RC Groups

RC Groups
    Scratchbuilt Indoor and Micro Models
        Micro Air Vehicle Science Project

#1 KatanaGuy Aug 10, 2003 12:35 AM

Micro Air Vehicle Science Project
I've been interested in MAV and UAV type planes for a year and a half. I'm interested in building these vehicles in the future, and have gained some experience by converting my Slowstick into a partial UAV with a cheap "Hong Kong Special" Ebay wireless camera.

In anticipation of school, which is in 2 weeks, I want to find out as much information on MAVs, UAVs, and RPVs. Any websites, tech papers, and people to contact will be appreciated.

What would also be very useful is general information on aerodynamics, airfoils, and plane design. I'd like to learn more about aeronautical engineering and flight.

I plane to design, build, and fly a working 3x sized (18 in) MAV for my science project early next year. I wonder if I will make it to the National Science Fair :eek: ?



#2 propfan Aug 10, 2003 09:13 AM


#3 Gordon Johnson Aug 10, 2003 04:21 PM


#4 KatanaGuy Sep 03, 2003 11:32 PM

Instead of two weeks to school, I'm now two weeks into it! I've experimented with my Slowstick UAV more, and have tried designing a small plane.

My current questions are:
1) How do I find the CG of a delta wing (Mathmaticly). I think I know how to do it graphicly, but that dosen't feel accurate enough.

2) How is the CG affected by haveing canards in front. Do I need to place the CG between the two according to their areas or something similar?



PS: To find the CG on a delta wing graphicaly, you take the wing root length, and put it on both sides of the wing tip, and visa-versa with the wing tip length, right? You then measure 30%-40% back on the Mean-Aerodynamic-Chord, and thats the CG, right?

#5 Graham Stabler Sep 04, 2003 03:19 AM

1) There is a good book on model aerondynamics called "model aerodynamics" it is in there. The best way is test gliding really. That's how they would do it for real if they could :)

2) Same book I suspect

As these are really just Aerodynamics questions you may consider posting in the modelling science section of the forums


#6 TeamSME Sep 04, 2003 06:26 PM

Well if ur scaling a plane down just use original cg/original span time x (new cg)/ span. Cross multiply. I just love algebra in my high school.

#7 Phreakish Sep 04, 2003 07:53 PM

the math part is really just to find the MAC... which is going to be the average chord length. The average chord then is as you suspect: (Cr + Ct)/2

Cr = root chord
Ct = Tip chord

Then its a matter of finding where you want your cg... a normal good starting point is 25%, so once you find your MAC, you use 25% of that as your cg... For a constant taper, your mac usually falls dead center on the wing profile.

The way we do it in my Aerospace engineering classes is this:

Draw the planform for the wing (top view outline). Find your MAC (mathematically if you wish), and if you like, you can verify it by measuring the chord at the center of the wing... From there, mark a dot on the root chord at 25% chord length (1/4 of the chord length from the leading edge. Then do the same at the tip. Connect these two dots to find your quarter-chord line (this is a very important line). Now, draw a line perpendicular to the centerline of your plane from the intersection of your quarter-chord, and your MAC line, to the centerline of your plane... follow? This will give you the exact location of where you want your cg to be on your model... You can do it mathematically, but you'll have to do more or less math depending on the shape of the wing... and to do it graphically works really well, never screwed me up so far ;)

#8 Aaron13 Sep 05, 2003 11:04 PM

dang your what? 17? how did u get into flight school? i want to. you could build a bit plane they can get pretty small. im building a lifter for my project but i cant get a hold of a 25KW power supply.

#9 Mr_Bazball Sep 06, 2003 12:58 PM

Thanks guys :rolleyes:
U just reminded me i need to start thinking about a science project for my physics class.

#10 JordanKBowles Sep 06, 2003 09:32 PM

i'm resreching mine now for my physics 2 class, I think i'm going to go with a sub 6" VTOL heli thats fully robotic

#11 Phreakish Sep 07, 2003 01:58 AM

actually, I'm 20, and a junior in Embry Riddle Aerospace University ;)

Anyhow, I forgot to answer #2... basically, you want your cg at the center of your lift... so, if you have canards, and they have null lift (symmetrical airfoil) then you should be fine, and it SHOULD fly like any other airplane, with the cg based on the wing alone... The same is done for std tail aircraft, but the tail is usually null lift (sym airfoil) so its not a consideration... if the same is true for your canards, you're fine. So long as you remember that if you're pulling up with canards, you're increasing the lift on the front, not decreasing it in the back (as a normal plane works), so AOA comes into effect... which is what causes the canards to typically stall before the wing (typically, not always).

Best way is to glide test... which you can do with no equipment on the aircraft... if it flies empty (and you dont add too much weight) then it'll fly fully loaded. You could add balast to make sure it'll fly with the load... glide testing really is the best way, thats how Ive gotten all my models to fly :)

25% mac is a rule of thumb, you'll NEED to adjust from there depending on how heavy the nose/tail is...

#12 Mr_Bazball Sep 07, 2003 08:31 PM


I think i'm going to go with a sub 6" VTOL heli thats fully robotic
I was just thinking of that too. Maybe one with an rffs100 and actuators. Also im thinking about designing a micro/submicro plane.


All times are GMT -5. The time now is 12:50 PM.