panzertank

i have mounted a engine on my avistar and i think ( to my best abililty and 1-2 hours adjusting) that it is on straight. but is there a way i can know for sure. someting i can make or get that will let me know?

alan0899

G'day Tank,
Look down from above, & standing behind the engine, with the prop horizontal, if it looks like it is straight or pointing slightly right, it will be fine.
But not to the left.

Flight testing is the best way to check.

meaden

You can measure from each tip of the prop (in the horizontal) to the same point on the vertical stab.

Like alan0899 said straight or slightly to the right (viewed from behind) should be fine.

kdc

Use a piece of cotton or thin string attached to the fin with pin to measure, its easier than a rule or tape.

Tired Old Man

My Feedback: (1)

Buy an incidence meter and follow the directions that come with it. If you're going to do any building or prefer checking an arf to see everything is in line with where it should be you need one.

da Rock

Using a prop to see how an engine points really is hard. Props often don't track both tips in the same plane. And measuring two differently angled tips is an art in itself.

I've got a couple of flat sticks I pulled out of the scrap bin years ago. I drilled a hole in their center (accurately located) and marked their centerline for measurements. It's amazing how much more accurately they work. Actually, it's amazing how inaccurate a prop can be for measurements.

You know how you measured the stabilizer when you installed it? Do the same with the stick/prop for the left/right thrust measurements. And when you turn the stick/prop vertical, you can compare it to the CL of the fuselage, but that's a real art.

BillS

I have often used wire (doesn't stretch) pinned to the top of the vertical Stabilizer. da Rock is correct about prop's not being very accurate and it is best to use only one blade of the prop an rotate 180 degrees. I usually measure the difference and calculate the angle. However during flight testing you are probably going to shim the engine for right thrust anyway.

Bill

Tired Old Man

My Feedback: (1)

You can also cut a circular plate about 16" (or less) in diameter out of 1/4" ply and drill a hole in the center for the prop shaft. Mount it on the engine and start measuring.

meaden

Hey, it's not a pattern plane...he just want's to know if it's straight or to the right a bit. Ultimately, the best way to know is to fly it.