OS40FS prop size?

OS40FS prop size?

Post by Stev » Wed, 23 Jun 2004 08:00:14



I'm considering using an OS40FS in a fun fly type plane, and wonder what sort
of performance I might get out of an APC 12.25 x 3.75 wide blade prop.
Anybody try this and have some RPM figures?  I'd probably use 5% nitro fuel.

Thanks,
--
Steve

 
 
 

OS40FS prop size?

Post by Stev » Thu, 24 Jun 2004 23:12:17


Quote:

>I'm considering using an OS40FS in a fun fly type plane, and wonder what sort
>of performance I might get out of an APC 12.25 x 3.75 wide blade prop.
>Anybody try this and have some RPM figures?  I'd probably use 5% nitro fuel.

>Thanks,

I'm still looking for this information.  rcfaq.com seems to be down, and I
can't find any other source of rpm & prop sizes at the moment.  The OS
Engines site lists props up to 12x7 for this engine but give no indication of
RPM.

So if anyone has this information - OS40FS RPM figures with a 12.25x3.75 prop
I'd be grateful for your help.

Thanks,
--
Steve

 
 
 

OS40FS prop size?

Post by Dr1Driv » Thu, 24 Jun 2004 23:40:00


Quote:
>So if anyone has this information - OS40FS RPM figures with a 12.25x3.75 prop
>I'd be grateful for your help.

For a Fun Fly-type plane, you need pull, not speed.  The .40 can easily handle
an 11-4 or even a 12-4.  Don't worry about the "recommended" RPMs, just
concentrate on how the plane flies.
Dr.1 Driver
"There's a Hun in the sun!"
 
 
 

OS40FS prop size?

Post by Stev » Thu, 24 Jun 2004 23:45:35


Quote:


>>I'm considering using an OS40FS in a fun fly type plane, and wonder what sort
>>of performance I might get out of an APC 12.25 x 3.75 wide blade prop.
>>Anybody try this and have some RPM figures?  I'd probably use 5% nitro fuel.

>>Thanks,
>I'm still looking for this information.  rcfaq.com seems to be down, and I
>can't find any other source of rpm & prop sizes at the moment.  The OS
>Engines site lists props up to 12x7 for this engine but give no indication of
>RPM.

>So if anyone has this information - OS40FS RPM figures with a 12.25x3.75 prop
>I'd be grateful for your help.

>Thanks,

OK, I think I'll give up on this.  I was looking for maybe 10500 RPM, and now
I don't think I'm going to get it from this engine.  I'll stick to 2-stroke
for this one.
--
Steve
 
 
 

OS40FS prop size?

Post by Stev » Fri, 25 Jun 2004 00:01:08



Quote:
>>So if anyone has this information - OS40FS RPM figures with a 12.25x3.75 prop
>>I'd be grateful for your help.

>For a Fun Fly-type plane, you need pull, not speed.  The .40 can easily handle
>an 11-4 or even a 12-4.  Don't worry about the "recommended" RPMs, just
>concentrate on how the plane flies.
>Dr.1 Driver

Sure! - but knowing the RPM I can calculate the thrust, and I figured RPM
would be the most likely figure to get.   I've flown it on a .37 with an 11x4
and need a little more grunt out of the hover.
Standard muffler limits me to 12000, a pipe gave me 13400 all with an 11x4
APC.  Pipe is much heavier of course and doesn't help with the balance I'm
seeking!  There's no room to move anything around so adding weight to
compensate is the only option - not a good idea in this plane!

I'd just wondered whether I might do better with a 4-stroke as torque/speed
curves for 2 & 4-strokes are quite different, and sometimes the lower
absolute power from a 4-stroker can still win the day with the right prop
choice.  In this case I would have a net weight loss on losing the pipe, and
might just have gained the rest in a more efficient prop at slower speed.
--
Steve

 
 
 

OS40FS prop size?

Post by Morris Le » Fri, 25 Jun 2004 06:01:37



Quote:


> >>I'm considering using an OS40FS in a fun fly type plane, and wonder what
sort
> >>of performance I might get out of an APC 12.25 x 3.75 wide blade prop.
> >>Anybody try this and have some RPM figures?  I'd probably use 5% nitro
fuel.

> OK, I think I'll give up on this.  I was looking for maybe 10500 RPM, and
now
> I don't think I'm going to get it from this engine.  I'll stick to
2-stroke
> for this one.
> --
> Steve

Good idea.  2-strokes have better power-to-weight ratios than 4-strokes.
You want to keep a fun-fly type plane as light as possible.

Morris