Is there an analytical tool to help with prop selection for glow engines? I use Motocalc for my electrics but am not aware of a similar tool for glow engines. I would also be interested in knowing about simple graphical/emperical tools folks might use for glow engine performance predictions where prop size and pitch are input variables. (Props have been around a lot longer than computers)

This may be what you are looking for - [link=http://freespace.virgin.net/barry.hobson/software/thrusthp.html]ThrustHP[/link]

I use it when choosing props etc.

AB,

I have an Excel spreadsheet with exactly the inputs you have asked for. I can't remember now where I downloaded it from - it doesn't come up on a search, but if you send me your email I'll send the file to you.

Cheers,

Mick.

Have a look at [link=http://mvvs.nl/prop-power-calculator.xls]My calc sheet[/link]
It allows several approaches to the problem, and with a bit of practice you can pinpoint the prop you need.

Thanks for the answers guys. But is there a program like Motocalc for glow powered planes? It would be nice to do actual aircraft performance predictions as well.

I use(d) Ecalc a lot doing just that.
Define a motor 100 rpm/v 1 mOhm Ri and Izero=0.1A, and use that as a glow engine substitute.
Please use "realistic" power figures, derived from prop rpm reports that the engine is capable of.
The problem is, that an electric motor reduces power as it unloads in flight, whilst a glow motor gains power most of the time, resulting in better than predicted in-flight glow engine performance.