What is the difference in performance between these two?

1. An engine that is mounted left or right of the fuselage centerline
2. An engine mounted with greater or less offset that called for in the plans

Which one of the above would be easier to trim out during a maiden?

You would have to be a lot more specific to get any kind of meaningful answer. Shifted off centerline how much (and left or right) and how much more/less offset than specified? Since most engines are mounted left of and above the centerline to provide right and down thrust, I have to assume your first query assumes the thrust washer is not titled back to the centerline otherwise the second query is sort of redundant.

The engine offset is designed at 3 degrees, placing the engine cowl far off center and looking aesthetically really bad/odd. I want to bring the cowl a little bit close to the center line of the fuselage, and then trim out the plane in flight.

To do this I can put a small shim (washer) behind the engine mount and reduce the offset to about 1.5 degrees, or “slide the engine mount (about 3/16”) to the left which would bring the cowl toward the centerline.

No change in downward thrust with either option.

G'day Scratchie,

It's normal to have the centre of the propeller or the spinner backplate on the centre line of the fuselage, so yes it looks like your engine would need to go to the left by a small amount. Or to put it another way the hole in the cowl should be on the centreline so therefore the engine drive washer/prop/spinner backplate should be a well. The engine gets mounted off to the left to make that happen.

So the correct thing to do is to move the engine and keep the side thrust.

You probably won't notice if the engine position or angle is slightly out when you fly the model though, unless you are into precision aerobatics, so as close as you can get it will be fine.

Dave H

No significant acrobatics, I'm more of a builder than flyer - my goal is only to bring the plane down in the condition it went up in...

Thanks for your help, will post pics when the plane is done and maiden after the snow melts.