whats a slow fly prop ?

[scuba steve]

hi guys,

 

i'm trying to replace the prop i got on a 2nd hand model.

 

on the back of the prop is written :

 

APC 10 x 3.8

 

when i google this to find a UK shop i keep getting the correct prop but is says 'slow fly'

 

can anyone explain this ? also what's 'pusher' or a 'tractor'

 

thanks

steve

[Tim Mackey]

First off, the writing is on the FRONT of the prop, so be sure to fit it the right way

Slow Fly means the prop is suited o slower lighter models only, and they tend to be more flexible and lightly constructed.

Pusher props are a throw back to IC days when you wanted an engine on the back to "push" the 'plane along. Because the engine only runs anticlockwise ( usually ) then a prop with the blades "pitched" the other way was needed.

Tractor = pull. Engine on front, so normal pitch blades.

Of course, we leccy guys have no need for such things, we simply reverse the direction of the motor and use a normal tractor prop - if fitting on a pusher motor configuration, then again...ensure the writing is always facing the front of the model, in the direction of flight.

[scuba steve]

right, so i put the writing facing outwards...got it

my model is a seagull extra 300 and the motor runs clockwise.

is it ok to buy the slow fly APC 10 x 3.8 prop then ?

i didn't know if there was a APC 10 x 3.8 non slow fly ?

steve

[Tim Mackey]

Nope the motor should run ANTICLOCKWISE when viewed from the front.

Prop fits with writing facing you as you fit it.

I wouldnt use a 10 x 3.8 slow fly on an extra 300 - I have the exact same model and it needs more pitch speed than a 3.8 will provide. I use a 12 x 6 regular (APCE)

 

"E" stands for electric

[scuba steve]

the motor is definitely running clockwise when viewed from the front....do you think that's why the prop was on backwards (with the writing on the back) which i'm pretty sure it was when i looked at the prop before i took it off ?

 

the 3 colour coded wires from ESC - motor are all matched too ???

 

shall i reverse the motor spin direction to anticlockwise by swapping the wires around ?

 

thanks for your advice on this by the way

 

steve

[Tim Mackey]

Possibly, but either way its WRONG!!

Ignore the colour coding, just swop any two wires with each other, and then confirm that

A) prop is fitted as I said before

B) motor and prop spin ANTI clock when viewed from the front.

[Steve Hargreaves - Moderator]

I don't want to rub salt into your wounds Steve but might this be the reason it crashed ?

 

A nice APC E prop of between 5 & 7 inch pitch is what you would probably need on your Extra...

[Glyn R]

Fitting a prop backwards does not alter the thrust direction but the prop will be aerodynamically inefficient. You cannot correct incorrect rotation by reversing the the prop. Just make sure the the prop is fitted at Tim says and the rotation is anticlockwise.

[Myron Beaumont]

I remember fitting a prop on backwards on purpose for first free flight trimming trials .

[scuba steve]

thanks for all the advice guys. i will do as instructed

 

i like to understand what i'm doing so can you point me towards links on, for example :

 

understanding electric RC plane flight....or things like that.

 

i'm seriously thinking of getting a Seagull Swift 40 Trainer 63" wing span. i want to chose motor, prop, esc, servo, battery for it but want to understand why i use what etc

 

many thanks

 

steve

[Tim Mackey]

Try HERE

HERE

[Tim Mackey]

HERE

 

HERE

[Gary Binnie]

Crikey Myron, I remember my dad doing that!!!

 

Also throwing a rag into it to stop it when it ran backwards (diesel), I'm confused now, what happens when you put the prop on backwards and the engine runs backwards as well?!!

 

Probably best not to launch it!

 

I have an RCM&E proper selector card pinned up in my shed, a free 'gizzit' with the mag some years ago, don't know if that could be done again and updated for leccie stuff? Some of the higher end motor company websites (AXI, Mega etc) give prop recommendations for different motors and aircraft combinations I think, worth a look in times of doubt!

 

GB

Edited By Gary Binnie on 29/07/2011 21:29:24

[Myron Beaumont]

Gary

Maybe you're a long lost son Did your dad wrap the engine (Mills .75 usually) in that rag after a crash and launch it vertically to see where it went as well ?

Sorry y'all ,H & S and all that .Oh dear . (and drifting off topic)

[Gary Binnie]

Yep, that's the technique he used, not read it in books though!!

 

To drift very slight more OT I do remember an engine falling out of a Luton Minor (Aeromodeller Plans Service) at Little Rissington, it just dethermalised itself down in a series of stalls, no damage!

 

Eric Coates was the scale judge if you remember him.

 

Happy days.

 

GB