user created planes

[wanestate]

I am wondering how good the physics are on G4 and others for planes that are user-created. Do they accurately model the flight of these planes? Which of the simulators does this best?

Also, can you create planes in standard CAD packages or do they have to be created within the simulator program?

[nemo_uk]

They vary a bit. There a two factors ...

1. The simulators overall physics
2. How the model physics has been set up

If the model is of an ARTF kit then you can pretty accurately assess how good a likeness the simulator model is. If however you are looking at something more bespoke were there are a lot of different set-ups (motors, props, batteries etc.) it is a bit more tricky. With G 3.5 and 4 is that you can edit all of the above. You can with a bit of time set it up to fly like your model within the limitations of the overall physics.

With regards CAD packages the simplest option is 3DS Max ($$$) or you can use Blender (free) although this makes the process a bit more time consuming.

more information ... here (http://www.knifeedge.com/KEmax/)

[wanestate]

What I'm hoping for is a little more ambitious I think. For a multi-semester school project, my team is designing and building an RC plane. We thought it would be beneficial if we could get a feel for how our design will perform before we actually build it. Ideally, if we improved our design we would see a resulting improvement in its flight as modelled by the simulator. Or if we made a poor design change, it would perform worse in the simulator.

Part of this question stems from my ignorance of how these simulators are designed. I don't know if they program these simulators with general equations of aerodynamics or if they just program in how each individual plane will handle. I imagine that the former case might lead them to draw up the model, program in its specifications, let the simulator model its behavior, compare this with the actual rc model, and then do some tweaking (hopefully minimal if their equations are good enough).

Obviously what I am hoping to do would require the former situation with some pretty powerful equations (probably based on extensive wind tunnel testing of model-sized planes or at least Reynold's # similarity situations). To be able to take a plane that I have designed, and based on its shape, weight and power specifications, etc that I input, give me a rough estimate of how it will perform.

If this is pretty hopeless, let me know please. G4 sounds like a pretty strong package except on the ground. If G4's "create a plane" works how I'm hoping, it would probably make up for that. But if not, I might go with something like FS one that I've heard models ground performance better.

My school has a few Solidworks licenses, so ideally we would use that software, although if there was good reason to, they could probably get a different package. There might be an autocad license somewhere on campus too...

[nemo_uk]

You should be able to do what you want to some degree. With G4 you create the visual mesh in a 3d package 3DS Max, Blender etc. Then you create the physics desciption of the aircraft inside the simulator. So you could have something that looks like a Goodyear blimp but flies like a helicopter.

Here is a screen shot of the aircraft editor.

http://img377.imageshack.us/img377/135/editorzd5.th.jpg (http://img377.imageshack.us/my.php?image=editorzd5.jpg)

You will notice there is a wireframe model overlayed on top of the visual model, this is the physics "model" for want of a better description. The physics model could for example have much larger ailerons than visual mesh, you never see the physics model it only controls the visual model. You can edit a lot of different parameters for each part of the model. E.g making the tail wheel heavier will move the C.O.G. back. Making ailerons bigger will increase the roll rate. You can make all these "tweaks" independent of the visual mesh you created in 3DS max or Blender.

Here is a link to PDF manual for G3, it might be worth taking a look at (the process of setting up aircraft has not changed much in G4) ...

http://www.knifeedge.com/downloads/RealFlight%20G3%20Manual.pdf

People have used G4 to prototype designs before ...

http://www.knifeedge.com/forums/showthread.php?t=20467

You might try PM'ing Carl to see what he thought of it ?

http://www.knifeedge.com/forums/member.php?userid=45754

[wanestate]

Thanks a lot. Your post answered a lot of questions, and those links have already been helpful.

[Pull-Up]

I have been using G4 to do this very thing too.

I am amazed at how accurate the sim is as a research & development tool. Not only does the sim teach someone to fly R/C, it has a powerful ability as a R&D package.

If you are not too anal, you can just select a plane in G4 (or download one from the user-created planes on the G4 web site Knifeedge.com) that closely matches the visual appearance of your plane.

In G4, it is much, much easier to modify the physics of any plane (size of wingspan, control surface size and positions, etc) than it is to create the visual model (super, super hard to do). The visual model is just that... a visual representation of the plane for your visual reference. The visual plane has nothing to do with how the sim creates the flight characteristics. The flight behaviour is entirely within the physics, which is easily modified within G4.

I am amazed at how accurate the sim is as a R&D tool. As a somewhat newbie, I have many ideas that I wish to test. One of these ideas was a plane style called Delanne. Do a Google on "Delanne wing". This is a plane with two main wings (one being in place where the stabilizer wing would normally be located). As you can imagine, this is a radical departure from a conventional plane design.

I created the Delanne plane in G4 using one of my favorite G4 planes. I just radically modified the physical parameters of the plane to convert it to a Delanne plane (as far as the sim viewed the physic of the plane).

I tested the plane by flying it for about 30 minutes (including making minor tweaks to the design and fine tuning it). AFTER learning how it flew in the sim, I did more Google searching on the Delanne configuration. To my amazement, the Google searching revealed exactly what the sim had revealed in regards to the flight characteristics of a Delanne plane.

I am using the sim to tweak my favorite plane (Telemaster) to have the traits that I desire the most. I tested different wing sizing, different dehideral settings, larger stabazilier size, etc. Using the sim as a R&D tool, I have redesigned the Telemaster to fly much more to my liking than the original. I am in the process of building the real RC plane based on the configuration in G4 that was most to my liking.