I am looking to build a plane for use as a camera platform. I was thinking of modeling it after the Predator B

I am going to build it as a flat bottom wing and need to get about 380 square feet.
Keeping the same basic shape as the predator wing, what dimensions should I use as my root cord, tip cord, and wingspan.
Also, for best lifting as i am needing to carry about a 10oz camera, what airfoil should I use?

380 square feet of wing area? You should be able to just ride in it and pop pictures of whatever you want. Pack a lunch and a 6-pack of Coke--it'll carry the load.

Are you sure you don't mean square inches?[&:]

A flat-bottom airfoil is always about the best for lifting weight.

You know.. you read a post a dozen times to make sure your not saying anything stupid and you go ahead and do it anyway.
Yes, 380 square inches.

That's not enough airplane for a 10oz. camera.
The motor and battery add a lot of weight, plus the camera...
You'll need a larger airplane.
Look for 6 feet or more span, average chord about 7-8 inches.
Pushers.... the c.g. goes waaaaaaaaaaaaay back!
The heavy stuff, the motor battery and camera MUST go up front.
This one had an extension shaft on the motor, carried a film camera, and needed nose weight.
That's a Gentle Lady wing.
I've tried a lot of shapes, and find a conventional wing-tail plane is easiest to work with.
The need to fly straight and level without too much effort devoted to flying, while concentrating on the position of the plane and the camera relative to where you want it to be is most important.

Why not just build a Kadet Senior?

Extend the wings by 1 or 2 bays on each side. Boucoup square inches!!! Lotsa lift. Big fuselage--plenty of room for cameras and batts. Flies fine on a 4-stroke .91 or 1.20. Easy to modify-- ailerons -- flaps -- taildragger -- camera mounts -- big fuel tank........etc...

Unless you've got a soft spot for that particular airplane--the Predator.

Keep in mind this bird doesn't need to do anything but go up, fly in a circle and come down.
Most guys use the [link=http://www.hobby-lobby.com/easystar.htm]Easy Star[/link]
Stock it weighs 24oz over 370 square inches.
With a brushless motor and 3 cell lipo they don't have any problems carrying a 9-10oz camera.


I am planning on using a Himax 2115 through a gear drive of either 4 to 1 or 6 to 1, whichever works better, a 3 cell lipo and a Castle Pheonix 25 speed controller. That should provide more thrust than the little outrunner pictured above.

Here is another model carrying a small film camera. Wingspan of 58 inches, constant cord of 7.5, weight approximatly 40oz with camera powered only by a brushless outrunner.
[link=http://www.rcuniverse.com/forum/m_3413400/anchors_3413400/mpage_1/key_easy%252Cstar/anchor/tm.htm#3413400]Link to thread[/link]

That's hilarious. But I know exactly what you mean. The mind just fills in the correcttion to make it appear smart ... until we post the thing and then the first guy comes along and rakes us over the coals....

By all means make a semi scale version if you really MUST use a pusher motor. But plan on increasing the wing chord. Models often do not translate well if scaled too small and wing chord is one of those things. Scaled to 400'ish sq inches the Predator planform will likely have a whopping huge 5 inch chord at the root and 3 at the tip or smaller. This will mean a high aspect ratio, which is good, but a terribly small Reynolds number for the airfoil, which is bad. Studys of sailplanes have shown that the minimum wing chord to achieve the best Reynolds bang for the buck is about 7 inches. This is why 2 meter gliders seldom have high aspect ratios but open class sailplanes do.

For your camera model a semi scale version with an aspect ratio of around 6 is going to offer the best all around performance. And 6 is pretty stubby. It ain't going to look very Predator like but at least you can use the planform.

Nose and tail moments are going to need to alter in order to ensure balancing without the need for weight. Perhaps make it so the wing can shift over a 3 or 4 inch range in order to balance the model at the best % of the chord.

The Predator uses a crazy long landing gear and that subfin to protect the prop. If you're hand launching then great but if you need gear it would be best to just use a dolly.

There's another issue too. WIth the motor and camera at the extreme ends of the fuselage like with the Predator you have a lot of inertia that is going to fight the ability of the model to pitch and dampen the pitching motion. Mass centralization may be better at model sizes to avoid any destabilizing and resonant cyclical issues.

With electrics it's easy to do twins. And a twin setup moves the motors out away from the camera. I'm thinking that an arrangment sort of like a C-119 Flying Boxcar may be sort of nice. The big pod offers up lots of options to mount the camera in various attitudes for different viewpoints.

I've played with the numbers a little bit. Based on the shape I am trying to achieve what works out best is a wingspan of 68 inches, root chord of 7.5 and tip chord of 4.5. But after looking at it, I think it would be difficult to build such a wing both light and strong. Not to mention it would be difficult to turn since I don't plan on using ailerons.
So I am thinking about a wingspan of 58 inches, root chord of 9 and tip chord of 5. That gives me 406 square inches. If I can keep the model under 45oz including the camera, i can keep my wing loading under 16oz/sqin so it should fly like a trainer.
Anyone see any problems with this idea?
How light do you think I could build such a wing?
What would be the difference between this wing and a 58 inch wing with a constant cord of 7?
What if any dihedral or polyhedral should i build into it?

For no ailerons, polyhedral.
The longer the wing the better.
Give yourself some playing room.
I've flown the GP Spirit 2M wing up to 65 oz with a AXI 2820/14 with extremely good performance on 8 Nimhs.
These all use the same wing.. the motor position dictates the nose length on the pushers.
On the pointy one, the camera is under the wing.
These all have a 90degree rotating camera mount, to look anywhere from directly down to directly to the side.

I've never seen a v-tail in that configuration before. How did it fly?
In reguard to the polyhedral, what percentage of the wing? Just a rough guestimate of your wing is about 30%

The inner panels have 2 inches at the break.
The outer panels 4 inches each, measured up from the inner panel flat on a board.
The pod and boom is popular for AP, especially with electrics.
Lots of prop clearance for a pusher.
Workable configuration are many...