Gentlemen,

What is the current amount of Engine Offset being used by the top contenders on their aircraft?

Is the same Engine Offset used for a 0.40 thru 0.75 cubic inch engines?

Is anyone using 0.0 degree Engine Offset?


Thanks for your advice.

t michael jennings                                                 
Knoxville, TN

Though not a top flyer, I generally put just enough downthrust to insure there is no upthrust and just enough offset to insure that there is no inset (if that makes sense). I go for a 1/4 degree of both downthrust and offset. When measured, it's very close to 0-0.

I used to think that most of the top flyers used a 0-0 setup, and was much surprised when I got a set of plans for the Chinese Skywriter, which won the World Champs a couple of times in the late 80's.  Those plans show 3 degrees of engine offset (side-mounted .60 engine).  

Kim Mortimore

Yup, you got it right. Two world champs told me the same...use just enough outboard offset to insure that you have no INBOARD offset.

Guess what I do?


W.

Mr. Powell,

What method do you use to get down thrust?

I seem to remember several years ago, there was a plastic wedge product that came in 1-2-and 3 degrees.  It was used on profile models for engine offset.

Are the wedges still on the market?

How should one get 1/4 degree down thrust on their engine?

Thanks for the info.


t michael jennings                   
Knoxville, TN.

Sams Hobby has the plastic wedges you remember.  It seems about a buck and a half or so.

Over .40, I have not been using engine offset but have, in some cases, added rudder offset.  I found that on a "porky" plane with a .40 at about 44-47 oz. can get real "loose" at the tops of some inside loops when flying a little slower lap times.  When that happens, the plane has no line tension and sort of goes where it wants.  Not a good thing.  A little rudder offset will "coax" it to fly away from you when it "gets loose" so you still have some slight tension.  This happens to me at anything over about 5.2 sec lap times.  At 5 sec. lap times there is not so much an issue but I don't always "hit it just right."

The down side, of course, is that more yaw gives more "surging" of the engine at the end of the run so there is no sharp engine cut off. 

Please bear in mind that I am by no mean a great flyer but because of that, I have built and "tweaked" a number of planes.