I figured I'd post this here in the beginner's forum since I am a beginner and this appears to be a "beginner type" question. I am flying a Trainer at my local club with an instructor. I have an OS .46 FX engine turning a 10x8 APC prop (see image 1). My instructor suggested that I get an 11x6 or possibly 11x4 prop instead of the 10x8, so I purchased. What a good student.

Now the interesting part. I have a 2" Dubro Spinner. The 10x8 prop fits perfectly, however, the 11" props are too wide to fit into the spinner! When I lay the 10x8 on top of the 11x4 the difference is quite startling. See image 2.

So my questions are:

1) Are there different "widths" of props that I need to be aware of (apparently so)? How does one tell? One prop says 10x8 while the other says 11x4 - nothing else.

2) How does one ensure that the prop they are about to purchase fits the spinner? Do I need to take the spinner with me to the LHS? What about online purchases ... how do I tell?

Am I wearing the dunce cap on this one?

Thanks all!

-MasterAlex