How do I determine what spinner sizes I need to get for my:

2 Stroke 40
2 Stroke 53
4 Stroke 52

If it help I have 10x7, 11x6, 12x7, 13x6 props for each engine based on power.

Thanks

I wouldn't buy any spinners until you have the engines installed in models. Usually the plans or instructions tell you what size of spinner is needed. Good luck, and welcome to RCU.
Bill

Spinner size is determined by the cowl.
What size do you need to look good on your cowl?

Makes sense... I was thinking it's based on the thickness of the prop but now it makes sense as the props width are normally the same as the pitch is noramally 6-7 and the length could vary...
Get a spinner size which looks good and complemtns the cowl.

Just as a note the 2 stroke 53 is going ina WOT 4 and the cowl is from carbon copy UK, its a glass fibre cowl.. with a 12x7 or 13x6 prop, havent decided yet!

Keep in mind that most spinners need to have the prop slots enlarged. Most spinner MFGRs cut the smallest hole they think will be needed because you can make it larger if you need to, but you can't make it smaller.

Good time for many of you to start thinking about asking for a Dremel Tool for Xmas!

If you are building a model from scratch, & have the freedom to make the cowl any size within reason -- for optimum aerodydamic & prop efficiency, the spinner diameter should be in the range of 20%-25% of the prop diameter.