Prop selection

[Matt Vicaradge]

Hi All,

 

This is my first post and I'm looking for some advice on prop selection. I have an Art-tech Corsair with a nasty 3 bladed prop that makes belly landing seem a bit dodgy, I have no idea what size 2 blade to fit instead and how this will affect the power train, Has anyone done anything similar? Or can anyone offer some wisdom on the matter?

 

It would be greatly appreciated,

 

Thanks,

 

Matt.

[Stephen Grigg]

What size is the 3 bladed prop Matt?

[John Privett]

Matt, as a rough guide,  add an inch to the diameter when switching from 3 to 2-bladed props.  And conversely if you need to replace a 2-blade with a 3-blade then go down an inch on diameter.  Pitch should stay the same.

[Matt Vicaradge]

Hi, thanks for the info. The Prop got smashed to atoms and thrown away last summer following the "accident" I've only just started to think about a repair job.

 

The websites that stock this plane tend to be a bit light on technical details like prop size and motor power and esc ratings and pretty much any other useful info you may need.

 

Still I can't bring myself to buy a mainstream trainer when I can get this back in the air for a few quid!

 

Thanks again for the advice, I shall continue to trall the net for the prop size. 

[Matt Vicaradge]

I've been doing some digging and it seems I had a 11x6 so I guess I'll try out a 12x6

 

I also found the following site;

http://www.mh-aerotools.de/airfoils/propuls2.htm

This seemed to agree with what's been said here. 

 

Thanks again. 

[Roberto Gava]

I can't follow the link.

There is anything wrong?

Or it is my explorer.

[Matt Vicaradge]

Dont Know,

It seems to work when I use it, I'm using Chrome.

 

Its basically some calcs on power and prop sizing with formulas to convert from a 2 bladed prop to a 3 or 4 bladed.  

[Roberto Gava]

For this I use Extended Prop Selector software.

In my experience, I'm not shure of the figures of consumed power against declared power of most IC engines.

I tend to believe that declared power data are very optimistic.

Once I asked Thunder Tiger technicians by mail and they answered me that they declared power figures on 15% nitro fuel, low oil percentage and small props to get the engine into its high revs band.

For example, they declare 1.4 Ps on a PRO .46 and this engine, with a 11x6 prop gets usually about 11500 rpm, that according to the calculations of the software is around 0.71 Hp.

[John Privett]

Roberto,  the magazines used to include a power-curve chart with engine reviews.  These always showed that maximum power was developed at revs far higher than were commonly used - at least in Europe.  Maybe the Americans, with fewer noise-sensitive sites, used smaller props to get more revs, power (and noise) from their engines?