Because I grew up around them and not electrics, I am more favored toward glow engines. The amazing thing I found is that although the general rule of thumb is to select a prop that takes advantage of its highest horsepower usually at its peak RPM, that some engines have an amazing torque curve at the lower RPM end.

The unsung .020 Pee Wee is such a torque engine. Change out the Cox 4x2 prop for a 5.25x3 prop, it will spin at a lower RPM but on a trainer / sport type aircraft, will maintain the same flight speeds but gain an additional minute of run time.

Cross scavenged Enya engines are like that too. Mid 1960's Enya .09-III TV flew an .049 ARF foamie like it was powered by an .049 with a 7x3 prop, which did not take advantage of its horsepower that peaked at a lower RPM. I imagine that a Tee Dee .09 would probably sing with such a prop. (I don't have a TD to compare with). Yet, with a 7x6 prop, it moved out with authority. I probably would have gotten similar results with an 8x4 prop.

But, since I already attained to senior stage, that Tee Dee .09 in a 36 inch biplane like Lee Renaud's (designer of the Q-Tee and S-Tee) Airtronics Gere Sport or 46 inch Hobby Shack The Real Thing parasol would probably be more like my speed. But, there is some truth in the analogy, "How many seniors does it take to replace a light bulb? Only 1, but it might take him all day."

NIce points about some of the older engines. For slow flying, fairly high drag types, I'm with you on the prop selection. The sound is nicer that way too.

I recommended the TD 020 because the model in question is very slick, low drag. We've had a lot of models similar to this in our club. They go pretty fast, and they are quite light, as this one is according to the specs. With an 049, I'd probably go with about a 5x4 prop so it would move out.

Just passing through here... don't normally visit 1/2A. But to GallopingGhost's point, yes the most direct way to compare an electric setup to a glow setup is by prop size and RPM. If you look at those "46 sized" electric motors they try to put on .40 sized planes... it's just ridiculous... e-fliers are spoiled from a power to weight stand-point and they get used to 1.5 or 2:1 power to weight ratios. A 46 sized electric motor will spin a 12x8 prop at 10-11k RPM. Does that sound like a .46 glow engine to you? lol

Originally Posted by ChillPhatCat

A 46 sized electric motor will spin a 12x8 prop at 10-11k RPM. Does that sound like a .46 glow engine to you? lol

Interestingly enough, I did a look-see on Sceptre Flight's archive of engine review articles, both for the earlier cross scavenged engines of the 1950's to mid 1970's and various Schneurles. Engines that typically use a 12x8 prop appear to be your run of the mill sport .60's Schneurles, for example:

sceptreflight.com Model Engine Tests: .60 Engine Shootout May 2003 MAN

Look at the performances of the engines on the 12x8 prop. No, it does not seem to match a .46 sport engine, which interestingly enough resorted to 12x6 max overall. Seems a 12x6 prop was the largest typical used on the .46's. The MDS .46 peaked around 18K on its stock silencer, a very respectable performer, but then in its own right the Russians didn't collude with American or Japanese manufacturers on that one.

(I speak hypothetically, because I am a smaller plane flyer and have not flown a plane using anything larger than .35 displacement. )

The electric RPM in 10-11k RPM is typical of the cross scavenged engines of the 1960's or earlier, before Schneurles become prevalent. For example, Peter Chinn's April 1962 Model Airplane News engine review: sceptreflight.com Model Engine Tests: Veco 45 RC (2nd review):

The manufacturer's recommendations include the use of the 12x6 Power Prop or 11x6 Top Flite propellers, Veco 108 bar type plug (as supplied) and K/B Supersonic-100 or similar mildly nitrated fuel. Our engine turned up 8,900 rpm on the 12x6 Power and 9,900 on the 11x6 Top Flite. We got 8,100 on the 13x5-1/2 Top FLite and 9,850 on the 12x5 Power-Prop - all on 5 percent nitro fuel. These figures are, of course, very good. Even so, Veco claims that 11,000 rpm on the 11x6 Top-Flite can be expected after a total of 8-10 hours have been logged using Supersonic-100.

As the performance curves show, maximum torque is reached at a moderate speed and power is developed where it is needed most, corresponding to the prop sizes best sutied to R/C work. Our test 45 R/C developed just on 0.63 bhp at approximately 11,700 rpm, an excellent performance but one which, we feel, the Veco can still better in due course.

The RPM numbers match for a control line flyer. Running burbling rich in a 4 cycle or 2 cycle. (Not all engines can 4 cycle like the venerable Testors McCoy's.) Those type RPM speeds were also typical of the older cross scavenged glow engines of the 1950's and 1960's. The Testors McCoy Red Head's peak HP was at around 11,500 RPM. (But because of the weaker metallurgy, one would expect may be 8K RPM burbling rich on a CL plane. Run it lean, it won't last long.) Because of the slightly lower HP of the cross scavenged, one can put a Schneurle .25, .28 on say a 42 inch wingspan Ringmaster, which will pull it through the stunt cycle same as the McCoy .35.

However, whatever engine used on the discussion ARF would be a good testament to flight at the 2022 Small in Arkansas, I imagine.