Prop size for fun fly?

[Trevor 25]

A general question about 3D fun fly planes (specifically my new Cougar 2000 with Irvine .39). Is it better the use a larger diameter smaller pitch prop (e.g. 11x6) or a smaller diameter larger pitch prop (e.g. 10x7). Also, is a fun fly better with a fast revving engine or slow revving? I think the smaller diameter might give better throttle response. Has anyone else got experience of this and know better?

[Darren 0]

I seem to remember some of the Hype 3D flyers using a 13x4.

 

I'm no 3D expert but I think you need big diameter and small pitch to give you fast acceleration/decceleration, after all you're not really interested in top speed.

[Nutz 0]

I think larger prop with smaller pitch but I am not 100% sure.

 

The larger prop will give you more thrust and the smaller pitch will give you faster acceleration. That’s my theory.

 

Maybe someone else can share there thoughts

[Lofty 5]

Steve Newman here

 

The bigger the prop and lesser the pitch the better for slow 3D or even F3A "patton ship" flying.

 

e.g I run a 13X6 on my Panic in the Avicraft Panic team " ", which is a good all rounder, but if I wanted to do much better / flater flat spins or even flat spin landings and take-off then I would put on a 14x6.........Also would have to change the CoG abit aswell to!

 

There are afew props out there made just for 3D flying, which are very wide & flat looking, with a very small amount of pitch.

But if you put one of them on, then that is all you will be able to do, that is why most people just stick with the well know prop sizes... e.g what the manufacturer say you should go with!

 

I know that APC do a IC prop, which is made / looks like a Electric prop, so you can get the performance you would get from an electric plane doing 3D or slow flyer, but on a IC engine!

 

The bigger the prop diameter and higher the pitch the longer it takes to get up to speed, but also mean you will slow down alot faster.....the prop acts like an air brake.

You will need to land at a much higher throttle setting!

Remember don't put a prop on the engine which is way out size / pitch of what they say to use! Can lead to back thing happening!

 

Also the better the prop, the more torque you get, so if you want to do torque rolls and torque spins, then you put a big ass prop on! You will not go anywhere fast, but you will prop hang nice as well as flat spin!

 

 

 

P.s I could be talking BS again or talking about something I haven't got a bl00dy clue about, but I've got away with it for 4 months now at work..........

Edited December 19, 2006 by Guest

[Nutz 0]

The bigger the prop diameter and lower the pitch the longer it takes to get up to speed, but also mean you will slow down alot faster.....the prop acts like an air brake.

 

I reckon that Steve bloke meant faster it takes to get up to speed.

 

But then again what does a heli pilot know................

[Lofty 5]

The bigger the prop diameter and lower the pitch the longer it takes to get up to speed, but also mean you will slow down alot faster.....the prop acts like an air brake.

 

I reckon that Steve bloke meant faster it takes to get up to speed.

 

But then again what does a heli pilot know................

 

 

Yes I also think he did as well, better edit it for him.................

 

He's up most of the night pracy for the Avicraft Panic team, which nobody in this club can get into.......which he keeps pointing out all the

time! So he going to make some mistakes, due to lack of sleep!

 

Also he wants to see if any of you are awake to spot the faults mistakes out

 

 

Or did he mean :-

 

The bigger the prop diameter & the higher the pitch the longer it take to get up speed!

 

We may never now!

[Spiffy 1]

Coarse pitch = maximum speed in the air but very slow getting up to speed-poor acceleration, poor braking effect - lower fuel consumption as a benefit.

Fine pitch =very fast acceleration and deceleration but low top speed, and higher fuel consumption.

 

It follows that if you choose a prop diameter too small with fine pitch the rpm will exceed the safe limits - probably overheat and seize. If you take the manufacturer's recommendation on prop size/ pitch then for 3D you can choose the next size up from the standard prop but lower the pitch, keeping the rpms in the useful power band for the engine. For 3D and limbo you need fast acceleration, and quick changes of power, so lower pitch from standard but prop size that gives the best power output in the engines useful rpm and power range. So if an engine's normal prop is a 10X6 for maximum power then you could use an 11X4 for example to keep revs high, with quick response, and good acceleration, but top speed in the air will be slower. A 10X7 would give higher airspeed but slower to get it up to maximum.

It's why modern aircraft have variable pitch props to keep the engines in the power band. Selecting fine pitch for take off for example, and coarse pitch and lower manifold pressure for cruising along, and using less fuel.

 

That's always been my understanding - so you suck it and see, have a selection of props to suit the type of flying you need.