How would the prop torque of two props rotating in the same direction effect the roll characteristics of a P-38 like airplane? Would the distance of the props from the centerline of the airplane have any influience upon this roll characteristic?

Bryan S winneyte

Although opposite rotating propellors were common on the P-38 and other planes of its era, models generally have more serious
problems with engine-out than torque effects. Most P-38 models crash due to one-engine out. The surface area for the verticals just isn't sufficient to maintain (or regain) control when one engine fails. Determining -which- engine has failed can take too much time, and the plane get into an unrecoverable attitude before the situation is assessable.
One of our club members has made 3 of them, all large. The first two crashed on their first (and only) flights. The 3rd lasted maybe 10 flights.
Scaled properly, the engines are too far out from the centerline. Each has a serious asymetric effect when it is the only running engine.
Placing the booms no further out than to clear the prop to used would help here.
Enlarging the verticals also.
And even go to a directional gyro.

Tall Paul, what size P-38 was that one? I had a 56" wingspan P-38 that flew awesome with two os 25. Had one engine flame outs a few times and always landed safely. The plans called for 3 degrees of outward thrust on each engine to compensate for a one engine out situation. I also had an old cessna 310 but the plans didnt call for the outward thrust but thank god I used it. Seems your friend's P-38 wasnt built with that offset thrust and what you said is exactly what happened. The original P-38 had opposite turning propellers spining in a direction to overcome the rolling motion created by the prop torque during one engine out. I actually saw a small twin Stick with 049s that did exactly what your friends airplane did when one engine died. After inspection one one engine was straight and the other one had inward thrust. To honor murphys law.....the one who remain running was the one with inward thrust and................well the twin stick had a lot of sticks laying around.

But to answer Bryans question, assuming both engines are running properly you should experience very little difference when the airplane rolls on each direction.

Bryan,
I had a Royal P-38 that would just fine to either side with
both engines running.
If an engine died it would immediately roll over into the dead
engine, so it was always easy to tell which died. :-)
I would just throttle back to half throttle on the still running
engine, roll out and bring it back to the field. Heart stopping
but not impossible.
Jerry

The first P-38, about 70 inch span, crashed in level flight after a 180 turn from takeoff. Probably poorly constructed.
The next 2 were large Ziroli's. The first of these died when throttle control was lost on one engine, which couldn't be turned off.
When the other engine quit, it rolled over and died.
The 2nd died due to one engine failure.. same thing.
Outthrust on a larger airplane is certainly something to consider, but if you're into scale, only the Ju-52 and Sunderland used it!
P-38s, Mosquitos, Comets... all poor choices for models which are not electric.
Speed must be kept up to maintain directional control.
Some means of engine cutoff isn't a bad idea. This could have saved the Zirolis, had a seperate remote kill-switch been available to the experienced pilots stuck with flying those.
.
Before and after..

Oh damn, that looks like a nice model. It hurts to see it in the trash and its not even mine. I guess thats true about the scale factor. I dont build for scale looks so I do what would make the airplane fly acceptable without sacrificing too much. Shame you couldnt get engines to spin backwards like the cox ones. That would take care of the torque that creates the rolling motion when one engine goes out.

I'm not sure how this would relate to the models, but on the real P-38, the props rotated outward. This meant that engine torque only added to the woes when an engine quit. On later twin-engine aircraft (I think the Twin Mustang was one), the props rotated inward. This torque would supposedly help rather than hinder during an engine-out situation.

I don't know if this helps anything, or if it just fuels the flames.

And I'm also sorry to see that beautiful P-38 in that condition. Sorry about the loss. It looked like it would have been a fun airplane when everything was running right...

Bob