Physics Corner

[abaser]

A recent question to me got me thinking that I really didn't know the answer to the question asked. So, I thought there should be a place to discuss just these types of questions. I can model, I can CS, but making these planes fly right is way over my head. So, please feel free to ask any physics questions here and maybe someone will be willing to help out. Questions can be anything regarding flight setup in RealFlight. Please keep posts here limited to questions and answers ONLY. No small talk please.

Let me start with the question that was asked to me. When I was learning to try and setup my models, I was advised to match the wireframe to the model as closely as possible. A good example of what I'm talking about, take my katana wings for example. There's a big fillet at the root that tapers quite a bit before the wing takes the usual shape. To match the wings with the wireframe, I matched the fillet with one wing then added another to finish the wing out. The question is, is this type of setup necessary, and does RF actually represent what I'm trying to create accurately using this method? Or, would it be more accurate to just make one wing model and go with an average area of the visual model?

 

[csgill75]

Many people do not know how to do physics, including some content creators. I used Doug Kaye's tutorials earlier on and real world experience on how similar real aircraft fly to start with and tweak to suit the individual aircraft

https://forums.realflight.com/showthread.php?t=17498

 

[Moto-Guzzi]

Good Question I've wondered for a while myself...

A lot of planes have very square/harsh angular wing tips and control surfaces in the physics model, but very rounded ones in real life

For "amusement purposes" I'll add 3-5 wing segments (sometimes more), to re-build them follow the "contours" more closely...P.I.A adding 3-5 individual control surfaces too, but hey, its my on line hobby...

Aside from "looking cool" in the editor, am I gaining anything? Does RF just calculate the total sum of area vs weight, and not consider the more rounded shape?

I dont know, but (with a lot of other tweaking) my half-scales seem to fly better with rounded surfaces than when I just scaling up the original "geometry" of wing shapes...

Extreme example here:

 

[jbourke]

RealFlight considers every wing segment so the extra work you are doing is absolutely changing how the aircraft flies.

The changes might be subtle, but they are there.

Jim

 

[Moto-Guzzi]

Good to know, thank you sir!

 

[abaser]

RealFlight considers every wing segment so the extra work you are doing is absolutely changing how the aircraft flies.

The changes might be subtle, but they are there.

Jim

Thanks Jim!

 

[technoid]

RealFlight considers every wing segment so the extra work you are doing is absolutely changing how the aircraft flies.

The changes might be subtle, but they are there.

Jim

Thanks Jim that's the confirmation I was looking for.

 

[abaser]

Next question, and this may seem really stupid to some, but when setting up the fuselage airfoils, are you supposed to try and match the shape of the fuselage as closely as possible or something else? And when it says sides or top/bottom, if I'm trying to match the shape, does sides mean looking at the plane from the side or from the top?

Like I've said before, I might can model them, and I can color them, but making them fly is Greek to me.

 

[abaser]

https://forums.realflight.com/download,s.php?do=file&id=18210
open this 6.5 epp f22 in the editor, look at the shape of the elevators, and the naming. they are complex shapes.
Every piece of the skin on any model , will affect, some aspects of flight. Some times, only drag. Models flying knife edge, all side lift, is crushiel.
Do a test a test on a model, increase the aerodynamics only on one side of a model, turn it all the way up on one wing, or side of fuse, or elevator.
just using the wrong air foil on the wings, or stab, or rudder, will change flight a lot.
something, missed a lot is speed, RF calculation, will miss lead you. I allays think how it should look at the field.

I understand all that. What I don't understand is how to really match up the airfoils to the surfaces. With the wings and tail surfaces you get somewhat of an outline of the airfoils to better match to those, but you don't get that change with the fuselage. If my fuselage is flat sides, do I find a flat bottom airfoil, or does one airfoil handle both sides so that RF will read it as flat on one side and rounded on the other?

Take these two planes, my Mustang and Citabria. How should I setup the fuselage airfoils and why? Two fairly different style fuselages that should react differently. I want to know how to do that without just guessing. I've never flown either model so I don't know how either should fly.