Wing-Ding

I wanted to make sure I understand the correct way to refer to thrust angle direction. If, for example, I am sitting in the airplane (pretending to sit) and there is some right thrust angle, does that mean the crankshaft is pointing a bit to my right?

I wanted to be sure since, using the above convention, the crankshaft of the mounted engine is actually pointing slightly to the left. Does anyone know a reason why this would be beneficial, or do I have an atypical ARF? I read a lot of the threads about thrust angle and I think I understand it, I'm just surprised to find left thrust on the 4*60 ARF.

Thanks.

cappio777

My Feedback: (2)

I think he meant looking from the front of the aircraft.

Wing-Ding

Actually, in my second paragraph I meant if you were sitting IN the plane (hypothetically) the crankshaft of the mounted engine in my 4*60 is pointing slightly to the left. It's my understanding that this is the wrong direction- if anything you want it pointing right (right thrust). Is that right? Thanks

Tired Old Man

My Feedback: (1)

The usual way is to have 2 or 3 degrees of right thrust. You would be correct in presuming that the front end of the crank would be slightly to the right of the aft end when you are sitting in the plane. I do hope that you are extremely small in stature if you intend to try sitting in the plane.

A lot of the new ARFs' have a unique motor mount that builds in the thrust angle when you mount the engine. If your mount comes in two halves, check to see if changing the mounts to the opposite sides of the engine will change your thrust angle to right thrust.

If not, install your engine at the angle the firewall is currently at. When you take it out for the first time, do several taxi tests prior to flying it. If the plane wnats to severely turn left at medium taxi speeds, install a washer or two under the left motor mount legs, between the motor mount and the firewall, to acheive right thrust.

The condition you have is not that big a deal to correct. Just remember to take (4) number 4 or 6 washers to the field with you on the first day of flight.

Wing-Ding

Thanks, Silversurfer. At one point, I was curious about whether or not the left thrust was caused by the motor mounts or the angle of the firewall. So I kept the motor mounts attached to the engine, but removed it from the firewall. I then put the engine and motor mounts on a flat surface with the crank sticking straight up. I placed a straightedge on the prop washer and then measured from each end of the straightedge to the flat surface. The measurements were the same. So the firewall must be out just a bit. I put two #6 washers between the firewall and the left side motor mount (viewed from sitting in the cockpit- that was quite a squeeze getting in there). This makes the crank just about perfectly straight. I will take your advice about bringing washers along with me so I can trim out the thrust angle if I need to during the first few flights. Thanks.