Hi folks,

Could someone explain to me what the different prop numbers/types mean? (10/6, 10/7, etc.) I have a Skyraider Mach II with an Evolution .46 (my second plane) and I want to know what type of prop to use on it.

My first airplane was an Hobbico Avistar with an OS .40 and I never bother to change out the wooden prop that came with it.

I'm still fairly new to the hobby so my aerobatics are limited to the simple stuff. Rolls, a little inverted flight, the occasional spin and then mostly takeoffs and landings. I'm not particularly interested in speed but better climb performance (than the Avistar) might be nice.

Suggestions please? Thanks!

I think about it like a manual transmission in a car. The last number in prop size being the gear. The higher the number the less RPM and more speed. The lower the number the more torque (pulling power), higher RPM and less speed.

With a .46 you can run a 9/9, 10/6, 11/5 or if you have the ground clearance---a 12/4 would give you excellent climb.

Looky here!!!!

Jett's chart pretty much spells out prop selection. You just need to remember this simple factoid. Pitch=speed, diameter=power. Pitch makes the plane go faster. Diameter (or length of prop) gives you more pulling power. You want a low pitch long prop for what you are asking for. Also to go up and down in prop sizes. You trade 1 for 1. In other words a 10-6, 11-5, 12-4 and so on would have about the same load on your engine. You can go the other way too 10-6, 9-7, 8-8. This is aproximate and is a good guide for experimenting.

I would lastly like to point out that different prop manufactuers props are not the same. Master Airscrew props load an engine differently than APC's. So when experimenting use the same brand and model prop. MAS makes several different series of props and they are all different. And plastic and wood are also different. You will get different loadings there as well.

Basicly pick a brand (I like APC's) and model and stay within their range and you should have no problems.

Mark Shuman

PS: This is for standard engines with standard fuel. Rinning high nitro(20% or more) and using tuned exhausts will change this. They are for more experienced modelers and I will not go into the changes for these applications here. Unless someone wants me to.

example:

10x6 prop: 10 represents the diameter of the prop in inches. 6 represents the number of inches the prop would travel forward in one revolution of the prop if the effeciency were 100% (no slip).

9x9= fast

12x4= slow