View Full Version : Design question...

10-04-2006, 07:41 PM
Over the months that I've been reading here, I have seen a few postings about the challenges of designing and building a new racer, of any class. Though most of the discussions centered around the Unlimited Class. Has anyone here put their grey matter to test by using X-Plane? Though I personally don't know very much about X-Plane, I have seen and read about others using it to design and test real world applications. Though I doubt any of us has the bucks laying around to build and fly a racer from scratch, I think it would be an interesting challenge to see what we could come up with.

Just a passing thought, a possilbe way to pass the time while we get ready for the next round at Reno.


PS: I wonder if X-Plane could be used to test airframe mods for results before actually making the changes to the airframe?

10-05-2006, 10:52 AM
I'll take a quick stab at this, if to do nothing else but to bump you up some.

X-Plane is a game. I wouldn't dream of putting a test pilot's life in danger over the results of a game. It might be a really good game but it will not surplant the current methods.

If you are serious about testing aircraft modifications you should look towards solidworks or better. Heck, I don't even know if solidworks cuts the mustard. You need software to input your design, which would be CAD, then you should validate it with computational fluid dynamics (CFD) for aerodynamics, finite element analysis to see if the modification can withstand the forces involved, then on to structured flight testing.

I think it could be interesting and fun to mess around with myriads of designs. We could probably have a blast! But, to take the designs from X-Plane into the real world.... I wouldn't do it. You could probably take them out of X-Plane and then into CAD software of your choice. So, maybe in a pre-liminary design you could test crazy ideas out relatively inexpensively, then if they show promise move into the software that actually is meant for this.

10-06-2006, 07:45 AM
You point out a couple of things I hadn't thought of. I do think it would be kinda fun to see ideas take form, if nothing else to see what they might even look like. I do have access to a variety of design tools, I'll have to check to see what all my bud in Sacramento has. My main interest would be from the theoretical side. To toss different ideas around and see what comes up.

I'll have to explore this a little further and see what comes of this. I'm going to see about making a quick trip to Sacramento this weekend and see what is available for me to use. I know that my bud has got a variety of design tools that he tinkers with. He is currently in the process of a designing a project that he can build and fly. Though he has been working on this for quite some time, his work load doesn't allow him to spend the time with it that he would like.

Many thanks for your input,


Only 341 Days 12 Min. to go!!!!!!!!!!!!

Hawker 73
11-28-2006, 02:00 AM
There is a design package available from DarCorp called AAA (for Advanced Airplane Analysis) which properly calculates flight performance, stability and control and other aerodynamic stuff. I have a copy of AAA-Homebuilt which is the low cost sub-sonic airplane version. It allows you to try out all sorts of configurations and should at least get you to a safe flying shape. It takes a bit of understanding though.

To do the full aircraft design task I think you need to cover;
1. Aerodynamic design. AAA or various text books.
2. Airframe structures and materials. Finite Element Analysis or hand calculation (see E H Bruhn "Analysis and Design of Flight Vehicle Structures")
3. Powerplant i.e. Engine, propeller, cooling
4. Systems; fuel system, boost systems, electrics, hydraulics etc.
5. Flight path; finding the best combination of power/drag and "g" at the pylons to manage the energy and acceleration of the airplane.

To do this thoroughly is a lifetimes study, practice and experience. Maybe we could start a discussion thread for each of these topics and see what we can learn. It will make watching the races more interesting as you can see and understand the tactics as pilots search for the optimum for their airplane.

I recently came across a video of the "507 mph" heat from 2003 on the web which shows different tactics and a different racing line taken by Rare Bare and Dago Red. This set me thinking about the factors that were affecting the lap times of these two very different aircraft. It seemed that Skip Holm in Dago Red was not banked as steeply as the Bear at each pylon and was therefore not pulling as many g. Pulling g increases the induced drag and that slows the aircraft. So Skip was trying to carry his speed through each turn at the expense of having to fly a wider radius around the pylon. The Bear went in tight with the induced drag "brakes" on, got the turn finished as quickly as possible with some loss of speed and then went for maximum acceleration down the next leg of the course. Were these tactics the correct ones for each aircraft? Maybe we could analyse the data for these two and see if a different flightpath would have changed the result.

team zipper
12-05-2006, 06:13 PM
As a rookie in formula one this year, I reasoned that flying a smooth low G route around the pylons would result in lower induced drag and better times. After the races, some old heads told me that just one wingspan greater radius on the turns would equal 300 feet loss per lap!
I would love to see some real world analysis of this question.
Zip Andre...Team Zipper Air Racing :cool:

12-14-2006, 08:14 PM
You guys certainly are asking good questions. With some of the telemetry/data acquisition going on now that includes GPS and G force, some of these questions are being answered internally with teams. I'm of the opinion that there's certainly a tradeoff between G force and distance around the course. Too many G's, you slow down. Less G's, you fly a longer course. This all depends on the aircraft, speed, and class being flown. G's do scrub speed off fast, so one has to look at the speed loss in the turn for a tighter course and see if that shorter distance is better off than flying wider and at a higher speed.


Bill Marsh
12-18-2006, 10:53 AM

Wasnt Wildfire done with Xplane.... no no IT WAS the Sanoflush F82 upgrade i belive.

GOD.... now i can get back 2 work after venting (flushing)