A New Model

[Mac]

Hello everybody.
I have a very basic question, that I'm sure a great many people have frequently asked.
When deciding to build a new model for PSS, what should you look for? I have looked at a lot of scale models for I/C with the idea of converting them to PSS, but what should you look for in a model.
What are the fundamental criteria; weight, wing span, profile. And what is the best style to build; warbird, jet liner, jet fighter?
What's the answer, anybody?

Mac.

[rc-pilot]

Hi Mac,

The best a/c to choose is the one you like. It's no matter whether it's a jet, an airliner or anything else. However, when you look at what it might turn out like you may have to rethink or alter the design. For example, try a Lockheed F104 Starfighter; will it fly as a glider without a significant increase in wing area? Highly unlikely, so you would have to revise the wing plan to give it enough area to come out at a wing loading suitable for the slope and conditions you hope to use. Then you may find that the wing has got so ridiculously off-scale that it no longer looks like a Starfighter, so it may be better to pick something else.

Regarding weight, section etc, don't expect a power model to have a particularly good section for sloping. Some do work reasonably well in good lift, others don't. It's probably better to replace the section by a proven glider section, especially if you want it to fly in light lift. Go for something with a good Cl and low drag at the range of Rn you expect to fly at. With power models you also need to review the structure, which is often reinforced in unnecessary places, and not reinforced where we need it to be. Power kits often include wood which is good for making kitchen tables or fences, but not for gliders, so you may have to substitute much of it for some better stuff.

Hope that helps, it's a very superficial answer to a series of questions that really need a whole book to discuss all the options.

[AndyB]

I suppose it depends on your local circumstances.

Mine are: small-ish hill, sometimes not much wind, 20 minutes walk from the car-park to the hill, and, er... somewhat error-prone piloting.

For me, that means
a) Carry two models in case there is an unscheduled model-hill interference event. This limits the size of model to that which can be carried in one hand for 20 minutes.
b) Build small-ish models (say, max about 50") because larger ones are more difficult to keep in the lift band when flying fast.
c) Build light, efficient models because I'm not carting them over half a mile if they won't fly when I get there. I normally try and build PSS models to less than 13 oz/sq ft (lately aiming for 10 or 11 oz/sq ft), they can always be ballasted up if there's enough wind. I normally find that selig S3021 is best on a model of that size at those sorts of wing loadings.

What's the best style? Well, I have this thing about early jet fighters, which is a bit unfortunate because they're probably the least easy. Your "thing" may be different, of course. Almost anything can be made to fly if you spend time tuning the c.g., control throws, etc...

A.