Adding flat washers under front of engine lugs. Still a practice ?

[frank mccune]

        Hi :

         Is this still a practice?

                                   Tia,

                                    Frank

[Terrence Durrill]

            I stopped putting offset washers under my engine mounts in the mid-1980's.  You will never miss them.            

[Dave Hull]

You may or may not want engine outthrust on a profile. Accomplishing this by putting flat washers under the lugs at the front two holes is the least desirable method. Any kind of wedge/shim--aluminum, phenolic, maple, molded plastic--is better in the long run. Washers on Lite Ply is a complete waste of time, if that is what you are up against.

Divot McSlow

[Peter in Fairfax, VA]

Brodak has thrust wedges, if that helps.

http://brodak.com/engines/engine-accessories/thrust-wedges/thrust-wedges-1-2-3-degrees.html

[Brett Buck]

        Hi :

         Is this still a practice?

  Yes, if I wanted to use offset, that's how I would do it. Put it between the engine mounting lug and aluminum engine pad.

    Brett

[Clint Ormosen]

  Yes, if I wanted to use offset, that's how I would do it. Put it between the engine mounting lug and aluminum engine pad.

    Brett

Yup, that's how I would do it too. But odds are you'll find engine offset a complete waste of time.

[Sean McEntee]

One of Bob Whitely's "Things that work" is 1 degree out thrust.  Stunthanger hobbies sells out thrust wedges in 1, 1.5 and 2 degree increments. 

[Ken Culbertson]

Much has been said about this over the years.  My 2 cents is that each design achieves line tension differently and even planes of the same design may differ.  Offset is only one of 5 or 6 things that determine line tension and the most important thing is that you achieve it, not necessarily how.  Engine offset is most effective in keeping line tension overhead when the lines go slack.  It is easy to adjust on a profile but rather hard on a full body fuselage.  Personally I build in 1-2 degrees and a touch of down thrust.  IMHO it is pointless to wast time on anything other than "wings level" trim until you achieve adequate overhead line tension and whatever works is what I use.

Ken

[BillP]

I've been using washers since first learning to fly and they worked fine...but in the last couple decades use homemade (alum or wood) and then Brodak's thrust wedges when he started selling them. If I use washers now its over the thrust wedges to tweak offset.

[Steve Helmick]

My opinion is that a bit of offset doesn't make the model fly much differently, BUT...WHEN the lines go slack, they will tighten up much quicker with offset than without. If you have to fly at a turbulent site, it can save your plane.    Steve

[Dan McEntee]

   When you look at a C/L model out on the end of the lines, and the center line of the fuselage as a tangent to the circle, the nose of the airplane is ahead of that tangent, and in effect already has some offset. The purpose of any out thrust of the engine is to counter engine torque. Like Sean mentioned, this was outlines pretty nicely in Bob Whitely's article "Things that always work." I usually add a degree of down thrust also. If you look at any R/C model, it has at least three degrees or more for the same purpose along with some down thrust. Free flight models also use this as part of a basic trim set up. Too much thrust and rudder offset can make a model crab to the right and that isn't good, so you shouldn't over do it.
   Type at you later,
   Dan McEntee