3D Robotics Comment by Chris Anderson on January 12, 2009 at 10:01pm

Very impressive! Can't wait for the in-flight videos...

Comment by Blair Davis on January 13, 2009 at 3:44am

Well I personally would like to wish you the best, I have revently added Robtic to my list of aviaion related hobbies. I am also working on a simuliar project and i have learnd alot, Mine started as a bet that I could make a Rocket do something but I am fast approaching the "impossible." at least there version of it. I like you idea, I am currently working on propulsion system for mine, after the rocket motor have been burned out I need smoething to keep that thing in the air right? Other wise I'll have an expensive "lawn dart" I have yet to do flight testing but that shouldn't take too long. I'll be laying up the Composit, body in a couple of weeks. I noticed that you had a mentor, how did you go about getting that set up I'm sure that their a huge help, well keep us posted and I'll do the same, looking foward to seeing your progress!

Moderator Comment by Gary Mortimer on January 13, 2009 at 9:08am

Well done, very cool, will look forward to flight tests.

G

Comment by Julian on January 13, 2009 at 1:02pm

@ Blair
Are you using the swing wing concept? If so, how are you turning yours, becuase I've grown tired of the bungee and pulley system I am curretly utilizing.

As for the lawn dart part, I know exactly what you're talking about...

Comment by Julian on January 13, 2009 at 1:13pm

The face says it all ^
As for my mentor, I am currently enrolled in an idependent research class at my highschool, and then I take my research to different science competitions (science fair among others). Last year I competed in a local competion, and one of the judges was a Lockheed Missle and Fire Control Director. He was amazed at what I had done, and felt that if I was pointed in the right direction I could have a more advanced project. He invited me to the Orlando facility, where I presented in front of a board of about 12 aerospace engineers and then I got a tour of their production and testing facilities, the unclassified stuff that is ;)
A few of the engineers gave me thei numbers, and I ended up with the chief Aerodynamisist as my mentor.

Comment by Paul Marsh on January 13, 2009 at 1:13pm

Julian,
Very nice project, and very impressive for one as young as you. Keep it going. Regarding the swing wing, you might want to search the internet and/or forums (RC Universe, RC Groups, etc.) for radio controlled F-14 projects. There are a number of swing-wing designs out there and they might give you some ideas on how to modify or improve your own.
Hope this helps.
Paul

Comment by Stephen Carlson on January 13, 2009 at 3:24pm

Bravo,

Keep at it. I went to the International Science and Engineering Fair in Phoenix 2005. You're definitely going to make it there man! The plane I used was of my own design as well, as pictured in my avatar; not nearly as polished as yours is, but same idea.

-Steve

Comment by Paul Marsh on January 13, 2009 at 3:31pm

Julian,
I was giving some thought to your swing wing issue. I wish I had a firm design or two to suggest, but here is some food for thought. Perhaps you could use components from a pneumatic retractable landing gear system. There are light weight systems out there, and you wouldn't even need a servo and valve to actuate the mechanism assuming the wings are held in place inside of a launch tube in a field system. The rotating component of the landing gear system would/could replace the current pivot point. Basically, instead of swinging a landing gear strut and wheel, the wing is being rotated. What would have been the landing gear strut would extend into the wing itself. Short of that, you might be able to simply use the pneumatic cylinders to extend and hold the wings in place. There might be room in the fuselage tube for a small air tank that holds just enough volume to wing the wings once. Usually, the landing gear pivot box has a locking mechanism built in so you wouldn't have to rely on air pressure to hold the wings in place once extended.

Again, just some ideas to get the design juices flowing.

Paul

Comment by bGatti on January 13, 2009 at 5:25pm

I built an f16 profile in two small sizes. I had a lot of problems getting stable flight out of the f16 shape. I note here that your swing moves the CP forward a huge amount. I don't know much about rocket CG/CP requirements but I'm concerned that your CP moves so much. (google sez cp should be 1-2 diameters behind cg - and length should be 10-20 times diameter - neither of which are clearly evidenced in the pictures)

1. Irregular diameter. Bearing in mind the folded wings create extra pressure within the context of the rocket tube, your length should be at least 10 times the effective diameter of the rocket profile. It appears the design may be shorter than recommended.


2. cp/cg Given the swept wings, the CP will move dramatically. Close evaluation of the f-15 for example reveals that the cp is largely maintained throughout the sweep; in a long, and fully exposed wing, the cp will move dramatically. If we accept that your CG is somewhere near your extended wing line, Then CP must be way back when swept - I think far more than two calibers (diameters). Another issue. "Diameter or caliber" refers to a normalized round shape, while your shape is unique and non-normal to the centerline - so there is no known reasonable cg/cp relationship. You might consider building a smaller rocket without moving parts and with the big wing shapes fixed in position, and play with the length, the fins, and the cg until you are satisfied with the rocket trajectory.

Best of luck.

Comment by Julian on January 13, 2009 at 5:46pm

I did this the previous year of research, and the rocket with the same CG location as the full size aircraft with wings swept all the way back had a relitivaly stable rocket flight path, and then again when I flew the fullsize aircraft last year from rocket takeoff it was reletivaly stable from a visual standpoint.
As far as CG goes, the rocket motor ejects its self after its burn time and as the wings swing foward to bring the Guardian to a near camber CG position, That plus the slight sweep of the wings give the aircraft a normal level of stability in horizontal flight.
Now I just have to put the two together with a heavier aircraft for this years project :)

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