Question about engine size ranges

If a model states a wide range of engine sizes (eg .19 to .35) how does that work? Is it that a .19 at full power will just about lift it and fly half decently, and a .35 if set to 4-2-4 will supply the right amount of power for level flight (4 stroking) and loads of power for manoevres (full power 2 stroking)?

It seems to me that I'd like to try a 424 setup, but I suspect that my engines need to be at full tilt in their current models to even begin a turn respectably. I may be wrong, maybe the power would come in just fine as soon as I started a manouvre.

Also, I'm still unsure how you can tell when you have enough power, or when you have too much power.

Just idle curiosity (for now)
Thanks
Jon

What this really meant was that, if you built lightly, and used 52 foot/.012 lines, a reasonably strong .19 would pull your plane adequately on a calmish kind of day. (If the mill in question happened to be a Veco 19 BB, more than adequately).

If you opted for a .35, you had more than ample power for these (roughly) 300 square inch jobs.

Truth of the matter, IMHO: Even these humble .35s (Foxes, McCoys, etc) moderately overpowered these airframes mentioned above, then and now.

And I am guilty. The shame of hanging a Fox .35 on a Yak.

A really good compromise is a Fox .25 for those typical profiles. But few others made this size engine at the time. .29s are closer to the "truth", but maybe still a bit much.

Of course, windy weather flying, which is part and parcel with Midwest flying, moots most of my argument, admittedly.

But: "Big" 'ol planes like Ares, Sabre Stunts, etc were "supposed" to be flown with .35s. Ditto for Shoestrings, Cosmic Winds, etc. Both can't be correct.

Enter ABC, Schneurle .20s. Everything changes. And your own calibration of what is suitable must change. True, you're running a higher rpm. But now, you're not that far South of the HP of the old .35 baffles.

Sure: Go ahead and hang a Len OS 35 FP (hell, make it a 40) on a Buster or something, and some lead in its nether regions, and fly the hell out of it, if you wish. But that somehow misses the Spirit of the original design.

Again, IMHO.

So for a given airplane it is a complex relationship between engine HP, engine weight, airplane weight, wing loading, airplane design, line length, propeller selection, and your skill level and aspirations, etc, etc.

>HI all,
>I know there have been lots
>of recent posts about engines
>sizes for particular models, but
>I have a more general
>question.
>
>If a model states a wide
>range of engine sizes (eg
>.19 to .35) how does
>that work? Is it
>that a .19 at full
>power will just about lift
>it and fly half decently,
>and a .35 if set
>to 4-2-4 will supply the
>right amount of power for
>level flight (4 stroking) and
>loads of power for manoevres
>(full power 2 stroking)?

There's no real rule. For example, the Nobler and the Ringmaster both said .19-.35, but there's no comparison in their real power requirements. I suggest you go by wing area and weight, and ignore the box-top requirements.

I don't think there's any way to build a reasonably decent model for both a 19 and a 35, at least for engines of comparable specific output.

I've seen plenty of posts about wing loadings, but not so much on weight/engine stuff. I did find an old 50's article that had 2 of the, then latest, models. They were very different and used different engines but had the same power to weight ratio. I used this to work out that my home-grown was far too heavy for the engine, and when I switched to a bigger one it flew much better.

I guess you need to own a decent spectrum of engines so that you can have one to suit any given model.