Someone once told me that the prop should have a blade at the 2 o'clock position when you turn the engine and it hits "that" compression point.....is this true? Something about airflow and the timing of the prop spinning in front of the carb.

I was taught to have the prop horizontal when it starts to hit compression just to aid in dead stick landings.
I really don't think it makes any diffirence in the way the engine runs. If it does it would not be enough to notice.

Timing's going to be the same no matter where the prop is. For me, it's just a matter of preference. I like mine at 9 and 3 O'clock. That way if I have a dead stick, or I ignore my timer and run out of fuel, I have increased my prop survival rate on a less than perfect landing.

Putting the prop in the 2 o'clock position comes from when an engine is started by hand. When the prop hits compression at 2 o'clock it's in the perfect position to "throw" the prop through the compression with a chicken stick. There is no timing or any other reason to position the prop like this.

For dead sticks you actually want to position the prop so that it is in the horizontal position (level with the ground). This way it's very difficult to strike the prop on the ground when you land. You also want to position the prop like this on planes like the Sig Wonder and Lanier Shrike that have no landing gear and are landed on their belly. When the engine is killed for a landing it will be level with the ground and won't be in the way when landing.

Hope this helps

Ken

i always set mine that way and because like was said here if you have a hard landing or bounce you will almost every time nick or break your propeller.

I would rather buy a prop than a finger/arm...(insert extremity here). Putting TDC at 2/8, or something close, is what I do for safety. I hand-prop all of my planes because ..... I have to.

Once, in a hurry, I mistakenly installed a prop at 3/9. It scared me so much that I flew once and re-installed the prop before the next flight.....comfort is comfortable.

I like mine set at 2 o'clock and as Ken said it is mostly for hand starting. If you set it there and just kind of flip it toward that position it will come to rest at 3 & 9 so it works out both ways. ENJOY !!! RED

I set mine to about 2 O'Clock

Actually 1:30

1:37pm on the first Tuesday of the month if you really want to get critical

Mike,
Thanks. I needed a good laugh this afternoon!!!!!!! This did it!!!

Ken

As said above, it doesn't effect the performance, but it is always nice to have it horizontal when the engine shuts down.

Happy Spinning!

So nothing then in the suggestion that having the prop at 90 degrees to TDC helps counteract the natural imbalance of a single piston engine?

I've always positioned props at 3/9 when the piston is at 12 (so to speak) irrespective of how the engine is positioned in the plane. have to admit that I've gone through quite a few props over the years but still got all my original engines...

Andy

Since a prop should be balanced, placing it should not do anything to counteract any balance or imbalance.

BTW, checking the balance of all your props is worthwhile if you'd like to keep not just your "original engines", but all your radio equipment and the airplanes they control for you. The props don't have to be absolutely perfectly balanced, but you do need to correct one every so often.

There is a school of thought that you're referencing.
Single cylinder engines that have cranks at 90degrees to the piston travel cannot be perfectly balanced. There are a couple of forces generated that can't be counteracted. So some people have suggested a somewhat "mystical magical method" of using an unbalanced prop to solve that imbalance. It works in theory. Lots of things do. But in practice this concept isn't worth doing.

That's why I don't bother balancing props.

Fair enough, so I'll position my props to avoid the ground from now on...

Thanks,
Andy

The theory is that you put the heavy blade of the unbalanced prop on the same positon as the crankshaft counter-balance. Then the engine runs smoother, and you don't have to balance the prop. Very useful when using wood props that may not have a constant density.