asked a zillion times but what is the take off rpm for a th LA .40, I'll be using an 11/5 prop.
Thanks

Title: Re: LA .40 rpm
Post by: Joe Messinger on April 06, 2008, 09:46:08 PM

 I don't rely on a tachometer too often to tune (mixture) my engines.  I usually try to adjust the needle to where I think the exhaust note -sounds -about right.  Fly the plane and make more adjustments if necessary.  After awhile, you can recognize the exhaust sound that produces the best engine run.

That being said, I have checked rpms and on the LA.40 engines I have, 10,000 rpms + or - a few seems about right.  I use APC 10.5X4.5 props on most of the .40s.

I'm sure others have differant methods that work for them.

Joe

Title: Re: LA .40 rpm
Post by: Alan Buck on April 07, 2008, 06:54:00 AM

I launch my la40 at 8800 to 9000 with 11/5 zinger on a cardinal 5% nitro . 62ft lines 46oz in weight and a tongue muffler

Title: Re: LA .40 rpm
Post by: Mark Scarborough on April 07, 2008, 08:39:49 AM

Dwayne,
It makes some difference whether this is a profile or built up airframe. profiles tend IMHO to pick up more rpm as you launch as a result of the head pressure in the tank changing, because the pickup tube is farther outside the needle valve than on a built up.  That said, My LAs launch on my profiles at about 9800 with a 3.75 pitch prop and a .282 venturi, Note however this is a .46