Fighterbird
 

A few days ago I read a post by someone (can't find it now) that suggested to get rid of the "wasted" prop that comes with this plane and buy a 5X5 carbon fibre prop. I was told by my LHS they did not carry them but they had a composite prop. So I got it and the adapter and it does not even push the plane on the ground!

Anybody have advice on a replacement prop for this plane that is markedly better than the original?

Fighterbird
 

You'd get better response if you posted this in the electrics forum.

Fighterbird
 

are you sure that you bought a pusher prop?

Highlander

Fighterbird
 

Come on! I know I'm new to this but I put it on the right way and it barely pushed the plane on the ground.

Fighterbird
 

sheeeesh Alrighty then ,but just for fun check it out , could be that you have purchased the wrong prop , would nt be the first time its happened ,


Highlander

Fighterbird
 

Being on the right way gas nothing to do with if its a pusher prop, a pusher V's puller the helix (?) of the prop is oposite, yes on an electric (and some glow like early ASP's) you can make the motor run oposite and use a puller prop BUT turning the prop round does NOT make it a pusher.

Fighterbird
 

1fly,
Yeah, humor us will ya'. Try turning the prop around.
(Highlander, with these electric things, you don't need a pusher prop.)

If you're another of the new guys who 'know it all', you don't need our help.

(My guess is, he'll turn the prop around, solve his problem, and never tell us. ;) )
Dennis-

Fighterbird
 

I will give it a try today. I really thought someone was yanking my cord when they asked if I put it on the right way. It did slightly push the plane forward the way I had it, but I will give it a try. And I will tell you the honest results!

I still did not understand, do I need to buy a pusher prop regardless of which way it is put on?

Fighterbird
 

Ifly

I will tell you I am no expert with the electric stuff,DB cherry says you dont need a pusher , I would believe him !!!!

Thanks for the info DB appreciate it ,

Highlander

Fighterbird
 

Yes, your airplane is a pusher and if you do no wireing changes to the motor to reverse it, you need a pusher prop. If you have an appropriate pusher prop installed backwards on your airplane it will still try to go forward but is very inefficient because the pitch profile is wrong. This is an old trick of early RC airplanes that flew with rudder only and climbed to steeply the prop was just turned around.

John

Fighterbird
 

Hmmmmmm;

very interesting !!!!!!!

Highlander

Fighterbird
 

Pftt pfttt excuse me while I spit out these feathers. I turned the prop around and it definitely worked better. I still need a flight test, but it was on backwards.
Sorry for my outburst but I thought I was get'n jerked around!

Now my question is what is the difference between a 5X5 and the suggested 6x4? I assume the first number is the diameter in inches and the next number has something to do with pitch??

5x5 vs 6x4
 

The first number is the diameter of the prop, and the second is the pitch. A 6x4 should pull (or push, in your case) harder than a 5x5, but it will have a lower top speed at a given rpm. Better acceleration, lower top-end speed. I'll let everyone else give the details, since I'm just a newbie myself :)

-Rick

Excellent Rick
 

And quite accurate. Normal rule of thumb dictates that to allow the engine/motor stay in the same RPM range (a desirable thing) that you need to increase pitch if you reduce diameter roughly one number or if you need to reduce pitch you increase diameter the same number.

The problem of this is when you reduce the diameter even though you will still move a similar amount of air by increasing the pitch but what you have done is increase what is called propellor disc loading, an important performance parameter and also applys to rotorcraft as well. The disc load is the aircrafts total weight divided by the disc area of the propellor. Increase diameter and decrease pitch or reducing diameter and increasing pitch will impart exactly the type of subtle performance changes described by Rick above.

By the way the second number 'pitch' is the exact distance in inchs that the prop would move forward in one revolution if it were operating in a theoretical solid.

Hope you found a little theory entertaining.

John :)